Regulation of the Pseudomonas aeruginosa toxA, regA and ptxR genes by the iron-starvation sigma factor PvdS under reduced levels of oxygen.
The level of environmental oxygen (EO) within various Pseudomonas aeruginosa infection sites is low (microaerobic), and this can affect the production of different virulence factors. Expression of the toxA gene, encoding exotoxin A (ETA), is regulated by regA, ptxR and pvdS. Moreover, the iron-starvation sigma factor PvdS directs the transcription of pyoverdine siderophore genes (e.g. pvdD). DNA-protein binding analysis using recombinant PvdS showed that the PvdS-RNA polymerase holoenzyme complex specifically bound the toxA, regA and ptxR promoter regions. All three promoters contain a PvdS-binding site, the iron-starvation box. To determine the relationship between these different genes and PvdS, we conducted a comparative analysis of toxA, regA, ptxR and pvdD transcription throughout the growth cycle of wild-type P. aeruginosa and its pvdS mutant in iron-deficient medium under aerobic-shaking (A-sh) and microaerobic-static (M-st) conditions. Under both EO conditions, optimal toxA, regA and pvdD expression and pyoverdine production required PvdS, while ptxR expression was moderately dependent on PvdS only under A-sh conditions. Expression of regA, pvdD and pyoverdine production in wild-type P. aeruginosa was significantly lower under M-st in comparison with A-sh conditions, while the opposite was observed for toxA and ptxR. Although low, the level of toxA expression and ETA production in the pvdS mutant were higher under M-st than under A-sh conditions. Transcription of pvdS and PvdS expression were also reduced by low EO. We propose that the regulation of toxA expression under aerobic conditions primarily involves PvdS, while an additional EO-responsive regulator(s) besides PvdS is required under low EO levels. Thus, PvdS may control the transcription of the ptxR, regA and toxA genes, and respond to EO by acting at different levels of the toxA regulatory cascade.
Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
Jennifer M
JM
Gaines
Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
Nancy L
NL
Carty
Department of Biology, University 'Roma Tre', Roma, I-00146, Italy.
Federica
F
Tiburzi
Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
Marko
M
Davinic
Department of Biology, University 'Roma Tre', Roma, I-00146, Italy.
Paolo
P
Visca
Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
Jane A
JA
Colmer-Hamood
Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
Abdul N
AN
Hamood
D036002:ADP Ribose Transferases / Q000235:genetics / Q000378:metabolism; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism; D005098:Exotoxins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D018869:Heat-Shock Response; D006801:Humans; D007501:Iron / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D005098:Exotoxins; D007501:Iron; D010100:Oxygen; D012808:Sigma Factor; D014157:Transcription Factors; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C093593:PvdS protein, Pseudomonas aeruginosa; C072722:RegA protein, Bacteria; C073470:LysR protein, Bacteria