Affiliation:
1. Departments of Civil and Environmental Engineering
2. Biological Sciences
3. Geological and Environmental Sciences, Stanford University, Stanford, California
Abstract
ABSTRACT
Caulobacter crescentus
is an oligotrophic α-proteobacterium with a complex cell cycle involving sessile-stalked and piliated, flagellated swarmer cells. Because the natural lifestyle of
C. crescentus
intrinsically involves a surface-associated, sessile state, we investigated the dynamics and control of
C. crescentus
biofilms developing on glass surfaces in a hydrodynamic system. In contrast to biofilms of the well-studied
Pseudomonas aeruginosa
,
Escherichia coli
, and
Vibrio cholerae
,
C. crescentus
CB15 cells form biphasic biofilms, consisting predominantly of a cell monolayer biofilm and a biofilm containing densely packed, mushroom-shaped structures. Based on comparisons between the
C. crescentus
strain CB15 wild type and its holdfast (
hfsA
; ΔCC0095), pili (Δ
pilA-cpaF
::Ω
aac3
), motility (
motA
), flagellum (
flgH
) mutants, and a double mutant lacking holdfast and flagellum (
hfsA
;
flgH
), a model for biofilm formation in
C. crescentus
is proposed. For both biofilm forms, the holdfast structure at the tip of a stalked cell is crucial for mediating the initial attachment. Swimming motility by means of the single polar flagellum enhances initial attachment and enables progeny swarmer cells to escape from the monolayer biofilm. The flagellum structure also contributes to maintaining the mushroom structure. Type IV pili enhance but are not absolutely required for the initial adhesion phase. However, pili are essential for forming and maintaining the well-defined three-dimensional mushroom-shaped biofilm. The involvement of pili in mushroom architecture is a novel function for type IV pili in
C. crescentus
. These unique biofilm features demonstrate a spatial diversification of the
C. crescentus
population into a sessile, “stem cell”-like subpopulation (monolayer biofilm), which generates progeny cells capable of exploring the aqueous, oligotrophic environment by swimming motility and a subpopulation accumulating in large mushroom structures.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
99 articles.
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