Endophytic Bacterial Diversity in the Young Radish and Their Antimicrobial Activity against Pathogens

Abstract

Endophytic bacteria have several ecological roles and can be used as biocontrol agents and also participate in antibiosis interactions. The diversity of endophytic bacteria associated with young radish (YR, yeulmu, Raphanus sativus L.) leaves and roots from Gyeongnam Agricultural Research and Extension Services in Jinju, Korea was investigated. A total of 264 colonies were isolated from the interior of YR leaves and roots. Phylogenetic analysis based on 16S rDNA, sequences indicated that the isolates belonged to four major phylogenetic groups: high G+C Gram positive bacteria, low G+C Gram positive bacteria, Proteobacteria, and Bacteroidetes. Endophytic bacteria from the phylum Proteobacteria were predominant in the leaf (61.3%) and root (52.1%) samples. Most colonies that exhibited extracellular enzymatic activity belonged to the genus Bacillus, and Bacillus subtilis (YRL02, YRL07, YRR03, and YRR10) exhibited the stronger activities in extracellular enzyme such as amylase, cellulase, xylanase, mannase, PGAase, DNase, protease, and esterase than other colonies. In addition, Enterobacter sp. YRL01 and B. subtilis YRL02 had the highest amount of inhibitory action against human pathogenic bacteria, while B.. subtilis YRR10 hand an inhibitory action against plant pathogenic fungi. Thus, these bacteria can be used as biocontrol agents against human and plant pathogens.