SURVIVAL OF INOCULATED BACILLUS-CEREUS SPORES AND VEGETATIVE CELLS INNON-PLANTED AND RHIZOSPHERE SOIL

The survival of vegetative cells and spores of an antibiotic-resistant Bacillus cereus (B11) inoculant was similar in wheat rhizosphere soil and non-planted soil over a period of 21 d. Reliable ways of producin g either spore or vegetative single cell inocula were developed. When applied to give densities ranging from 1 x 10(2) t o 1 x 10(7) g(-1) s oil, B11 spores survived for at least 21 d at levels similar to those introduced but numbers of vegetative cells decreased by 1-2 orders of magnitude within the first 48 h and the extent of decrease was proport ionately greater at low inoculum density. There was no significant dif ference after 21 d between total counts (vegetative cells + spores) or spore counts in either the rhizosphere or non-planted soil, regardles s of whether the inoculant was composed of vegetative or spore cells. There was no difference between the changing spore-to-vegetative cell ratio within total cell counts between rhizosphere and non-planted soi l. Inoculating soil with a mixture of Bacillus B11 (2 x 10(7) g(-1)), Flavobacterium P25 (3 x 10(8) g(-1)) and Arthrobacter A109 (2 x 10(8) g(-1)) increased the survival of P25 and A109 but decreased the surviv al of B11 in both non-planted and rhizosphere soil compared with each bacterium inoculated alone. For example, at day 21 in rhizosphere soil there were 1 x 10(6) g (-1) A109 (single inoculant) and 1 x 10(7) g(- 1) A109 (mixed inoculum) and in non-planted soil 1 x 10(5) g(-1) (sing le) and 1 x 10(7) g(-1) (mixed). Thus, neither the survival nor the ph ysiological state of Bacillus B11 was affected by the presence of deve loping wheat roots but survival was negatively affected by the presenc e of other inoculants.