Biology subjects

Bosak, T.

Publications and source records attributed to Bosak, T..

3 recordsLinked to original sources

bioRxiv2024

Heat flows solubilize apatite to boost phosphate availability for prebiotic chemistry

Phosphorus is an essential building block of the most prominent biomolecules, such as polynucleic acids, and has likely played that role since the beginning of life. Despite this importance for prebiotic chemistry, phosphate could not be supplied by the atmosphere, and had to be fueled mainly by geological phosphate sources. However, phosphorus was scarce in Earths rock record and often bound in poorly soluble minerals, with the calcium phosphate mineral apatite as key example. While specific chemical boundary conditions that bind calcium have been used to address this so-called phosphate problem, a fundamental process that solubilizes and enriches phosphate from geological sources remains elusive. Here, we show that ubiquitous heat flows through rock cracks can liberate phosphate from apatite by the selective removal of calcium. Phosphates surprisingly strong thermophoresis not only achieves its 100-fold up-concentration in aqueous solution, in particular it also boosts its solubility by two orders of magnitude. We show that the heat-flow-solubilized phosphate can feed the synthesis of trimetaphosphate, increasing the conversion 260-fold compared to the thermal equilibrium case. Heat flows thus enhance solubility as a geological parameter to unlock apatites as phosphate source for prebiotic chemistry, providing a key element in solving early lifes phosphate problem.

biophysics↗

bioRxiv2022

Functional gene analysis and cultivation experiments predict the degradation of diverse extracellular polysaccharides by ubiquitous taxa in pustular microbial mats from Shark Bay, Western Australia

Microbial exopolymeric substances (EPSs) form the organic, polysaccharide-rich matrix of marine microbial mats and can mediate the binding and precipitation of carbonate minerals therein. Here, we investigate the molecular ecology of carbohydrate degradation and production in pustular mats from Shark Bay, Western Australia, by analyzing 84 metagenome-assembled genomes (MAGs) and the composition of microbial communities enriched from a pustular mat on various polysaccharide substrates. The annotation of 4000 genes from hundreds of carbohydrate-active enzyme (CAZyme) families in the MAGs and mapping of polysaccharide-degrading CAZymes to their predicted substrates identify trends in the distribution and localization of degradation-associated CAZymes across different bacterial phyla. The compositions of microbial communities enriched on a range of polysaccharides inoculated with pustular mat material support the predicted trends. The combined metagenomic and experimental analyses reveal a widespread potential for EPS degradation among MAGs from Shark Bay pustular mats and suggest distinct roles for some phyla that are reported at high abundances in mats. Specifically, Bacteroidetes are likely to be primary degraders of polysaccharide EPSs, alongside Planctomycetes and a small subset of Alphaproteobacteria and Gammaproteobacteria. Planctomycetes, some Bacteroidetes, Verrucomicrobia, Myxococcota and Anaerolineae are also predicted to favor degradation of sulfated substrates, which are present in the EPS matrix of pustular mats. Large sets of functionally varied CAZymes without signal peptides tagging them for export implicate Anaerolineae and Verrucomicrobia in degrading the downstream products of primary EPS degradation. ImportanceModern marine microbial mats are rich in exopolymeric substances (EPSs) -- complex, high molecular weight polymers secreted by bacteria -- that mediate the formation of carbonate minerals and the preservation of microbial textures in mats. However, the organisms involved in EPS cycling in these mats have not been identified and the links between EPS degradation, carbonate precipitation, and microbial ecology in mats remain poorly understood. We define distinct roles in EPS cycling for many major microbial taxa that are both ubiquitous and abundant in pustular microbial mats from Shark Bay, Australia. The large genomic potential of these microbes for the modification and degradation of diverse extracellular organic polymers provides a blueprint for future studies aimed at quantifying and verifying the specific contributions of these microbes to EPS degradation, carbon cycling and carbonate precipitation.

microbiology↗

bioRxiv2021

Organic electron donors and terminal electron acceptors structure anaerobic microbial communities and interactions in a permanently stratified sulfidic lake

The extent to which nutrients structure microbial communities in permanently stratified lakes is not well understood. This study characterized microbial communities from the anoxic layers of the meromictic and sulfidic Fayetteville Green Lake (FGL), NY, and investigated the roles of organic electron donors and terminal electron acceptors in shaping microbial community structure and interactions. Bacterial communities from the permanently stratified layer below the chemocline (monimolimnion) and from enrichment cultures inoculated by lake sediments were analyzed using 16S rRNA gene sequencing. Results showed that anoxygenic phototrophs dominated microbial communities in the upper monimolimnion (21 m), which harbored little diversity, whereas the most diverse communities resided at the bottom of the lake (~52 m). Organic electron donors explained 54% of the variation in the microbial community structure in aphotic cultures enriched on an array of organic electron donors and different inorganic electron acceptors. Electron acceptors only explained 10% of the variation, but were stronger drivers of community assembly in enrichment cultures supplemented with acetate or butyrate compared to the cultures amended by chitin, lignin or cellulose. We identified a range of habitat generalists and habitat specialists in both the water column and enrichment samples using Levins index. Network analyses of interactions among microbial groups revealed Chlorobi and sulfate reducers as central to microbial interactions in the upper monimolimnion, while Syntrophaceae and other fermenting organisms were more important in the lower monimolimnion. The presence of photosynthetic microbes and communities that degrade chitin and cellulose much below the chemocline supported the downward transport of microbes, organic matter and oxidants from the surface and the chemocline. Collectively, our data suggest niche partitioning of bacterial communities by interactions that depend on the availability of different organic electron donors and terminal electron acceptors. Thus, light, as well as the diversity and availability of chemical resources drive community structure and function in FGL, and likely in other stratified, meromictic lakes.

microbiology↗