AimsThis work evaluated the antibacterial activity of a water-soluble Moringa oleifera seed lectin (WSMoL) by evaluating its effect on growth, survival and cell permeability of Bacillus sp., Bacillus cereus, Bacillus pumillus, Bacillus megaterium, Micrococcus sp., Pseudomonas sp., Pseudomonas fluorescens, Pseudomonas stutzeri and Serratia marcescens. In addition, the effect of lectin on membrane integrity of most sensitive species was also evaluated. All the tested bacteria are able to cause biocorrosion and some are also responsible for human infections. Methods and ResultsWSMoL inhibited the bacterial growth, induced agglutination and promoted the leakage of proteins from cells of all strains. Bactericidal effect was detected against Bacillus sp., B.pumillus, B.megaterium, Ps.fluorescens and Ser.marcescens. The bacteriostatic effect of lectin was evident with only 6h of incubation. Fluorescence microscopy of Ser.marcescens showed that WSMoL caused loss of cell integrity and indicated an anti-biofilm activity of the lectin. ConclusionsWSMoL was active against the bacteria by inhibiting growth and affecting cell permeability. The lectin also interfered with membrane integrity of Ser.marcescens, the most sensitive species. Significance and Impact of the StudyThe study indicates that WSMoL was active against bacteria that cause serious problems in both industrial and health sectors. Also, the study contributes for the state-of-art' on antibacterial mechanisms of lectins.