Microbiota from Intestinal Gut of Dawkinsia filamentosa (Valenciennes,1844) as Indicator of Environmental Condition

Aims: To isolate and identify the gut associated micro-organisms present in the gastrointestinal tract of freshwater fish Dawkinsia filamentosa.

Place and Duration of Study: Sampling site: The fish samples were collected from the river Gadana, located at the foot hills of Western Ghats, Alwarkurichi, Tenkasi district, Tamil Nadu, India. Place: Sri Paramakalyani Centre for Environmental Sciences, Manonmaniam Sundaranar University, Azhwarkurichi, Tenkasi, Tamilnadu, India (Latitude 8o20’N; Longitutde 77o10’E). Duration: The research was done during December 2021 and April 2022.

Methodology: The fish samples were anaesthetized and surface sterilized followed by aseptic dissectionby using sterile scalpel and needle. The gut contents were removed and homogenized well and isolation of Gut micro biome was done by means of serial dilution. The identification of gastrointestinal bacteria was done by performing various biochemical tests such as Gram staining, Motility, Indole test, Methyl red test, Voges Proskauer test, Citrate utilization test, Triple sugar Iron test, Catalase test, Oxidase test, Urease test, Nitrate test, Starch hydrolysis and Carbohydrate Fermentation Test. The fungi present in gastrointestinal tract is identified with lacto phenol cotton blue staining followed by microscopic observations.

Results: The overall bacterial load of gastrointestinal material ranged from 47 x10-7 to 219 x10-5 cfu/g. A total of six bacterial strains and four fungi strains were isolated. Several biochemical tests were used to identify the bacterial isolates. The six bacterial isolates were tentatively identified as Pseudomonas sp., Aeromonas sp., Staphylococcus sp., Bacillus sp., Enterobacter sp., and Vibrio sp. and the four fungi species isolated from the gutwere Aspergillus flavus, Aspergillus niger, Beauveria basiana, and Penicillium sp.

Conclusion: The current research revealed that, Dawkinsia filamentosa has a variety of microbiota in its gut. Microbial species from freshwater environments may be able to augment fish feed with these bacteria in commercial aquaculture operations. Additionally, these findings have aided in the development of possible remedies, enhanced knowledge of host-microbe interactions in other vertebrates, and enhanced aquaculture practices. The benefits of identifying gut microbiota in fishes is, it helps to study about the host nutrient catabolism and immune defence mechanism against the disease-causing pathogens.