New Filamentous Phage Released from Xanthomonas campestris pv. oryzae Harbouring a Covalently Closed Circular DNA of 7.1kb

Abstract

One of 88 strains of Xanthomonas campestris pv. oryzae harboured a covalently closed circular DNA (cccDNA) of 7.1 kb and released a filamentous phage into culture fluid. This strain M8883 easily lost the 7.1 kb cccDNA by subculturing five times, and the cured strains lost phage productivity. The filamentous phage released from strain M8883 was different from Xf and Xf2 phages in host range, particle length and molecular size of the replicative form DNA (RF), and was designated Xf8883. The electrophoretic pattern of the 7.1 kb cccDNA digested with HinfI or MspI was identical to that of Xf8883-RF isolated from M8819 infected with Xf8883. Furthermore, strain M8819 transformed with the 7.1 kb cccDNA acquired the productivity of a filamentous phage which was identical with Xf8883. From these results, it is concluded that the 7.1 kb cccDNA may be RF of a new filamentous phage, Xf8883. Electrophoretic analysis of the HaeIII, RsaI and HinfI fragments of Xf8883-RF and Xf-RF suggested that the two phages, Xf8883 and Xf, were closely related but not identical.