Surface Cell Density Effects on Escherichia coli Gene Expression during Cell Attachment

Escherichia coli attachment to a
surface initiates a complex series of interconnected signaling and
regulation pathways that promote biofilm formation and maturation.
The present work investigates the effect of deposited cell density
on E. coli cell physiology, metabolic
activity, and gene expression in the initial stages of biofilm development.
Deposited cell density is controlled by exploiting the relationship
between ionic strength and bacterial attachment efficiency in a packed
bed column. Distinct differences in cell transcriptome are analyzed
by comparing sessile cultures at two different cell surface densities
and differentiating ionic strength effects by analyzing planktonic
cultures in parallel. Our results indicate that operons regulating
trypotophan production and the galactitol phosphotransferase system
(including dihydroxyacetone phosphate synthesis) are strongly affected
by cell density on the surface. Additional transcriptome and metabolomic
impacts of cell density on succinate, proline, and pyroglutamic acid
systems are also reported. These results are consistent with the hypothesis
that surface cell density plays a major role in sessile cell physiology,
commencing with the first stage of biofilm formation. These findings
improve our understanding of biofilm formation in natural and engineered
environmental systems and will contribute to future work ranging from
pathogen migration in the environment to control of biofouling on
engineered surfaces.