Abstract
Plant pathogenic bacteria spread along hyphae on agar, the extent depending on the bacterium-fungus combination and nutrients in the medium. Spread near Pythium ultimum was better than near Rhizopus stolonifer and Trichoderma koningii. Cells of Pseudomonas syringae pv. lachrymans were static masses adjacent to old hyphae of P. ultimum motile in narrow water bands adjacent to middle-aged hyphae, and not detected near young hyphae. P. ultimum was not inhibited by any of 5 bacterial pathogens. Growth of R. stolonifer and T. koningii was inhibited by some bacteria, and young hyphae of R. stolonifer avoided bacteria on agar surfaces by growing under them. Bacteria spread via hyphae 2-3 mm across an air gap and 7.5 mm on a glass surface. Results are discussed in relation to the ecology of plant pathogenic bacteria and to fungus culture contamination by bacteria.