A light and electron microscope study of the interaction of soil bacteria with Phytophthora cinnamomi Rands

Light- and electron-microscopic examination showed that bacteria became associated with the hyphae and asexual reproductive structures of P. cinnamomi in soil. In suppressive soils this association appears to be correlated with hyphal lysis, inhibition of zoospore production, and sporangial breakdown. One notable feature of the microbial association between P. cinnamomi and soil bacteria is the formation of extensive slime material. Many of the bacteria isolated from the fungal hyphosphere display antagonism to the growth of P. cinnamomi in vitro. The bacteria are morphologically varied and include Pseudomonas, Bacillus, and Streptomyces spp. These observations suggest that the appropriate manipulation of the antagonistic bacteria may provide a means of biological control of P. cinnamomi.