Neobacillus rhizophilus sp. nov. and Neobacillus citreus sp. nov., isolated from the citrus rhizosphere soil.

Abstract

Two Gram-staining positive strains, FJAT-49825T and FJAT-50051T were isolated from a citrus rhizosphere soil sample. Strains FJAT-49825T and FJAT-50051T showed the highest 16S rRNA gene sequence similarity with the type strain of Neobacillus cucumis (98.4-98.5%). The 16S rRNA gene sequence similarity between strains FJAT-49825T and FJAT-50051T was 99.8%. Strain FJAT-49825T optimally grew at 35°C, pH 6.0 in the absence of NaCl while strain FJAT-50051T grew at 40°C, pH 7.0 and in presence of 2% NaCl (w/v). Both strains contained meso-2,6-diaminopimelic acid as the cell-wall diamino acid. The respiratory quinone of strains FJAT-49825T and FJAT-50051T was MK-7. The polar lipids of strain FJAT-49825T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified aminolipid and unidentified lipid whereas strain FJAT-50051T polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified phospholipid and unidentified lipid. The major fatty acids (> 10%) in both strains were iso-C15:0 and anteiso-C15:0. The genomic DNA G + C content of strains FJAT-49825T and FJAT-50051T were 40.8 and 41.1%, respectively. The average nucleotide identity and digital DNA-DNA hybridization value between strains FJAT-49825T and FJAT-50051T and with other members of the genus Neobacillus were lower than the cut-off value (95-96/70%) for interspecies identity. Based on the results, strains FJAT-49825T and FJAT-50051T represent two novel species of the genus Neobacillus, for which the names Neobacillus rhizophilus sp. nov. and Neobacillus citreus sp. nov. are proposed. The type strains are FJAT-49825T (= GDMCC 1.2592T = JCM 34834T) and FJAT-50051T (= GDMCC 1.2593T = JCM 34835T).