Corallococcus caeni sp. nov., a novel myxobacterium isolated from activated sludge.

Two myxobacterial strains (KH5-1 and NO1) were isolated from the activated sludge tanks treating municipal sewage wastewater in Japan. These strains were recognised as myxobacteria based on their phenotypic characteristics of swarming colonies and fruiting bodies. Phylogenetic analyses using the 16S rRNA gene revealed that strains KH5-1 and NO1 were affiliated with the genus Corallococcus, with the closest neighbours being Corallococcus exercitus AB043A (99.77% and 99.84%, respectively). Genome comparisons using orthologous average nucleotide identity (orthoANI) and digital DNA-DNA hybridisation similarity (dDDH) with strains KH5-1 and NO1 and their phylogenetically close relatives in Corallococcus spp. were below the thresholds. The major cellular fatty acids of strains KH5-1 and NO1 were iso-C (31.9%, 30.0%), summed feature 3 (comprising Cω7c and/or Cω6c) (20.2%, 17.7%), and iso-C (12.1%, 14.8%), and the major respiratory quinone was found to be menaquinone (MK)-8. Based on the phenotypic, chemotaxonomic, and phylogenetic evidence, strains KH5-1 and NO1 represent a new species in the genus Corallococcus, for which the proposed name is Corallococcus caeni sp. nov. The type strain is KH5-1 (= NCIMB 15510 = JCM 36609).