Abstract

Oyster-associated microbiomes represent a dynamic interface between marine hosts and their environment, yet the diversity, evolution, and functional potential of their associated cyanobacteria remain poorly understood. For microbial organisms, such as cyanobacteria, survival requires adaptation to several environmental pressures, including higher metal concentrations and osmotic stress. To investigate these adaptations, two cyanobacterial strains, CENA647 and CENA648, were isolated from oyster surfaces sampled along the Amazon coast. Genomic analysis and untargeted metabolomics were conducted to investigate the taxonomy and functional potential of these strains. Both genomes exhibited high completeness (>99.2%) and low contamination (<2.2%). The total lengths differed, with 8.3 Mbp for CENA647 and 6.5 Mbp for CENA648. The genome size correlated with the number of identified coding regions: 7593 for CENA647 and 5541 for CENA648. Phylogenetic analysis highlights their taxonomic relationships within cyanobacteria adapted to fluctuating salinity, including the first description of the genus Thainema in South America. Comparative genome mining revealed extensive genetic repertoires associated with osmoregulation and metal resistance, consistent with adaptation to oyster-associated environments. Both strains shared predicted metabolites annotated in the metabolomes, with a wide range of compound classes, including amino acids, terpenes, fatty acids, and peptides, as well as several unannotated molecular features. Overall, our findings expand current knowledge of oyster-associated cyanobacteria and highlight their metabolic diversity in the Amazon region, as well as genomic traits that may be associated with adaptation to dynamic estuarine environments.

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