Biology subjects

Mondav, R.

Publications and source records attributed to Mondav, R..

4 recordsLinked to original sources

bioRxiv2022

Network analysis uncovers associations in the turnover of C1 molecules in a winter lake

The generation and consumption of single carbon molecules (CO2 and CH4) by aquatic microbial communities is an essential aspect of the global carbon budget. Organic carbon flow (warm sunlit regimes) is depicted as beginning at the surface with autochthonous fixation followed by biomass settling to sediments, CO2 respiration to the atmosphere, and outflow. We sought to broaden understanding of C1 cycling and consortia by examining the microbial community of a below-ice lake water column in which both input and output are likely disrupted due to ice cover. By analysing the microbial community composition and co-occurrence network of an ice-covered lake timeseries, we were able to identify potential consortia involved in C1 cycling. The network confirmed known associations supporting the efficacy of such analyses but also pointed to previously unknown potential associations. Further and contrary to typical organic carbon flow under warm sunlit regimes, we found support for upward flow of recently fixed carbon in cold low-light conditions under-ice in winter.

microbiology↗

bioRxiv2022

Biogenic methane cycling is controlled by microbial cohorts

The generation and consumption of methane by aquatic microbial communities is an important contribution to the global carbon budget. We sought to broaden understanding of consortia members and interactions by combining multiple methods including analysis of natural and cultivated microbial communities. By analysing the microbial community composition and co-occurrence patterns of a lake time-series we were able to identify potential consortia involved in methane cycling. In combination with methane flux, we also analysed the community composition and co-occurrence patterns of reduced microbial model communities with inoculum from the same lake. While the network analyses confirmed many known associations, when combined with results from mixed cultures, we noted new players in methane cycling. Cultivated model communities were shown to be an effective method to explore the rarer but still important players in methane cycling and for identifying new putative members. Here we show that using multiple methods to approach the complex problem of methane cycling consortia yields not just insights into the known taxa but highlights potential new members creating new hypotheses to be tested.

microbiology↗

bioRxiv2020

Streamlined freshwater bacterioplankton Nanopelagicales (acI) and Ca. Fonsibacter (LD12) thrive in functional cohorts

While fastidious microbes can be abundant and ubiquitous in their natural communities, many fail to grow axenically in laboratories due to auxotrophies or other dependencies. To overcome auxotrophies these microbes rely on their surrounding cohort. A cohort may consist of kin (ecotypes) or more distantly related organisms (community) with the cooperation being reciprocal or non-reciprocal, and expensive (Black Queen hypothesis) or costless (byproduct). These metabolic partnerships (whether at single species population or community level) enable dominance by and coexistence of these lineages in nature. Here we examine the relevance of these cooperation models to explain the abundance and ubiquity of the dominant fastidious bacterioplankton of a dimictic mesotrophic freshwater lake. Using both culture dependent (minimalist mixed cultures) and culture independent (SSU rRNA gene time series and environmental metagenomics) methods we independently identified the primary cohorts of Actinobacterial genera "Ca. Planktophila" (acI-A) and "Ca. Nanopelagicus" (acI-B), and the Proteobacterial genus "Ca. Fonsibacter" (LD12). While "Ca. Planktophila" and "Ca. Fonsibacter" had no correlation in their natural habitat, they have the potential to be complementary in laboratory settings. We also investigated the bi-functional catalase-peroxidase enzyme KatG (a common good which "Ca. Planktophila" is dependent upon) and its most likely providers in the lake. Further we found that while ecotype and community cooperation combined may explain "Ca. Planktophila" population abundance, the success of "Ca. Nanopelagicus" and "Ca. Fonsibacter" is better explained as a community byproduct. Ecotype differentiation of "Ca. Fonsibacter" as a means of escaping predation was supported but not for overcoming auxotrophies. IMPORTANCEThis study examines evolutionary and ecological relationships of three of the most ubiquitous and abundant freshwater bacterial genera: "Ca. Planktophila" (acI-A), "Ca. Nanopelagicus" (acI-B), and "Ca. Fonsibacter" (LD12). Due to high abundance, these genera might have a significant influence on nutrient cycling in freshwaters worldwide and this study adds a layer of understanding to how seemingly competing clades of bacteria can co-exist by having different cooperation strategies. Our synthesis ties together network and ecological theory with empirical evidence and lays out a framework for how the functioning of populations within complex microbial communities can be studied.

microbiology↗

bioRxiv2017

Microbial Network, Phylogenetic Diversity And Community Membership In The Active Layer Across A Permafrost Thaw Gradient

Biogenic production and release of methane (CH4) from thawing permafrost has the potential to be a strong source of radiative forcing. We investigated changes in the active layer microbial community of three sites representative of distinct permafrost thaw stages at a palsa mire in northern Sweden. The palsa sites with intact permafrost, and low radiative forcing signature had a phylogenetically clustered community dominated by Acidobacteria and Proteobacteria. The bog with thawing permafrost and low radiative forcing signature was dominated by hydrogenotrophic methanogens and Acidobacteria, had lower alpha diversity, and midrange phylogenetic clustering, characteristic of ecosystem disturbance affecting habitat filtering, shifting from palsa-like to fen-like at the waterline. The fen had no underlying permafrost, and the highest alpha, beta and phylogenetic diversity, was dominated by Proteobacteria and Euryarchaeota, and was significantly enriched in methanogens. The mire microbial network was modular with module cores consisting of clusters of Acidobacteria, Euryarchaeota, or Xanthomonodales. Loss of underlying permafrost with associated hydrological shifts correlated to changes in microbial composition, alpha, beta, and phylogenetic diversity associated with a higher radiative forcing signature. These results support the complex role of microbial interactions in mediating carbon budget changes and climate feedback in response to climate forcing.

ecology↗