Isolation and enumeration of amylase, cellulase and protease-producing autochthonous bacteria in the proximal intestine (PI) and distal intestine (DI) of three species of Indian major carps, catla (Catla catla), mrigal (Cirrhinus mrigala) and rohu (Labeo rohita), were investigated using the conventional culturebased technique. Population levels of amylolytic strains were the highest in the PI of catla and the lowest in the DI of rohu. The highest viable count of cellulase and protease-producing bacteria was recorded in the DI and PI of mrigal respectively. Among the bacteria isolated,10 strains (¢ve from PI and ¢ve from DI) were selected as potent enzyme producers according to a quantitative enzyme assay. The chosen strains were further identi¢ed by 16S rRNA gene sequence analysis. The ¢ve strains isolated from catla showed high similarity to Citrobacter sp. clone W2, Enterobacter sp. JA24, Bacillus coagulans strain TR, uncultured bacterial clone Hel3bc04 and Bacillus cereus strain UST2006-BC004. The four strains isolated from mrigal were most closely related to Bacillus sp. KCd2, uncultured bacterial clone Hel3bd09, B. cereus strain BU040901-020 and Citrobacter freundii strain YRL11, while the strain isolated from rohu probably belonged to Bacillus sp. GV.

Isolation and enumeration of phytase-producing bacterial £ora in the foregut and hindgut regions of the gastrointestinal tracts of 10 culturable freshwater teleosts of di¡erent feeding habits, namely rohu (Labeo rohita), catla (Catla catla), mrigal (Cirrhinus mrigala), bata (Labeo bata), kalbasu (Labeo calbasu), Nile tilapia (Oreochromis niloticus), climbing perch (Anabas testudineus), common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix) and grass carp (Ctenopharyngodon idella), have been carried out. Microbial culture of the gut mucosa on selected nutrient media following the enrichment culture technique was performed for bacterial isolation. The bacterial isolates were screened on the basis of their enzyme-producing ability. The bacterial population on the tryptone soya agar (TSA) plate was maximum in the hindgut region of bata, followed by mrigal and minimum in the foregut region of Nile tilapia. In modi¢ed phytase screening medium (MPSM), phytase-producing strains were recorded at higher densities in the foregut region of mrigal and grass carp and minimum in the foregut region of bata. In case of the hindgut, maximum phytase-producing strains were present in grass carp and mrigal and minimum in rohu. In general, in MPSM, the bacterial population was lower in the hindgut region of all the 10 species of ¢sh examined. The phytase-producing ability of the selected 31 strains (16 from the foregut and 15 from the hindgut region) was determined by clearing zones on phytate-containing plates. Among these isolates, 22 strains (12 from the foregut and 10 from the hindgut region) were selected as potent phytase producers according to a quantitative enzyme assay. The highest phytase activity was observed in the bacterial strains LF1 and LH1 isolated from the fore and the hindgut regions of rohu respectively. Both the strains were identi¢ed as Bacillus licheniformis on the basis of phenotypic characteristics as well as 16S rDNA sequence analysis.

Mondal S., Roy T., Sen S.K., Ray A.K. 2008. Distribution of enzyme-producing bacteria in the digestive tracts of some freshwater fish. Acta Ichthyol. Piscat. 38 (1): 1-8.Background. The information on gut microflora in fish is scanty and there is a paucity of knowledge regarding microbial enzyme activity in fish gastrointestinal tracts. Although some information is available on the enzymeproducing bacteria in fish digestive tracts, almost nothing is known about their distribution in different regions of the gut. In the present study, an attempt has been made to investigate the distribution of enzyme-producing microflora in the foregut and hindgut regions of seven culturable freshwater teleosts. Materials and Methods. Isolation and enumeration of aerobic bacterial flora in the foregut and hindgut regions of the gastrointestinal tracts of seven freshwater teleosts of different feeding habits, namely rohu, Labeo rohita; catla, Catla catla; mrigal, Cirrhinus mrigala; bata, Labeo bata; orange-fin labeo, Labeo calbasu; Nile tilapia, Oreochromis niloticus; and climbing perch, Anabas testudineus, have been carried out. Microbial culture of the gut mucosa on selected nutrient media, following the enrichment culture technique, was done for bacterial isolation. Bacterial isolates were qualitatively screened on the basis of their extracellular enzyme-producing ability. The selected strains were further quantitatively assayed for amylase, cellulase and protease activities.Results. In general, bacterial population was lower in the foregut region of all the seven species of fish examined. Amylolytic strains were present in higher densities in the foregut region of orange-fin labeo and bata (12.20 × 10 3 CFU · g -1 gut tissue and 11.50 × 10 3 CFU · g -1 gut tissue, respectively) in comparison to the hindgut region. The cellulolytic population exhibited maximum densities in the hindgut region of bata (7.20 × 10 3 CFU · g -1 gut tissue) followed by the foregut region of the same fish (5.50 × 10 3 CFU · g -1 gut tissue). Amylolytic and cellulolytic bacterial flora was not detected in both the fore and hindgut regions of climbing perch. Proteolytic bacterial flora was found in all the species of fish studied and the maximum count was observed in the hindgut region of bata (13.40 × 10 3 CFU · g -1 gut tissue), orange-fin labeo (9.00 × 10 3 CFU · g -1 gut tissue), Nile tilapia (8.30 × 10 3 CFU · g -1 gut tissue) and climbing perch (7.20 × 10 3 CFU · g -1 gut tissue). Minimum count of proteolytic bacterial flora was observed in the foregut region of all the fishes studied. Peak amylase and cellulase activities were exhibited by bacterial strains isolated from the foregut of orange-fin labeo (266.43 ± 0.15 U) and the hindgut of bata (64.01 ± 0.42 U), respectively. Maximum protease activity was exhibited by a strain isolated from the hindgut region of orange-fin labeo (44.33 ± 0.09 U), followed by the strains isolated from the hindgut regions of climbing perch (32.87 ± 0.12 U), bata (29.71 ± 0.11 U), and Nile tilapia (29.46 ± 0.11 U). C...

Isolation and enumeration of aerobic bacterial flora in the foregut and hindgut regions of the gastrointestinal tract of bata, Labeo bata, were carried out on selected nutrient media following the enrichment culture technique. Four bacterial isolates were qualitatively screened on the basis of their extracellular enzyme‐producing ability. The selected strains were further quantitatively assayed for amylase, cellulase, and protease activities. Amylolytic strains were present in higher densities in the foregut region, whereas the cellulolytic and proteolytic populations exhibited maximum densities in the hindgut region. Peak amylase, cellulase, and protease activities were exhibited by bacterial strains BF2 and BH4, isolated from the foregut and hindgut regions, respectively. Both the strains are Gram‐positive rods, motile, and capable of forming endospores. They can tolerate a wide range of temperatures (25–42 C and 25–55 C in cases of BF2 and BH4, respectively) and pH (5–11). On the basis of phenotypic characteristics and 16S rDNA sequence analysis, the strains were identified as Bacillus licheniformis (BF2, GenBank Accession Number: EF635428) and Bacillus subtilis (BH4, GenBank Accession Number: EF032683). The study provides scope for further research on the use of the enzyme‐producing fish gut bacteria in aquafeeds, especially for the larval stages.

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