Azohydromonas caseinilytica sp. nov., a Nitrogen-Fixing Bacterium Isolated From Forest Soil by Using Optimized Culture Method

Abstract

A bacterial strain, designated strain G-1-1-14(T), was isolated from Kyonggi University forest soil during a study of previously uncultured bacterium. The cells of strain G-1-1-14(T) were motile by means of peritrichous flagella, Gram-stain-negative, rod-shaped, and able to grow autotrophically with hydrogen and fix nitrogen. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain G-1-1-14(T) belonged to the genus Azohydromonas. The closest species of strain G-1-1-14(T) were Azohydromonas ureilytica UCM-80(T) (98.4% sequence similarity), Azohydromonas lata IAM 12599(T) (97.5%), Azohydromonas riparia UCM-11(T) (97.1%), and Azohydromonas australica IAM 12664(T) (97.0%). The genome of strain G-1-1-14(T) was 6,654,139 bp long with 5,865 protein-coding genes. The genome consisted of N-2-fixing genes (nifH) and various regulatory genes for CO2 fixation and H-2 utilization. The principal respiratory quinone was ubiquinone-8, and the major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, and phosphatidylglycerol. The major fatty acids were summed feature 3 (iso-C-15(:)0 2-OH and/or C-16(:)1 omega 7c), C-16(:)0, summed feature 8 (C-18(:)1 omega 7c and/or C-18(:)1 omega 6c), and cyclo-C-17(:)0. The DNA G + C content was 69.9%. The average nucleotide identity (OrthoANI), in silico DNA-DNA hybridization (dDDH), and conventional DDH relatedness values were below the species demarcation values for novel species. Based on genomic, genetic, phylogenetic, phenotypic, and chemotaxonomic characterizations, strain G-1-1-14(T) represents a novel species within the genus Azohydromonas, for which the name Azohydromonas caseinilytica sp. nov. is proposed. The type strain is G-1-1-14(T) (= KACC 21615(T) = NBRC 114390(T)).