Cultivation of Heterotrophic Marine Bacteria Along the Pacific Coast of North America

Environmental factors can vary geographically and seasonally along the Pacific Coast which may affect abundance and survival of marine heterotrophic bacteria. This project involves isolation of cultures from seawater samples collected from beaches from Baja California to Northern Oregon (January - August 2010). Huntington Beach monthly samples were collected for comparison (2010 - 2012). It was hypothesized that heterotrophic marine bacteria would display significant differences in diversity and abundance between samples taken in cold (8.6-14.8 °C) and warm (15-22.5 °C) waters (geographic shifts) and between samples (seasonal shifts). Bacteria were enumerated via serial dilution (MPNs) in marine broth followed by streak plate isolation.  There was no significant  bacterial abundance difference between seasons after comparison of winter and summer MPNs (unpaired t-test, p-value 0.057). Within the seasons, there were no strong relationships between temperature and abundance (winter R² = 0.005, summer R² = 0.127). Isolated cultures were characterized by gram staining and light microscopy. Ongoing experiments may identify shifts in the diversity (community structure) across geographical boundaries or seasons. Characterization and identification of heterotrophic marine bacteria indicate a diverse assemblage of isolated cultures and we are currently identifying them by nucleic acid extractions, PCR amplification, and sequencing of 16S rRNA genes. Preliminary analysis shows diverse groups including Gamaproteobacteria, Flavobacteria, Actinobacteria, Alphaproteobacteria, and Bacillus spp., with some evidence of seasonal differences. Salinity tolerance experiments were done using treatments of 3.5%, 15%, and 23% salinity. The salinity experiment results suggest marine heterotrophic bacteria grow in 3.5% and not in higher salinity concentrations.