K-058. Validation of Physiological Properties of Shewanella spp. Based on Phylogenetics and Genomics

Y. wang1, J. Kan1, T. V. Karpinets2, A. Obraztsova1, K. Nealson1;
1Univ. of Southern California, Los Angeles, CA, 2Univ. of Tennessee, Oak Ridge, TN.

Background: Members of genus Shewanella have been isolated from various environmental conditions, and been recognized for utilizing a diverse array of electron acceptors, including solid phase iron and manganese oxides. These special physiological characteristics make it an attractive model for linking ecophysiology of the organism to its genotype. Nineteen sequenced strains of Shewanella spp provide an opportunity for employing bioinformatics to predict phenotypic traits of the species from their genomic content, but still require experimental validations. Our objective of this study was to compare physiological properties among Shewanella spp and to provide comprehensive experimental data to validate or to discover the linkage between ecophysiology of the species/strains and their genetic characteristics. Methods: We tested the effects of salinity and temperature, and the utilization of a variety of carbon sources on 13 sequenced strains in SF minimal medium. The optical density readings (OD600) were recorded to monitor the bacterial growth. An OD-based scoring system was developed to quantify the phenotypic traits of the species and to compare them with the 16S rRNA gene based phylogeny and ITS-DGGE profiles. Results: This study confirmed environmental versatility of the genus and bioinformatic predictions on carbon source utilization. Significant differences in the adaptability of Shewanella to temperature and salinity exist on both species and strain levels. Ribosomal RNA gene-based phylogeny provided useful information about evolutionary relationship among species/strains, and ITS-DGGE showed a higher resolution compared with 16s rRNA; However, but both offered limited predictions on the physiological features. Experimental results verified most of the predicted metabolic pathways of various carbon sources, while BiologTM data were inadequate in phenotypic characterization. Conclusion: Physiological properties vary among Shewanella species and strains, regardless the isolation environments. Culture-based experiments provide the most comprehensive information to validate computational predictions of phenotypic traits in bacterial species/strains.