Identification and Characterization of Bacterial Isolates from Spring Lake, Texas

Abstract

Eight bacterial isolates were retrieved from a biofilm during a homoserine lactone recruitment experiment in Spring Lake, Texas. On the basis of morphology, cellular fatty acid analysis, and 16S-23S intergenic transcribed spacer region sequencing, seven of the eight isolates were identified as Chromobacterium violaceum. A polyphasic approach to taxonomy was used to characterize the eighth, potentially novel isolate, A62-14B. The isolate was identified as a gamma proteobacterium, sharing 95-96% 16S rRNA gene sequence similarity to the genera Rheinheimera and Alishewanella. The 16S rRNA gene sequence data allowed for a novel species designation for isolate A62-14B, but did not resolve genus level relationships. Fatty acid analysis supported an association at the genus level of isolate A62-14B with Rheinheimera. Further physiological and morphological characterization via biochemical tests and electron microscopy revealed that the isolate shared a variety of key phenotypic traits with both related genera. It was concluded that isolate A62-14B represented a novel species, but a generic designation could not be assigned. The characterization of this organism revealed the short comings currently in bacterial taxonomy, including issues with a lack of taxon sampling, inability to compare and fully characterize unculturable organisms, and the lack of stringent control over experimental conditions for the comparison of organisms.