Microalgae have potential as antibacterial compounds, the content of microalgae which has the activity of amino acids, terpenoids, florotanins, steroids, phenolics, acrylic acids and halogenated ketones can be used as an antimicrobial. In this research, screening and isolation of microalgae which can be used as antibacterial has been done at Talago Biru, Koto Baru, West Sumatera and the content of secondary metabolites were identified. The isolation was done by using agar plate and serial dilution methods. Isolates were identified morphological and molecular, it is known as a type of Chlorella sp. Best harvest time was determined by Spectrophotometric method at 450 nm is obtained in day 20 on the stationary phase. Based on phytochemical test, this isolate positively contain phenolics, saponins, steroids and triterpenoids, then the antibacterial activity of microalgae extracted with methanol was tested. It is known that the isolates has potential as an antibacterial, were seen from the test results provided by the zone of inhibition against four isolates of bacteria test with extract concentrations of 10 mg / mL, 100 mg / mL and 500 mg / mL respectively E .Coli 8 mm, 10 mm and 12 mm, Salmonella bacteria typhii 10.5 mm, 9 mm, 9 mm, Staphylococcus aureus 9 mm, 10 mm and 10 mm as well as the bacteria Bacillus cereus 10 mm, 10.5 mm, and 11 mm with a comparator amoxycillin as a positive control and 0.1% DMSO as a negative control.
