The symbiotic association between rhizobia and legume roots is a complex process involving many steps. An infection thread is a tubular structure of host origin formed during the infection of legume roots by rhizobia. Previous studies with batch cultures have reported that optimal attachment of rhizobia to root hairs coincides with nutrient limitation. In this study, the ability of chemostat-grown, nutrient-limited cells to form infection threads with its symbiotic partner was investigated. Rhizobia were grown in a chemostat in synthetic media under C- or N-limiting conditions. Infection-thread formation was examined after inoculation of seedlings with a rhizobial cell suspension from each treatment. The number of infection threads was estimated by light microscopy after staining root sections with o-toluidine. Exopolysaccharide (EPS) production was also measured, and the cellular content and electrophoretic pattern of lipopolysaccharide (LPS) determined semiquantitatively. N-limited cells showed a markedly higher infectivity (measured as infection-thread formation) than C-limited cells. With one of the two bean cultivars used, the number of infection threads produced by N-limited cells was higher than that produced by exponentially growing cells in batch cultures. The higher infectivity of N-limited cells was correlated with higher EPS production. Electrophoretic analysis of LPS showed that C- and N-limited cells shared a common profile but the relative concentration of short LPS forms differed.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error