A review of the bacterial flora of teleosts and elasmobranchs, including methods for its analysis

Abstract

Techniques for the quantitative and qualitative analysis of the commensal bacterial flora of fish are reviewed. The literature concerning the commensal bacterial flora of fish indicates that teleost skin often features 10a-107 organisms per cm2 of skin, representing the following taxa, in descending numerical order, Achromobacter, Pseudomonas, Flavobacterium and Cytoghaga species also coryneform organisms. Actively feeding teleosts appear to have an alimentary canal bacterial flora similar to that of the skin and gills, often there are from 10s-108 organisms per 1.0 g, wet weight, of tissue. According to the limited data available for elasmobranchs Gram-positive bacteria are the predominant component of the bacterial flora on the skin of sharks, though the bacterial flora of North Sea skate (Raja spp.) is reported as being similar to that of teleosts. The commensal flora of fish, particularly of teleosts, is related t o their environment and is influenced by environmental changes that affect the quality of the water. Regular monitoring of the water of commercial fish ponds and aquaria for bacterial quality, temperature, dissolved oxygen concentration and pH, combined with a base-line knowledge of the water's quality, may provide an advanced indication of the presence of bacteria potentially able to produce diseased conditions, and factors that will enhance their growth.

Distribution of extracellular enzyme-producing bacteria in the digestive tracts of 4 brackish water fish species

“…However, the endosymbiotic community among the brackish water fish species has remained poorly investigated (Esakkiraj et al, 2009). Digestive tracts of endotherms are colonized mainly by obligate anaerobes (Finegold et al, 1983), while the predominant bacterial genera isolated from most fish guts have been aerobes or facultative anaerobes (Trust and Sparrow, 1974;Horsley, 1977;Sakata, 1990;Bairagi et al, 2002;Ghosh et al, 2002a). In the present investigation, aerobic/facultative anaerobic extracellular enzyme-producing bacterial symbionts were detected in the GI tracts of 4 brackish water fish species.…”

Distribution of enzyme-producing bacteria in the digestive tracts of some freshwater fish

“…The bacteria entering along with the diet of fish during ingestion may adapt themselves in the gastrointestinal tract and form a symbiotic association. Within the digestive tract of fish large numbers of microbes are present (Trust et al 1979, Rimmer and Wiebe 1987, Clements 1991, Luczkovich and Stellwag 1993, Ringø and Strom 1994, Clements and Choat 1995, which is much higher than in the surrounding water indicating that the digestive tracts of fish provide favourable ecological niches for these organisms (Trust and Sparrow 1974, Horsley 1977, Austin and AlZahrani 1988, Sakata 1990). However, the gastrointestinal microflora of fish appears to be simpler than those of endotherms.…”

“…However, the gastrointestinal microflora of fish appears to be simpler than those of endotherms. While the digestive tracts of endotherms are colonized mainly by obligate anaerobes (Finegold et al 1983), the predominant bacterial genera/species isolated from most fish guts have been aerobes or facultative anaerobes (Trust and Sparrow 1974, Horsley 1977, Sakata 1990, Bairagi et al 2002. In the present study, attention has been focused on the aerobic gastrointestinal bacteria of seven Indian freshwater teleosts.…”

Production of amylase by the intestinal microflora in cultured freshwater fish

“…Although many ecological studies on the gut Intestinal bacteria were isolated from five specimens each of microflora of fish have been presented (e.g. Horsley 1977 ; ayu (Plecoglossus altivelis ; 25-38 g body weight), carp (Cyp- Sugita and Deguchi 1988 ;Cahill 1990), only recently have rinus carpio ; 21-56 g), Japanese eel (Anguilla japonica ; 20-reports concerning their functions appeared. The intestinal 45 g) and tilapia (Oreochromis niloticus ; 19-460 g), and four specimens of channel catfish (Ictalurus punctatus ; 4-5 g) as or genus level using a modified scheme (Sugita et al 1981) and anaerobes ranged from 1·1×10 6 to 3·7×10 8 cfu g −1 and from 1·3×10 3 to 1·6×10 8 cfu g −1 , respectively.…”