Phylogenetic and enzymatic diversity of deep subseafloor aerobic microorganisms in organics- and methane-rich sediments off Shimokita Peninsula.
"A meta-enzyme approach" is proposed as an ecological enzymatic method to explore the potential functions of microbial communities in extreme environments such as the deep marine subsurface. We evaluated a variety of extra-cellular enzyme activities of sediment slurries and isolates from a deep subseafloor sediment core. Using the new deep-sea drilling vessel "Chikyu", we obtained 365 m of core sediments that contained approximately 2% organic matter and considerable amounts of methane from offshore the Shimokita Peninsula in Japan at a water depth of 1,180 m. In the extra-sediment fraction of the slurry samples, phosphatase, esterase, and catalase activities were detected consistently throughout the core sediments down to the deepest slurry sample from 342.5 m below seafloor (mbsf). Detectable enzyme activities predicted the existence of a sizable population of viable aerobic microorganisms even in deep subseafloor habitats. The subsequent quantitative cultivation using solid media represented remarkably high numbers of aerobic, heterotrophic microbial populations (e.g., maximally 4.4x10(7) cells cm(-3) at 342.5 mbsf). Analysis of 16S rRNA gene sequences revealed that the predominant cultivated microbial components were affiliated with the genera Bacillus, Shewanella, Pseudoalteromonas, Halomonas, Pseudomonas, Paracoccus, Rhodococcus, Microbacterium, and Flexibacteracea. Many of the predominant and scarce isolates produced a variety of extra-cellular enzymes such as proteases, amylases, lipases, chitinases, phosphatases, and deoxyribonucleases. Our results indicate that microbes in the deep subseafloor environment off Shimokita are metabolically active and that the cultivable populations may have a great potential in biotechnology.
Kobayashi
Tohru
T
Extremobiosphere Research Center of Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima, Yokosuka, 237-0061, Japan. kobayashit@jamstec.go.jp
Koide
Osamu
O
Mori
Kozue
K
Shimamura
Shigeru
S
Matsuura
Takae
T
Miura
Takeshi
T
Takaki
Yoshihiro
Y
Morono
Yuki
Y
Nunoura
Takuro
T
Imachi
Hiroyuki
H
Inagaki
Fumio
F
Takai
Ken
K
Horikoshi
Koki
K
D001419:Bacteria / Q000201:enzymology; D004798:Enzymes / Q000235:genetics*; D005798:Genes, Bacterial; D014644:Genetic Variation; D019015:Geologic Sediments; D007564:Japan; D008697:Methane / Q000737:chemistry*; D008957:Models, Genetic; D009930:Organic Chemicals; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012623:Seawater / Q000382:microbiology
D004798:Enzymes; D009930:Organic Chemicals; D012336:RNA, Ribosomal, 16S; D008697:Methane