
Water Science and Technology Vol 41 No 4-5 pp 139145 © IWA Publishing 2000
Detachment of Aeromonas hydrophila and Pseudomonas aeruginosa due to
variations in nutrient supply
L.K. Sawyer* and S.W. Hermanowicz**
*
Department of Civil and Environmental Engineering, University of California
at Berkeley, Berkeley, CA 947201710, U.S.A.
**
Department of Civil and Environmental Engineering, University of California
at Berkeley, Berkeley, CA 947201710, U.S.A.
ABSTRACT
Growth and detachment rates of Aeromonas hydrophila and Pseudomonas
aeruginosa were measured to determine if nutrient depletion causes
detachment of attached cells. A glass parallel plate, continuous
observation flow cell placed on a phase contrast microscope was used
to monitor bacterial behaviour on the surface under defined flow and
mass transfer conditions. Shear stress was held constant at
3 N m+2. Images were taken every 15 minutes, and
digital image analysis was used to quantify specific growth, detachment
and accumulation rates for the attached organisms. An observable parameter
proportional to the nutrient depletion at the surface was used to determine
the effect of nutrient depletion on detachment rates. Increases in the
depletion parameter corresponded with increases in detachment rate after
the cells were rod, but the depletion parameter was not scaleable between
different experiments. These experiments showed that as nutrients were
depleted, detachment increased. If the detachment mechanism postulated in this work is more universal and applicable to other microbial species,
new methods of detachment control through dynamic changes of nutrient
supply might be devised.
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