A Bacterial Endophyte, Pseudomonas brassicacearum YC5480, Isolated from the Root of Artemisia sp. Producing Antifungal and Phytotoxic Compounds

Abstract

An endophytic bacterial strain YC5480 producing antifungal and phytotoxic compounds simultaneously was isolated from the surface sterilized root of Artemisia sp. collected at Jinju area, Korea. The bacterial strain was identified as a species of Pseudomonas brassicacearum based on its 16S rRNA gene sequence analysis and physiological and biochemical characteristics. The seed germination and growth of monocot and dicot plants were inhibited by culture filtrate (1/10-strength Tryptic Soy Broth) of the strain. The germination rate of radish seeds in the culture filtrate differed in various culture media. Only 20% of radish seeds germinated in the culture media of 1/2 TSB for 5 days incubation. Mycelial growth of fungal pathogens, Colletotrichum gloeosporioides, Fusarium oxysporum and Phytophthora capsici was also inhibited by the culture filtrate of the strain YC5480. An antifungal compound, KS-1 with slight inhibitory activity of radish seed germination at 1,000 ppm and a seed germination inhibitory compound, KS-2 without suppression of fungal growth were produced simultaneously in TSB. The compounds KS-1 and KS-2 were identified to be 2,4-diacetylphloroglucinol (DAPG) and 2,4,6-trihydroxyacetophenone (THA), respectively.

Diversity and Characterization of Endophytic Bacteria Associated with Tidal Flat Plants and their Antagonistic Effects on Oomycetous Plant Pathogens

“…Six plant species were collected from the tidal flat of Namhae Island (N 34°50'15.62"; E 127°53'32.72") located at the middle of southern part in Korea (Table 1). For the isolation of endophytic bacteria from plant roots, some modifications were made in a previously described isolation process (Chung et al, 2008). Root pieces were washed several times with running tap water and surface sterilized by stepwise washing in 70% ethanol for 5 min, 1.0% NaOCl for 10 min, 70% ethanol for about 10 sec and, finally, washed with sterile distilled water several times.…”

“…Many bacteria on the root surface and in the rhizosphere benefit plants. In particular, some bacteria residing in the interior of plant tissues and intercellular spaces provide benefits to the host, which include plant growth promotion and induction of plant defense mechanisms, by providing growth-stimulating or resistance-inducing substances or producing antibiotics for outcompeting fungal pathogens Brooks et al, 1994;Chert et al, 1995;Chung et al, 2010;Chung et al, 2008;Ryu et al, 2003), without causing harm (Schulz and Boyle, 2006). The bacteria benefit by being protected from the competitive and high-stress environment of the soil compared to bacteria restricted to the rhizosphere and the rhizoplane (Rosenblueth and Martínez-Romero, 2006).…”

Bacillus graminis sp. nov., an endophyte isolated from a coastal dune plant

“…Isolation was carried out as described previously (Chung et al, 2008). Root pieces were washed several times with running tap water and surface sterilized by stepwise washing in 70 % ethanol for 5 min, 1.0 % NaOCl for 10 min and 70 % ethanol for about 10 s and finally washed several times with sterile distilled water.…”

Amorphus suaedae sp. nov., isolated from the root of a tidal flat plant, Suaeda maritima

“…A root fragment of the plant was surface-sterilized with 70 % ethanol for 5 min, 1.0 % NaOCl for 10 min and 70 % ethanol for about 10 s and rinsed several times with distilled water (Chung et al, 2008). The samples was serially diluted in distilled water and an aliquot was spread on one-tenth strength R2A (1/10 R2A) medium in filtered seawater.…”