Thermomonas fusca sp. nov. and Thermomonas brevis sp. nov., two mesophilic species isolated from a denitrification reactor with poly( -caprolactone) plastic granules as fixed bed, and emended description of the genus Thermomonas

Abstract

Previously, 22 aerobic Gram-negative bacteria were isolated from biofilms growing on granules of the synthetic polyester poly(ε-caprolactone); the granules were used as a fixed bed in a denitrification reactor. All the strains showed similar fatty acid profiles. The 16S rRNA gene sequences of five strains were phylogenetically related to Thermomonas spp. Repetitive extragenic palindromic DNA-PCR (REP-PCR) fingerprinting revealed four groups, and DNA hybridizations between representative strains showed that the strains belonged to two new species within the genus Thermomonas, for which the names Thermomonas fusca (type strain LMG 21737^T=DSM 15424^T) and Thermomonas brevis (type strain LMG 21746^T=DSM 15422^T) are proposed. Both species are able to grow at low temperatures, but not at 50 °C, and are non-haemolytic. Both species can be differentiated by several other phenotypic features from earlier described species of the genus Thermomonas. Cell extracts contain mainly branched fatty acids, with C_15 : 0 iso, C_17 : 1 iso ω9c, C_11 : 0 iso 3OH and C_11 : 0 iso as main constituents. The G+C content of the DNA of the novel species is between 67·6 and 68·7 mol%.