Methylophilus aquaticus sp. nov., a New Aerobic Methylotrophic Bacterium Isolated from a Freshwater Reservoir

Abstract

A new restricted facultative methylotroph, strain LTK^T, isolated from the water of a small freshwater reservoir, was found to carry out the KDPG variant of the ribulose monophosphate pathway of С₁ meta-bolism. The cells of the isolate were aerobic, gram-negative, non-spore-forming, nonmotile rods reproducing by binary fission. The isolate was mesophilic and neutrophilic; it synthesized indole derivatives. Hexadecanoic (C_16:0) and cis-9-hexadecenoic (C_16:1ω7) acids were the major fatty acids, and Q₈ was the major ubiquinone. Phosphatidylethanolamine and phosphatidylglycerol were the dominant phospholipids, while diphosphatidylglycerol was not present. Activities of α-ketoglutarate dehydrogenase and glutamate dehydrogenase were not revealed. Ammonium was assimilated via the enzyme system of the glutamate cycle. The 16S rRNA gene sequence of strain LTK^T exhibited high similarity to those of Methylophilus species: 99.6% to M. leisingeri DM11^T and 99.4% to M. flavus Ship^T. DNA‒DNA homology between strain LTK^T and M. leisingeri DM11^T and M. flavus Ship^T was 47 and 40%, respectively. Based on these data, strain LTK^T was assigned to the new species, Methylophilus aquaticus sp. nov. (= VKM B-3159^T = JCM 32032^T = CCUG 70602^T).