Marine Biotechnology is the science in which marine organisms are used in full or partially tomake ormodify products. Themarine environmentmay contain 80%of worldÂs plant and animal species, and many bioactive compounds have been extracted from various marine animals like lunicates, sponges, soft cords, sea horse, nudibranches, algae, and marine organisms. These compounds were used in pharmacodynamic properties. The water sampleswere collected frommarine ecosystemand the samples were transferred into 100ml of f/2medium.After transferring the flaskwere kept it for incubation at 25oC, at a light intensity of 10 ìmol m-2 s-1 provided by cool white fluorescent tubes and with a light/dark cycle of 14 h / 10 h for one month to get mass growth of microalgae. It was identified as Chloromonas spp. One month culture was centrifuged and pellets were collected for extract preparation using acetone, ethanol, chloroform, butanol and petroleum ether. The extracts were used in different concentrations (10ìl, 15ìl, 20ìl and 25ìl) to determine the antibacterial activity against Grampositive and Gramnegative bacteria viz. Bacillus cereus,Micrococcus luteus, Staphylococcus aureus, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, Klebsiella pneumoniae and Salmonella enteriditis organisms by agar well diffusion method. From that acetone, petroleumether and ethanol extracts showed greatest antibacterial activity against Gramnegative than Grampositive organisms. Particularly acetone extract exhibited higher antibacterial activity against Bacillus cereus and Staphylococcus aureus.