Biology subjects

Seneca Cardoso da Silva, J.

Publications and source records attributed to Seneca Cardoso da Silva, J..

3 recordsLinked to original sources

bioRxiv2026

Kineochelins - a novel group of siderophores from an Antarctic bacterium

BackgroundThe global rise of antimicrobial resistance has intensified the search for new microbial metabolites from underexplored environments and taxonomic groups. Extreme and geographically isolated habitats, such as Antarctic terrestrial ecosystems, represent promising reservoirs of novel biosynthetic diversity, particularly among rare and difficult-to-cultivate actinomycetes, where chemical mediators are thought to play key roles in microbial persistence and interaction under resource-limited conditions. ResultsHere, we report the characterization of kineochelins, a previously undescribed group of siderophores produced by an Antarctic isolate, Actinokineospora sp. UV203 representing difficult to cultivate actinomycetes. Structural elucidation revealed a set of closely related congener molecules with a mixed-ligand architecture consistent with metal-chelating activity. Genome mining combined with transcriptomic analysis identified the involvement of a dedicated nonribosomal peptide synthetase-encoding biosynthetic gene cluster responsible for kineochelin production. Comparative genomic analyses showed that, although kineochelin biosynthetic genes share limited homology with those of known mixed-ligand siderophores, their biosynthetic pathways differ substantially in gene content and organization, indicating a distinct evolutionary lineage. Functional characterization of kineochelins demonstrated strong and selective iron chelation, with pronounced affinity for ferric and ferrous iron. Crude culture extracts inhibited the growth of bacterial strains isolated from the same Antarctic environment, suggesting that kineochelin-associated chemistry contributes to iron-mediated competitive interactions within native microbial communities. In addition, kineochelin-enriched fractions exhibited selective inhibitory activity against the opportunistic yeast pathogen Nakaseomyces glabratus and a clinical isolate of Saccharomyces cerevisiae associated with invasive infection. ConclusionsTogether, these findings expand the known chemical and biosynthetic diversity of the genus Actinokineospora and demonstrate that Antarctic rare actinomycetes are a valuable source of novel natural products with potential relevance for microbial ecology and biotechnology. The ecological activities of kineochelins highlight the role of iron acquisition in shaping microbial interactions in extreme environments and underscore the biotechnological potential of metabolites derived from underexplored polar microorganisms.

microbiology↗

bioRxiv2025

Single-cell mass accumulation reveals bacterioplankton growth rate in native seawater

AO_SCPLOWBSTRACTC_SCPLOWThe growth of marine microbial communities drives biogeochemical cycling of carbon and other elements, yet the growth rates of individual species within complex ocean ecosystems remain poorly understood. In particular, the coexistence of a large diversity of copiotrophic bacteria, which are capable of fast growth but typically remain at low abundance, has been interpreted as a feast or famine existence. Here we show that contrary to the notion of infrequent growth, Vibrio bacteria exhibited consistent growth rates in coastal ocean samples, despite representing only a small fraction of the total community. These observations were enabled by a suspended microchannel resonator (SMR), which we adapted to function as a single-cell chemostat. By maintaining a continuous supply of native seawater around each trapped cell, we prevented nutrient depletion and used the SMRs high mass precision to resolve growth rates that are otherwise undetectable. Vibrio species displayed significantly larger cell mass and faster growth than other community members across samples collected at different temporal intervals from days to years. Surprisingly, their growth was consistently limited by carbon, contrary to the expectation that heterotrophic bacteria in the euphotic zone would be limited by nitrogen and phosphorus due to competition with algae. The correlation between cell mass and growth rate of Vibrionaceae in seawater followed established growth laws derived from laboratory conditions, suggesting that growth physiology observed in pure cultures is applicable to wild bacterial populations. Overall, our findings suggest that rare species may play a disproportionately large role in the marine carbon cycle, with rapid biomass turnover driven by a combination of high growth rates balanced by intense predation.

microbiology↗

bioRxiv2025

Model substrate particles uncover dynamics of microbial communities associated with particulate organic matter decomposition in soil

Soil organic matter is the largest terrestrial reservoir of organic carbon. Its particulate fraction, particulate organic matter (POM), serves as a resource and surface for microbial colonization. Degradation of complex biopolymers like cellulose and chitin requires extracellular enzymes produced by phylogenetically diverse microbes. Despite their importance for carbon cycling, the structure and spatio-temporal dynamics of POM-associated microbial communities in soil and how specific substrates influence them remain poorly understood. This study investigated whether microbial communities associated with POM change in composition and richness over time and whether chitin and cellulose select for distinct fungal and bacterial taxa. We incubated self-manufactured, millimetre-sized model substrate particles containing chitin or cellulose in soil under laboratory and field conditions. We assessed particle-associated communities at multiple time points over a 50-day-long incubation in the lab and after 47 days in the field. Our results show that community structure and temporal dynamics of particle-associated microbial communities were substrate-specific. While microbial biomass increased on both particle types, chitin-associated microbial communities exhibited stronger temporal changes. Communities on chitin and cellulose particles were enriched in specific bacterial and fungal genera compared to communities in the surrounding soil. We demonstrate that microbial communities associated with model chitin particles underwent notable temporal changes, including decreased microbial richness and shifts in community composition over the incubation period. This study shows the potential of model particles to advance our understanding of particle- and substrate-associated microbial communities in soil.

microbiology↗