SEASONAL DISTRIBUTIONS OF DOMINANT 16S RIBOSOMAL-RNA-DEFINED POPULATIONS IN A HOT-SPRING MICROBIAL MAT EXAMINED BY DENATURING GRADIENT GEL-ELECTROPHORESIS

Denaturing gradient gel electrophoresis analysis of PCR-amplified 16S rRNA gene segments was used to examine the distributions of bacterial populations within a hot spring microbial mat (Octopus Spring, Yellows tone National Park), Populations at sites along the thermal gradient o f the spring's effluent channel were surveyed at seasonal intervals, N o shift in the thermal gradient was detected, and populations at spati ally or temperature-defined sites exhibited only slight changes over t he annual sampling period, A new cyanobacterial 16S rRNA sequence type was detected at temperatures from 63 to 75 degrees C. A new green non sulfur bacterium-like sequence type was also detected at temperatures from 53 to 62 degrees C. Genetically unique though closely related cya nobacterial and green nonsulfur bacterium-like populations were succes sively distributed along the thermal gradient of the Octopus Spring ef fluent channel. At least two cyanobacterial populations were detected at each site; however, a limited ability to detect some cyanobacterial populations suggests that only dominant populations were observed.