Publications by authors named "M G Weinbauer"

48 Publications

Viral Lysis Alters the Optical Properties and Biological Availability of Dissolved Organic Matter Derived from Picocyanobacteria.

Appl Environ Microbiol 2021 01 15;87(3). Epub 2021 Jan 15.

State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiamen, China

Phytoplankton contribute almost half of the world's total primary production. The exudates and viral lysates of phytoplankton are two important forms of dissolved organic matter (DOM) in aquatic environments and fuel heterotrophic prokaryotic metabolism. However, the effect of viral infection on the composition and biological availability of phytoplankton-released DOM is poorly understood. Here, we investigated the optical characteristics and microbial utilization of the exudates and viral lysates of the ecologically important unicellular picophytoplankton Our results showed that DOM produced by viral lysis (Pro-vDOM) with phages of three different morphotypes (myovirus P-HM2, siphovirus P-HS2, and podovirus P-SSP7) had higher humic-like fluorescence intensities, lower absorption coefficients, and higher spectral slopes than DOM exuded by (Pro-exudate). The results indicate that viral infection altered the composition of -derived DOM and might contribute to the pool of oceanic humic-like DOM. Incubation with Pro-vDOM resulted in a greater dissolved organic carbon (DOC) degradation rate and lower absorption spectral slope and heterotrophic bacterial growth rate than incubation with Pro-exudate, suggesting that Pro-vDOM was more bioavailable than Pro-exudate. In addition, the stimulated microbial community succession trajectories were significantly different between the Pro-exudate and Pro-vDOM treatments, indicating that viral lysates play an important role in shaping the heterotrophic bacterial community. Our study demonstrated that viral lysis altered the chemical composition and biological availability of DOM derived from , which is the numerically dominant phytoplankton in the oligotrophic ocean. The unicellular picocyanobacterium is the numerically dominant phytoplankton in the oligotrophic ocean, contributing to the vast majority of marine primary production. releases a significant fraction of fixed organic matter into the surrounding environment and supports a vital portion of heterotrophic bacterial activity. Viral lysis is an important biomass loss process of However, little is known about whether and how viral lysis affects -released dissolved organic matter (DOM). Our paper shows that viral infection alters the optical properties (such as the absorption coefficients, spectral slopes, and fluorescence intensities) of released DOM and might contribute to a humic-like DOM pool and carbon sequestration in the ocean. Meanwhile, viral lysis also releases various intracellular labile DOM, including amino acids, protein-like DOM, and lower-molecular-weight DOM, increases the bioavailability of DOM, and shapes the successive trajectory of the heterotrophic bacterial community. Our study highlights the importance of viruses in impacting the DOM quality in the ocean.
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http://dx.doi.org/10.1128/AEM.02271-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7848921PMC
January 2021

Aquatic Viruses and Climate Change.

Curr Issues Mol Biol 2021 13;41:357-380. Epub 2020 Sep 13.

University of Vienna, Faculty of Life Sciences, Functional and Evolutionary Ecology, Limnology Unit, Vienna, Austria.

The viral component in aquatic systems clearly needs to be incorporated into future ocean and inland water climate models. Viruses have the potential to influence carbon and nutrient cycling in aquatic ecosystems significantly. Changing climate likely has both direct and indirect influence on virus-mediated processes, among them an impact on food webs, biogeochemical cycles and on the overall metabolic performance of whole ecosystems. Here we synthesise current knowledge on potential climate-related consequences for viral assemblages, virus-host interactions and virus functions, and in turn, viral processes contributing to climate change. There is a need to increase the accuracy of predictions of climate change impacts on virus- driven processes, particularly of those linked to biological production and biogeochemical cycles. Comprehension of the relationships between microbial/viral processes and global phenomena is essential to predict the influence on as well as the response of the biosphere to global change.
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http://dx.doi.org/10.21775/cimb.041.357DOI Listing
September 2020

Viral control of biomass and diversity of bacterioplankton in the deep sea.

Commun Biol 2020 05 22;3(1):256. Epub 2020 May 22.

State Key Laboratory of Marine Environmental Science, Fujian Key Laboratory of Marine Carbon Sequestration, College of Ocean and Earth Sciences, Xiamen University (Xiang'an), 361102, Xiamen, Fujian, China.

Viral abundance in deep-sea environments is high. However, the biological, ecological and biogeochemical roles of viruses in the deep sea are under debate. In the present study, microcosm incubations of deep-sea bacterioplankton (2,000 m deep) with normal and reduced pressure of viral lysis were conducted in the western Pacific Ocean. We observed a negative effect of viruses on prokaryotic abundance, indicating the top-down control of bacterioplankton by virioplankton in the deep-sea. The decreased bacterial diversity and a different bacterial community structure with diluted viruses indicate that viruses are sustaining a diverse microbial community in deep-sea environments. Network analysis showed that relieving viral pressure decreased the complexity and clustering coefficients but increased the proportion of positive correlations for the potentially active bacterial community, which suggests that viruses impact deep-sea bacterioplankton interactions. Our study provides experimental evidences of the crucial role of viruses in microbial ecology and biogeochemistry in deep-sea ecosystems.
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http://dx.doi.org/10.1038/s42003-020-0974-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7244761PMC
May 2020

Effects of elevated pCO2 and feeding on net calcification and energy budget of the Mediterranean cold-water coral Madrepora oculata.

J Exp Biol 2016 10 28;219(Pt 20):3208-3217. Epub 2016 Jul 28.

Sorbonne Universités, UPMC Université Paris 06, Observatoire Océanologique de Villefranche, Villefranche-sur-mer 06230, France.

Ocean acidification is a major threat to calcifying marine organisms such as deep-sea cold-water corals (CWCs), but related knowledge is scarce. The aragonite saturation threshold (Ω) for calcification, respiration and organic matter fluxes were investigated experimentally in the Mediterranean Madrepora oculata Over 10 weeks, colonies were maintained under two feeding regimes (uptake of 36.75 and 7.46 µmol C polyp week) and exposed in 2 week intervals to a consecutively changing air-CO mix (pCO) of 400, 1600, 800, 2000 and 400 ppm. There was a significant effect of feeding on calcification at initial ambient pCO, while with consecutive pCO treatments, feeding had no effect on calcification. Respiration was not significantly affected by feeding or pCO levels. Coral skeletons started to dissolve at an average Ω threshold of 0.92, but recovered and started to calcify again at Ω≥1. The surplus energy required to counteract dissolution at elevated pCO (≥1600 µatm) was twice that at ambient pCO Yet, feeding had no mitigating effect at increasing pCO levels. This could be due to the fact that the energy required for calcification is a small fraction (1-3%) of the total metabolic energy demand and corals even under low food conditions might therefore still be able to allocate this small portion of energy to calcification. The response and resistance to ocean acidification are consequently not controlled by feeding in this species, but more likely by chemical reactions at the site of calcification and exchange processes between the calicoblastic layer and ambient seawater.
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http://dx.doi.org/10.1242/jeb.127159DOI Listing
October 2016

Colonization and release processes of viruses and prokaryotes on artificial marine macroaggregates.

FEMS Microbiol Lett 2016 Jan 13;363(1):fnv216. Epub 2015 Nov 13.

CNRS, UMR 7093, LOV, Observatoire Océanologique, 06230 Villefranche-sur-Mer, France Sorbonne Universités, UPMC, Université Paris 06, UMR 7093, LOV, Observatoire Océanologique, 06230 Villefranche-sur-Mer, France Aix Marseille Université, CNRS/INSU, Université de Toulon, IRD, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Marseille, France.

Marine organic aggregates are sites of high of viral accumulation; however, still little is known about their colonization processes and interactions with their local bacterial hosts. By taking advantage of a novel approach (paramagnetic functionalized microsphere method) to create and incubate artificial macroaggregates, we examined the small-scale movements of viruses and bacteria between such marine snow particles and the surrounding water. The examination of the codynamics of both free-living and attached viral and bacterial abundance, over 12 hours of incubation in virus-free water, suggests that aggregates are rather comparable to viral factories than to viral traps where a significant part of the virions production might be locally diverted to the water column. Also, the near-zero proportion of lysogenized cells measured in aggregates after mitomycin-C induction seems to indicate that lysogeny is not a prominent viral reproduction pathway in organic aggregates where most viruses might rather be virulent. Finally, we hypothesize that, contrary to bacteria, which can use both strong attachment and detachment from aggregates (two-way motion of bacteria), the adsorption of planktonic viruses appears to be numerically negligible compared to their massive export from the aggregates into the water column (one-way motion of viruses).
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http://dx.doi.org/10.1093/femsle/fnv216DOI Listing
January 2016
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