The bactericidal activity of lectins from nitrogen-fixing bacilli

Abstract

Lectins I and II isolated from the nitrogen-fixing soil bacterium Paenibacillus polymyxa 1460 were found to be able to suppress the growth of Rhizobium leguminosarum 252 and Bacillus subtilis 36 at nearly all the concentrations tested (from 1 to 10 micrograms/ml). Lectin I was also inhibitory to Azospirillum brasilense 245 and Erwinia carotovora subsp. citrulis 603, while lectin II exerted bactericidal activity against Xanthomonas campestris B-610 and B-611 and A. brasilense 245. The bacillar lectins incubated with Rhizobium and Azospirillum cells caused leakage of low-molecular-weight substances from the cells, presumably resulting from impairment of the membrane barrier function. We believe that one of the possible mechanisms of the bacterial growth inhibition by lectins is mediated by the lectin-specific receptors occurring on the bacterial membrane, whose interaction with the lectin molecules induces conformational alterations in the membrane and concurrent malfunction of the metabolism of bacterial cells.