The major groups of seaweed such as Padina pavonica and Dictyota dichotoma in Brown algae, Halimeda macroloba and Chaetomorpha antenninain green algae and the Red algae Gracilaria parvispora were examined for the presence of beneficial compounds and activity in symbiotically associated bacteria. Totally 40 isolated colonies were obtained and 10 physically similar strains were randomly selected and evaluate their antibacterial activity against human pathogens using the disc diffusion method. The strain A1 and D2 show the potential activity against all the pathogen, remarkably strain D2 had 15mm of inhibition zone againstProteus mirabilis, while A1 shows 13mm inhibition in Bacillus cereus and Proteus mirabilis. The GC-MS analysis on ethyl acetate extract of Strain A1 and D2 shows the presence of antimicrobial bioactive compounds. Based on the 16S rRNA gene sequences the isolates A1 and D2 were identical to Vibrio harveyi(KU197879.1) and Photobacterium rosenbergii (MN339950.1)respectively.

Keywords: Seaweed associated bacteria, Antimicrobial activity, GC-MS analysis,16S rRNA gene sequences.