N-192. Transduction as a Mechanism of Microbial Diversity and Evolution in Soda Lakes

H. C. Pinkart1, M. Storrie-Lombardi2;
1Central Washington Univ., Ellensburg, WA, 2Kinohi Res. Inst., Pasadena, CA.

For the past five years haloalkaline Soap Lake (Grant Co., WA) has been the site of an NSF Microbial Observatory project devoted to identifying critical geochemical and microbial characteristics of the monimolimnion sediment and water column. Soap Lake and similar soda lakes are subject to repeated transient periods of extreme evaporation followed by relatively abundant water influx, yet maintain high genetic and metabolic diversity. It has been argued that this repetitive cycle for salinity, alkalinity, and sulfur concentration has been a major driver for prokaryote evolution and diversity. Lateral or horizontal gene transfer (HGT) involves acquisition of entire sets of genes encoding a completely functional metabolic system. It is likely that transduction is responsible for HGT in these systems where system chemistry would limit transformation. This study sought to identify evidence of transduction though characterization of phage integrases present in various transition zones in the Soap Lake. It was found that integrases were most abundant and diverse at transition areas (chemocline, shore) subject to fluxes in oxygen tension and salinity. The presence of these sequences in water column samples and from isolates at these sites makes it likely that transduction is a major mechanism for generation of genetic diversity in soda lake environments.