Characterization of bacteriocin from lactic acid bacteria and its antibacterial activity against Ralstonia solanacearum causing tomato wilt

K. Narasimha Murthy, M. Malini, K. Soumya, Fazilath Uzma, Savitha J, S.R Niranjana, C. Srinivas

Plant Science Archives 1(1), 44-58, 2016.


Bacterial wilt caused by Ralstonia solanacearum is a major disease in solanaceous plants. It is one of the most destructive bacterial diseases of tomato and other economically important crops. One hundred isolates of R. solanacearum were obtained from rhizosphere soil of tomato fields in different parts of Karnataka. Forty strains of lactic acid bacteria (LAB) were isolated from soil samples. Among 40 LABs, isolate 35showed a maximum zone of inhibition (22–26 mm) against R. solanacearum by agar overlay method and it was identified as Lactobacillus paracasei by 16S rRNA analysis. The bacteriocin from the culture supernatant was found to be proteinaceous in nature. It was 60%stable at temperature range of 30-32 °C for 30 days. It showed maximum antagonistic activity at a pH range of 4-10. Antibacterial activity increased with up to 1% surfactants and decreased at low concentration of metal ions at 0.5mg/l. The antimicrobial substance was sensitive to the proteolytic action of trypsin. Seed germination and seedling vigour enhanced upon treatment with bacteriocin. Under greenhouse conditions, bacteriocin treatment increased the plant growth promotion and reduced wilt by 57.48% and 54.77% by seed treatment and soil drench methods respectively. In the present study, it is the first report that bacteriocin exhibits antagonistic activity and increases the plant growth promotion against R. solanacearum in vitro and invivo. These important results recommend that soil may be a common source for the isolation of bacteriocin producing lactic acid bacteria and can be used as biocontrol agent.