Genomic and phenotypic characterization of indigenous violacein-producing Chromobacterium amazonense SAM215 from lake...

The genus Chromobacterium, found in diverse ecosystems, is well known for its production of violacein, quorum-sensing ability, and considerable biotechnological importance. While C. violaceum has been extensively studied, other species, including C. amazonense, have received relatively little attention. This study reports phenotypic characterization and genomic analysis of the indigenous Chromobacterium amazonense strain SAM215, isolated from Bijoypur Lake, Netrokona, Bangladesh. The violacein-producing purple colony was selected and characterized, exhibiting high salinity tolerance (up to 12.5% NaCl), resistance to beta-lactam antibiotics, tolerance to metal ions, and strong biofilm formation. Notably, disruption of the biofilm under shaking conditions significantly diminished violacein production. The de novo-assembled genome (4.14 Mbp), identified as C. amazonense, comprised 4104 protein-coding genes and 53 RNA genes. Genomic analysis revealed genes associated with metal tolerance, stress adaptation, antimicrobial compound production, plant-growth-promoting traits, and enzymes such as chitinases, suggesting a genomic repertoire of biotechnological interest. However, multiple genes associated with antibiotic resistance and virulence factors, including secretion systems and hemolysin, were also identified. Preliminary in vivo pathogenicity assessment in Swiss albino (Mus musculus) mice (n = 3) showed reduced survival at 10⁶ and 10⁸ CFU/mL doses (i.p.), although the study was not statistically powered to determine significance. Integrating the available genomic data with the observed phenotypic characteristics provided a better understanding of the biology of Chromobacterium amazonense.