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

摘要

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 ℃. The highest number of colony-forming units (CFU) was observed on DR2A agar plates at 4 ℃, 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 Betaproteo-bacteria (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.