Publications by authors named "Sergio Arévalo"

8 Publications

  • Page 1 of 1

Heterocyst septa contain large nanopores that are influenced by the Fra proteins in the filamentous cyanobacterium .

J Bacteriol 2021 Apr 12. Epub 2021 Apr 12.

Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC and Universidad de Sevilla, Américo Vespucio 49, E-41092 Seville, Spain

Multicellular heterocyst-forming cyanobacteria such as grow as chains of cells forming filaments that, under diazotrophic conditions, contain two cell types: vegetative cells that perform oxygenic photosynthesis and N-fixing heterocysts. Along the filament, the intercellular septa contain a thick peptidoglycan layer that forms septal disks. Proteinaceous septal junctions connect the cells in the filament traversing the septal disks through nanopores. The operon encodes proteins needed to make long filaments in FraC and FraD, located at the intercellular septa, are involved in the formation of septal junctions. Using a superfolder-GFP fusion, here we show that FraE is mainly localized to the poles of the heterocysts, consistent with the requirement of FraE for constriction of the heterocyst poles to form the "heterocyst neck". A insertional mutant was impaired by 22% to 38% in transfer of fluorescent calcein from vegetative cells to heterocysts. Septal disks were inspected in murein sacculi from heterocyst-enriched preparations. Unexpectedly, the diameter of the nanopores in heterocyst septa was about 1.5- to 2-fold larger than in vegetative cell septa. The number of these nanopores was 76% and 6% of the wild-type number in or a mutant, respectively. Our results show that FraE is mainly involved in heterocyst maturation whereas FraC and FraD are needed for the formation of the large nanopores of heterocyst septa as they are for vegetative cell nanopores. Additionally, arrays of small pores conceivably involved in polysaccharide export were observed close to the disks in the heterocyst murein sacculi preparations.Intercellular communication, an essential attribute of multicellularity, is required for diazotrophic growth in heterocyst-forming cyanobacteria such as , in which the cells are connected by proteinaceous septal junctions that are structural analogs of metazoan connexons. The septal junctions allow molecular intercellular diffusion traversing the septal peptidoglycan through nanopores. In the operon encodes septal proteins essential for intercellular communication. FraC and FraD are components of the septal junctions along the filament, whereas here we show that FraE is mainly present at the heterocyst poles. We found that the intercellular septa in murein sacculi from heterocysts contain nanopores that are larger than those in vegetative cells, establishing a previously unknown difference between heterocyst and vegetative cell septa in .
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JB.00081-21DOI Listing
April 2021

Coexistence of Communicating and Noncommunicating Cells in the Filamentous Cyanobacterium .

mSphere 2021 01 13;6(1). Epub 2021 Jan 13.

Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Seville, Spain

In filamentous heterocyst-forming (N-fixing) cyanobacteria, septal junctions join adjacent cells, mediating intercellular communication, and are thought to traverse the septal peptidoglycan through nanopores. Fluorescence recovery after photobleaching (FRAP) analysis with the fluorescent marker calcein showed that cultures of sp. strain PCC 7120 grown in the presence of combined nitrogen contained a substantial fraction of noncommunicating cells (58% and 80% of the tested vegetative cells in nitrate- and ammonium-grown cultures, respectively), whereas cultures induced for nitrogen fixation contained far fewer noncommunicating cells (16%). A single filament could have communicating and noncommunicating cells. These observations indicate that all (or most of) the septal junctions in a cell can be coordinately regulated and are coherent with the need for intercellular communication, especially under diazotrophic conditions. Consistently, intercellular exchange was observed to increase in response to N deprivation and to decrease rapidly in response to the presence of ammonium in the medium or to nitrate assimilation. Proteins involved in the formation of septal junctions have been identified in and include SepJ, FraC, and FraD. Here, we reevaluated rates of intercellular transfer of calcein and the number of nanopores in mutants lacking these proteins and found a strong positive correlation between the two parameters only in cultures induced for nitrogen fixation. Thus, whereas the presence of a substantial number of noncommunicating cells appears to impair the correlation, data obtained in diazotrophic cultures support the idea that the nanopores are the structures that hold the septal junctions. Multicellularity is found in bacteria as well as in eukaryotes, and the filamentous heterocyst-forming (N-fixing) cyanobacteria represent a simple and ancient paradigm of multicellular organisms. Multicellularity generally involves cell-cell adhesion and communication. The cells in the cyanobacterial filaments are joined by proteinaceous septal junctions that mediate molecular diffusion. The septal junctions traverse the septal peptidoglycan, which bears holes termed nanopores. Our results show that the septal junctions can be coordinately regulated in a cell and emphasize the relationship between septal junctions and nanopores to build intercellular communication structures, which are essential for the multicellular behavior of heterocyst-forming cyanobacteria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/mSphere.01091-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7845620PMC
January 2021

A novel septal protein of multicellular heterocystous cyanobacteria is associated with the divisome.

Mol Microbiol 2020 06 24;113(6):1140-1154. Epub 2020 Feb 24.

Institute of General Microbiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.

Cyanobacteria are unique among the eubacteria as they possess a hybrid Gram phenotype, having an outer membrane but also a comparably thick peptidoglycan sheet. Furthermore, the cyanobacterial divisome includes proteins specific for both the Gram types as well as cyanobacteria-specific proteins. Cells in multicellular cyanobacteria share a continuous periplasm and their cytoplasms are connected by septal junctions that enable communication between cells in the filament. The localization of septal junction proteins depends on interaction with the divisome, however additional yet unknown proteins may be involved in this process. Here, we characterized Alr3364 (termed SepI), a novel septal protein that interacts with the divisome in the multicellular heterocystous cyanobacterium Anabaena sp. strain PCC 7120. SepI localized to the Z-ring and the intercellular septa but did not interact with FtsZ. Instead, SepI interacted with the divisome proteins ZipN, SepF and FtsI and with the septal protein SepJ. The inactivation of sepI led to a defect in cell filament integrity, colony and cell morphology, septum size, nanopore formation and peptidoglycan biogenesis, and inability to differentiate heterocysts. Our results show that SepI plays a role in intercellular communication and furthermore indicate that SepI functions in the coordination of septal junction localization during cell division.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/mmi.14483DOI Listing
June 2020

Pentapeptide-repeat, cytoplasmic-membrane protein HglK influences the septal junctions in the heterocystous cyanobacterium Anabaena.

Mol Microbiol 2020 04 13;113(4):794-806. Epub 2020 Jan 13.

Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Seville, Spain.

N -fixing heterocystous cyanobacteria grow as chains of cells that are connected by proteinaceous septal junctions, which traverse the septal peptidoglycan through nanopores and mediate intercellular molecular transfer. In the model organism Anabaena sp. strain PCC 7120, proteins SepJ, FraC and FraD, which are localized at the cell poles in the intercellular septa, are needed to produce septal junctions. The pentapeptide-repeat, membrane-spanning protein HglK has been described to be involved in the deposition of the heterocyst-specific glycolipid layer, but the hglK mutant also showed intercellular septa broader than in the wild type. Here we found that hglK mutant of Anabaena is impaired in the expression of heterocyst-related genes coxB2A2C2 (cytochrome c oxidase) and nifHDK (nitrogenase), indicating a defect in heterocyst differentiation. HglK was predominantly localized at the intercellular septa and was required to make long filaments, produce a normal number of nanopores and express full intercellular molecular transfer activity. However, the effects of hglK inactivation were not additive to those of the inactivation of sepJ and/or fraC-fraD. We suggest that HglK contributes to the architecture of the intercellular septa with an impact on the function of septal junctions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/mmi.14444DOI Listing
April 2020

ZipN is an essential FtsZ membrane tether and contributes to the septal localization of SepJ in the filamentous cyanobacterium Anabaena.

Sci Rep 2019 02 26;9(1):2744. Epub 2019 Feb 26.

Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Américo Vespucio 49, E-41092, Seville, Spain.

The organismic unit of heterocyst-forming cyanobacteria is a filament of communicating cells connected by septal junctions, proteinaceous structures bridging the cytoplasms of contiguous cells. This distinct bacterial organization is preserved during cell division. In Anabaena, deletion of the zipN gene could not be segregated. We generated strain CSL109 that expresses zipN from a synthetic regulatable promoter. Under conditions of ZipN depletion, cells progressively enlarged, reflecting restricted cell division, and showed drastic morphological alterations including cell detachment from the filaments, to finish lysing. In contrast to the wild-type localization in midcell Z-rings, FtsZ was found in delocalized aggregates in strain CSL109. Consistently, the proportion of membrane-associated to soluble FtsZ in fractionated cell extracts was lower in CSL109. Bacterial two-hybrid analysis showed that ZipN interacts with FtsZ and other cell-division proteins including cytoplasmic Ftn6 and SepF, and polytopic FtsW, FtsX, FtsQ and FtsI. Additionally, ZipN interacted with the septal protein SepJ, and in CSL109 depletion of ZipN was concomitant with a progressive loss of septal specificity of SepJ. Thus, in Anabaena ZipN represents an essential FtsZ membrane tether and an organizer of the divisome, and it contributes to the conformation of septal structures for filament integrity and intercellular communication.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-019-39336-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6391411PMC
February 2019

Specific mutations in the permease domain of septal protein SepJ differentially affect functions related to multicellularity in the filamentous cyanobacterium .

Microb Cell 2018 Oct 16;5(12):555-565. Epub 2018 Oct 16.

Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC and Universidad de Sevilla, Américo Vespucio 49, E-41092 Seville, Spain.

Filamentous, heterocyst-forming cyanobacteria are multicellular organisms in which growth requires the activity of two interdependent cell types that exchange nutrients and regulators. Vegetative cells provide heterocysts with reduced carbon, and heterocysts provide vegetative cells with fixed nitrogen. Additionally, heterocyst differentiation from vegetative cells is regulated by inhibitors of differentiation produced by prospective heterocysts and heterocysts. Proteinaceous structures known as septal junctions join the cells in the filament. The SepJ protein is involved in formation of septal junctions in the model heterocyst-forming cyanobacterium sp. strain PCC 7120. SepJ bears extra-membrane and membrane (permease) domains and is located at the cell poles in the intercellular septa of the filament. Here we created mutants that produce SepJ proteins altered in the permease domain. Some of these mutant SepJ proteins did not provide functions needed for to form long filaments and (in some cases) differentiate heterocysts, identifying amino acids and amino acid stretches that are important for the structure or function of the protein. Some other mutant SepJ proteins fulfilled filamentation and heterocyst differentiation functions but failed to provide normal communication function assessed via the intercellular transfer of the fluorescent marker calcein. These mutant SepJ proteins bore mutations in amino acids located at the cytoplasmic face of the permease, which could affect access of the fluorescent marker to the septal junctions. Overall, the data are consistent with the idea that SepJ carries out multiple roles in the multicellular function of the filament.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.15698/mic2018.12.661DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6282017PMC
October 2018

Control of Propionibacterium acnes by natural antimicrobial substances: Role of the bacteriocin AS-48 and lysozyme.

Sci Rep 2018 08 6;8(1):11766. Epub 2018 Aug 6.

Microbiology Department, Faculty of Sciences, C/Fuentenueva s/n, University of Granada, 18071, Granada, Spain.

We report the high susceptibility of several clinical isolates of Propionibacterium acnes from different sources (skin, bone, wound exudates, abscess or blood contamination) to the head-to-tail cyclized bacteriocin AS-48. This peptide is a feasible candidate for further pharmacological development against this bacterium, due to its physicochemical and biological characteristics, even when it is growing in a biofilm. Thus, the treatment of pre-formed biofilms with AS-48 resulted in a dose- and time-dependent disruption of the biofilm architecture beside the decrease of bacterial viability. Furthermore, we demonstrated the potential of lysozyme to bolster the inhibitory activity of AS-48 against P. acnes, rendering high reductions in the MIC values, even in matrix-growing cultures, according to the results obtained using a range of microscopy and bioassay techniques. The improvement of the activity of AS-48 through its co-formulation with lysozyme may be considered an alternative in the control of P. acnes, especially after proving the absence of cytotoxicity demonstrated by these natural compounds on relevant human skin cell lines. In summary, this study supports that compositions comprising the bacteriocin AS-48 plus lysozyme must be considered as promising candidates for topical applications with medical and pharmaceutical purposes against dermatological diseases such as acne vulgaris.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-018-29580-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6079106PMC
August 2018

Optimization of genotypic and biochemical methods to profile P. acnes isolates from a patient population.

J Microbiol Methods 2017 10 18;141:17-24. Epub 2017 Jul 18.

Microbiology Department, Faculty of Sciences, C/Fuentenueva s/n. University of Granada, 18071 Granada, Spain. Electronic address:

Propionibacterium acnes is a key factor in the pathogenesis of acne vulgaris, although currently it is also being associated with medical-device infections. The aim of this work was to validate a safe and quick identification and typing of 24 clinical isolates of Propionibacterium acnes, applying a range of biochemical as well as genetic methods, and investigating the pathogenic potential to associate the different types with human health. RAPD-PCRs revealed the existence of two discernible clusters in correspondence with the phylogroups I and II, according to the PAtig gene polymorphism, leading them to be assigned as P. acnes subsp. acnes subsp. nov. Biotyping according to the pattern of sugar fermentation evidenced that all the isolates from acne and the majority from opportunistic infections fit the biotype I-B3. Consistent with the multiplex touchdown analysis, nearly all the isolates included in this biotype belonged to the subgroups IA1 (the exception being four strains classified as IB). The remaining ones were assigned to phylogroup II, considered to be part of the normal cutaneous microbiota. The susceptibility to three antibiotics was also investigated to explore the relations with the virulence, although no clear trend was identified.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.mimet.2017.07.008DOI Listing
October 2017