울릉분지에 서식하고 있는 Ultramicrobacteria의 분리 동정 및 군집 구조 분석

Abstract

The size of bacteria in marine environment is various. The smallest sized microbe is called ultramicrobacteria (UMB) which have cell volume less than 0.1μm3. The size of these tiny microorganisms challenges views about the minimal size of a living cell, thus we tried to discriminate real UMB by High-throughput cultivation (HTC) method.First, approximately 200 liters of sea water sample were successively filtered through 0.2 and 0.1μm-pore size filters to analyze the microbial diversity. At the same time UMB samples were incubated for 3-6month at 15˚C by HTC-extinction method. A total 303 clones of bacterial group were derived from 5 major lineages, α-, β-, γ- and δ-Proteobacteria, and Chloroflexales. γ-Proteobacteria represents a dominant bacterial group in the fraction of non-UMB and UMB by 85% and 78%, respectively. Microbial isolate by HTC method represent that 384 isolates were retrieved from 240 samples and they mostly affiliated into 2 major lineages, γ and α-Proteobacteria, by 73.8% and 25.2%, respectively. Among the conditions for cultivation, most various isolate was detected by seawater medium supplemented with Vitamin B12 solution. The result, however, implies that novel UMB-isolates could not be cultivated as many as the number of novel clones. It likely seems that UMB comprises of unique microbial community which is hardly cultivated. [Supported by MEGRC]