Characterization of Filamentous Bacteriophage Lf from Xanthomonas Campestris pv. Campestris

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Abstract
A filamentous phage, .vphi.Lf, which specifically infects Xanthomonas campestris pv. campestris was isolated. The phage particle measured 1000 (.+-. 200) .times. 8 nm. It formed turbid plaques of about 1 mm in diameter. During multiplication, the progeny virions extruded into the medium without retarding host cell growth. Stocks were stable for 6 months at 4.degree. C and survived treatment at 80.degree. C for 10 min. Treatment with chloroform, ethanol or acetone completely destroyed infectively; ethyl ether and methanol inactivated 98 to 99% of the phage. SDS-polyacrylamide gel electrophoresis showed a major coat protein band of approximate Mr 4000 whereas as immunoprecipitation test detected the existence of two coat protein species. The phage genome was shown to be a single-stranded DNA molecule. A physical map was constructed and the DNA size was calculated to be 5.9 kb. Cells treated with Tris-HCl containing CaCl2 and polyethylene glycol 6000 were transfected by replicative form DNA at a frequency of 3.4 .times. 103 p.f.u./.mu.g.