Soybean Lectin Enhances Biofilm Formation byBradyrhizobium japonicumin the Absence of Plants

Abstract

Soybean lectin (SBL) purified from soybean seeds by affinity chromatography strongly bound toBradyrhizobium japonicumUSDA 110 cell surface. This lectin enhanced biofilm formation byB. japonicumin a concentration-dependent manner. Presence of galactose during biofilm formation had different effects in the presence or absence of SBL. Biofilms were completely inhibited in the presence of both SBL and galactose, while in the absence of SBL, galactose was less inhibitory. SBL was very stable, since its agglutinating activity ofB. japonicumcells as well as of human group A+ erythrocytes was resistant to preincubation for one week at60°C. Hence, we propose that plant remnants might constitute a source of this lectin, which might remain active in soil and thus favorB. japonicumbiofilm formation in the interval between soybean crop seasons.