Community structure of culturable bacteria on surface of Gulkana Glacier, Alaska

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Viable bacterial communities on the surface of Gulkana Glacier (Alaska) were investigated using a cultivation method. Viable bacteria were isolated using R2A, diluted-R2A (DR2A), LB, diluted-LB (DLB), and xylose agar at 4, 15 and 25 °C. The highest number of colony-forming units (CFU) was observed on DR2A agar plates at 4 °C, ranging from 10^4-10^5 CFU mL^<-1>. A collection of 234 morphologically distinct isolates was obtained in total. The glacial snow and ice sample was dominated by Betaproteobacteria (97 isolates) and Gammaproteobacteria (87 isolates). The bacterial communities were examined by amplifying 16S rRNA genes from the isolates, and 34 phylotypes with >99% similarities were obtained. Of these phylotypes, 26 (76.5%) were similar to those phylotypes found in bacteria that were previously recorded from cold environments. Five of the phylotypes appeared in the clone library of a previous independent cultivation study, corresponding with 6.5% in the clone library. Our results suggest that cold environments harbor common phylotypes of culturable bacteria, which could possibly lead to a better understanding of bacterial diversity on glaciers in combination with molecular studies.