Journal Article
Spatial colonization patterns and interaction of bacteria on inoculated sugar beet seed [1994]
Fukui, R. (University of Hawaii at Manoa, Honolulu); Poinar, E.I.; Bauer, P.H.; Schroth, M.N.; et al.
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Development and spatial distribution of microcolonies of Pseudomonas spp. and Bacillus subtilis GB03 inoculated singly and in combination on sugar beet (Beta vulgaris) seed were observed with a scanning electron microscope (SEM). SEM examination of seed directly after inoculation with Pseudomonas strain 33-2 or ML5 at population densities of approximately 10(4) cfu per seed revealed a random distribution of individual cells. By 24 h, when population densities had reached the stationary phase (approximately 10(6) cfu per seed), microcolonies had developed in a random pattern over the seed surface. However, even at these populations, only 10-40% of the seed surface was colonized. Most microcolonies developed as separate entities on the indented surface of cells of the perianth and the operculum. The colonization patterns at 48 h were similar to those at 24 h, except that the colonies were larger. Since the number of cfu measured by dilution plating (detectable population) was similar at both time periods, it was assumed that many cells were dead or dormant in the larger microcolonies. The spatial colonization patterns were entirely different, depending on the density of the initial inoculum. The entire seed surface was covered when sufficient inoculum was applied to attain a detectable population size of approximately 10(7) cfu per seed. Yet, even when the detectable population size increased to 10(7) cfu per seed following growth from an initial inoculum de
nsity of 10(4) cfu per seed, only 40-50% of the seed surface was colonized. This indicates the need for differentiating among live, dormant, and dead cells. The spatial colonization pattern of strain GB03 differed greatly from Pseudomonas strains. At temperatures favoring its growth, microcolonies of GB03 were located primarily near the basal pore of the seed, whether inoculated singly or coinoculated with Pseudomonas putida 33-2. In coinoculations, few microcolonies of 33-2 developed near the basal pore
