Arcobacter lacus sp. nov. and Arcobacter caeni sp. nov., two novel species isolated from reclaimed water.

Two strains (RW43-9T and RW17-10T) recovered from secondary treated wastewater from the Wastewater Treatment Plant (WWTP) in Reus (Spain) were characterized by a polyphasic taxonomic study, showing evidence that they represented two novel Arcobacter species. Based on the 16S rRNA gene for strain RW43-9T, the closest relative was Arcobacter butzleri LMG 10828T (99.9 % similarity), while for strain RW17-10T it was Arcobacter venerupis CECT 7836T (99.4 %). Additionally, multilocus phylogenetic analysis of five concatenated housekeeping genes (atpA, gyrA, gyrB, hsp60 and rpoB) showed that the two strains formed separate branches that are different from known Arcobacter species. Whole genome sequences of the two strains (RW43-9T and RW17-10T) were obtained and they were compared with those of the type strains of their nearest species. Using average nucleotide identity and in silico DNA-DNA hybridization gave values that were below 96 and 70 %, respectively. These results clearly confirm that they represent novel species. Additionally, the phenotypic characterization of the strains allowed their differentiation from other species. Therefore, the strains are proposed as representing two novel species with the names Arcobacter lacus sp. nov. (type strain RW43-9T=CECT 8994T=LMG 29062T) and Arcobacter caeni sp. nov. (type strain RW17-10T=CECT 9140T=LMG 29151T).