Characterization of a Chromobacterium haemolyticum population from a natural tropical lake

Aim: To study genetic diversity of Chromobacterium haemolyticum isolates recovered from a natural tropical lake. Methods and Results: A set of 31 isolates were recovered from a bacterial freshwater community by conventional plating methods and subjected to genetic and phenotypic characterization. The 16S ribosomal RNA (rRNA) gene phylogeny revealed that the isolates were related most closely with C. haemolyticum. In addition to the molecular data, our isolates exhibited strong β-haemolytic activity, were nonviolacein producers and utilized i-inositol, d-mannitol and d-sorbitol in contrast with the other known chromobacteria. Evaluation of the genetic diversity in the 16S rRNA gene, tRNA intergenic spacers (tDNA) and 16S-23S internal transcribed spacers (ITS) unveiled different levels of genetic heterogeneity in the population, which were also observed with repetitive extragenic palindromic (rep)-PCR genomic fingerprinting using the BOX-AR1 primer. tDNA- and ITS-PCR analyses were partially congruent with the 16S rRNA gene phylogeny. The isolates exhibited high resistance to β-lactamic antibiotics. Conclusion: The population genetic heterogeneity was revealed by 16S rRNA gene sequence, ITS and BOX-PCR analysis. Significance and Impact of the Study: This study provides for the first time an insight into the genetic diversity of phylogenetically close isolates to C. haemolyticum species.