Biology subjects

Pacheco-Valenciana, A.

Publications and source records attributed to Pacheco-Valenciana, A..

4 recordsLinked to original sources

bioRxiv2026

A streamlined and abundant Nitrosopumilus population retains vitamin biosynthesis under high purifying selection in the Baltic Sea

Genome streamlining is expected to favor the loss of costly biosynthetic functions, raising the question of what benefit justifies the continued maintenance of complex pathways in small genomes. Here, we investigated this question in an abundant Nitrosopumilus population from the Baltic Sea that combined a streamlined genome (1.4 Mbp) with substantial biosynthetic capacity for vitamins B1, B7, and B12. We found three lines of evidence that support the biological significance of this retention. First, phylogenomic analysis of 1,077 archaeal species representatives showed that B-vitamin biosynthesis is broadly conserved across ammonia-oxidizing archaea (AOA), indicating maintenance over deep evolutionary timescales. Second, genes associated with B-vitamin biosynthesis tended to be under stronger purifying selection than the genomic background across Baltic Sea metagenomes, consistent with selection preserving these functions in current environmental populations. Third, measurements in the cultured relative Nitrosopumilus maritimus showed B-vitamins and related precursors in both intracellular and extracellular fractions, providing a potential route through which these retained functions could influence metabolite availability beyond the producing cell. Together, our findings suggest that retained biosynthetic pathways in highly streamlined microorganisms reveal functions that are beneficial for the success of a natural population, while also pointing to their potential importance for other community members coexisting within the same environment.

microbiology↗

bioRxiv2026

Baltic Sea microbial cohorts exhibit catabolic specialization and anabolic interdependencies across environmental gradients

Microbial communities are structured by environmental gradients and metabolic interactions, yet the genomic characteristics and metabolic functions of co-occurring populations remain underexplored. Here, we investigated co-occurring microbial cohorts across the Baltic Sea, a system characterized by strong salinity, temperature, and oxygen gradients. For this, we used a genomic catalog consisting of 701 species-representative genomes to recruit reads from 112 metagenomes and infer cohort structure, environmental distributions, and metabolic potential. We identified nine microbial cohorts that showed strong associations with environmental gradients, indicating deterministic assembly. Cohorts differed markedly in genomic traits, with the most abundant and prevalent taxa associated with smaller, streamlined genomes, while a low-oxygen cohort with larger genomes contributed disproportionately to nitrogen and sulfur transformations. Across cohorts, biosynthetic potential was unevenly distributed. Amino acid biosynthesis pathways were frequently complete, whereas B-vitamin pathways were typically incomplete and rarely encoded in full by individual genomes. Metabolites with low pathway completeness showed consistent taxonomic partitioning, with biosynthetic capabilities distributed across taxa rather than collectively encoded within cohorts. Together, these results show that Baltic Sea microbial cohorts are ecologically structured assemblages whose genomic repertoires reflect catabolic specialization and anabolic interdependencies. Our findings highlight microbial cohorts as a useful framework for linking environmental gradients, genome traits, and the organization of metabolic functions in natural microbial communities.

microbiology↗

bioRxiv2025

Microbial model communities reveal widespread auxotrophies in abundant bacteria

Microorganisms thrive in complex communities shaped by intricate interactions, yet the extent and ecological implications of biosynthetic dependencies in natural communities remain underexplored. Here, we used a dilution approach to cultivate 204 microbial model communities from the Baltic Sea and recovered 527 metagenome-assembled genomes (MAGs) that dereplicated into 72 species-clusters (>95% average nucleotide identity - ANI). Of these species, at least 70% represent previously uncultivated lineages. Combined with 1073 MAGs from Baltic Sea metagenomes, we generated a genomic catalog of 701 species-clusters. Our results show that cultures with more than 3 species included microorganisms with smaller genome sizes, lower biosynthetic potential for amino acids and B vitamins, and higher prevalence and abundance in the environment. Moreover, biosynthetic genes were distributed across genomes within the same model community, indicating metabolic interdependencies. Our results demonstrate that cultivating bacteria in dilution model communities facilitates access to previously uncultivated but abundant species that likely depend on metabolic partners for survival. Together, our findings highlight the value of community-based cultivation for unraveling ecological strategies. Finally, we confirm that metabolic interdependencies and genome streamlining are widespread features of successful environmental microorganisms.

microbiology↗

bioRxiv2025

The ecological success of freshwater microorganisms is mediated by streamlining and biotic interactions

Genome size is known to reflect aspects of the eco-evolutionary history of prokaryotic species, including their lifestyle, environmental preferences, and habitat breadth. However, it remains uncertain how strongly genome size is linked to microbial prevalence, relative abundance and co-occurrence in the environment. To address this gap, we present a systematic and global-scale evaluation of the relationship between genome size, relative abundance and prevalence in freshwater ecosystems, including 80,561 medium-to-high quality genomes. We identified 9,028 species (defined by ANI >95%) across a manually curated dataset of 636 freshwater metagenomes and calculated their relative abundance. Our results show that prokaryotes with reduced genomes exhibited higher prevalence and relative abundance, and a greater prevalence than expected based on their mean abundance, suggesting that genome streamlining may promote cosmopolitanism. Furthermore, our network analysis revealed that prokaryotes with reduced genomes are found in co-occurrent groups comprising up to 295 species. The species in these groups potentially possess a diminished capacity for synthesizing essential metabolites such as vitamins, amino acids and nucleotides, which may foster complex metabolic interdependencies within the community. Moreover, the fitness advantage of losing biosynthetic functions appears to be frequency dependent: while nucleotide biosynthesis is the most retained biosynthetic function, amino acid and then vitamin biosynthesis are more frequently lost. Our study finds that genome size is linked to microbial community structure and ecological adaptation to freshwaters. Our results underscore genome streamlining as a central ecological and evolutionary strategy that both shapes and is shaped by community dynamics, ultimately fostering interdependences among prokaryotes.

microbiology↗