摘要Objective:To determine the phytochemicals and screen the antimicrobial potential of Desmococcus olivaceus(D. olivaceus)andChlorella vulgaris (C. vulgaris) against human bacterial pathogens. <br> Methods:D. olivaceusandC. vulgaris were collected and confirmed through morphological structures. Phytochemicals were analyzed and confirmed by chemical methods. Thin layer chromatography was performed to evaluate the bioactive compounds present in the solvent extracts. Antimicrobial activity of the extract obtained from dried green microalgae was tested against Gram negative and Gram positive bacteria using agar disc diffusion method. The Gram negative bacteria likeKlebsiella pneumonia,Proteus mirabilis,Vibrio cholerae,Salmonella typhi,Escherichia coli and Gram positive bacteria including Staphylococcus aureus,Bacillus subtilis,Enterococcus sp.,Clostridium botulinum (C. botulinum) andNocardia sp. were selected for analysis. The cultures were obtained from Microbial Culture Maintenances Laboratory, Department of Medical Microbiology, Rajah Muthaiah Medical College, Annamalai University, Tamil Nadu, India. <br> Results: Seven bioactive compounds were detectedviz., phenols, tannin, flavanoids, saponins, terpenes, carbohydrates, alkaloids and steroids. In Gram negative bacteria,Proteus mirabilis treated with ethanol extract ofD.olivaceus showed the maximum inhibition zone (17.2 mm), whereas in Gram positive bacteria,C. botulinumtreated with diethyl ether extract showed inhibition zone of 19.0 mm. In test forC. vulgaris,Gram negative bacteriaSalmonella typhi treated with ethanol extractshowed the maximum inhibition zone (13.0 mm), whereas in Gram positive bacteria,C. botulinum treated with chloroform extract ofC.vulgarisshowed the maximum inhibition zone of 15 mm. <br> Conclusions: The results clearly indicated thatD. olivaceus andC. vulgaris contain promising antibacterial compounds.