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Pseudomonas aeruginosa transposable bacteriophages D3112 and B3 require pili and surface growth for adsorption
C Roncero1, A Darzins, M J Casadaban
1Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637.
Abstract:
Pseudomonas aeruginosa transposable bacteriophages D3112 and B3 were found to require pili for infection. Seventy mutants of P. aeruginosa PAO selected by resistance to D3112 or B3 were also resistant to the phage not used in the selection and suggested that the receptors of these two phages are identical. Of five resistant mutants examined, all were defective in the production of pili and did not adsorb either phage. P. aeruginosa PAK strains altered in pilus expression, such as hyperpiliated or nonpiliated mutants, adsorbed the phage but were not productively infected, implying that an additional host function was required for infection. The cell-associated lipopolysaccharide was not required for D3112 or B3 infection, since mutants deficient in O side-chain and core biosynthesis were still capable of adsorption and productive infection. This is in contrast to Escherichia coli mutator phages Mu and D108, which are dependent on lipopolysaccharide for adsorption. The P. aeruginosa phages adsorbed only to cells grown on solid media or in liquid media supplemented with agents that increase the macroviscosity, such as polyvinylpyrrolidone. Adsorption time course studies of D3112 and B3 using cells grown in solid media revealed similar but not identical adsorption patterns. These studies suggested that expression of the D3112 and B3 cell receptor is induced by growth on solid media.
Insights
Pseudomonas aeruginosa phages D3112 and B3 require pili for infection. Receptor studies indicate pili are essential, with optimal phage adsorption occurring on solid media, suggesting induced receptor expression.
Area of Science:
- Microbiology
- Virology
- Bacteriology
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen.
- Transposable bacteriophages like D3112 and B3 are important tools for studying bacterial genetics.
- Bacterial pili play diverse roles, including adhesion and phage interaction.
Purpose of the Study:
- To investigate the infection mechanism of Pseudomonas aeruginosa transposable bacteriophages D3112 and B3.
- To identify the host cell receptors and essential factors for phage D3112 and B3 infection.
- To compare the infection requirements of P. aeruginosa phages with those of E. coli phages Mu and D108.
Main Methods:
- Isolation and characterization of phage-resistant Pseudomonas aeruginosa mutants.
- Analysis of pilus production and phage adsorption in wild-type and mutant strains.
- Assessment of lipopolysaccharide (LPS) involvement in phage infection.
- Evaluation of phage adsorption under different growth conditions (solid vs. liquid media).
Main Results:
- Phages D3112 and B3 require pili for infection, and their receptors are identical.
- Phage-resistant mutants were defective in pilus production and phage adsorption.
- While pili are essential, an additional host function is required for productive infection.
- Lipopolysaccharide is not required for D3112 and B3 infection, unlike E. coli phages Mu and D108.
- Phage adsorption is enhanced on solid media, suggesting induced receptor expression.
Conclusions:
- Pili are essential for Pseudomonas aeruginosa phage D3112 and B3 infection.
- Phage receptor expression is likely induced by growth on solid media.
- The infection mechanism differs from that of E. coli mutator phages Mu and D108, highlighting phage-host specificity.