Composition of cultivable enteric bacteria from the intestine of Antarctic fish (family Nototheniidae)

In this study, the intestinal bacteria of wild Antarctic fish (family Nototheniidae) were examined using traditional culture-based techniques. Bacterial flora of the gut contents of four marine fish species (Notothenia coriiceps, Trematomus bernacchii, Trematomus hansoni, and Trematomus newnesi) was investigated to describe the allochthonous bacteria inhabiting these Nototheniidae fish. A set of 43 fresh and healthy fish was analyzed and intestinal bacteria were retrieved using the dilution plate technique on selective media Endo agar and XLDA agar. A total of 133 different bacterial isolates were obtained and initially characterized by key phenotypical tests. Notothenoid fish gut microbiota showed low species diversity of isolates and intestines were inhabited by 3 different isolates per fish on average. The bacterial colonization of the intestine content of Trematomus newnesi was poor. Curiously, the Gram-negative non-fermenters, including Pseudomonas sp., Vibrio sp., and Alcaligenes-like isolates represented the majority (59%) of intestine isolates grown on the used selective media for enteric bacteria. Based on preliminary identification, only 54 isolates (41%) were tentatively determined as enteric bacteria. The identification of 54 isolates of Gram-negative fermenting rods to the species level was achieved using biochemical characterization by commercial kits ENTEROtest 24 and Biolog GN2 MicroPlate. Results showed that Enterobacter cloacae phenon and Aeromonas hydrophila were predominant bacterial species in the free-living fish intestine from the group of fermenting Gram-negative rods.