NATURAL ASSEMBLAGES OF MARINE-BACTERIA EXHIBITING HIGH-SPEED MOTILITYAND LARGE ACCELERATIONS

Natural communities of marine bacteria, an isolate (FMB-Bf3) from one marine community, and Escherichia coli were examined by video microsco py for the magnitude and uniformity of their speed, Natural communitie s formed tight microswarms that shelved higher speeds (mean = 230 mu m s(-1)) than did E. coli (15 mu m s(-1)) or FhlB-BD (mean 62 mu m s(-1 )), Outside the microsffarms, the marine bacteria slowed to 45 mu m s( -1). Between turns, in mid run, and while travelling in straight lines , the natural-community bacteria accelerated up to 1,450 mu m s(-2) wh ile the cultured bacteria showed maximum accelerations of 70 and 166 m u m s(-2). The frequency distribution of speed change for the marine b acteria,vas skewed towards a few large negative accelerations and a ra nge of positive accelerations. The general pattern was one of relative ly slow increases in speed followed by abrupt declines, The results in dicate that the mechanical generation and energetic maintenance, as we ll as the environmental function, of bacterial motility need reapprais al. We conclude that the standard bacterial motility parameters of low and uniform speed, derived from culture-based studies, are not necess arily applicable to marine bacterial communities.