Factors Affecting Growth of Bdellovibrio on Rhizobium
Abstract
The extent ofdecline in the population density of Rhizobium sp. exposed to Bdellovibno was markedly reduced in the presence of montmorillonite, kaolinite or vermiculite but not by a soil clay fraction. Increasing levels of montmorillonite reduced the numbers of vibrios that appeared in a two-membered culture and allowed for greater survival of the rhizobia. Bdellovibrio and not Rhizobium spwas retained when mixed with the three clay minerals, but no appreciable retention was evident with the soil clay fraction. Suspensions of colloidal soil organic matter protected the hosts from parasitism, although aqueous
extracts of soil did not affect the relationship. Cells from old Rhizobium sp. cultures were attacked only after a lag phase, but rhizobia that had been stored were more rapidly
lysed than cells tested immediately after removal from the growth medium. The possible significance of these findings to the survival of rhizobia in soils containing Bdellovibrio is
discussed. Key words: Bdellovibrio - Clay Minerals - Parasitism- Rhizobium - Soil Ecology
Citation
Arch. Microbiol. 103, 37-43 (1975)Publisher
Laboratory of Soil Microbiology, Department of Agronomy, Cornell University Ithaca, New York