Alginate production in Pseudomonas aeruginosa and the associated mucoid phenotype of isolates from cystic fibrosis patients are under the control of the algU mucABCD cluster. This group of genes encodes AlgU, the P. aeruginosa equivalent of the extreme heat shock σ factor σE in Gram-negative bacteria, the AlgU-cognate anti-σ factor MucA, the periplasmic protein MucB and a serine protease homologue, MucD. While mucA, mucB or mucD act as negative regulators of AlgU, the function of mucC is not known. In this study the role of mucC in P. aeruginosa physiology and alginate production has been addressed. Insertional inactivation of mucC in the wild-type P. aeruginosa strain PAO1 did not cause any overt effects on alginate synthesis. However, it affected growth of P. aeruginosa under conditions of combined elevated temperature and increased ionic strength or osmolarity. inactivation of mucC in mucA or mucB mutant backgrounds resulted in a mucoid phenotype when the cells were grown under combined stress conditions of elevated temperature and osmolarity. Each of the stress factors tested separately did not cause comparable effects. The combined stress factors were not sufficient to cause phenotypically appreciable enhancement of alginate production in mucA or mucB mutants unless mucC was also inactivated. These findings support a negative regulatory role of mucC in alginate production by P. aeruginosa, indicate additive effects of muc genes in the regulation of mucoidy in this organism and suggest that multiple stress signals and recognition systems participate in the regulation of algu-dependent functions.
BoucherJ.C.,
Martinez-SalazarJ.M.,
SchurrM.J.,
MuddM.H.,
YuH.,
DereticV.1996; Two distinct loci affecting conversion to mucoidy in Pseudomonas aeruginosa in cystic fibrosis encode homologs of the serine protease HtrA.. J Bacteriol 178:511–523
ChiE.,
BartlettD.H.1995; An rpo-like locus controls outer membrane protein synthesis and growth at cold temperature and high pressures in the deep-sea bacterium Photobacterium sp. strain SS9.. Mol Microbiol 17:713–726
CoyneM.J.,
RussellK.S.,
CoyleC.L.,
GoldbergJ.B.1994; The Pseudomonas aeruginosa algC gene encodes phosphogluco- mutase, required for the synthesis of a complete lipopoly- saccharide core.. J Bacteriol 176:3500–3507
De Las PenasA.,
ConnollyL.,
GrossC.A.1997; The σE-mediated response to extracytoplasmic stress in Escherichia coli is transduced by RseA and RseB, two negative regulators of σE.. Mol Microbiol 24:373–385
DereticV.,
GovanJ.R.,
KonyecsniW.M.,
MartinD.W.1990; Mucoid Pseudomonas aeruginosa in cystic fibrosis: mutations in the muc loci affect transcription of the algR and algD genes in response to environmental stimuli.. Mol Microbiol 4:189–196
DereticV.,
SchurrM.J.,
BoucherJ.C.,
MartinD.W.1994; Conversion of Pseudomonas aeruginosa to mucoidy in cystic fibrosis: environmental stress and regulation of bacterial virulence by alternative sigma factors.. J Bacteriol 176:2773–2780
DeVriesC.A.,
OhmanD.E.1994; Mucoid-to-nonmucoid conversion in alginate-producing Pseudomonas aeruginosa often results from spontaneous mutations in algT, encoding a putative alternate sigma factor, and shows evidence for autoregulation.. J Bacteriol 176:6677–6687
ElzerP.H.,
PhillipsR.W.,
RobertsonG.T.,
RoopR.M.III1996; The HtrA stress response protease contributes to resistance of Brucella abortus to killing by murine phagocytes.. Infect Immun 64:4838–4841
EricksonJ.W.,
GrossC.A.1989; Identification of the sigma subunit of Escherichia coli polymerase: a second sigma factor involved in high-temperature gene expression.. Genes Dev 3:1462–1471
FyfeJ.A.M.,
GovanJ.R.W.1980; Alginate synthesis in mucoid Pseudomonas aeruginosa: a chromosomal locus involved in control.. J Gen Microbiol 119:443–450
GoldbergJ.B.,
GormanW.L.,
FlynnJ.,
OhmanD.E.1993; Amutation in algN permits trans activation of alginate production by algT in Pseudomonas species.. J Bacteriol 175:1303–1308
JohnsonK.,
CharlesI.,
DouganG.,
PickardD.,
O’GaoraP.,
CostaG.,
AliT.,
MillerI.,
HormaecheC.1991; The role of a stress-response protein in Salmonella typhimurium virulence.. Mol Microbiol 5:401–407
LamJ.,
ChanR.,
LamK.,
CostertonJ.W.1980; Production of mucoid microcolonies by Pseudomonas aeruginosa within infected lungs in cystic fibrosis.. Infect Immun 28:546–556
LipinskaB.,
SharmaS.,
GeorgopoulosC.1988; Sequence analysis and regulation of the htrA gene of Escherichia coli: a σ32- independent mechanism of heat-inducible transcription.. Nucleic Acids Res 16:10053–10067
LonettoM.A.,
BrownK.L.,
RuddK.E.,
ButtnerM.J.1994; Analysis of the Streptomyces coelicolor sigE gene reveals the existence of a subfamily of eubacterial RNA polymerase σ factors involved in the regulation of extracytoplasmic functions.. Proc Natl Acad Sci USA 86:7573–7577
MartinD.W.,
HollowayB.W.,
DereticV.1993a; Character-ization of a locus determining the mucoid status of Pseudomonas aeruginosa: AlgU shows sequence similarities with a Bacillus sigma factor.. J Bacteriol 175:1153–1164
MartinD.W.,
SchurrM.J.,
MuddM.H.,
DereticV.1993b; Differentiation of Pseudomonas aeruginosa into the alginate- producing form: inactivation of mucB causes conversion to mucoidy.. Mol Microbiol 9:497–506
MartinD.W.,
SchurrM.J.,
YuH.,
DereticV.1994; Analysis of promoters controlled by the putative sigma factor AlgU regulating conversion to mucoidy in Pseudomonas aeruginosa: relationship to stress response.. J Bacteriol 176:6688–6696
MecsasJ.,
RouviereP.E.,
EricksonJ.W.,
DonohueT.J.,
GrossC.A.1993; The activity of σE, an Escherichia coli heat-inducible σ-factor, is modulated by expression of outer membrane proteins.. Genes Dev 7:2618–2628
MissiakasD.,
MayerM.P.,
LemaireM.,
GeorgopoulosC.,
RainaS.1997; Modulation of the Escherichia coli aσE (RpoE) heat-shock transcription-factor activity by the RseA, RseB and RseC proteins.. Mol Microbiol 24:355–371
MohrC.D.,
DereticV.1990; Gene-scrambling mutagenesis: generation and analysis of insertional mutations in the alginate regulatory region of Pseudomonas aeruginosa.. J Bacteriol 172:6252–6260
RouviéreP.E.,
De Las PenasA.,
MecsasJ.,
LuGZ.,
RuddK.E.,
GrossC.A.1995; rpoE, the gene encoding the second heat- shock sigma factor, σE, in Escherichia coli.. EMBO J 14:1032–1042
SchurrM.J.,
MartinD.W.,
MuddM.H.,
DereticV.1994; Gene cluster controlling conversion to alginate-overproducing phenotype in Pseudomonas aeruginosa: functional analysis in a heterologous host and role in the instability of mucoidy.. J Bacteriol 176:3375–3382
SchurrM.J.,
YuH.,
BoucherJ.C.,
HiblerN.S.,
DereticV.1995; Multiple promoters and induction by heat shock of the gene encoding the alternative sigma factor AlgU (σE) which controls mucoidy in cystic fibrosis isolates of Pseudomonas aeruginosa.. J Bacteriol 177:5670–5679
SchurrM.J.,
YuH.,
Martinez-SalazarJ.M.,
BoucherJ.C.,
DereticV.1996; Control of AlgU, a member of the σE-like family of stress sigma factors, by the negative regulators MucA and MucB and Pseudomonas aeruginosa conversion to mucoidy in Cystic Fibrosis.. J Bacteriol 178:4997–5004
SpeertD.P.1994; Pseudomonas aeruginosa infections in patients with cystic fibrosis.. In Pseudomonas aeruginosa Infections and Treatment pp. 183–236BaltchA.L.,
SmithR.P.
Edited by New York: Marcel Dekker, Inc;
WozniakD.J.,
OhmanD.E.1994; Transcriptional analysis of the Pseudomonas aeruginosa genes algR, algB and algD reveals a hierarchy of alginate gene expression which is modulated by algT.. J Bacteriol 176:6007–6014
WuJ.,
WeissB.1991; Two divergently transcribed genes, soxR and soxS, control a superoxide response regulon of Escherichia coli.. J Bacteriol 173:2864–2871
YuH.,
SchurrM.J.,
BoucherJ.C.,
Martinez-SalazarJ.M.,
MartinD.W.,
DereticV.1996; Molecular mechanism of conversion to mucoidy in Pseudomonas aeruginosa.
. In Pseudomonas pp. 384–397SilverS.,
NakazowaT.,
HaasD.
Edited by Washington, DC: American Society for Microbiology;
YuH.,
SchurrM.J.,
DereticV.1995; Functional equivalence of Escherichia coli σE and Pseudomonas aeruginosa AlgU: E. coli rpoE restores mucoidy and reduces sensitivity to reactive oxygen intermediates in algU mutants of P. aeruginosa.. J Bacteriol 177:3259–3268