Transition from planktonic cells to biofilm in E. coli : the CsgD regulon. Gualdi, L., Brombacher, E.*, and Landini P. Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano; *Swiss Federal Institute of Environmental Technology (EAWAG), Switzerland.
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Transition from planktonic cells to biofilm in E. coli: the CsgD regulon.
Gualdi, L., Brombacher, E.*, and Landini P.
Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano;
*Swiss Federal Institute of Environmental Technology (EAWAG), Switzerland
Adhesion Microcolony Maturation
presence of a specific adhesion factor
Inducer of cellulose
“GGDEF MOTIF” PROTEIN
bcsA, bcsB, bcsC, bcsZ
(cellulose synthesis in E. coli)
cy-di-GMP acts as an allosteric activator
of cellulose synthase machinery
From Camilli and Bassler, Science 2006
According to the GA experiments, CsgD also controls the following genes/operons (among others):
gsk (GMP biosynthesis)
pyrBI (pyrimidine metabolism)
gatYZAB (transport of galactitol, possibly
a signal for curli regulation?)
ymdA (putative fimbrial gene, likely
part of the csgBAC operon)
yoaD (unkown, potential PDE-A)*
yaiB (unknown function)
Involved in nucleotide
* Enzymes involved in c-di-GMP breakdown
Plac curli/cellulose matrix?
The yoaD gene encodes a potential
IPTG+ - + -
Inhibition of biofilm formation by yoaD expression would be consistent with a PDE role for the YoaD protein (inhibition of cellulose biosynthesis), but….
Why would both postitive (csgBA, adrA) and negative (yoaD) factors for bacterial cell aggregation be regulated by the same mechanism?
Relative expression ratio
(csgD expression/no csgD
Optical density (OD600nm)
=yoaD expression (PDEA)
=adrA expression (DGC)
Adapted from Camilli and Bassler, Science 2006
CsgD - +
CsgD - +
rpoS curli/cellulose matrix? regulon
CsgD seems to activate expression of rpoS-dependent proteins
WT curli/cellulose matrix?
1 2 3 4
1 2 3 4
- + - +
Indeed, CsgD-dependent alteration in protein expression
requires a functional rpoS gene
- + - +
CsgD curli/cellulose matrix?
How does CsgD affect sS-dependent expression?
yaiB= unknown gene
regulated by CsgD
yaiB now annotated as iraP and identified as a factor for sS stabilization
CsgD affects curli/cellulose matrix?sS intracellular concentrations
in a manner dependent on IraP
1 2 3 4 5 6 7
- + - + - +
CsgD induction of biofilm formation: curli/cellulose matrix?
part of a “general stress response”?
Oxidative stress genes
Resistance to desiccation