Isolation and identification of bacterial fauna associated with male and female of horseshoe crabs

Abstract

The data on distribution and diversity of bacteria associated with horseshoe crabs are still limited. An experiment was conducted to isolate bacterial fauna associated with different organs of male and female of horseshoe crab, to screen useful compound produced from bacteria isolates and to characterize the bacteria found on the protosoma, opisthosoma, and book gills of horseshoe crabs from the species Tachypleus gigas and Carcinoscorpius rotundicauda. Samples of horseshoe crabs were collected from Cherating, Pahang. A total of 4 7 Gram-negative isolates and three Gram-positive isolates were obtained and characterized. Number of isolates from C. rotundicauda is higher than T gigas. The isolates were cultured in AMS cultivation method to mimic the real environment of the bacteria. Test that was conducted to screen the bioactive compound was Disc Diffusion Test (DDT). Results from DDT test were determined through the inhibition zones found around the disc implemented with compounds produced by bacteria. Two isolates that showed positive result in DDT were identified using biochemical tests and analysis of 16S rDNA gene fragment. No bands were appeared during agarose gel electrophoresis. The biochemical tests used were starch hydrolysis test, catalase test, oxidase test, MR-VP test, Sulfur Indole Mortility (SIM test), and Triple Sugar Iron (TSI agar test).The genus of bacteria were Pseudomonas sp. and Neisseria sp. As a conclusion, total numbers of Gram-negative bacteria are dominant compared to Gram-positive bacteria associated with horseshoe crabs ..