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 lomoniglob

Two bacterial strains, designated D2-102^T and MBA3-11^T, were isolated from mangrove surface sediment and cordgrass <i>Spartina alterniflora</i> 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 <i>Actomonas aquatica</i> WL0086^T of 97.6-98.4%, followed by <i>Synoicihabitans lomoniglobus</i> LMO-M01^T of 95.5-95.7%. Phylogeny of the 16S rRNA gene placed the two strains into two novel monophyletic branches neighboured by <i>Actomonas</i> and <i>Synoicihabitans</i> of the phylum <i>Verrucomicrobiota</i>. The digital DNA-DNA hybridization and average nucleotide identity among strain D2-102^T, strain MBA3-11^T, <i>A. aquatica</i> WL0086^T and <i>S. lomoniglobus</i> LMO-M01^T 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 C_16:0, iso-C_14:0 and anteiso-C_15:0. The major polar lipids of the two strains included diphosphatidylglycerol, phosphatidylglycerol and two phospholipids, while phosphatidylethanolamine was only present in strain MBA3-11^T. Based on the polyphasic taxonomic study, strains D2-102^T and MBA3-11^T represented two novel species, and thus, <i>Actomonas mangrovi</i> sp. nov., and <i>Actomonas spartinae</i> sp. nov. were proposed with type strain D2-102^T (=MCCC 1K09973^T=KCTC 102446^T) and type strain MBA3-11^T (=MCCC 1K09525^T=KCTC 102445^T), respectively. Furthermore, based on the phylogeny of the 16S rRNA gene, genomic, phenotypic (including chemotaxonomic) analyses, <i>S. lomoniglobus</i> Ahmad <i>et al</i>. 2024 should be transferred to the genus <i>Actomonas</i> as <i>Actomonas lomoniglobus</i> comb. nov. This study expanded the bacterial diversity and ecological distribution of the genus <i>Actomonas</i>.