Transfer of a chromosomal locus responsible for mucoid colony morphology in Pseudomonas aeruginosa isolated from cystic fibrosis patients to P. aeruginosa PAO

Macgeorge, Jenny; Korolik, Victoria; Morgan, A F; Asche, Valerie; Holloway, B. W.

doi:10.1099/00222615-21-4-331

Cited by 37 publications

(42 citation statements)

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“…6) as in strain CF1, although the actual nucleotides that have been altered or are missing are different (37). The identification of muc-3739 as a mutation in mucA is in a good agreement with the previously reported genetic mapping data (34) showing a close linkage of muc-3739 with pruAB at 67.5 min.…”

Section: Resultssupporting

confidence: 80%

“…1A). The algW locus carried on pMO011809 suppresses mucoidy in a subset of mucoid P. aeruginosa strains which include PAM425 (carrying a muc mutation transferred from a mucoid CF isolate, Ps3739, into the PAO background [34]) and a mucoid clinical isolate, CF31 (Table 2 and Fig. 1C).…”

Section: Resultsmentioning

confidence: 99%

“…One group of muc mutations is cotransducible with pruAB at 67.5 min, while the mapping data for the other locus are consistent with its position between hisI at 69 min and proB at 71 min (14,17). More recent work has confirmed the location for a subset of muc mutations at 67.5 min (13,34) and their effects on expression of alginate-specific genes (6). The molecular characterization of the genes corresponding to muc alleles cotransducible with pruAB has been achieved only recently (35)(36)(37)(38).…”

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Two distinct loci affecting conversion to mucoidy in Pseudomonas aeruginosa in cystic fibrosis encode homologs of the serine protease HtrA

et al. 1996

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Conversion to a mucoid, exopolysaccharide alginate-overproducing phenotype in Pseudomonas aeruginosa is associated with chronic respiratory infections in cystic fibrosis. Mucoidy is caused by muc mutations that derepress the alternative factor AlgU, which in turn activates alginate biosynthetic and ancillary regulatory genes. Here we report the molecular characterization of two newly identified genes, algW and mucD, that affect expression of mucoidy. The algW gene, mapping at 69 min, was isolated on the basis of its ability to suppress mucoidy and reduce transcription of the alginate biosynthetic gene algD. The predicted primary structure of AlgW displayed similarity to HtrA (DegP), a serine protease involved in proteolysis of abnormal proteins and required for resistance to oxidative and heat stress in enteric bacteria. Inactivation of algW on the chromosome of the wild-type nonmucoid strain PAO1 caused increased sensitivity to heat, H 2 O 2 , and paraquat, a redox cycling compound inducing intracellular levels of superoxide. This mutation also permitted significant induction of alginate production in the presence of subinhibitory concentrations of paraquat. Two new genes, mucC and mucD, were identified immediately downstream of the previously characterized portion (algU mucA mucB) of the gene cluster at 67.5 min encoding the alternative factor AlgU and its regulators. Interestingly, the predicted gene product of mucD also showed similarities to HtrA. Inactivation of mucD on the PAO1 chromosome resulted in conversion to the mucoid phenotype. The mutation in mucD also caused increased sensitivity to H 2 O 2 and heat killing. However, in contrast to algW mutants, no increase in susceptibility to paraquat was observed in mucD mutants. These findings indicate that algW and mucD play partially overlapping but distinct roles in P. aeruginosa resistance to reactive oxygen intermediates and heat. In addition, since mutations in mucD and algW cause conversion to mucoidy or lower the threshold for its induction by reactive oxygen intermediates, these factors may repress alginate synthesis either directly by acting on AlgU or its regulators or indirectly by removing physiological signals that may activate this stress response system.Pseudomonas aeruginosa is an opportunistic pathogen causing acute infections in individuals with compromised defense mechanisms, such as burned or neutropenic patients. Another notorious and in many aspects unique infection caused by P. aeruginosa is its characteristic association with the respiratory tract of patients with cystic fibrosis (CF) (8,41,53). This chronic infection differs from the acute disseminated disease by being localized almost exclusively to the lumen of the respiratory tract (1,26,53). Furthermore, the protracted colonization of the respiratory tract is accompanied by a distinct set of phenotypic changes of the bacterium (8, 53). For example, P. aeruginosa strains colonizing CF patients often convert to a mucoid, exopolysaccharide alginate-overproducing phenotype (17), los...

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

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confidence: 85%

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Two distinct loci affecting conversion to mucoidy in Pseudomonas aeruginosa in cystic fibrosis encode homologs of the serine protease HtrA

et al. 1996

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“…Such mucoid strains arise following enrichments with agents such as phages (25, 26), pyocins (21), and antibiotics (17) that apparently select against the less-resistant nonmucoid strains, indicating that most P. aeruginosa strains probably carry genes necessary for alginate production (although these genes are normally silent) and that some mechanism activates their expression. The alginate production (Alg+) phenotype is unstable, and mucoid strains routinely convert back to the typical nonmucoid form in the laboratory (17, 18).The genetic change responsible for alginate conversion (both turning on and turning off of alginate production) occurs in one region of the chromosome near the genes for hisI and pru (11,13,14,24) and located at approximately 68 min on the revised (30) chromosome. This chromosomal locus responsible for alginate conversion is termed algS (11) and is distant from the large cluster of genes that encode several enzymes involved in the biosynthesis of alginate and that are located near argF at 34 min (7) on the revised (30) linkage map.…”

mentioning

confidence: 99%

“…The genetic change responsible for alginate conversion (both turning on and turning off of alginate production) occurs in one region of the chromosome near the genes for hisI and pru (11,13,14,24) and located at approximately 68 min on the revised (30) chromosome. This chromosomal locus responsible for alginate conversion is termed algS (11) and is distant from the large cluster of genes that encode several enzymes involved in the biosynthesis of alginate and that are located near argF at 34 min (7) on the revised (30) linkage map.…”

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confidence: 99%

Use of a gene replacement cosmid vector for cloning alginate conversion genes from mucoid and nonmucoid Pseudomonas aeruginosa strains: algS controls expression of algT

1988

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Pseudomonas aeruginosa can convert to a mucoid colony morphology by a genetic mechanism called alginate conversion; this results in the production of copious amounts of the exopolysaccharide alginate. The mucoid phenotype of P. aeruginosa is commonly associated with its ability to cause chronic pulmonary tract infections in patients with cystic fibrosis. In this study we isolated the cis-acting locus involved in alginate conversion, called algS, from both mucoid and nonmucoid isogenic strains. We then examined the role of aigS in the control of algT, a trans-active gene required for alginate production in P. aeruginosa. We used a new cosmid cloning vector, called pEMR2, that permitted both the cloning of large DNA fragments and their subsequent gene replacement in P. aeruginosa. To verify the predicted properties of this vector, we isolated and tested a pEMR2 hisl+ clone. Using cloned algS-containing ONA and a method for gene replacement, we constructed isogenic strains of P. aeruginosa that had TnSO adjacent to aigS on the chromosome. Two pEMR2 clone banks containing genomic fragments from isogenic algS(On) (exhibiting the alginate production phenotype) and algS(Off) (exhibiting the non-alginate production phenotype) strains were constructed, and TnSO0 served as an adjacent marker to select for clones containing the respective aigS allele. The pEMR2 algS(On) and pEMR2 algS(Off) clones were shown to contain the indicated algS allele by gene replacement with the chromosome of strains that carried the opposite allele. To test whether aigS controls the expression of the adjacent aIgT gene, we constructed a pLAFRI algS(Off)T clone and showed it to be unable to complement an algT::TnSOl mutation in trans. In contrast, a pLAFR1 algS(On)T clone did complement algT::TnSO in trans. Thus, aigS appears to control the activation of algT expression, bringing about alginate conversion.Pseudomonas aeruginosa is capable of converting to a mOucoid colony morphology by a genetic mechanism called alginate conversion (11). This mucoid phenotype is indicative of the production of a viscous exopolysaccharide known as alginate (9). When P. aeruginosa causes chronic and lethal pulmonary infections in patients with cystic fibrosis, the bacteria usually undergo alginate conversion in vivo (8, 36), resulting in a poor prognosis for the patient. Alginate production appears to confer upon the organisms an increased resistance to opsonic phagocytosis (32), an adherence mechanism (38), and may also clog small airways in the lungs (37). Several reports have shown that typical nonmucoid laboratory strains of P. aeruginosa can also undergo alginate conversion. Such mucoid strains arise following enrichments with agents such as phages (25, 26), pyocins (21), and antibiotics (17) that apparently select against the less-resistant nonmucoid strains, indicating that most P. aeruginosa strains probably carry genes necessary for alginate production (although these genes are normally silent) and that some mechanism activates their expression. The algina...

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Genetics of alginate biosynthesis in Pseudomonas aeruginosa

Ohman¹,

Goldberg²

1990

Pseudomonas Infection and Alginates

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Transfer of a chromosomal locus responsible for mucoid colony morphology in Pseudomonas aeruginosa isolated from cystic fibrosis patients to P. aeruginosa PAO

Abstract: Transfer of a chromosomal locus responsible for mucoid colony morphology in Pseudomonas aeruginosa isolated from cystic fibrosis patients to P. aeruginosa PA0

Cited by 37 publications

References 24 publications

Two distinct loci affecting conversion to mucoidy in Pseudomonas aeruginosa in cystic fibrosis encode homologs of the serine protease HtrA

Two distinct loci affecting conversion to mucoidy in Pseudomonas aeruginosa in cystic fibrosis encode homologs of the serine protease HtrA

Use of a gene replacement cosmid vector for cloning alginate conversion genes from mucoid and nonmucoid Pseudomonas aeruginosa strains: algS controls expression of algT

Genetics of alginate biosynthesis in Pseudomonas aeruginosa

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