Characterization and Identification of Gut-Associated Phytase-Producing Bacteria in Some Freshwater Fish Cultured in Ponds

Abstract

Khan A., Ghosh K. 2012. Characterization and identification of gut-associated phytase-producing bacteria in some fresh water fish cultured in ponds. Acta Ichthyol. Piscat. 42 (1): 37-45.Background. Phytase produced by gut bacteria increases the availability of phosphorus and other important nutrients in ruminants by virtue of enzymatic hydrolysis of the phytic acid, an antinutritional factor present in the majority of plant feedstuffs. This topic, however, has been insufficiently investigated in fish. This study was intended: to evaluate the presence of phytase-producing autochthonous bacteria in the gastrointestinal (GI) tracts of 14 freshwater teleost fishes; and to identify the most promising phytase-producing strains by phenotypic characterization and 16S rDNA. Materials and methods. The GI tracts were removed and divided into proximal (PI) and distal (DI) intestine.Homogenates of intestinal segments were spread onto sterilized tryptone soya agar and modified phytase screening media (MPSM) plates to determine autochthonous culturable heterotrophic and phytase-producing microbiota, respectively. Data were presented as log viable counts (LVC) g-1 intestine. Out of 95 phytase-producing isolates, primarily selected 32 isolates were studied for phytase-assay using MPSM broth. Promising phytase-producing isolates were evaluated for other exo-enzymes (amylase, cellulase, protease, lipase) using 4 selective media. Two most promising phytase-producing isolates were identified by phenotypic characterization and 16S rDNA.Results. Population of heterotrophic bacteria was highest (LVC = 8.29 g -1 intestine) in the DI of Gudusia chapra followed by DI of Hypophthalmichthys molitrix (LVC = 6.82 g -1 intestine). However, more than log 4 reduction of the phytase-producing bacteria was observed compared to heterotrophic bacteria. Phytase-producing microbiota was highest in the PI of G. chapra (LVC = 3.95 g -1 intestine) followed by PI of Labeo calbasu (LVC = 3.78 g -1 intestine). The strain LB1.4 isolated from DI of Labeo bata showed highest phytase activity (2.33 ± 0.006 U · mL -1 ) followed by the strain GC1.2 (2.19 ± 0.018 U · mL -1 ) isolated from PI of G. chapra. Both isolates were efficient in producing other exo-enzymes. Phenotypic characterization and nucleotide homology analysis revealed that the isolates LB1.4 and GC1.2 were similar to Bacillus subtilis and Bacillus atrophaeus, respectively. Conclusion. Autochthonous phytate degrading bacteria were present in the GI tract of fish that might endow ecological advantages to overcome the anti-nutritional effects of plant phytate.Keywords: Gut bacteria, phytase, Bacillus, freshwater teleost, 16S rDNA During the last decade there has been an improved understanding on the importance of commensal intestinal microbiota in fish ). The gut microbiota may be categorized as either autochthonous (indigenous; adherent) or allochthonous (transient) depending upon its ability to adhere and colonize the mucus layer in the digestive tract (Ringø and Birkbeck 1999, Ringø et al. 2003). P...

Comparative efficacy of phytase from fish gut bacteria and a commercially available phytase in improving the nutritive value of sesame oilseed meal in formulated diets for fingerlings of rohu, Labeo rohita (Actinopterygii: Cypriniformes: Cyprinidae)

“…In our study, the overall growth performance of rohu fi ngerlings remained low compared to its growth in natural and farm conditions. A similar growth trend has also been reported with other nutritional experiments conducted on Indian major carps including rohu (Ravi and Devaraj 1991, Bairagi et al 2002, 2004, Benkappa and Varghese 2003, Khan et al 2012, Roy et al 2014. As fi shes are poikilotherms, drastic change in their surrounding water temperature will infl uence their metabolic processes, behaviour, migration, growth, reproduction, and survival (Fry 1971, Pörtner 2001.…”

“…Roy et al (2009) fi rst confi rmed the existence of phytase-producing bacteria in the gastrointestinal tracts of fi sh. The inclusion of microbial phytase in the feed is an approach to increase phytate phosphorus bioavailability (Sardar et al 2007, Cao et al 2008, Khan and Ghosh 2012. Das and Ghosh (2015) also reported effi cacy of sesame oil cake after bioprocessing through fermentation with a phytase-producing fi sh gut bacterium.…”

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

“…The rate of microflora present within the GI tract of fish is much higher than that of the surrounding water, indicating that the GI tract of fish provides favorable ecological niches for these microorganisms (Mondal et al, 2008). However, isolation and identification alone might not give a realistic depiction of the gut microflora in different regions of the GI tract with an appraisal of their likely function (Khan and Ghosh, 2012). Therefore, it was considered legitimate in the present study to quantify heterotrophic bacteria along with specific extracellular enzyme-producing bacteria in different regions of the GI tracts in the fish species studied, as the major endeavor in the present study was to gather information on extracellular enzyme-producing gut bacteria in some brackish water fishes.…”

“…During the last decade, there has been an improved understanding of the importance of commensal intestinal microflora in fish (Bairagi et al, 2002;Ghosh et al, 2002aGhosh et al, , 2010Ringø et al, 2010;Khan and Ghosh, 2012;Mandal and Ghosh, 2013). The gut microflora may be categorized as either autochthonous (indigenous) or allochthonous (transient) depending upon its ability to colonize and adhere to the mucus layer in the digestive tract (Ringø and Birkbeck, 1999;Ringø et al, 2003).…”

Autochthonous Phytase-Producing Bacteria Isolated From the Gastrointestinal Tracts of Four Indian Freshwater Teleosts: Characterization and Identification

“…Autochthonous phytaseproducing bacteria have been isolated from the gastrointestinal (GI) tract of different fish species and a number of studies have also been done on phytase producing resident gut bacteria in the Indian major carps (Roy et al, 2009; Khan et al, 2011Khan et al, , 2012Das and Ghosh, 2013;Dan and Ray, 2014). In spite of some limited information on phytase-producing fish gut bacteria, more research is needed to get clear ideas about the phytase producing bacteria that are able to colonize within the GI tract of freshwater teleosts.…”