Description of Fervidibacillus gen. nov. with Two Species, Fervidibacillus albus sp. nov., and Fervidibacillus halotolerans sp. nov., Isolated from Tidal Flat Sediments and Emendation of Misclassificed Taxa in the Genus Caldibacillus.

Two Gram-stain-positive, motile, endospore-forming, facultatively anaerobic strains, designated MEBiC13591 ^T and MEBiC13594 ^T , were isolated from tidal flat sediment of the Incheon City on the west coast of Korea. Growth of both novel strains was observed at pH 5-9 (optimum, pH 7-7.5), and in 0-8% NaCl (optimum, 2% for MEBiC13591 ^T and 3% for MEBiC13594 ^T ). Strains MEBiC13591 ^T and MEBiC13594 ^T grew optimally at 50 °C, (37.5-56.1 °C) and 44 °C (20.7-50.7 °C), respectively. The main cellular fatty acids of strain MEBiC13591 ^T were iso-C _15: 0 , anteiso-C _15: 0 , iso-C _16: 0 , iso-C _17: 0 and anteiso-C _17: 0 , while those for strain MEBiC13594 ^T were C _14: 0 , iso-C _14: 0 , iso-C _15: 0 , anteiso-C _15: 0 and C _16: 0 . In both taxa, the major isoprenoid was MK-7. The genomic DNA G + C contents were 34.1 and 37.0 mol% for MEBiC13591 ^T and MEBiC13594 ^T , respectively. A 16S rRNA gene sequence analysis revealed that the novel strains showed high similarity with members of the genera Aeribacillus (95.0%) and Caldibacillus (93.5-94.5%); however, showed lower than 90% with Caldibacillus debilis Tf ^T . Phylogenetic and Phylogenomic analysis revealed that two novel strains comprised distinct phyletic line with members formerly assigned to Caldibacillus. Based on genomic indices, such as AAI and ANI, members formerly affiliated with Caldibacillus and Bacillus as well as the novel strains should be classified into five independent genera. Based on the phenotypic, genomic and biochemical data, strains MEBiC13591 ^T and MEBiC13594 ^T represent two novel species in the novel genus, for which the names Fervidibacillus albus gen. nov., sp. nov. (MEBiC13591 ^T [= KCCM 43317 ^T  = KCTC 43181 ^T  = JCM 33662 ^T  = MCCC 1K04565 ^T ]), and Fervidibacillus halotolerans sp. nov. (MEBiC13594 ^T [= KCTC 43182 ^T  = JCM 34001 ^T ]) are proposed. Three additional genera Caldifermentibacillus, Palidibacillus, and Perspicuibacillus are also proposed by reclassification of the several species with valid names that formerly affiliated with the genera Caldibacillus.
(© 2023. The Author(s), under exclusive licence to Microbiological Society of Korea.)