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Role of an alginate lyase for alginate transport in mucoid Pseudomonas aeruginosa.
- Source :
-
Infection and immunity [Infect Immun] 2005 Oct; Vol. 73 (10), pp. 6429-36. - Publication Year :
- 2005
-
Abstract
- The opportunistic pathogen Pseudomonas aeruginosa secretes a capsule-like polysaccharide called alginate that is important for evasion of host defenses, especially during chronic pulmonary disease of patients with cystic fibrosis (CF). Most proteins for alginate biosynthesis are encoded by the 12-gene algD operon. Interestingly, this operon also encodes AlgL, a lyase that degrades alginate. Mutants lacking AlgG, AlgK, or AlgX, also encoded by the operon, synthesize alginate polymers that are digested by the coregulated protein AlgL. We examined the phenotype of an DeltaalgL mutation in the highly mucoid CF isolate FRD1. Generating a true DeltaalgL mutant was possible only when the algD operon was under the control of a LacI(q)-repressed trc promoter. Upon induction of alginate production with isopropyl-beta-D-thiogalactopyranoside, the DeltaalgL mutant cells were lysed within a few hours. Electron micrographs of the DeltaalgL mutant showed that alginate polymers accumulated in the periplasm, which ultimately burst the bacterial cell wall. The requirement of AlgL in an alginate-overproducing strain led to a new model for alginate secretion in which a multiprotein secretion complex (or scaffold, that includes AlgG, AlgK, AlgX, and AlgL) guides new polymers through the periplasm for secretion across the outer membrane. In this model, AlgL is bifunctional with a structural role in the scaffold and a role in degrading free alginate polymers in the periplasm.
- Subjects :
- Alginates analysis
Bacterial Proteins genetics
Biological Transport
Gene Deletion
Genes, Lethal
Glucuronic Acid analysis
Glucuronic Acid metabolism
Hexuronic Acids analysis
Hexuronic Acids metabolism
Isopropyl Thiogalactoside pharmacology
Mutation
Operon genetics
Periplasm chemistry
Periplasm metabolism
Polysaccharide-Lyases genetics
Promoter Regions, Genetic drug effects
Pseudomonas aeruginosa genetics
Pseudomonas aeruginosa ultrastructure
Alginates metabolism
Bacterial Proteins physiology
Polysaccharide-Lyases physiology
Pseudomonas aeruginosa enzymology
Subjects
Details
- Language :
- English
- ISSN :
- 0019-9567
- Volume :
- 73
- Issue :
- 10
- Database :
- MEDLINE
- Journal :
- Infection and immunity
- Publication Type :
- Academic Journal
- Accession number :
- 16177314
- Full Text :
- https://doi.org/10.1128/IAI.73.10.6429-6436.2005