Infection of legumes by Rhizobium sp. is a complex sequence of events that precede symbiotic association between bacteria and plant culminating in fixation of N. Degradative enzymes have been suggested to be involved in precise and localized dissolution of the root hair cell wall for the entry of rhizobial cells into the plant. Attempts have been made in R. leguminosarum bv. trifolii strain hrt 27, to mutagenically improve the ability of rhizobia to degrade legume root cell wall carbohydrates. A mutant M20 with 155.5% cellulase content in relation to its parent was identified which behaved as a super-nodulating rhizobia. Cellulose degrading enzymes were found to have a predominant role compared to similarly acting pectinase in the symbiotic infection of clover (Trifolium alexandrinum).