title: Fe-Si biominerals in the Vilyuchinskie hot springs, Kamchatka Peninsula, Russia.
abstract: The micromorphological structure of microbial mats (biomats) from the hot springs of the Vilyuchinskaya hydrothermal system, Kamchatka Peninsula, Russia, were investigated. The Vilyuchinskie hot springs had a discharge temperature of 55-56 degrees C and Na-Ca-HCO3-type waters rich in silicic and boric acids. Water and biomats had high concentrations of Fe, Mn, Sr, and As. Enumeration of total bacterial abundance (TBA) demonstrated a low density of bacterial populations. However, the fractions of metabolically active bacteria and respiring iron-oxidizing bacteria in the hot-spring water were high, comprising 68 and 21% of TBA, respectively. Scanning electron microscopy equipped with an energy dispersive X-ray spectrometer (SEM-EDX) showed that unicellular rod-shaped bacteria about 5-microm long predominated in the brown biomats. The mineral capsules of these bacteria contained large amounts of Fe and Si. Extracellular and intracellular particles were observed by transmission electron microscopy. Fe-oxidizing bacteria were isolated from the biomats on agar plates with selective medium. Therefore, it can be concluded that microorganisms inhabiting the biomats of the Vilyuchinskie hot springs are essential for the deposition of Fe-minerals at neutral pH.
authors.affiliation: Graduate School of Science and Technology, Kanazawa University, Japan. belkovan@mail.ru
authors.forename: Natalia L
authors.initials: NL
authors.lastname: Belkova
authors.forename: Julia R
authors.initials: JR
authors.lastname: Zakharova
authors.forename: Kazue
authors.initials: K
authors.lastname: Tazaki
authors.forename: Viktor M
authors.initials: VM
authors.lastname: Okrugin
authors.forename: Valentina V
authors.initials: VV
authors.lastname: Parfenova
mesh_terms: D000838:Anions; D002412:Cations; D045482:Hot Springs / Q000737:chemistry* / Q000592:standards; D007501:Iron / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis; D012426:Russia; D012825:Silicon / Q000032:analysis*
chemical_list: D000838:Anions; D002412:Cations; D009930:Organic Chemicals; D007501:Iron; D012825:Silicon