Biology subjects

Bosak, T.

Publications and source records attributed to Bosak, T..

5 recordsLinked to original sources

bioRxiv2026

Minimizing methane emissions during the degradation of sewage sludge in a sulfate-rich bioreactor

Simultaneous removal of organic waste and industrial gypsum was assessed in continuous flow-through bioreactors that treat sulfate-rich sewage sludge. Metabolic fluxes, the composition of microbial communities, and profiles of organic matter in the presence of different organic loads were tracked over [~]190 days. The addition of a pre-enriched microbial community enhanced the rates of sulfate reduction during the establishment of the sludge blanket, but microbial diversity in established reactors depended primarily on organic loading. Organic removal rates were comparable to those in standard anaerobic digesters, but methane production accounted for [~]1% of electron flow compared to >70% in traditional systems. Stoichiometric analyses revealed that molar COD: sulfate ratios below [~]1 favored complete oxidation of acetate by sulfate-reducing bacteria (SRB) and those above [~]2.1 permitted either complete or incomplete oxidation, allowing sulfate reduction and methanogenesis to co-occur. Sequencing of the 16S rRNA confirmed these trends by revealing that the faster-growing SRB that do not oxidize acetate were more abundant at higher organic loads and during the establishment of the sludge blanket, whereas complete oxidizers became more abundant when the molar COD: sulfate ratio was [≤]3.2. In reactors that had been seeded with the pre-enriched communities, acetate-oxidizing SRB became prevalent over the incomplete oxidizers 25-50 days earlier. These results enable targeted design and control of microbial processes and bioreactors that remove waste organics and gypsum while producing less methane due to the competition for acetate between methanogenic archaea and SRB that oxidize acetate.

microbiology↗

bioRxiv2026

Organic availability and microbial competition for acetate suppress methane emissions during the conversion of gypsum in sewage sludge

Conventional anaerobic digestion emits methane from organic waste. Here, we investigate a sulfate-based alternative that suppresses methane production and generates alkaline solutions that may sequester carbon by carbonate precipitation. Although methanogenesis is known to occur when reduced organic carbon is replete and sulfate is limiting, it remains unclear whether methane emissions during microbial conversion of waste gypsum are primarily driven by community composition or organic availability. By comparing fluxes of electrons from organic matter toward sulfate or methane in microbial communities grown on different organic loads, we show that community composition, microbial growth, and organic availability collectively determine sulfide and methane fluxes. Lower organic loads increase the importance of syntrophic interactions with fermenters and competition between sulfate reducing bacteria and methanogens due to scarcity of substrates. Microbes present in the original sewage sludge reduce less sulfate, produce more methane, and generate less alkalinity compared to the communities enriched by multiple cycles of growth in the presence of sulfate and sewage sludge. The inoculation of communities enriched at low organic loadings in the presence of sulfate decreases the production of methane by enabling the growth of sulfate reducing bacteria from the order Desulfobacterales that can oxidize acetate to CO2 and compete with methanogens for acetate. The use of such enrichments in sludge treatment systems can stimulate the removal of organic substrates and waste gypsum, while suppressing methane production, over timescales comparable to those in the current sludge treatment systems that do not contain sulfate.

microbiology↗

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↗