Existence of Novel Thermophilic Sulfur Oxidizing Bacteria in Hot Spring Sulfur-Turf Microbial Mats in Japan
Hiroyuki YAMAMOTO*a, Yonosuke MAKIb, Akira HIRAISHIc, Kenji KATOd, Hiroshi X. CHIURAe, and Akira SHIMIZUf
a Department of Microbiology, St. Marianna University School of Medicine, Kawasaki 216, Japan
b Laboratory of Biology, Faculty of Humanities and Social Sciences, Iwate University, Morioka 020, Japan
c Department of Ecological Engineering, Toyohashi University of Technology, Toyohashi 441, Japan
d Laboratory of Biology, School of Allied Medical Sciences, Shinshu University, Matsumoto 390, Japan
e Department of Biology, Division of Natural Sciences, International Christian University, Mitaka 181, Japan
f Department of Biology, Faculty of Science, Nara Women's University, Nara 630, Japan
Sulfur-turf microbial mats are macroscopic white filaments or bundles consisting of colorless sulfur bacteria and elemental sulfur particles, and occur in sulfide- containing hot springs in Japan. Phylogenetic analysis of the 16S rDNA clones derived from the sulfur-turf mats showed that their phylotypes were related to the Aquifex-Hydrogenobacter group, the most deeply branching lineage of the domain Bacteria so far described. However, the sulfur-turf phylotypes were distinguishable from any described species of the Aquifex-Hydrogenobacter complex at the order or subdivision level. These results suggest that a novel (hyper) thermophilic bacterium belonging to this new clade predominate in the sulfur-turf microbial mat. The sulfur- turf biomat may be a living model of the pristine ecosystem that existed on primeval Earth and was possibly based on energy production through a sulfur cycle.
