Biology subjects

Anestis, K.

Publications and source records attributed to Anestis, K..

3 recordsLinked to original sources

bioRxiv2026

Wastewater-impacted Skagerrak Sea microbiomes anaerobically demethylate micropollutants

Methylated micropollutants such as naproxen and caffeine persist in wastewater effluents and accumulate in coastal sediments, including Hakefjorden, Skagerrak Sea, yet their anaerobic fate and role in methane emissions remain unresolved. Here we traced the fate and microbiome responses to {superscript 1}3C-labeled naproxen and caffeine in sediment microcosms. We show that naproxen underwent rapid O-demethylation to desmethylnaproxen, with 90% {+/-} 15.5% removed within 25 days, producing primarily {superscript 1}3CO2 and some {superscript 1}3CH. Naproxen enriched methylotrophic and hydrogenotrophic Methanomicrobia, alongside Lokiarchaeia, Bathyarchaeia, and bacterial taxa like Eubacterium and Syntrophomonadaceae. Metagenomics revealed O-demethylation genes in enriched bacterial MAGs affiliated with uncultured Thermoanaerobaculia, indicating a bacterial demethylation potential. In contrast, caffeine was largely recalcitrant to degradation ([~]85% {+/-} 5% remaining), yet its 13C-labeled N-methyl groups fueled {superscript 1}3CH production, coinciding with enrichment of Bathyarchaeia and Methanosarcina. These results show that methylated micropollutants can activate both bacterial and archaeal demethylation pathways in coastal sediment microbiomes.

microbiology↗

bioRxiv2025

Genome-centric metagenomics reveals novel electroactive syntrophs in a conductive particle-dependent consortium from coastal sediments

Conductive particles are abundant in coastal sediments, yet the organisms and pathways that use them for methane production remain unclear. We applied long-read, genome-resolved metagenomics to a sediment-derived consortium that remained dependent on granular activated carbon (GAC) for a decade. We identified a particle-obligate food web of electrogenic syntrophic acetate oxidizers (SAO), an electrotrophic methanogen, and necromass recyclers. The dominant SAO electrogen was a new genus, Candidatus Geosyntrophus acetoxidans (<70% ANI/AAI to described taxa), encoding a streamlined extracellular electron-transfer system: one porin-cytochrome conduit (PCC), 47 multiheme cytochromes, conductive pili, and acetate uptake/utilization genes. A second SAO electrogen, Lentimicrobium sp., carried two giant PCC-like clusters, suggesting an alternative acetate-oxidation route. Electrons flowed via GAC to a Methanosarcina (<89% ANI/AAI to described taxa) equipped with the multiheme cytochrome MmcA and a Rnf/Fpo/HdrDE circuit for EET-driven CO2-reducing methanogenesis. Particle-free lines lost both partners and methanogenic activity, establishing particles as the determinant of persistence. This first genomic blueprint of a natural CIET-SAO consortium identifies potential genomic markers (distinct PCCs, MmcA) for in-situ detection and reveals a particle-bound route from acetate to methane likely operating as a fundamental electron-transfer unit in geoconductor-rich anoxic sediments.

microbiology↗

bioRxiv2025

Cell Surface Differences within the Genus Methanosarcina Shape Interactions with the Extracellular Environment

Methanosarcina are metabolically versatile methanogenic archaea that can perform extracellular electron transfer (EET), with important ecological and biotechnological implications. These archaea are broadly classified into two types (Type I and Type II) based on their energy metabolism and are also differ in their aggregation-disaggregation behavior, cell surface properties, and electron transfer strategies. Type I Methanosarcina typically form large multicellular aggregates within a methanochondroitin extracellular matrix, thrive in organic-rich environments, play a key role in anaerobic digestion during wastewater treatment and can perform EET. However, their mechanism of EET remains unresolved. In contrast, Type II Methanosarcina rely on multiheme c-type cytochromes for EET and are better adapted to low-organic, mineral-rich environments such as deep-sea sediments and aquifers, where they contribute to methane emissions. Despite their significance, the molecular mechanisms behind EET in Methanosarcina-- particularly for Type I--remain poorly understood. This review highlights what is known and what is unknown regarding the surface biology of Methanosarcina, their EET strategies, and biogeochemical and industrial roles, emphasizing the need for further research to unlock their full potential in sustainable methane management.

microbiology↗