Abstract
A thread-like structure released from the cell surface of Xanthomonas oryzae isolate N5828 was observed with an electron microscope. Since the centrifuged supernatant of the cell suspension of this bacterium produces plaques on the plates seeded with X. oryzae N5850, the thread-like structure was suspected to be one of the filamentous phages. The plaque forming agent in the centrifuged supernatant of N5828 was propagated by the addition of the susceptible isolate N5850 and was sedimented with 2% polyethylene glycol, followed by low speed centrifugation. The preparation thus obained was further purified by subjecting it to rate-zonal densitygradient centrifugation. The fraction containing plaque forming agent had a UV absorption spectrum typical of nucleoprotein, and there exists close correlation between UV absorption at 260nm and the titer of a plaque forming unit. Electron microscopic observation of the purified preparation reveals thread-like structures of 900-1000nm in length without any contaminants. These results indicate that the thread-like structure released from bacterial cells is one of the filamentous phage.
