Fe-Si biominerals in the Vilyuchinskie hot springs, Kamchatka Peninsula, Russia

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°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-μm 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. [Int Microbiol 2004; 7(3):193–198

05 Belkova F-RG.qxp

Summary. 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°C and Na-Ca-HCO 3 -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-µm 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. [Int Microbiol 2004; 7(3):193-198

Comparison of bacterial diversity and species composition in three endemic Baikalian sponges

Baikalian sponges are unique organisms with many species harboring symbiotic microbes that produce novel bioactive compounds. To investigate bacterial diversity of three species of Baikalian sponges, specimens of Lubomirskia baicalensis, Baikalospongia intermedia and Swartschewskia papyracea collected from Lake Baikal were processed by pyrosequencing. We found differences in the species composition and diversity in bacteria among these sponges. Cyanobacteria accounted for the highest proportion and the second group was Proteobacteria in three sponges. The bacterial communities in B. intermedia and L. baicalensis were highly similar but less similar to the bacterial community associated with S. papyracea. Diversity of the bacterial community in S. papyracea was higher than in L. baicalensis and B. intermedia. In particular, the relative abundance of Actinobacteria was higher in S. papyracea. Bacterial species in phyla Acidobacteria and Gemmatimonadetes were only found in S. papyracea.Sponge-symbionts have the ecological important functions and produce a diverse pharmacological metabolites. Bacteria associated with freshwater sponges have been much less studied. Our study describes diversity of bacteria in Baikalian sponges, specially, those of S. papyracea for the first time. We provide additional knowledge into freshwater sponge-associated microbiota