S. Heise et G. Gust, Influence of the physiological status of bacteria on their transport into permeable sediments, MAR ECOL-PR, 190, 1999, pp. 141-153
Starving and grown cultures of the heterotrophic, marine isolate FL2 were e
xposed to a defined flow at a hydrodynamically smooth, sandy sediment-water
interface with a partially homogeneous bottom shear stress pattern but loc
alized high advective inflow. Since transport-determining properties like c
ell size, hydrophobicity, motility and exopolymer production all change dur
ing starvation, we compared the distribution of differently nourished cells
and microspheres at the surface and in the sediment after 3 d of exposure.
We found different sorting processes between particles and bacteria, and b
etween starving and grown cells, calling into question the transfer of labo
ratory results from exponentially grown cultures to in situ conditions and
generally the substitution of bacteria by particles in transport experiment
s. While microspheres were distributed according to the advective flow and
only weakly retained by interactions with sediment particles, grown bacteri
a showed a spatially homogeneous distribution over the sediment surface. On
e suggestion is that active movement renders them independent of advective
inflow once they have contact with the sediment. Starved cells, however, ac
cumulated at the surface area of highest advective flow. They excreted exop
olymers different from those in exponential phase, and, consequently, forme
d aggregates of up to 7 mu m in diameter, which were then retained at the s
urface due to straining. if this accumulation turns out to be a widespread
behaviour of copiotrophic bacteria, possible consequences-both ecological a
nd also regarding pathogenic bacteria in coastal zones-have to be considere
d.