Studies on the antimicrobial activity of a locally isolated lactic acid bacterium and its application on -infected plants

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Abstract

Background
Lactic acid bacteria (LAB) have proven a great inhibitory effect toward phytopathogenic bacteria and fungi, giving them the importance as natural biological control agents without hazards to the surrounding eco-system.
Objective
This study aims for the local isolation of a lactic acid bacterial strain active against different microorganisms especially phytopathogens.
Materials and methods
Of the 40 isolated bacterial strains, 36 were preliminarily characterized as LAB using both Gram staining and catalase test methods. Their antimicrobial activities were then tested against different bacterial and fungal strains. The most potent isolate was molecularly identified and tested, , on different pathogens, and then, , against infected plants.
Results and conclusion
Results revealed that 17 isolates showed antimicrobial activities against and four of them were solely effective against (inhibition zones of diameters ranging between 0.4 and 0.8 cm). However, only isolate 32 showed satisfactory antimicrobial activity (inhibition zones of ∼0.8 cm) against both of the two aforementioned test microorganisms. Moreover, isolate 32, molecularly identified as , was also found to be active against , a common phytopathogen fungus that affects many economically important crops. The addition of 1.5% (v/v) of the 24-h old fermentation broth of this isolate, , resulted in a shrinking percent of the fungus growth of more than 51% and gave very promising results when applied in the field experiment. Therefore, the use of the selected LAB culture broth as a bioagent to control some plant pathogens, as well as a plant growth stimulator, could be a promising approach to reduce the economic losses in agricultural crops.

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