title: Dynamic transition of chemolithotrophic sulfur-oxidizing bacteria in response to amendment with nitrate in deposited marine sediments.
abstract: Although environmental stimuli are known to affect the structure and function of microbial communities, their impact on the metabolic network of microorganisms has not been well investigated. Here, geochemical analyses, high-throughput sequencing of 16S rRNA genes and transcripts, and isolation of potentially relevant bacteria were carried out to elucidate the anaerobic respiration processes stimulated by nitrate (20 mM) amendment of marine sediments. Marine sediments deposited by the Great East Japan Earthquake in 2011 were incubated anaerobically in the dark at 25∘C for 5 days. Nitrate in slurry water decreased gradually for 2 days, then more rapidly until its complete depletion at day 5; production of N2O followed the same pattern. From day 2 to 5, the sulfate concentration significantly increased and the sulfur content in solid-phase sediments significantly decreased. These results indicated that denitrification and sulfur oxidation occurred simultaneously. Illumina sequencing revealed the proliferation of known sulfur oxidizers, i.e., Sulfurimonas sp. and Chromatiales bacteria, which accounted for approximately 43.5% and 14.8% of the total population at day 5, respectively. These oxidizers also expressed 16S rRNA to a considerable extent, whereas the other microorganisms, e.g., iron(III) reducers and methanogens, became metabolically active at the end of the incubation. Extinction dilution culture in a basal-salts medium supplemented with sulfur compounds and nitrate successfully isolated the predominant sulfur oxidizers: Sulfurimonas sp. strain HDS01 and Thioalkalispira sp. strain HDS22. Their 16S rRNA genes showed 95.2-96.7% sequence similarity to the closest cultured relatives and they grew chemolithotrophically on nitrate and sulfur. Novel sulfur-oxidizing bacteria were thus directly involved in carbon fixation under nitrate-reducing conditions, activating anaerobic respiration processes and the reorganization of microbial communities in the deposited marine sediments.
authors.affiliation: Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.
authors.forename: Tomo
authors.initials: T
authors.lastname: Aoyagi
authors.affiliation: Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Kimura
authors.affiliation: Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.
authors.forename: Namiha
authors.initials: N
authors.lastname: Yamada
authors.affiliation: Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Navarro
authors.affiliation: Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology Sapporo, Japan.
authors.forename: Hideomi
authors.initials: H
authors.lastname: Itoh
authors.affiliation: Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ogata
authors.affiliation: Institute of Industrial Science, The University of Tokyo Tokyo, Japan.
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Sakoda
authors.affiliation: Graduate School of Agriculture, Tokyo University of Agriculture and Technology Tokyo, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Katayama
authors.affiliation: Department of Food and Environmental Sciences, Faculty of Science and Engineering, Ishinomaki Senshu University Ishinomaki, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Takasaki
authors.affiliation: Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hori
keywords: environmental stimuli; high-throughput sequencing; marine sediment; sulfur-oxidizing bacteria; the Great East Japan Earthquake in 2011