Publications by authors named "ZhiXun Guo"

32 Publications

Biochemical, metabolic, and immune responses of mud crab (Scylla paramamosain) after mud crab reovirus infection.

Fish Shellfish Immunol 2022 Jun 30;127:437-445. Epub 2022 Jun 30.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, Guangdong, 510300, PR China. Electronic address:

Mud crab reovirus (MCRV) is a serious pathogen that leads to large economic losses in the mud crab farming. However, the molecular mechanism of the immune response after MCRV infection is unclear. In the present study, physiological, transcriptomic, and metabolomic responses after MCRV infection were investigated. The results showed that MCRV infection could increase lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase activities. MCRV infection decreased antioxidant enzyme activity levels, induced oxidative stress, and caused severe histological damage. Transcriptome analysis identified 416 differentially expressed genes, including 354 up-regulated and 62 down-regulated genes. The detoxification, immune response, and metabolic processes-related genes were found. The results showed that two key pathways including phagocytosis and apoptosis played important roles in response to MCRV infection. The combination of transcriptomic and metabolomic analyses showed that related metabolic pathways, such as glycolysis, citrate cycle, lipid, and amino acid metabolism were also significantly disrupted. Moreover, the biosynthesis of unsaturated fatty acids was activated in response to MCRV infection. This study provided a novel insight into the understanding of cellular mechanisms in crustaceans against viral invasion.
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http://dx.doi.org/10.1016/j.fsi.2022.06.058DOI Listing
June 2022

Mechanism of Cadmium Exposure Induced Hepatotoxicity in the Mud Crab (): Activation of Oxidative Stress and Nrf2 Signaling Pathway.

Antioxidants (Basel) 2022 May 17;11(5). Epub 2022 May 17.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, China.

Cadmium, one of the most toxic heavy metals, can cause severe oxidative damage to aquatic animals. However, the mechanism whereby the mud crabs respond to cadmium exposure remains unclear. This study investigated the effects of cadmium exposure on oxidative stress and histopathology changes and evaluated the role of the Nrf2 signaling pathway in regulating responses to cadmium-induced hepatotoxicity were investigated in mud crabs. Mud crabs were exposed to 0, 0.01, 0.05, and 0.125 mg/L cadmium for 21 d. The present results indicated that cadmium exposure increased hydrogen peroxide (HO) production, lipid peroxidation and tissue damage, but decreased the activity of superoxide dismutase (SOD) and catalase (CAT), and caused lipid peroxidation and tissue damage. The results of an integrated biomarker index analysis suggested that the toxicity of cadmium was positively related to cadmium concentration. The expression levels of the Nrf2 signaling pathway (Nrf2, metallothionein, and cytochrome P450 enzymes) were up-regulated after cadmium exposure. Silencing of Nrf2 in vivo decreased antioxidant gene (SOD, CAT, and glutathione S-transferase) expression, suggesting that Nrf2 can regulate antioxidant genes. Knocking down Nrf2 in vivo also significantly decreased the activity of SOD and CAT after cadmium exposure. Moreover, silencing of Nrf2 in vivo enhanced HO production and the mortality rates of mud crabs after cadmium exposure. The present study indicated that cadmium exposure induced hepatotoxicity in the mud crab by increasing HO content, which decreased the antioxidant capacity, leading to cell injury. In addition, the Nrf2 is activated to bound with antioxidant response element, initiating the expression of antioxidant enzyme genes during cadmium induced hepatotoxicity in the mud crabs.
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http://dx.doi.org/10.3390/antiox11050978DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9137997PMC
May 2022

Wnt5b plays a negative role in antibacterial response in Pacific white shrimp Penaeus vannamei.

Dev Comp Immunol 2022 08 18;133:104411. Epub 2022 Apr 18.

State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, PR China; Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-sen University, Guangzhou, PR China. Electronic address:

The Wnt family genes are essentially implicated in development and growth in animals. Accumulating clues have pointed to the importance of Wnts in invertebrate immunity, but the underlying mechanisms are still unclear to date. The Wnt5b has been known to promote white spot syndrome virus (WSSV) infection in shrimp but its role in antibacterial response remains unclear. In the current study, we focused on the involvement of Wnt5b in Vibrio parahaemolyticus infection in Pacific white shrimp Penaeus vannamei. We demonstrated that the expression of Wnt5b was regulated by the IMD-Relish and JAK-STAT pathways but not the Dorsal pathway and was suppressed upon bacterial infection. Although Wnt5b did not affect the cellular immunity in shrimp, it was involved in regulation of humoral immunity. Silencing of Wnt5b in vivo significantly increased expression of several antimicrobial peptides but decreased that of many immune functional proteins including C-type lectins and lysozymes. Treatment with recombinant Wnt5b protein increased the susceptibility of shrimp to V. parahaemolyticus infection, while silencing of Wnt5b in vivo showed an opposite result. These suggested that Wnt5b plays a negative role in antibacterial response in shrimp. Together with previous reports, the current study shows that Wnt5b functions as an inhibitor for shrimp immunity, which is a potential target for improving immune responses against infection.
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http://dx.doi.org/10.1016/j.dci.2022.104411DOI Listing
August 2022

A Dicer2 from Scylla paramamosain activates JAK/STAT signaling pathway to restrain mud crab reovirus.

Dev Comp Immunol 2022 02 7;127:104267. Epub 2021 Oct 7.

State Key Laboratory for Biocontrol / School of Life Sciences, Sun Yat-sen University, Guangzhou, PR China; Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-sen University, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), 519000, Zhuhai, PR China. Electronic address:

A Dicer2 gene from Scylla paramamosain, named SpDicer2, was cloned and characterized. The full length of SpDicer2 mRNA contains a 121 bp 5'untranslated region (UTR), an open reading frame (ORF) of 4518 bp and a 3' UTR of 850 bp. The SpDicer2 protein contains seven characteristic Dicer domains and showed 34%-65% identity and 54%-79% similarity to other Dicer protein domains, respectively. The mRNA of SpDicer2 was high expressed in hemocytes, intestine and gill and low expressed in the eyestalk and muscle. Moreover, expression of SpDicer2 was significantly responsive to challenges by mud crab reovirus (MCRV), Poly(I:C), LPS, Staphylococcus aureus and Vibrio parahaemolyticus. SpDicer2 was dispersedly presented in the cytoplasm except for a small amount in the nucleus. SpDicer2 could activate SpSTAT to translocate from the cytoplasm to the nucleus, and significantly increase the transcription activity of the wsv069 promoter, suggesting that SpDicer2 activated the JAK/STAT pathway. Furthermore, silencing of SpDicer2 in vivo increased the mortality of MCRV infected mud crab and the viral load in tissues and down-regulated the expression of multiple components of Toll, IMD and JAK-STAT pathways and almost all the examined immune effector genes. These results suggested that SpDicer2 could play an important role in defense against MCRV via activating the JAK/STAT signaling pathways in mud crab.
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http://dx.doi.org/10.1016/j.dci.2021.104267DOI Listing
February 2022

Functional characterization of VscCD, an important component of the type Ⅲ secretion system of Vibrio harveyi.

Microb Pathog 2021 Aug 18;157:104965. Epub 2021 May 18.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, China; Innovative Institute of Animal Healthy Breeding, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China. Electronic address:

Vibrio harveyi is a Gram-negative bacterium that occurs widely in the ocean and a kind of pathogenic bacteria associated with vibriosis in grouper. We investigated whether the VscCD protein of the type Ⅲ secretion system (T3SS) was important for pathogenicity of V. harveyi. Mutations to the vscC and vscD genes (ΔvscCD) and complementation of the ΔvscCD mutant (C-ΔvscCD) were created. Moreover, the biological characteristics of the wild-type (WT) and mutant strains of V. harveyi 345 were compared. The results showed that deletion of the vscCD genes had no effect on bacterial growth, swimming/swarming ability, secretion of extracellular protease, or biofilm formation. However, as compared with the V. harveyi 345: pMMB207 (WT) and complementary (C-ΔvscCD) strains, the ΔvscCD: pMMB207 (ΔvscCD) mutant displayed decreased resistance to acid stress, HO, and antibiotics. In addition, infection of the pearl gentian grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatu) showed that as compared with the WT and C-ΔvscCD strains, the ΔvscCD strain significantly reduced cumulative mortality of the host. The colonization ability of the ΔvscCD mutant in the spleen and liver tissues of the pearl gentian grouper was significantly lower than that of the WT and C-ΔvscCD strains. In the early stage of infection with the ΔvscCD strain, the expression levels of IL-1β, IL-16, TLR3, TNF-α, MHC-Iα, and CD8α were up-regulated to varying degrees. As compared with the WT and C-ΔvscCD strains, luxR expression was significantly up-regulated in the ΔvscCD strain, while the expression of vcrH and vp1668 was significantly down-regulated. As an important component of the T3SS, VscCD seemed to play a significant role in the pathogenesis of V. harveyi.
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http://dx.doi.org/10.1016/j.micpath.2021.104965DOI Listing
August 2021

Transcriptional programs of infectious spleen and kidney necrosis virus (ISKNV) in vitro and in vivo.

Virus Genes 2020 Dec 8;56(6):749-755. Epub 2020 Oct 8.

State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, P. R. China.

Infectious spleen and kidney necrosis virus (ISKNV), causing serious infectious diseases to marine and freshwater fishes, is the type species of the genus Megalocytivirus, family Iridoviridae. In this study, the transcriptional programs of ISKNV in vitro (MFF-1 cells) and in vivo (spleens from mandarin fish) were investigated using real-time PCR. Transcription of all the putative open reading frames (ORFs) of ISKNV was verified. The temporal expression patterns of ISKNV ORFs in vitro and in vivo, including peak expression times (PETs) and relative maximal expression levels, were determined and compared. The K-means clustering with Spearman rank correlation was generated in heat maps constructed based on ISKNV ORF expression profiles in vivo and in vitro. The current study may provide a global picture of ISKNV infection at the transcription level and help better understand the molecular pathogenic mechanism of megalocytiviruses.
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http://dx.doi.org/10.1007/s11262-020-01800-1DOI Listing
December 2020

Prevalence, virulence genes, and antimicrobial resistance of Vibrio species isolated from diseased marine fish in South China.

Sci Rep 2020 08 31;10(1):14329. Epub 2020 Aug 31.

Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510300, China.

Here, 70 potential Vibrio pathogens belonging to nine species, dominated by Vibrio harveyi, were isolated and identified from diseased aquacultured marine fish in South China. Subsequently, the prevalence of 11 virulence genes and the resistance to 15 antibiotics in these strains were determined. Most strains possessed atypical virulence genes in addition to typical virulence genes. Notably, hflk and chiA originating from V. harveyi, and flaC associated with V. anguillarum were detected in more than 40% of atypical host strains. Multidrug resistance was widespread: 64.29% strains were resistant to more than three antibiotics, and the multi-antibiotic resistance index ranged from 0.00 to 0.60. The proportions of strains resistant to the antibiotics vancomycin, amoxicillin, midecamycin, and furazolidone all exceeded 50%; nevertheless, all strains were sensitive to florfenicol, norfloxacin, and ciprofloxacin. Furthermore, both virulence genes and antibiotic resistance were more prevalent in Hainan than in Guangdong, owing to the warmer climate and longer annual farming time in Hainan. These results therefore suggest that warming temperatures and overuse of antibiotics are probably enhancing antibiotic resistance and bacterial infection. This study reveals that pathogenic Vibrio spp. with multi-antibiotic resistance are highly prevalent among marine fish in South China and thus warrant further attention. The results will provide helpful guidance for ecological regulation and local antibiotic use in the control of marine fish farming' Vibrio diseases in South China, facilitating the implementation of national green and healthful aquaculture.
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http://dx.doi.org/10.1038/s41598-020-71288-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7459350PMC
August 2020

The LARK protein is involved in antiviral and antibacterial responses in shrimp by regulating humoral immunity.

Dev Comp Immunol 2021 01 9;114:103826. Epub 2020 Aug 9.

State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, PR China; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, PR China; Institute of Aquatic Economic Animals and Guangdong Provice Key Laboratory for Aquatic Economic Animals, Sun Yat-sen University, Guangzhou, PR China. Electronic address:

The LARK proteins containing a C2HC-type zinc finger motif and two RNA recognition motifs are conserved across vertebrates and invertebrates. Previous studies have suggested that invertebrate LARKs and their mammalian counterparts, the RBM4 proteins, regulate gene expression by affecting RNA stability and post-transcriptional processing, participating in multiple life processes. In the current study, the LARK gene from Pacific white shrimp Litopenaeus vannamei was identified and functionally explored in the context of immunity. The LARK protein was mainly present in the nucleus of its expression vector-transfected S2 cells, and the LARK mRNA was detectable in all the tested shrimp tissues. Expression of LARK in gill was up-regulated by immune stimulation with various pathogens. In vivo experiments demonstrated that LARK played positive roles in both antiviral and antibacterial responses and silencing of LARK could make shrimp more susceptible to infection with Vibrio parahaemolyticus and white spot syndrome virus (WSSV). Although silencing of LARK did not affect the phagocytic activity of hemocytes, it regulated expression of many components of the NF-κB and JAK-STAT pathways and a series of immune function proteins. These suggested that LARK could be mainly involved in regulation of humoral immunity. The current study could help reveal the roles of LARK/RBM4 in immunity and further explore the regulatory mechanisms of shrimp immunity.
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http://dx.doi.org/10.1016/j.dci.2020.103826DOI Listing
January 2021

A double chitin catalytic domain-containing chitinase targeted by c-Jun is involved in immune responses in shrimp.

Dev Comp Immunol 2020 12 29;113:103808. Epub 2020 Jul 29.

State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, PR China; Southern Laboratory of Ocean Science and Engineering (Guangdong, Zhuhai), Zhuhai, 519000, China; Institute of Aquatic Economic Animals and Guangdong Provice Key Laboratory for Aquatic Economic Animals, Sun Yat-sen University, Guangzhou, 510275, PR China. Electronic address:

Chitinases are a group of chitin-degrading enzymes widely distributed in organisms. Chitinases containing two chitin catalytic domains have been widely found in arthropods but their functions remain unclear. In this study, a member of these chitinases from Litopenaeus vannamei (dChi) was identified and functionally studied in the context of immunity. The promoter of dChi contained activator protein 1 (AP-1) binding sites and could be regulated by c-Jun. The recombinant dChi protein showed no bacteriostatic activity in vitro but knockdown of dChi in vivo increased the mortality of shrimp and the bacterial load in tissues after Vibrio parahaemolyticus infection, suggesting that dChi could play a positive role in antibacterial responses. However, silencing of dChi expression significantly decreased the mortality of WSSV-infected shrimp and down-regulated the viral load in tissues, indicating that dChi could facilitate WSSV infection. We further demonstrated that dChi was involved in regulation of the bacterial phagocytosis of hemocytes and expression of a series of immune related transcription factors and antimicrobial peptides. These indicated that the roles of dChi in antibacterial responses and anti-WSSV responses in vivo could result from its regulatory effects on the immune system. Taken together, the current study suggests that double chitin catalytic domain-containing chitinases could be important players in immune regulation in crustaceans.
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http://dx.doi.org/10.1016/j.dci.2020.103808DOI Listing
December 2020

What drives changes in the virulence and antibiotic resistance of Vibrio harveyi in the South China Sea?

J Fish Dis 2020 Aug 18;43(8):853-862. Epub 2020 Jun 18.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China.

To understand the driving environmental factors in changes of bacterial virulence and antibiotic resistance, we determined the prevalence, antibiotic resistance and antibiotic resistance and virulence genes of Vibrio harveyi isolated from diseased marine fish in south coastal China. We isolated 2, 52 and 53 V. harveyi strains from Fujian, Hainan and Guangdong, respectively, and identified them by multilocus sequence analysis of 16S rRNA-toxR -rctB. Nine typical virulence genes were represented at a higher average in Hainan (7.39 ± 0.24) than in Guangdong (6.91 ± 0.28). Five atypical virulence genes were detected in some isolates. In particular, flaC and vvh were detected in more than 60% of isolates. Their average number was significantly higher in Hainan (2.30 ± 0.20) than in Guangdong (1.70 ± 0.10). Multidrug resistance was widespread with an average resistance to 4.57 ± 0.18 of 15 antibiotics. Both the average number of antibiotic resistance and antibiotic resistance genes were higher in Hainan (5.25 ± 0.27 and 1.11 ± 0.15, respectively) than in Guangdong (3.87 ± 0.21 and 0.75 ± 0.10, respectively). This study demonstrated that there were more virulence genes and greater drug resistance in Hainan than in Guangdong, suggesting that warmer temperature and antibiotics pollutants probably enhance antibiotic resistance and bacterial infection.
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http://dx.doi.org/10.1111/jfd.13197DOI Listing
August 2020

Rapid environmental change shapes pond water microbial community structure and function, affecting mud crab (Scylla paramamosain) survivability.

Appl Microbiol Biotechnol 2020 Mar 8;104(5):2229-2241. Epub 2020 Jan 8.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510300, China.

The aquatic microbial community is sensitive to environmental change; however, the impacts of those changes combined with disease outbreaks affecting S. paramamosain are unknown. Thus, from March to October, we explored the interaction between aquacultural environmental conditions and microbial composition and function in open-air aquaculture ponds containing S. paramamosain in Southern China. The microbial community structure was significantly positively correlated with microbial community function. The environment variables such as temperature and salinity during May and June changed more quickly compared with other periods, resulting changes in the structure and function of the microbial community affected S. paramamosain survivability, with higher crab mortality observed from May to June compared with other periods. These included changes in the relative abundance of Microtrichales, Synechococcales, Rhodobacterales, Chitinophagales, and SAR11_clade, and corresponding functions associated with glycolysis and/or gluconeogenesis, porphyrin and chlorophyll metabolism, photosynthetic proteins, and transcription factors. These changes could impact S. paramamosain mortality and be used to evaluate the health status of the ponds. Though the environment variables during July~October changed slowly comparing to May and June, the ponds microflora changed which benefit S. paramamosain survivability with correspondingly low S. paramamosain mortality. Therefore, rapid environmental change alters the structure and function of the aquatic microflora, increasing S. paramamosain mortality.
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http://dx.doi.org/10.1007/s00253-019-10328-wDOI Listing
March 2020

A shrimp gene encoding a single WAP domain (SWD)-containing protein regulated by JAK-STAT and NF-κB pathways.

Dev Comp Immunol 2020 03 13;104:103537. Epub 2019 Nov 13.

State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, PR China; Guangdong Province Key Laboratory for Aquatic Economic Animals, Sun Yat-sen University, Guangzhou, PR China; Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, PR China. Electronic address:

Regulation of immune responses in animals is largely governed by the JAK-STAT and NF-κB pathways, which are conserved across vertebrates and invertebrates. At present, the relationship between these two pathways in invertebrates remains unclear. In the current study, a novel antimicrobial peptide termed LvSWD5 belonging to the Crustin family was identified from Pacific white shrimp Litopenaeus vannamei. The mature LvSWD5 peptide containing a single WAP domain (SWD) could directly bind bacteria and fungi and inhibit the growth of both Gram-positive and -negative bacteria in vitro. The LvSWD5 promoter was predicted to contain binding sites for STAT and NF-κB and could be regulted by the JAK-STAT and Relish pathways. The expression of LvSWD5 was up-regulated during bacterial, viral and fungal infections and silencing of LvSWD5 in vivo affected the expression of a series of immune related genes and decreased the phagocytic activity of hemocytes against V. Parahaemolyticus. Moreover, the susceptibility of shrimp to V. parahaemolyticus and white spot syndrome virus (WSSV) was significantly increased after silencing of LvSWD5, indicating that LvSWD5 could be involved in antibacterial and antiviral responses. These suggested that the JAK-STAT and NF-κB pathways could converge at the promoter level of a common target gene to regulate the immunity in shrimp.
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http://dx.doi.org/10.1016/j.dci.2019.103537DOI Listing
March 2020

Horizontal gene transfer contributes to virulence and antibiotic resistance of Vibrio harveyi 345 based on complete genome sequence analysis.

BMC Genomics 2019 Oct 22;20(1):761. Epub 2019 Oct 22.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510300, China.

Background: Horizontal gene transfer (HGT), which is affected by environmental pollution and climate change, promotes genetic communication, changing bacterial pathogenicity and drug resistance. However, few studies have been conducted on the effect of HGT on the high pathogenicity and drug resistance of the opportunistic pathogen Vibrio harveyi.

Results: V. harveyi 345 that was multidrug resistant and infected Epinephelus oanceolutus was isolated from a diseased organism in Shenzhen, Southern China, an important and contaminated aquaculture area. Analysis of the entire genome sequence predicted 5678 genes including 487 virulence genes contributing to bacterial pathogenesis and 25 antibiotic-resistance genes (ARGs) contributing to antimicrobial resistance. Five ARGs (tetm, tetb, qnrs, dfra17, and sul2) and one virulence gene (CU052_28670) on the pAQU-type plasmid p345-185, provided direct evidence for HGT. Comparative genome analysis of 31 V. harveyi strains indicated that 217 genes and 7 gene families, including a class C beta-lactamase gene, a virulence-associated protein D gene, and an OmpA family protein gene were specific to strain V. harveyi 345. These genes could contribute to HGT or be horizontally transferred from other bacteria to enhance the virulence or antibiotic resistance of 345. Mobile genetic elements in 71 genomic islands encoding virulence factors for three type III secretion proteins and 13 type VI secretion system proteins, and two incomplete prophage sequences were detected that could be HGT transfer tools. Evaluation of the complete genome of V. harveyi 345 and comparative genomics indicated genomic exchange, especially exchange of pathogenic genes and drug-resistance genes by HGT contributing to pathogenicity and drug resistance. Climate change and continued environmental deterioration are expected to accelerate the HGT of V. harveyi, increasing its pathogenicity and drug resistance.

Conclusion: This study provides timely information for further analysis of V. harveyi pathogenesis and antimicrobial resistance and developing pollution control measurements for coastal areas.
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http://dx.doi.org/10.1186/s12864-019-6137-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6805501PMC
October 2019

A novel sRNA srvg17985 identified in Vibrio alginolyticus involving into metabolism and stress response.

Microbiol Res 2019 Dec 17;229:126295. Epub 2019 Jul 17.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, China; Tropical Aquaculture Research and Development Centre, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Hainan, China. Electronic address:

Vibrio alginolyticus is an opportunistic pathogen that is a threat to the aquaculture industry. Evidence has revealed critical roles for small RNAs (sRNAs) in bacterial physiology and pathology by modulating gene expression post transcription. However, little information about sRNA-mediated regulation in V. alginolyticus is available. We experimentally verified the existence and characterized the function of sRNA srvg17985 in V. alginolyticus ZJ-T. We identified a 179 nt and growth-phase-dependent transcript with a σ70 promoter and a ρ-independent terminator. The transcript consisted of five stem-loops and was conserved in Vibrio spp. Phenotype microarray assays showed that deletion of srvg17985 led to less use of Gly-Glu as a carbon source but a gain in ability to use l-phenylalanine as a nitrogen source. Srvg17985 regulated the osmotic stress response with stronger tolerance to NaCl but weaker tolerance to urea. In addition, srvg17985 inhibited the deamination of l-serine at pH 9.5 and promoted the hydrolysis of X-beta-d-glucuronide, thus affecting the pH stress response. Bioinformatics by IntaRNA and TargetRNA2 identified 45 common target mRNAs, some of which probably contributed to the observed phenotypes. These results indicated that srvg17985 regulated environmental adaptation. The results provide valuable information for in-depth studies of sRNA-mediated regulation mechanisms of the complex physiological processes of V alginolyticus and provide new targets for antibacterial therapeutics or attenuated vaccines for Vibrio spp.
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http://dx.doi.org/10.1016/j.micres.2019.126295DOI Listing
December 2019

Molecular typing of Streptococcus agalactiae isolates of serotype Ia from tilapia in southern China.

FEMS Microbiol Lett 2019 07;366(13)

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, Guangdong Province, PR China.

Streptococcus agalactiae is an important pathogen of tilapia causing enormous economic losses worldwide. In this study, multilocus sequence typing indicated that 75 S. agalactiae isolates from tilapia in southern China belonged to sequence type-7, as well as belonging to serotype Ia, as confirmed by multiplex PCR assay. The putative-virulence gene profiles and genetic variation of these strains were determined by three sets of multiplex PCR and multi-virulence locus sequencing typing (MVLST), respectively. Analysis of putative-virulence gene profiles showed that each strain harbored 18 putative-virulence genes but lacked lmb and scpB. Three putative-virulence genes (srr-1, bibA and fbsA) were further selected for MVLST analysis. Our data showed that the strains had 14 MVLST types (1-14) and clustered in three groups (Groups I-Ⅲ). The period of time during 2013 and 2014 was an important turning point for the differentiation of the putative-virulence genes of S. agalactiae, as type 1 within Group Ⅱ became the predominant MVLST type. There were significant differences in MVLST types of S. agalactiae isolated from different tilapia farming regions. MVLST assay may improve the discriminatory power and is suitable for understanding the epidemiology of S. agalactiae serotype Ia and screening multivalent vaccine candidate strains.
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http://dx.doi.org/10.1093/femsle/fnz154DOI Listing
July 2019

Expression of lactate dehydrogenase is induced during hypoxia via HIF-1 in the mud crab Scylla paramamosain.

Comp Biochem Physiol C Toxicol Pharmacol 2019 Nov 2;225:108563. Epub 2019 Jul 2.

Key Laboratory of Aquatic Product Processing, Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, Guangdong 510300, PR China; Shanghai Ocean University, Shanghai 201206, PR China. Electronic address:

Lactate dehydrogenase (LDH) is a key enzyme involved in anaerobic metabolism in most organisms. In the present study, we determined the structure and function of LDH sequence in Scylla paramamosain (SpLDH) by gene cloning, expression and RNA interference techniques in order to explore the genetic characteristics of LDH and its relationship with HIF-1 during hypoxia. The full-length cDNA was 1453 bp with an open reading frame (ORF) of 996 bp, and encoded a polypeptide of 332 amino acids. Homology analysis showed that the SpLDH gene is highly similar to arthropods. The SpLDH transcript increased after hypoxia in all tested tissues. The silencing of HIF-1 blocked the increase in LDH mRNA and activity, which were induced by hypoxia in gill and muscle tissues. Our results indicated that SpLDH expression was regulated transcriptionally by HIF-1.
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http://dx.doi.org/10.1016/j.cbpc.2019.108563DOI Listing
November 2019

Diversity and abundance of antibiotic resistance of bacteria during the seedling period in marine fish cage-culture areas of Hainan, China.

Mar Pollut Bull 2019 Apr 5;141:343-349. Epub 2019 Mar 5.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, China. Electronic address:

Antibiotic resistance has become an important focus of research in the aquaculture environment. However, few studies have evaluated antibiotic resistance during the seedling period in marine fish cage-culture areas. In this study, culture-dependent methods and quantitative polymerase chain reaction were used to identify and detect cultivable heterotrophic antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs), respectively, during the seedling period in a marine fish cage-culture areas of Hainan, China. Bacterial resistance to amoxicillin, erythromycin, and gentamicin was generally high (average on 27.67%, 23.61% and 37.32%, respectively), whereas resistance to furazolidone and nitrofurantoin was generally low (average on 0.14% and 7.425%). Alteromonas (32.72%) and Vibrio (24.77%) were the dominant genus of ARB. Most ARB were opportunistic pathogens, belonging to the phylum Proteobacteria (96.02%). The abundance of sul family genes was higher than that of tet family genes. Overall, the abundance of ARGs and the resistance rates in HW was highest.
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http://dx.doi.org/10.1016/j.marpolbul.2019.02.069DOI Listing
April 2019

Corrigendum: Identification of a Novel Small RNA in ZJ-T and Its Characterization With Phenotype MicroArray Technology.

Front Microbiol 2019 31;10:21. Epub 2019 Jan 31.

Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.

[This corrects the article DOI: 10.3389/fmicb.2018.02394.].
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http://dx.doi.org/10.3389/fmicb.2019.00021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6365953PMC
January 2019

Coupled changes of bacterial community and function in the gut of mud crab (Scylla Paramamosain) in response to Baimang disease.

AMB Express 2019 Feb 2;9(1):18. Epub 2019 Feb 2.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 309 of Building Keyan, 231 Xingang Xi Road, Guangzhou, China.

Increasing evidence has revealed a close association between intestinal bacterial community and hosts health. However, it is unclear whether and what extend Baimang disease alters the intestinal microbiota in mud crab (Scylla paramamosain). Here, we conducted intestinal contents Illumina sequencing of healthy and Baimang diseased mud crab (S. paramamosain) to understand bacterial community variations among health status. In addition, bacterial functional predication was used to investigate whether and how the bacteria variations further change their functions? The phyla of Proteobacteria, Fusobacteria, Cyanobacteria, Tenericutes, Firmicutes, Bacteroidetes, and Spirochaetae constituted over 96.44% of the total intestinal bacteria, with being the dominant taxa. The 7 most significantly different orders, including the increased four orders of Clostridiales, Entomoplasmatales, Bacteroidales, and Mycoplasmatales and the decreased three orders of Vibrionales, Campylobacterales, and Fusobacteriales, accounted for 61.14% dissimilarity, probably being the indicator taxa of Baimang disease. Accordingly, 12 Kyoto Encyclopedia of Genes and Genomes orthologies in level 3 shifted significantly at the diseased crabs. Especially, bacterial secretion system, secretion system, lipopolysaccharide biosynthesis proteins and Vibrio cholerae pathogenic cycle, being related to bacterial virulence, were reduced. In addition, the reduced butanoate metabolism, and induced methane metabolism and one carbon pool by folate were important metabolic processes of probiotic, such as Bacteroides spp. and Clostridium spp., with playing critical roles in host health. This study suggests that Baimang disease coupled altered the intestinal bacterial communities and functions, providing timely information for further analysis the influencing mechanism of Baimang disease in mud crab (S. paramamosain).
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http://dx.doi.org/10.1186/s13568-019-0745-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6359999PMC
February 2019

Spatial and temporal variation of antibiotic resistance in marine fish cage-culture area of Guangdong, China.

Environ Pollut 2019 Mar 12;246:463-471. Epub 2018 Dec 12.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510300, China. Electronic address:

The rapid emergence and dissemination of antibiotic resistance poses a threat to human health and to the marine environment. We have investigated the abundance and diversity of antibiotic resistance genes (ARGs) and of antibiotic-resistant bacteria (ARB), during the seedling period, rearing period, and harvesting period in seven marine fish cage-culture areas in Guangdong. Spatial and temporal variations of AGRs and ARB were also analyzed. Culture-based methods and quantitative PCR were used to detect ARB and ARGs. Bacterial resistance rates were no significantly different within farming periods. The proportion of antibiotic-resistant bacteria was extremely low (average on 1.15%), except for oxytetracycline-resistant bacteria (average on 34.15%). Vibrio was the most common ARB. Sul1, tetB, and ermB, had the highest relative abundance. The abundance of ARGs in the harvesting period was significant highest. The total abundance of ARGs was highest at Raoping and lowest at Dayawan and Liusha. Most ARGs were associated with opportunistic pathogens. The environmental factors effecting ARB and ARGs are complex, and no key factors were identified. This study provides a theoretical basis for assessing the harmfulness of ARGs and ARB to food safety and human health.
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http://dx.doi.org/10.1016/j.envpol.2018.12.024DOI Listing
March 2019

Prevalence and distribution of antibiotic resistance in marine fish farming areas in Hainan, China.

Sci Total Environ 2019 Feb 21;653:605-611. Epub 2018 Oct 21.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture and Rural Affairs, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, China. Electronic address:

Antibiotic resistance represents a global health crisis for humans, animals, and for the environment. Transmission of antibiotic resistance through environmental pathways is a cause of concern. In this study, quantitative PCR and culture-dependent bacteriological methods were used to detect the abundance of antibiotic resistance genes (ARGs) and the quantity of culturable heterotrophic antibiotic-resistant bacteria (ARB) in marine fish farming areas. The results indicated that sul and tet family genes were widely distributed in marine fish farming areas of Hainan during both rearing and harvesting periods. Specifically, sul1 and tetB were the most dominant ARGs. The total abundance of ARGs increased significantly from the rearing to the harvesting period. A total of 715 ARB strains were classified into 24 genera, within these genera Vibrio, Acinetobacter, Pseudoalteromonas, and Alteromonas are opportunistic pathogens. High bacterial resistance rate to oxytetracycline (OT) was observed. The numbers of OT- and enrofloxacin-resistant bacteria dropped significantly from rearing the period to the harvesting. The co-occurrence pattern showed that Ruegeria and tetB could be indicators of ARB and ARGs, respectively, which were found in the same module. Redundancy analysis indicated that salinity was positively correlated with the most dominant ARB, and was negatively correlated with the most dominant ARGs. These findings demonstrated the prevalence and persistence of ARGs and ARB in marine fish farming areas in China.
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http://dx.doi.org/10.1016/j.scitotenv.2018.10.251DOI Listing
February 2019

Identification of a Novel Small RNA in ZJ-T and Its Characterization With Phenotype MicroArray Technology.

Front Microbiol 2018 5;9:2394. Epub 2018 Oct 5.

Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.

Small non-coding RNAs (sRNAs) are important modulators of gene expression and are involved in the pathogenesis and survival of prokaryotes. However, few studies have been conducted with , which limits our ability to probe the regulation of virulence and environmental adaptation by sRNAs in this opportunistic pathogen. In this study, the sRNA candidate was identified in ZJ-T. The precise transcript end, secondary structure, and sequence conservation were determined. A null mutant was constructed and characterized by using Phenotype MicroArray (PM) technology. target prediction was conducted by IntaRNA and TargetRNA2. Subsequently, a 107 nt transcript was validated with a sigma70 promoter at the 5' end and a Rho-independent terminator at the 3' end. The sRNA had four stem-loop structures and was conserved among , and . Deletion of in ZJ-T led to a weaker utilization of D-mannose, D-melibiose, lactulose, and inosine as carbon sources but stronger utilization of L-cysteine as nitrogen source. Moreover, the mutant showed stronger resistance to osmotic stress but weaker resistance to pH stress. Additionally, a total of 22 common targets were identified and several were related to the observed phenotype of the mutant. This study indicated that the novel sRNA, , is conserved and restricted to spp., affecting the utilization of several carbon and nitrogen sources and the response to osmotic and pH stress. These results extend our understanding of sRNA regulation in and provide a significant resource for the further study of the precise target mRNAs of , which may provide targets for antibacterial therapeutic or attenuated vaccines against spp.
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http://dx.doi.org/10.3389/fmicb.2018.02394DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6186989PMC
October 2018

Epidemiological characterization of VNNV in hatchery-reared and wild marine fish on Hainan Island, China, and experimental infection of golden pompano (Trachinotus ovatus) juveniles.

Arch Virol 2015 Dec 9;160(12):2979-89. Epub 2015 Sep 9.

Key Laboratory of Aquatic Product Processing, Ministry of Agriculture, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510300, Guangdong, People's Republic of China.

The current epidemiological situation of viral nervous necrosis virus (VNNV) on Hainan Island was investigated. A total of 490 hatchery-reared fish and 652 wild fish were sampled for VNNV detection from March 2013 to May 2014. Positive detection rates of 84.53% (153/181) and 0.97 % (3/309) were obtained in diseased and healthy hatchery-reared samples, respectively, by conventional RT-PCR. However, using more-sensitive nested RT-PCR, the positive detection rates in healthy hatchery-reared fish reached up to 64.08% (198/309), suggesting that asymptomatic VNNV carriers commonly exist among larvae and juveniles breeding on Hainan Island. In wild-fish samples, 2.6% (17/652) and 34.2% (223/652) positive detection rates were observed using RT-PCR and nested RT-PCR, respectively, indicating that wild fish may be a potential reservoir for VNNV. Phylogenetic analysis showed that all 52 VNNV isolates from cultured fish belong to the RGNNV genotype, but 2 out of 48 VNNV isolates from wild fish samples were found to be of the SJNNV genotype. This study is the first to confirm the existence of SJNNV-genotype VNNV in China. Golden pompano, an important fish species for culture, was selected as a fish model to investigate the optimal conditions for RGNNV disease progression in artificial infection experiments. The effects of temperature, salinity, and fish size were evaluated. Results showed that 28 °C and 20 ‰ are the optimal infection temperature and salinity, respectively, and golden pompano juveniles with small body sizes are more susceptible to RGNNV. These findings are highly consistent with those conditions involved in the natural outbreak of RGNNV.
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http://dx.doi.org/10.1007/s00705-015-2590-0DOI Listing
December 2015

Susceptibility of farmed juvenile giant grouper Epinephelus lanceolatus to a newly isolated grouper iridovirus (genus Ranavirus).

Vet Microbiol 2015 Jun 24;177(3-4):270-9. Epub 2015 Mar 24.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture, The South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, PR China. Electronic address:

A ranavirus was isolated from the diseased farmed groupers (Grouper iridovirus in genus Ranavirus, GIV-R), Epinephelus hybrids (blotchy rock cod, Epinephelus fuscoguttatus ♀×giant grouper, Epinephelus lanceolatus ♂), in Sanya, Hainan, in July 2013. In this study, susceptibility of farmed juvenile giant grouper E. lanceolatus to GIV-R was determined by intraperitoneally injection. The cumulative mortality reached to 81% at 5 day post infection. Histologically, severe degeneration with massive pycnotic nuclei in spleen and kidney tissues was observed, and some small-size inclusion body-bearing cells (IBCs) existed in spleen. Hemorrhage and infiltration of inflammatory cells were presented in gill, liver and heart along with tissue degeneration and necrosis of varying severity. The results of immunohistochemistry analysis showed that the strongest immunolabellings were obtained from the kidney and spleen tissues, while intermediate intensity signals were observed in the heart, stomach, gill and liver tissues, and the weakest signals were obtained from the intestine and brain, but no signal was obtained in eyes. Electron microscopy revealed that spleen of moribund fish contained many viral particles in cytoplasm. Interestingly, in surviving fish, abnormal hypertrophic cells were observed in both splenic corpuscle and renal corpuscle, while no hypertrophic cell was observed in the other parts of spleen and kidney tissues. Moreover, immunolabellings only stained the hypertrophic cells in splenic corpuscle and renal corpuscle. This indicated that splenic corpuscle and renal corpuscle play an important role in GIV-R infection and replication.
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http://dx.doi.org/10.1016/j.vetmic.2015.03.017DOI Listing
June 2015

A new species of Glugea Thélohan, 1891 in the red sea bream Pagrus major (Temminck & Schlegel) (Teleostei: Sparidae) from China.

Syst Parasitol 2014 Oct 10;89(2):175-83. Epub 2014 Sep 10.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510300, Guangdong, China.

A new microsporidian species is described from farmed red sea bream Pagrus major (Temminck & Schlegel) (Teleostei: Sparidae). Large numbers of spherical whitish xenomas were observed throughout the visceral organs of the host. Histological examination showed that the microsporidia caused several xenomas that were embedded in the intestinal muscularis externa or submucosa. Light and transmission electron microscopy examination of the spores also revealed morphological features typical of species of Glugea Thélohan, 1891. This microsporidian parasite has two different types of mature spores: microspores and macrospores. The spores are elongate-ovoid, with a large posterior vacuole. The polaroplast is bi-partite, with anterior and posterior parts comprising densely packed lamellae and loose membranes, respectively, and occupies approximately the anterior half of the spore. The polar filament is anisofilar, with 12-13 coils in a single layer almost touching the posterior spore wall. Comparison of the small subunit rDNA sequences revealed 92.7-98.1% identity with the sequences available from other Glugea spp. from piscine hosts. Phylogenetic analysis demonstrated that the microsporidian species studied clustered within the Glugea clade with strong support. Based on the differences in the morphological characteristics and molecular data, the microsporidian infecting P. major is considered to represent a species new to science, Glugea pagri n. sp.
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http://dx.doi.org/10.1007/s11230-014-9519-yDOI Listing
October 2014

Rapid detection of mud crab dicistrovirus-1 using loop-mediated isothermal amplification.

J Virol Methods 2014 Nov 27;208:171-6. Epub 2014 Aug 27.

Key Laboratory of Aquatic Product Processing, Ministry of Agriculture, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, China.

Mud crab dicistrovirus-1 (MCDV-1) was isolated from the mud crab (Scylla paramamosain), resulting in mass mortality and widespread economic loss in China. In this study, a detection method for MCDV-1 using loop-mediated isothermal amplification was developed. Two pairs of primers targeting the VP2 gene were designed. These primers were the outer primers F3 and B3, and the inner primers FIP and BIP. Optimal amplification was carried out using 0.2 μmol/L F3/B3, 1.6 μmol/L FIP/BIP, 6 mmol/L Mg(2+), 0.8 mmol/L dNTPs, and 0.8 mol/L betaine, and completed in 1h at 62°C. The products demonstrated a ladder pattern on agarose gel electrophoresis and could also be detected visually according to turbidity, or by adding SYBR Green I and observing a color change from orange to green. The proposed method could specifically amplify MCDV-1 gene fragments. Sensitivity assay revealed that six copies of the viral genome could be detected by this method, which was 1000-fold more sensitive than that of conventional PCR using constructed plasmid as amplification template. At clinical sample level, sensitivity of LAMP was 100-fold higher than that of conventional PCR.
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http://dx.doi.org/10.1016/j.jviromet.2014.08.014DOI Listing
November 2014

Trypanosoma epinepheli n. sp. (Kinetoplastida) from a farmed marine fish in China, the brown-marbled grouper (Epinephelus fuscoguttatus).

Parasitol Res 2014 Jan 11;113(1):11-8. Epub 2013 Oct 11.

Key Laboratory of South China Sea Fishery Resources Exploitation & Utilization, Ministry of Agriculture, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, Guangdong, China, 510300,

An outbreak of trypanosomosis occurred in farmed Epinephelus fuscoguttatus in Xincun Bay, province of Hainan, South China Sea. The infected fish showed loss of appetite, lethargy, emaciation, severe anemia, and splenomegaly. Light and scanning electron microscopic examination of bloodstream trypomastigotes revealed morphological features typical for small-sized marine fish trypanosomes. The trypanosome possesses a short body length (mean 22.3 μm, range 17.6-25.9 μm) and narrow body width (mean1.7 μm, range 1.3-2.0 μm), a central nucleus, a narrow but distinct undulating membrane, and a relatively long free flagellum (mean 10.1 μm, range 7.4-13.3 μm). The kinetoplast is situated at approximately one quarter of body length from posterior extremity. The division process of this trypanosome was observed in the peripheral blood of the host, and occurred by transverse constriction at a point between the kinetoplasts. Comparison of the small subunit rDNA (SSU rDNA) sequences revealed that the trypanosome from E. fuscoguttatus showed 93.4-97.1% identity with the available sequences from Trypanosoma spp. from other piscine hosts. Phylogenetic analysis supported the existence of an aquatic clade, and the present trypanosome grouped with other marine fish trypanosomes, in a subclade together with Trypanosoma senegalense. Based on the differences in morphological characteristics, host species, and molecular data, the trypanosome infecting E. fuscoguttatus is considered to be a new species, for which we propose the name Trypanosoma epinepheli n. sp.
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http://dx.doi.org/10.1007/s00436-013-3626-6DOI Listing
January 2014

Identification and expression analysis of a CC chemokine from cobia (Rachycentron canadum).

Fish Physiol Biochem 2013 Jun 7;39(3):459-69. Epub 2012 Sep 7.

Key Laboratory of South China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture, South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, Guangdong, China.

Chemokines are small, secreted cytokine peptides known principally for their ability to induce migration and activation of leukocyte populations and regulate the immune response mechanisms. The cobia (Rachycentron canadum), a marine finfish species, has a great potential for net cage aquaculture in the South China Sea. We isolated and characterized a CC chemokine cDNA from cobia-designated RcCC2. Its cDNA is 783 bp in length and encodes a putative protein of 110 amino acids. Homology and phylogenetic analysis revealed that the RcCC2 gene, which contains four conserved cysteine residues, shares a high degree of similarity with other known CC chemokine sequences and is closest to the CCL19/21 clade. The mRNA of RcCC2 is expressed constitutively in all tested tissues, including gill, liver, muscle, spleen, kidney, head kidney, skin, brain, stomach, intestine and heart, but not blood, with the highest level of expression in gill and liver. The reverse transcription quantitative polymerase chain reaction was used to examine the expression of the RcCC2 gene in immune-related tissues, including head kidney, spleen and liver, following intraperitoneal injection of the viral mimic polyriboinosinic polyribocytidylic acid, formalin-killed Vibrio carchariae (bacterial vaccine) and phosphate-buffered saline as a control. RcCC2 gene expression was up-regulated differentially in head kidney, spleen and liver during 12 h after challenge. These results indicate that the RcCC2 gene is inducible and is involved in immune responses, suggesting RcCC2 has an important role in the early stage of viral and bacterial infections.
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http://dx.doi.org/10.1007/s10695-012-9711-4DOI Listing
June 2013

Structural insights into the classification of Mud Crab Reovirus.

Virus Res 2012 Jun 6;166(1-2):116-20. Epub 2012 Mar 6.

State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, People's Republic of China.

Cryo-electron microscopy was applied to analyze mud crab reovirus (MCRV), which causes 'sleeping disease' in mud crab, Scylla serrata, a marine species cultured in China. We present here the three dimensional structure of MCRV at 13.8Å resolution. The outer capsid shell is composed of 260 trimers with complete T=13 icosahedral symmetry. A major difference between MCRV and previously reported aquareoviruses is that it lacks a pentameric turret structure. These results together with recently published molecular biological evidence (Deng et al., 2012) indicate that, from a structural perspective, MCRV should be classified as a new member of the family Reoviridae.
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http://dx.doi.org/10.1016/j.virusres.2012.02.025DOI Listing
June 2012

Identification of a cobia (Rachycentron canadum) CC chemokine gene and its involvement in the inflammatory response.

Fish Shellfish Immunol 2012 Jan 14;32(1):204-10. Epub 2011 Oct 14.

South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, Guangdong 510300, China.

The chemokines regulate immune cell migration under inflammatory and physiological conditions. We investigated a CC chemokine gene (RcCC1) from cobia (Rachycentron canadum). The full-length RcCC1 cDNA is comprised 673 nucleotides and encodes a four-cysteine arrangement 99-amino-acid protein typical of known CC chemokines. The genomic DNA of RcCC1 consists of three exons and two introns. Phylogenetic analysis showed that RcCC1 was closest to the MIP group of CC chemokines. Quantitative real-time RT-PCR (qRT-PCR) analysis revealed RcCC1 was constitutively expressed in all tissues examined, with relative strong expression in gill, blood, kidney, spleen, and head kidney. The RcCC1 transcripts in the head kidney, spleen, and liver were quickly up-regulated after stimulation with formalin-inactivated Vibrio carchariae (bacterial vaccine) or polyriboinosinic polyribocytidylic acid (poly I:C). These results indicate RcCC1 not only plays a role in homeostasis, but also may be involved in inflammatory responses to bacterial and viral infection.
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http://dx.doi.org/10.1016/j.fsi.2011.10.005DOI Listing
January 2012
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