ABSTRACT: Motility characteristics of a phylogenetically diverse collection of widespread marine bacteria were investigated using phase contrast microscopy in combination with digital image analysis. Thirty-eight isolated bacteria were identified by sequencing the 16S rDNA and an additional 46 unidentified isolates were included in this study. The identified bacteria were g-Proteobacteria (e.g. Vibrio and Pseudoalteromonas), a-Proteobacteria (e.g. Roseobacter and Caulobacter), members of the Cytophaga group and a Gram-positive strain. The mean swimming speed of the investigated bacteria growing in Zobell medium ranged from 11 to 38 µm s^-1, with a majority of the bacteria having a mean speed of 15 to 25 µm s^-1. Maximum speeds reached 75 µm s^-1. Acceleration ranged from 80 to 189 µm s^-2 with an average of 121 µm s^-2. Mean run times ranged between 0.105 and 0.323 s. A significant positive correlation between growth rate and mean swimming speed was found. A total of 70% of the bacterial isolates showed a turn angle larger than 150° (range 127 to 180°), demonstrating that reversal of swimming direction is an important strategy for bacteria in the marine environment, in contrast to the biased random walk exhibited by enteric bacteria.

KEY WORDS: Bacterial motility · Swimming speed · Acceleration · Nutrient patches · Bacterioplankton

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Published in AME Vol. 28, No. 3 (2002) on July 24
Print ISSN: 0948-3055; Online ISSN: 1616-1564. Copyright © Inter-Research, Oldendorf/Luhe, 2002