Fervidicella metallireducens gen. nov., sp. nov., a thermophilic, anaerobic bacterium from geothermal waters

Abstract

A strictly anaerobic, thermophilic bacterium, designated strain AeBT, was isolated from microbial mats colonizing a run-off channel formed by free-flowing thermal water from a bore well (registered number 17263) of the Great Artesian Basin, Australia. Cells of strain AeBT were slightly curved rods (2.5-6.0x1.0 孩 that stained Gram-negative and formed spherical terminal to subterminal spores. The strain grew optimally in tryptone-yeast extract-Casamino acids medium at 50 à(range 37-55 é and pH 7 (range pH 5-9). Strain AeBT grew poorly on yeast extract (0.2 %) and tryptone (0.2 %) as sole carbon sources, which were obligately required for growth on other energy sources. Growth of strain AeBT increased in the presence of various carbohydrates and amino acids, but not organic acids. End products detected from glucose fermentation were ethanol, acetate, CO2 and H2. In the presence of 0.2 % yeast extract, iron(III), manganese(IV), vanadium(V) and cobalt(III) were reduced, but not sulfate, thiosulfate, sulfite, elemental sulfur, nitrate or nitrite. Iron(III) was also reduced in the presence of tryptone, peptone, Casamino acids and amyl media (Research Achievement), but not starch, xylan, chitin, glycerol, ethanol, pyruvate, benzoate, lactate, acetate, propionate, succinate, glycine, serine, lysine, threonine, arginine, glutamate, valine, leucine, histidine, alanine, aspartate, isoleucine or methionine. Growth was inhibited by chloramphenicol, streptomycin, tetracycline, penicillin, ampicillin and NaCl concentrations >2 %. The DNA G+C content was 35.4ᱠmol%, as determined by the thermal denaturation method. 16S rRNA gene sequence analysis indicated that strain AeBT is a member of the family Clostridiaceae, class Clostridia, phylum 'Firmicutes', and is positioned approximately equidistantly between the genera Sarcina, Anaerobacter, Caloramator and Clostridium (16S rRNA gene similarity values of 87.8-90.9 %). On the basis of 16S rRNA gene sequence comparisons and physiological characteristics, strain AeBT is considered to represent a novel species in a new genus, for which the name Fervidicella metallireducens gen. nov., sp. nov. is proposed; the type strain is AeBT (=JCM 15555T=KCTC 5667T).