Lysogeny in Bradyrhizobium japonicum and its effect on soybean nodulation

H. M. Abebe, M. J. Sadowsky, B. K. Kinkle, E. L. Schmidt

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Abstract

Rhizobiophage V, isolated from soil in the vicinity of soybean roots, was strongly lytic on Bradyrhizobium japonicum 123B (USDA 123) but only mildly lytic on strain L4-4, a chemically induced small-colony mutant of 123. Numerous bacteriophage-resistant variants were isolated from L4-4 infected with phage V; two were studied in detail and shown to be lysogenic. The two, L4-4 (V5) and L4-4 (V12), are the first reported examples of temperate-phage infection in B. japonicum. Phage V and its derivative phages V5 and V12 were closely related on the basis of common sensitivity to 0.01 M sodium citrate and phage V antiserum, phage immunity tests, and apparently identical morphology when examined by electron microscopy. However, the three phages differed in host range and in virulence. Lysogens L4-4 (V5) and L4-4 (V12) were immune to infection by phages V and V5 but not to infection by V12. Southern hybridization analysis confirmed the incorporation of phage V into the genomes of strains L4-4 (V5) and L4-4 (V12) and also demonstrated the incorporation of phage V into the genome of a phage V-resistant derivative of USDA 123 designated 123 (V2). None of the three lysogens, L4-4 (V5), L4-4 (V12), or 123B (V2), was able to nodulate soybean plants. However, Southern hybridization profile data indicated that phage V had not incorporated into any of the known B. japonicum nodulation genes.

Original languageEnglish (US)
Pages (from-to)3360-3366
Number of pages7
JournalApplied and environmental microbiology
Volume58
Issue number10
StatePublished - Oct 21 1992

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