The temperature range for strain Sp-1 was 5–45 °C, with the optimum at 35 °C;

pH range was from 5.5 to 8, with the optimum at 6.2. The cells grew at NaCl concentrations from 0% to 2.5%. FeS, FeSO4 and FeCO3 were used as Fe(II) sources for lithotrophic growth. The strain was unable to use , , S0, and Fe(OH)3 as electron acceptors for anaerobic growth. H2 was not used as an electron donor in mineral media with nitrates. Strain Sp-1 used acetate, succinate, citrate, lactate, malate, fumarate, propionate, pyruvate, butyrate, propanol, glycerol, yeast extract and peptone for organotrophic growth. Weak growth occurred on amino acids alanine, histidine, aspartate and glutamate. Sugars, oxalate, formate, benzoate, ethanol, butanol, proline, leucine, asparagine, glutamine, phenylalanine, tryptophan and casein hydrolysate were not utilized. Ammonium salts, , N2O, urea, yeast extract and peptone were Romidepsin concentration used as nitrogen sources. , histidine, aspartate and casein hydrolysate were not used. The major fatty acids in the cells of strain Sp-1 are as follows: 11-octadecenoic Apoptosis inhibitor (18 : 1ω7c), 31.1%; cyclopropane-nonadecanoic (19 : 0 cyc), 27%;

and hexadecanoic acids (16 : 0), 15.9%. Among the polar lipids of the cell membranes, phosphatidylethanolamine and two unidentified aminophospholipids were revealed. Ubiquinone Q–10 was the major respiratory lipoquinone. The strain was sensitive to amikacin, lincomycin, neomycin, polymyxin, streptomycin, rifampicin

and nalidixic acid. The strain was resistant to ampicillin, bacitracin, vancomycin, gentamycin, kanamycin, mycostatin, novobiocin, penicillin and tetracycline. Phylogenetic analysis based on 16S rRNA gene sequence comparison acetylcholine showed that novel isolate Sp-1 was closely related to members of two different orders Sneathiellales and Rhodospirillales within the class Alphaproteobacteria (Table 1). A neighbour-joining tree (Fig. 2) revealed that strain Sp-1 formed a separate branch within the order Sneathiellales, showing 80% of bootstrap value. Although strain Sp-1 could use O2 as an electron acceptor for Fe(II) oxidation under microaerobic conditions, the physiology and biochemistry of Fe(II) oxidation were investigated in anaerobic cultures to avoid the competition with the processes of rapid Fe(II) oxidation in the experiments. Biochemical analysis of the enzymes involved in the chain of reactions of nitrate reduction coupled to Fe(II) oxidation revealed significant differences in their activity. For example, the activity of nitrate reductase of strain Sp-1 was 46 nmol (min mg protein)−1, while the nitrite reductase activity was 30 times lower and did not exceed 1.4 nmol (min mg protein)−1. Unbalanced enzymatic activities in the chain of nitrate reduction reactions resulted in the accumulation of equimolar nitrite concentrations (up to 4.