Enzyme-producing bacteria isolated from fish gut: a review

Abstract

Digestion of food depends on three main factors: (i) the ingested food and the extent to which the food is susceptible to the effects of digestive enzymes, (ii) the activity of the digestive enzymes and (iii) the length of time the food is exposed to the action of the digestive enzymes. Each of these factors is affected by a multitude of secondary factors. The present review highlights the experimental results on the secondary factor, enzymatic activity and possible contribution of the fish gut microbiota in nutrition. It has been suggested that fish gut microbiota might have positive effects to the digestive processes of fish, and these studies have isolated and identified the enzyme-producing microbiota. In addition to Bacillus genera, Enterobacteriaceae and Acinetobacter, Aeromonas, Flavobacterium, Photobacterium, Pseudomonas, Vibrio, Microbacterium, Micrococcus, Staphylococcus, unidentified anaerobes and yeast are also suggested to be possible contributors. However, in contrast to endothermic animals, it is difficult to conclude the exact contribution of the gastrointestinal microbiota because of the complexity and variable ecology of the digestive tract of different fish species, the presence of stomach and pyloric caeca and the relative intestinal length. The present review will critically evaluate the results to establish whether or not intestinal microbiota do contribute to fish nutrition.

Atlantic Salmon (Salmo salar L.) Gastrointestinal Microbial Community Dynamics in Relation to Digesta Properties and Diet

“…However, greater understanding of how GI tract microbiota functionally influence salmon physiology including the redundancy [72] of such influences is needed to determine this. This would require utilisation of metagenomic technologies for assessing salmon gene expression and protein abundances [73] coupled to bacterial-mediated processes including enzymatic and metabolomic characteristics [13]. Indeed, recent transcriptome studies of Atlantic salmon exposed to chronic high temperature and hypoxia indicate down-regulation of transcripts encoding proteins involved in the protection against oxidative stress and a metabolic rate suppression that ultimately results in reduced growthOur data also suggests aerobic microbes are found in the digesta and also associated with sloughed off intestinal cast material suggesting possibly some level of GI tract epithelium association or interaction though this remains to be clearly defined.…”

Gut content microbiota of introduced bigheaded carps ( Hypophthalmichthys spp.) inhabiting the largest shallow lake in Central Europe

“…During the past three decades, an increasing attention was paid to studying the versatile role of microbes in the nutrition of fishes Nayak, 2010;Ray et al, 2012;Ghanbari et al, 2015). Microorganisms may contribute to fish nutrition either directly as part of the ingested and digested food Matĕna et al, 1995;Kamjunke and Mehner, 2001) or indirectly by colonizing their digestive tracts and participating in digestion processes, influencing absorption and synthesis of important nutrients (Ray et al, 2012;Li et al, 2013;Clements et al, 2014).…”

“…Microorganisms may contribute to fish nutrition either directly as part of the ingested and digested food Matĕna et al, 1995;Kamjunke and Mehner, 2001) or indirectly by colonizing their digestive tracts and participating in digestion processes, influencing absorption and synthesis of important nutrients (Ray et al, 2012;Li et al, 2013;Clements et al, 2014). So far, we have evidence of direct usage of microbes as food only in a limited number of fish species.…”

Diversity of autochthonous bacterial communities in the intestinal mucosa of grass carp (Ctenopharyngodon idellus) (Valenciennes) determined by culture-dependent and culture-independent techniques

“…Gastrointestinal (GI) microbiota play a key role in several important physiological functions of the host, including food digestion, development of the mucosal system, angiogenesis and protection against disease (Macfarlane & Macfarlane 1997;Hooper, Midtvedt & Gordon 2002;Ray, Ghosh & Ringø 2012). GI bacteria can be classified as autochthonous (able to adhere and colonize the host's epithelial surface or associated with microvilli) or allochthonous (incidental visitors of the GI tract that are eventually rejected without colonizing) (Ringø & Birkbeck 1999).…”