Bacterial microflora in the gastro-intestinal tract of Dover sole (Solea solea L.), with emphasis on the possible role of bacteria in the nutrition of the host

There was a progressive increase in the size of the aerobic heterotrophic bacterial populations along the gastro-intestinal tract of farmed Dover sole. Moreover, higher counts were recorded in juvenile than in adult animals. Thus, in juvenile fish, 5.2 x 10⁵, 8.0 x 10⁵ and 9.8 x 10⁶ aerobic heterotrophs/g were recovered from the stomach/foregut, midgut and hindgut/rectum, respectively. In adult fish, comparative samples revealed the presence of only 3.0 x 10⁴, 7.0 x 10⁴ and 2.3 x 10⁵ bacteria/g, respectively. These bacteria were equated with Acinetobacter, Alcaligenes, Enterobacteriaceae representatives, Flavobacterium, Micrococcus, Photobacterium, Staphylococcus and Vibrio. Of the compounds tested, many isolates, particularly those recovered from the hindgut/rectum, degraded p-nitrophenyl-ß-N-acetylglucosamide, chitin and collagen. Consequently, it is likely that such organisms may contribute to nutritional processes within Dover sole.