Psychrotolerant enterobacters inhabiting the gut of Antarctic fishes of the family Nototheniidae and description of Enterobacter hoffmannii subsp. nototheniae subsp. nov.
Vol.15,No.2(2025)
The gut microbiota of four Antarctic marine fish species – Notothenia coriiceps, Trematomus bernacchii, Trematomus hansoni, and Trematomus newnesi – were analysed, with a particular focus on the members of the Enterobacter cloacae complex. Nineteen isolated strains were characterised by rep-PCR, automated ribotyping, extended phenotyping, and MALDI-TOF MS analysis. Fingerprinting methods grouped the psychrotolerant isolates into two distinct groups, representing the dominant enteric bacteria in the gut contents of these fish. Following their preliminary identification as members of the Enterobacter cloacae complex, additional phylogenetic analyses were conducted using the 16S rRNA and rpoB genes, as well as fatty acid analysis and whole-genome sequencing of two representatives selected based on their fingerprints. All results indicated that the analysed group represents a new autochthonous Enterobacter taxon inhabiting the gut of fish of the family Nototheniidae. Based on average nucleotide identity (ANI) and in silico DNA–DNA hybridization (dDDH) values, the “Enterobacter hoffmannii”, the effectively published but non-valid name, was the most closely related species to representatives of both groups of isolates from the gut of the above-specified notothenioid fish. The name Enterobacter hoffmannii subsp. nototheniae subsp. nov. is proposed, with the type strain P5473T (= CCM 8629T = LMG 34031T), for isolates of Group 1. At the same time, the name Enterobacter hoffmannii subsp. hoffmannii subsp. nov. is suggested for isolates of Group 2, with the existing type strain DSM 14563T = LMG 30171T.
Enterobacter cloacae complex; psychrotolerant; taxonomy; Notothenia; Antarctica
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