Evaluation of extracellular enzyme-producing autochthonous gut bacteria in walking catfish, Clarias batrachus (L.)

Abstract

The present study was carried out to screen autochthonous gut bacteria in freshwater air breathing walking catfish, Clarias batrachus Linnaeus. Altogether, 100 extracellular enzyme-producing bacteria were isolated from the foregut (FG) and hindgut (HG) regions. Data were presented as log viable counts g -1 gut (LVC). The occurrence of heterotrophic bacterial population was higher in the FG region (LVC = 8.25) than the HG (LVC= 7.3). Similarly, proteolytic, amylolytic and lipolytic bacteria in FG outnumbered (LVC=7.25, 6.77 and 5.23 respectively) the HG (LVC=6.38, 5.58 and 4.04 respectively). However, occurrence of cellulolytic bacteria in both, FG and HG was less (LVC=2.1 and 1.34 respectively) in comparison to the other extracellular enzymeproducing bacteria. Out of the 100 bacterial isolates, 22 isolates were primarily selected through qualitative assay of extracellular enzyme activities. Among them, 3 promising isolates were chosen as potent extracellular enzyme producers on the basis of cumulative scores (≥11) of the qualitative assay and quantitative enzyme assay. Maximum protease activity was revealed by the strain FG10 (201±2.40U), while FG43 exhibited maximum amylase (208.3±10.8U) and lipase (4.73±0.05U) activities. Among the strains isolated from the HG, the highest protease (188.3±1.2U), amylase (97.6±0.46U) and lipase (3.7±0.11U) activities were recorded with the strain HG01. The isolates (FG10, FG43 and HG01) were studied through 16S rRNA partial gene sequence analyses and were identified as Bacillus aryabhattai (KP784311), B. flexus (KR809411), and B. cereus (KR809412), respectively. Further studies are to be conducted to evaluate the efficacy of these strains in vivo to improve the overall health status of the C. batrachus juveniles.

Effects of probiotics-encapsulated live feed on growth and survival of juvenile Clarias batrachus (Linnaeus, 1758) after differential exposure to pathogenic bacteria

“…Production of extracellular enzymes to assist digestion could be the reason behind improvement in growth performance of hosts with the administration of probiotics (Ray et al, 2012). Enzyme-producing ability of B. cereus used in the recent study has been documented earlier (Dey et al, 2016). Therefore, although not addressed in this pilot study, improved growth and survivability in the probiotic exposed groups might be attributed to the enhanced nutrient utilization and lower stressor levels as indicated elsewhere (Al-Dohail et al, 2009).…”

“…Autochthonous, extracellular enzyme-producing Bacillus aryabhattai KP784311, B. flexus KR809411 and B. cereus KR809412 were previously isolated from the gut of adult C. batrachus (Dey et al, 2016) and their probiotic features had been documented (Dey et al, 2017). Antibacterial activity of the putative probiotic strains was tested against pathogenic Aeromonas hydrophila (MTCC 1739), by crossstreaking and agar well-diffusion as described by Mukherjee et al (2016).…”

“…Although antibiotics are traditionally used to solve this problem (Hu et al, 2007), the use of antibiotics has been criticized since they can alter the gut microbiota and might lead to develop resistant bacteria population (Verschuere et al, 2000). Alternatively, likely application of gut associated bacteria as probiotics in catfish has been apprehended in some of the recent investigations (Banerjee et al, 2015;Dey et al, 2016). Besides, magur juveniles require protein rich food to ensure proper growth and survival (Kiriratnikom and Kiriratnikom, 2012).…”

Applications of plant ingredients for tropical and subtropical freshwater finfish: possibilities and challenges

“…In comparison with the population level of amylolytic, lipolytic and proteolytic bacteria, occurrence of cellulolytic bacteria was less in carnivorous walking catfish (Dey et al . ). In contrast, herbivorous grass carp fed on grass with high‐fibre content harboured higher proportion of cellulolytic bacteria, and the dominant cellulolytic genera were Aeromonas , Bacillus , Brevibacillus, Citrobacter , Enterobacter , Enterococcus , Hydrotalea , Klebsiella , Pseudomonas , Raoultella and some other unclassified bacteria (Li et al .…”

“…() presented information on microbial cellulase activity, but more recently, abundance of cellulose‐degrading bacteria has been further revealed in the GI tract of walking catfish ( Clarias batrachus ; Dey et al . ), grass carp (Li et al . , ; Wang et al .…”