Seasonal variation of antibacterial activities in the green alga Ulva pertusa Kjellman.

The present study was performed to screen out the extracts of algae and assess the seasonal variation in antimicrobial activity of Ulva pertusa against Gardnerella vaginalis. Seasonal variation in antibacterial activity was observed, with the extracts showing no activity during summer and autumn, and showing antibacterial activity from early winter (December) to middle spring (April). The maximum value of antimicrobial activity (6.5 mm inhibition zone at 5 mg disk(-1)) of U. pertusa against G. vaginalis was observed in April. Otherwise, for both chlorophyll a and b, the highest content (2.87 mg g(-1) and 1.37 mg g(-1)) was observed in March 2009. These results may reflect variation in cellular chemical compositions such as secondary metabolite(s) rather than chlorophyll and biological activities according to season.