Neoroseomonas alba sp. nov., Neoroseomonas nitratireducens sp. nov., Paraoseomonas indoligenes sp. nov and Paraoseomonas baculiformis sp. nov., isolated from the rhizosphere of paddy soil.

Abstract

Four novel Gram-stain negative bacteria, designated as HAJ6T, PWR1T, SG15T and SSH11T, were isolated from the soil sample of paddy fields from Goyang in the Republic of Korea. The isolated strains were aerobic, short-rod or rod shaped, non-sporulating. They grew optimally at 30°C, pH 7 and without additional NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that they belong to the genus of Neoroseomonas and Pararoseomonas and closely relate to Neoroseomonas terrae DS-48T (97.5%; HJA6T), Neoroseomonas rubea MO17T (99.4%; PWR1T), Pararoseomonas pecuniae N75T (97.3%; SG15T) and Pararoseomonas rosea 173-96T (97.8%; SSH11T). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of the isolates with the most closely related strains were 72.9-90.9% and 19.1-42.5%, respectively. The major fatty acids in the isolates were C16:0, C19:0 cyclo ω8c, C18:1 2-OH and summed feature 8 (composed of C18:1 ω7c and/or C18:1 ω6c), and the predominant quinone was ubiquinone 10. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, and other unidentified polar lipids. Based on the draft genome sequences, the genomic DNA G + C content of HAJ6T, PWR1T, SG15T and SSH11T were 69.5%, 72.0%, 70.8% and 69.7%, respectively. All isolates produced indole-3-acetic acid (IAA), a type of plant growth hormone in the presence of L-tryptophan. Physiological and biochemical tests and 16S rRNA sequence analysis clearly revealed that the isolates were novel species belonging to the genus Neoroseomonas and Pararoseomonas. Their proposed names were as follows: Neoroseomonas alba sp. nov. for strain HJA6T (= KACC 21545T = NBRC 114316T), Neoroseomonas nitratireducens sp. nov. for strain PWR1T (= KCTC 82687T = NBRC 114490T), Pararoseomonas indoligenes sp. nov. for strain SG15T (= KCTC 82686T = NBRC 114481T) and Paraoseomonas baculiformis sp. nov. for strain SSH11T (= KCTC 82685T = NBRC 11482T).