Description of Actomonas mangrovi sp. nov. and Actomonas spartinae sp. nov., isolated from mangrove surface sediment and cordgrass root, respectively, and transfer of Synoicihabitans lomoniglobus Ahmad et al. 2024 to Actomonas as Actomonas lomoniglobus comb. nov.

Two bacterial strains, designated D2-102T and MBA3-11T, were isolated from mangrove surface sediment and cordgrass Spartina alterniflora root, respectively, using the dilution-to-extinction method. The two strains were Gram-stain-negative, coccus-shaped, non-motile, catalase-positive and oxidase-positive. The 16S rRNA genes of the two strains had the highest sequence similarities with Actomonas aquatica WL0086T of 97.6-98.4%, followed by Synoicihabitans lomoniglobus LMO-M01T of 95.5-95.7%. Phylogeny of the 16S rRNA gene placed the two strains into two novel monophyletic branches neighboured by Actomonas and Synoicihabitans of the phylum Verrucomicrobiota. The digital DNA-DNA hybridization and average nucleotide identity among strain D2-102T, strain MBA3-11T, A. aquatica WL0086T and S. lomoniglobus LMO-M01T were 19.5-22.8%, and 74.6-79.7%, respectively. The respiratory quinones of the two strains were both menaquinone-7. The major fatty acids (>10%) of the two strains were C16:0, iso-C14:0 and anteiso-C15:0. The major polar lipids of the two strains included diphosphatidylglycerol, phosphatidylglycerol and two phospholipids, while phosphatidylethanolamine was only present in strain MBA3-11T. Based on the polyphasic taxonomic study, strains D2-102T and MBA3-11T represented two novel species, and thus, Actomonas mangrovi sp. nov., and Actomonas spartinae sp. nov. were proposed with type strain D2-102T (=MCCC 1K09973T=KCTC 102446T) and type strain MBA3-11T (=MCCC 1K09525T=KCTC 102445T), respectively. Furthermore, based on the phylogeny of the 16S rRNA gene, genomic, phenotypic (including chemotaxonomic) analyses, S. lomoniglobus Ahmad et al. 2024 should be transferred to the genus Actomonas as Actomonas lomoniglobus comb. nov. This study expanded the bacterial diversity and ecological distribution of the genus Actomonas.