GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 1984
IFREMER, Actes de Colloques, 3, 1986, pp. 243-247
27
EFFECTS OF ENVIRONMENTAL CONDITIONS ON THE SESSILE EXISTENCE
OF AN ESTUARINE SEDIMENT BACTERIUM
G.G. GEESEY, S.D. SALAS, M.W. MITTELMAN
California State University, LONG BEACH, California, 90840 (USA)
ABSTRACT - A submerged glass coverslip technique was developed to determine dissolved organic nutrient uptake
by adherent cells of a sediment isolate of Enterobacter cloacae. Cells which colonized the coverslips in swirling
culture flasks during anaerobic growth remained firmly attached during manipulations employed to determine
uptake of radiolabeled glucose by the adherent population. The attached cells were capable of a more rapid rate of
glucose uptake than free cells. Lineweaver-Burk plots demonstrated different glucose uptake kinetics for the 2 cell
populations. The data suggest that physiological changes occur in cells soon after they become attached to surfaces.
These changes appear to enhance the metabolic activity of the adherent population.
Key words : bacterial attachment, glucose uptake, estuarine sediment.
RÉSUMÉ - Pour déterminer le taux d’absorption de composés organiques dissous, par les cellules fixées d’une
souche d’Enterobacter cloacae, isolée d’un sédiment, une technique d’immersion de lamelles de verre a été mise au
point. Les cellules qui colonisent les lamelles en anaérobiose, le flacon étant sous agitation constante, restent
fermement fixées durant les manipulations de détermination de l’absorption de glucose marqué par la population
adhérente. Les cellules fixées présentent un taux d’absorption du glucose supérieur à celui des cellules libres. Les
tracés de Lineweaver-Burk montrent des cinétiques d’absorption du glucose différentes pour les deux types de
cellules. Ces observations suggèrent que des changements physiologiques apparaissent chez les cellules, dès qu’elles
se fixent aux surfaces. Ces changements semblent accroître l’activité métabolique de la population fixée.
Mots clés : fixation bactérienne, absorption du glucose, sédiment estuarien.
INTRODUCTION
Sessile or attached microorganisms are found in great abundance in aquatic environments.
They are commonly concentrated on the surfaces of submerged macrophytes, detritus, and
sediment particles. Their densities are often many orders of magnitude greater than the
free-floating, planktonic bacterial population (Geesey et al., 1978).
One of the characteristic features of sessile bacteria in various aquatic systems is their
tendency to elaborate extracellular polymers. These polymers appear to serve as
holdfasts, anchoring the cell to a surface and ensuring its sessile existence. Recently,
Moriarty and Hayward (1982) demonstrated that most sediment bacteria are enveloped
in an extracellular network of fibers. Coral reef sediments, in particular, are heavily
populated by slime-embedded bacteria. These exopolymers, which are synthesized by the
bacteria, restrict the dissemination of replicating cells and lead to microcolony development on the surface.
It is known that some bacteria fluctuate between a sessile and free or “swarmer” existence
(Costerton et ai, 1981). We know very little, however, about the environmental conditions which control a cell’s tendency to shift from a free-floating to a sessile nature. Zobell
( 1943) suggested that the sessile state provided bacteria better access to nutrients concen243
IFREMER, Actes de Colloques, 3, 1986, pp. 243-247
27
EFFECTS OF ENVIRONMENTAL CONDITIONS ON THE SESSILE EXISTENCE
OF AN ESTUARINE SEDIMENT BACTERIUM
G.G. GEESEY, S.D. SALAS, M.W. MITTELMAN
California State University, LONG BEACH, California, 90840 (USA)
ABSTRACT - A submerged glass coverslip technique was developed to determine dissolved organic nutrient uptake
by adherent cells of a sediment isolate of Enterobacter cloacae. Cells which colonized the coverslips in swirling
culture flasks during anaerobic growth remained firmly attached during manipulations employed to determine
uptake of radiolabeled glucose by the adherent population. The attached cells were capable of a more rapid rate of
glucose uptake than free cells. Lineweaver-Burk plots demonstrated different glucose uptake kinetics for the 2 cell
populations. The data suggest that physiological changes occur in cells soon after they become attached to surfaces.
These changes appear to enhance the metabolic activity of the adherent population.
Key words : bacterial attachment, glucose uptake, estuarine sediment.
RÉSUMÉ - Pour déterminer le taux d’absorption de composés organiques dissous, par les cellules fixées d’une
souche d’Enterobacter cloacae, isolée d’un sédiment, une technique d’immersion de lamelles de verre a été mise au
point. Les cellules qui colonisent les lamelles en anaérobiose, le flacon étant sous agitation constante, restent
fermement fixées durant les manipulations de détermination de l’absorption de glucose marqué par la population
adhérente. Les cellules fixées présentent un taux d’absorption du glucose supérieur à celui des cellules libres. Les
tracés de Lineweaver-Burk montrent des cinétiques d’absorption du glucose différentes pour les deux types de
cellules. Ces observations suggèrent que des changements physiologiques apparaissent chez les cellules, dès qu’elles
se fixent aux surfaces. Ces changements semblent accroître l’activité métabolique de la population fixée.
Mots clés : fixation bactérienne, absorption du glucose, sédiment estuarien.
INTRODUCTION
Sessile or attached microorganisms are found in great abundance in aquatic environments.
They are commonly concentrated on the surfaces of submerged macrophytes, detritus, and
sediment particles. Their densities are often many orders of magnitude greater than the
free-floating, planktonic bacterial population (Geesey et al., 1978).
One of the characteristic features of sessile bacteria in various aquatic systems is their
tendency to elaborate extracellular polymers. These polymers appear to serve as
holdfasts, anchoring the cell to a surface and ensuring its sessile existence. Recently,
Moriarty and Hayward (1982) demonstrated that most sediment bacteria are enveloped
in an extracellular network of fibers. Coral reef sediments, in particular, are heavily
populated by slime-embedded bacteria. These exopolymers, which are synthesized by the
bacteria, restrict the dissemination of replicating cells and lead to microcolony development on the surface.
It is known that some bacteria fluctuate between a sessile and free or “swarmer” existence
(Costerton et ai, 1981). We know very little, however, about the environmental conditions which control a cell’s tendency to shift from a free-floating to a sessile nature. Zobell
( 1943) suggested that the sessile state provided bacteria better access to nutrients concen243