Pilus-dependent, double-stranded DNA bacteriophage for Caulobacter.

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RESUMO

Caulobacter phage phi 6, previously reported to adsorb specifically to bacterial flagella, was shown here to attach to pili more frequently than to flagella. Phage phi 6 was shown to contain double-stranded DNA by circular dichroism spectroscopy and thermal denaturation accompanied by a hyperchromic shift at 260 nm. Morphologically, phage phi 6 fits group B2 (H.-W. Ackermann, in A. I. Laskin and H. A. Lechevalier, ed., Handbook of Microbiology, vol. 1, p. 638-643, 1973) with a long, noncontractile tail and an elongate head. Pilus-less mutants of the host Caulobacter vibrioides CV6 are phage phi 6 resistant, whereas flagellum-less mutants, which produce pili, are phage susceptible. Treatments of susceptible cells which remove or immobilize pili and flagella, e.g., blending or cyanide, inhibited phage phi 6 infection. Our evidence suggests that phage of phi 6 initiates infection in a manner similar to the pilus-specific phages for Pseudomonas described previously (D. E. Bradley, Virology 51:489-492, 1973; D. E. Bradley and T. L. Pitt, J. Gen. Virol. 24:1-15, 1974).

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