ENHANCEMENT OF NITROGEN-FIXATION IN ANABAENA-FLOS-AQUAE (CYANOBACTERIA) VIA LOW-DOSE ULTRASONIC TREATMENT

Low-dose (50 W), short-duration (5 min) ultrasonic treatments were del ivered to log phase batch cultures of the cyanobacterium A nabaena flo s-aquae grown in nitrogen-free medium. Near the mid-point of nine-day experimental periods, ultrasonically-treated cultures exhibited higher growth rates, enhanced chlorophyll a content, and greater acetylene r eduction capacity when compared to cultures grown with reciprocal shak ing alone. Heterocyst frequency was markedly higher in ultrasonically- treated cultures over the duration of five-day experimental periods.