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J. Bacteriol., 02 1995, 907-915, Vol 177, No. 4
GA James, DR Korber, DE Caldwell and JW Costerton
Surface growth of an Acinetobacter sp. cultivated under several nutrient
regimens was examined by using continuous-flow slide culture,
phase-contrast microscopy, scanning confocal laser microscopy, and computer
image analysis. Irrigation of attached coccoid stationary- phase
Acinetobacter sp. cells with high-nutrient medium resulted in a transition
from coccoid to bacillar morphology. Digital image analysis revealed that
this transition was biphasic. During phase I, both the length and the width
of cells increased. In contrast, cell width remained constant during phase
II, while both cell length and cell area increased at a rate greater than
in phase I. Cells were capable of growth and division without morphological
transition when irrigated with a low-nutrient medium. Rod-shaped cells
reverted to cocci by reduction-division when irrigated with starvation
medium. This resulted in conservation of cell area (biomass) with an
increase in cell number. In addition, the changes in cell morphology were
accompanied by changes in the stability of cell attachment. During phase I,
coccoid cells remained firmly attached. Following transition in
high-nutrient medium, bacillar cells displayed detachment, transient
attachment, and drifting behaviors, resulting in a spreading colonization
pattern. In contrast, cells irrigated with a low-nutrient medium remained
firmly attached to the surface and eventually formed tightly packed
microcolonies. It is hypothesized that the coccoid and bacillar
Acinetobacter sp. morphotypes and associated behavior represent specialized
physiological adaptations for attachment and colonization in low-nutrient
systems (coccoid morphotype) or dispersion under high-nutrient conditions
(bacillar morphotype).
Copyright © 1995, American Society for Microbiology
Digital image analysis of growth and starvation responses of a surface- colonizing Acinetobacter sp
Department of Biological Sciences, University of Calgary, Alberta, Canada.
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