Functional Modification of the Plasmid RP1-specified Pilus by Caulobacter vibrioides

Abstract

Caulobacter strains which contain plasmid R P 1 are resistant to carbenicillin, kanamycin and tetracycline and can serve as donors of the plasmid, but such R+ strains are not susceptible to the RPl-specific phage PRR1. Since both conjugation and phage PRRl infection are mediated by the plasmid-specified pilus, the lack of phage binding suggests some functional alteration of the pilus. In this report we demonstrate that R P l pili are produced by Caulobacter R+ cells, but unlike the RP1 pili produced by PRRl-susceptible strains, the Caulobacter R+ pili do not inactivate phage PRR 1. Antibody produced against Caulobacter R+ pili prevents phage P R R l binding to R P l pili from PRRl-susceptible strains of Pseudomonas aeruginosa and Escherichia coli, and also inhibits plasmid transfer by those strains. Antibody produced against R P l pili from P. aeruginosa and E. coli inhibits plasmid transfer both by those strains and by Caulobacter R+ donors. Phage P R R l rendered non-infectious by RNAase treatment prevents plasmid transfer by P. aeruginosa and E. coli but not by Caulobacter.

Phage tf-1: A Filamentous Bacteriophage Specific for Bacteria Harbouring the IncT Plasmid pIN25

“…Analogous situations with other phages and plasmids have repeatedly been encountered (Bradley et al, 1981 a, b;Coetzee et al, 1979, 19856) and an explanation may be that while still providing adequate phage receptors, different species may not be able to support phage multiplication. Also, in some cases, pili may be modified in a particular bacterial plasmid host to prevent adsorption (Hua et al, 1981). Nevertheless the fact that the Proteus and Providencia pIN25-harbouring strains were not lysed by the phage is surprising considering the derivation of these plasmids (see Introduction).…”

Phages C-2 and J: IncC and IncJ Plasmid-Dependent Phages, Respectively

“…The case of phage J may be due to salmonellae failing to provide a suitable intracellular environment for multiplication of this phage. Another explanation could be that a hostproduced structural change in plasmid-coded pili occurred which reduced or prevented phage adsorption while leaving the conjugation function of the pilus intact (see Hua et al, 1981 …”

Bacteriophage M: an Incompatibility Group M Plasmid-specific Phage

“…The phenomenon of plasmid-specific phages not forming plaques or not propagating on species of all bacterial genera harbouring a plasmid which confers sensitivity, has been encountered repeatedly (Olsen & Thomas, 1973;Bradley, 1977;Bradley etal., 1981 a ;Coetzee et al, 1979;Sirgel et al, 1981 ;Hua et al, 1981). The behaviour of plasmids RIP69 and R831b in P. mirabilis PM5006 and plasmids R471 and R446b in E. coli strain 553 may be further examples ( Table 1).…”