The microalgae are of significant attraction as natural source of bioactive molecules. Twenty four different fresh water algal species were screened for their antibacterial activity and biomolecules. Bactericidal activity was tested against two gram+ve and four gram-ve bacteria. Maximum antibacterial activity was observed in methanol extracts and least in aqueous extracts. Maximum activity (14 mm) was observed in the extracts of Nostoc, Lyngbya, Mougeotia and Pithophora sp. Gram-positive bacteria were more susceptible than gram-negative bacteria. Thirteen algal species are associated with tannins and phenols, 11 species with steroids, 5 species with flavonoids and 8 species with saponins. Maximum chlorophyll a was recorded with Ulothrix (5.6 mg/g) and least in Tolypothrix (0.5 mg/g). Chlorophyll b was recorded maximum in Vaucheria (4.2 mg/g) and least in Cylindrospermum (0.6 mg/g). Maximum carotenoid content is recorded in Ulothrix (4.5 mg/g) and least in Tolypothrix and Oscillatoria (0.6 mg/g). Range of protein content is 4-20% with maximum yield in Cylindrospermum sp. (20%) and least in Hydrodictyon (4%). Carbohydrate content ranged from 14–35% with maximum yield in Mougeotia (35%) and least in Tolypothrix (14%). Their pharmacological activities and bioactive molecules can be highly exploited .

Keywords: fresh water algae, antibacterial activity, phycochemicals, phycopigments

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