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Appl. Environ. Microbiol., Mar 1995, 877-882, Vol 61, No. 3
JG Mitchell, L Pearson, A Bonazinga, S Dillon, H Khouri and R Paxinos
The motility characteristics of natural assemblages of coastal marine
bacteria were examined. Initially, less than 10% of the bacteria were
motile. A single addition of tryptic soy broth caused an increase in the
motile fraction of cells but only after 7 to 12 h. Motility peaked at 15 to
30 h, when more than 80% of cells were motile. These results support the
proposal that energy limits motility in the marine environment. Cell speeds
changed more than an order of magnitude on timescales of milliseconds and
hours. The maximum community speed was 144 (mu)m s(sup-1), and the maximum
individual burst velocity was 407 (mu)m s(sup-1). In uniform medium, speed
was an inverse function of tryptic soy broth concentration, declining
linearly over 0.001 to 1.0%. In media where concentration gradients
existed, the mean speed was a function of position in a spatial gradient,
changing from 69 to 144 (mu)m s(sup-1) over as little as 15 to 30 (mu)m.
The results suggest that marine bacteria are capable of previously
undescribed quick shifts in speed that may permit the bacteria to rapidly
detect and keep up with positional changes in small nutrient sources. These
high speeds and quick shifts may reflect the requirements for useful
motility in a turbulent ocean.
Copyright © 1995, American Society for Microbiology
Long Lag Times and High Velocities in the Motility of Natural Assemblages of Marine Bacteria
Biological Sciences, Flinders University, Adelaide, South Australia 5001, Australia
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