Cellvibrio diazotrophicus sp. nov., a nitrogen-fixing bacteria isolated from the rhizosphere of salt meadow plants and emended description of the genus Cellvibrio

Abstract

Two Gram-reaction-negative, aerobic, nitrogen-fixing, rod-shaped bacteria, designated strains E20 and E50T, were isolated from the rhizosphere of salt meadow plants Plantago winteri and Hordeum secalinum, respectively, near Münzenberg, Germany. Based on the 16S rRNA gene sequence analysis both strains E20 and E50T are affiliated with the genus Cellvibrio , sharing the highest similarity with Cellvibrio gandavensis LMG 18551T (96.4 %) and (97.1 %), respectively. Strains E20 and E50T were oxidase and catalase-positive, grew at a temperature range between 16 and 37 °C and in the presence of 0–5 % NaCl (w/v). The DNA G+C contents were 52.1 mol% (E20) and 51.6 mol% (E50T). Major fatty acids of strains E20 and E50T were summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH), C16 : 0, C18 : 1ω7c, C12 : 0, C18 : 0 and C12 : 0 3-OH. The DNA–DNA relatedness of the strains to Cellvibrio gandavensis LMG 18551T was 39 % for strain E20 and 58 % for strain E50T. The nitrogen fixation capability of strains E20 and E50T was confirmed by the acetylene reduction assay. On the basis of our polyphasic taxonomic study, strains E20 and E50T represent a novel species of the genus Cellvibrio , for which the name Cellvibrio diazotrophicus is proposed. The type strain of Cellvibrio diazotrophicus is E50T ( = LMG 27267T = KACC 17069T). An emended description of the genus Cellvibrio is proposed based on the capability of fixing nitrogen and growth in presence of up to 5 % NaCl (w/v).