Predatory Organisms with Untapped Biosynthetic Potential: Descriptions of Novel Corallococcus Species C. aberystwythensis sp. nov., C. carmarthensis sp. nov., C. exercitus sp. nov., C. interemptor sp. nov., C. llansteffanensis sp. nov., C. praedator sp. nov., C. sicarius sp. nov., and C. terminator sp. nov

Corallococcus spp. are common soil-dwelling organisms which kill and consume prey microbes through the secretion of antimicrobial substances. Two species of Corallococcus have been described previously (Corallococcus coralloides and Corallococcus exiguus). A polyphasic approach, including biochemical analysis of fatty acid methyl esters, substrate utilization, and sugar assimilation assays, was taken to characterize eight Corallococcus species strains and the two type strains. The genomes of all strains, including that of C. exiguus DSM 14696T (newly reported here), shared an average nucleotide identity below 95% and digital DNA-DNA hybridization scores of less than 70%, indicating that they belong to distinct species. In addition, we characterized the prey range and antibiotic resistance profile of each strain, illustrating the diversity of antimicrobial activity and, thus, the potential for drug discovery within the Corallococcus genus. Each strain gave a distinct profile of properties, which together with their genomic differences supports the proposal of the eight candidate strains as novel species. The eight candidates are as follows: Corallococcus exercitus sp. nov. (AB043AT ^T DSM 108849 ^T NBRC 113887 ^T), Corallococcus interemptor sp. nov. (AB047A ^T DSM 108843 ^T NBRC 113888 ^T), Corallococcus aberystwythensis sp. nov. (AB050A ^T DSM 108846 ^T NBRC 114019 ^T), Corallococcus praedator sp. nov. (CA031B ^T DSM 108841 ^T NBRC 113889 ^T), Corallococcus sicarius sp. nov. (CA040B ^T DSM 108850 ^T NBRC 113890 ^T), Corallococcus carmarthensis sp. nov. (CA043D ^T DSM 108842 ^T NBRC 113891 ^T), Corallococcus llansteffanensis sp. nov. (CA051B ^T DSM 108844 ^T NBRC 114100 ^T), and Corallococcus terminator sp. nov. (CA054A ^T DSM 108848 ^T NBRC 113892 ^T). Corallococcus is a genus of predators with broad prey ranges, whose genomes contain large numbers of gene clusters for secondary metabolite biosynthesis. The physiology and evolutionary heritage of eight Corallococcus species strains were characterized using a range of analyses and assays. Multiple metrics confirmed that each strain belonged to a novel species within the Corallococcus genus. The strains exhibited distinct patterns of drug resistance and predatory activity, which mirrored their possession of diverse sets of biosynthetic genes. The breadth of antimicrobial activities observed within the Corallococcus genus highlights their potential for drug discovery and suggests a previous underestimation of both their taxonomic diversity and biotechnological potential. Taxonomic assignment of environmental isolates to novel species allows us to begin to characterize the diversity and evolution of members of this bacterial genus with potential biotechnological importance, guiding future bioprospecting efforts for novel biologically active metabolites and antimicrobials.