Identification of Odontella aurita by rbcL gene sequence - a high antibacterial potential centric marine diatom

The antibacterial potential of centric marine diatoms has been compared against the clinical pathogens and identified the potential diatom by rbcL gene sequencing. Totally, five diatoms namely Odontella aurita, Thalassiosira subtilis, Chaetoceros curvisetus, Skeletonema costatum and Coscinodiscus centralis were isolated from Cuddalore coastal waters. The diatoms were morphologically identified and isolated using micro capillary-pipette and serial dilution method. The isolated diatoms were cultured in Guillard's f/2 medium to get biomass for the antibacterial study. The dried biomass of the cultured diatoms was individually extracted with methanol, ethanol and hexane. All the obtained extracts were tested against Staphylococcus haemolyticus, Proteus vulgarius and Vibrio alginolyticus. The crude ethanol extract of O. aurita was exhibited highest zone of inhibition against all the test pathogens. The MIC of O. aurita was recorded as 50 μg/ml against both Staphylococcus haemolyticus and Proteus vulgarius whilst 75 μg/ml against Vibrio alginolyticus. This study indicates that O. aurita possesses antibacterial activities but the release of antibiotics depends on physical or chemical rupture of algal cells and extractive solvents. Based on the maximum antibacterial activity, O. aurita was further identified by rbcL gene sequencing. The rbcL gene could be an identical region for the species level identification of diatoms.