Biology subjects

Mayers, K.

Publications and source records attributed to Mayers, K..

3 recordsLinked to original sources

bioRxiv2025

Diversity, abundance, and biogeography of CO2 fixing microorganisms in peatlands

Microbial communities play a crucial role in the carbon (C) dynamic of peatlands-- a major terrestrial C reservoir. While heterotrophic microorganisms attracted much attention over the past decades due to their role in peatland greenhouse gases emissions, CO2 fixing microorganisms (CFMs) remained particularly overlooked. Here, by leveraging metabarcoding and digital droplet PCR (ddPCR), we provide a comprehensive survey of CFM communities, including oxygenic phototrophs, chemoautotrophs and aerobic anoxygenic phototrophic bacteria (AAnPBs), in different peatland types. We demonstrate that CFMs are very abundant and diverse in peatlands, with on average 1021 CFMs contributing up to 40% of the total bacterial abundance. In particular, we show that oxygenic phototrophs (mostly Cyanophyceae and Palmophylloceae) are the most abundant CFMs, closely followed by chemoautotrophs (Proteobacteria) and AAnPBs (Vulcanimicrobiia). Using a joint-species distribution model, we further find that CFMs aggregate into six major clusters with different niche size. These clusters constitute the core and specific CFM microbiome. The core microbiome, which the occurrence is strongly influenced by temperature and nutrients, directly modulate the diversity and abundance of CFMs. Our findings highlight the importance of CFM diversity and abundance in peatlands, further reveal their complex structuration in link with environmental conditions and suggest that changes in environmental conditions could shift CFMs communities. These results are the foundation to better understand the role of CFMs for the peatland C cycle inputs.

microbiology↗

bioRxiv2024

Development of a ddPCR approach for the absolute quantification of soil microorganisms involved in atmospheric CO2 fixation

Carbon fixing microorganisms (CFMs) play a crucial role in soil carbon (C) cycling contributing to carbon uptake and sequestration through various metabolic pathways. Despite their significance, quantification of the absolute abundance of CFMs in soils remains elusive. This study employed a digital droplet PCR (ddPCR) approach to quantify the abundance of key and emerging CFM pathways in fen and bog across different depths (0-15 cm). Targeting total prokaryotes (16S rRNA gene), oxygenic phototrophs (23S rRNA gene), aerobic anoxygenic phototrophic bacteria (AAnPB, pufM gene), and chemoautotrophs (cbbL gene), we optimized ddPCR conditions to achieve absolute quantification of these genes. Overall, our results revealed that oxygenic phototrophs were the most abundant CFMs, constituting 12% of total prokaryotic abundance, followed by chemoautotrophs (10%) and AAnPBs (9%). Fen exhibited higher gene concentrations than bog. Depth variations were also observed, differing between fen and bog for all genes. Our findings highlight the abundance of oxygenic phototrophs and chemoautotrophs in peatlands, challenging previous estimations that relied solely on oxygenic phototrophs for microbial CO2 fixation assessments. Incorporating absolute gene quantification is crucial for a comprehensive understanding of microbial contributions to soil processes, shedding light on the intricate mechanisms of soil functioning in peatlands.

microbiology↗

bioRxiv2021

Viral infection switches the balance between bacterial and eukaryotic recyclers of organic matter during algal blooms

Algal blooms are hotspots of marine primary production and play central roles in microbial ecology and global nutrient cycling. When blooms collapse, organic carbon is transferred to higher trophic levels, microbial respiration or sinking in proportions that depend on the dominant mortality agent. Viral infection can lead to bloom termination, but its impact on the fate of carbon remains an open question. Here, we characterized the consequences of viral infection on the microbiome composition and biogeochemical landscape of marine ecosystems by conducting a large-scale mesocosm experiment. Moniroting of seven induced coccolithophore blooms, which showed different degrees of viral infection, revealed that only high levels of viral infection caused significant shifts in the composition of free-living bacterial and eukaryotic assemblages. Intriguingly, viral infection favored the growth of eukaryotic heterotrophs (thraustochytrids) over bacteria as potential recyclers of organic matter. By combining modeling and quantification of active viral infection at a single-cell resolution, we estimate that viral infection can increase per-cell rates of extracellular carbon release by 2-4.5 fold. This happened via production of acidic polysaccharides and particulate inorganic carbon, two major contributors to carbon sinking into the deep ocean. These results reveal the impact of viral infection on the fate of carbon through microbial recyclers of organic matter in large-scale coccolithophore blooms.

microbiology↗