Effects of initial inoculation density of Paenibacillus polymyxa on colony formation and starch-hydrolytic activity in relation to root rot in ginseng

To examine the relationships between population growth and biological characters of the plant-growth-promoting rhizobacterium Paenibacillus polymyxa GBR-1. Population growth, colony formation, starch-hydrolytic activity, and ginseng root rot caused by P. polymyxa GBR-1 isolated from a rotten ginseng...

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Bibliographic Details
Published in:Journal of applied microbiology 2010-08, Vol.109 (2), p.461-470
Main Authors: Jeon, Y.H, Kim, S.G, Hwang, I, Kim, Y.H
Format: Article
Language:English
Subjects:
Bacteria
beta-Amylase - metabolism
Biological and medical sciences
Biological control
Biological properties
Cell culture
Colonies
colony formation
Extracellular polymers
Filtrate
Fluorescence
Fluorescence in situ hybridization
Fundamental and applied biological sciences. Psychology
Ginseng
ginseng tissue rotting
Incubation
initial inoculum
Inoculation
Inoculum
Microbiology
Paenibacillus - growth & development
Paenibacillus - metabolism
Paenibacillus polymyxa
Paenibacillus polymyxa GBR-1
Panax - growth & development
Panax - microbiology
Pest Control, Biological
Plant Diseases - microbiology
Plant Roots - microbiology
Plant tissues
Population density
Population growth
Root rot
Signs and symptoms
Starch
Starch - metabolism
starch hydrolysis
Transmission electron microscopy
Vegetative cells
β-Amylase
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Summary:To examine the relationships between population growth and biological characters of the plant-growth-promoting rhizobacterium Paenibacillus polymyxa GBR-1. Population growth, colony formation, starch-hydrolytic activity, and ginseng root rot caused by P. polymyxa GBR-1 isolated from a rotten ginseng root were examined in vitro and in vivo at high [1 x 10⁸ colony-forming units (CFU) ml⁻¹] and low (1 x 10⁶ CFU ml⁻¹) initial inoculum densities. Paenibacillus polymyxa GBR-1 showed strong starch-hydrolytic activity on modified starch agar with relatively low starch content, but only at certain incubation temperatures (18 and 23°C); the high-density inoculum produced bacterial colonies about nine times thicker than those formed from the lower inoculum density. Light, scanning electron, and transmission electron microscopy showed that the thick colonies from the high-density inoculum were filled with extracellular polymeric substances (EPS), in which a relatively small number of ovoid-rod-shaped bacterial cells (mostly endospore-bearing cells) were distributed. In contrast, the thin colonies from the low-density inoculum were composed of massive vegetative cells with a rectangular rod shape and minimum EPS. Fluorescent in situ hybridization (FISH) revealed that the β-amylase gene was expressed only in bacterial cells from the thick colonies formed from the high-density inoculum, but not in those from the low-density inoculum. The culture filtrate from the thick colonies produced a hydrolytic clear zone on modified starch agar, degraded starch granules in various manners, and produced rot symptoms on ginseng root tissues. The biological properties of colony formation, starch hydrolysis, and ginseng tissue rotting by P. polymyxa GBR-1 are interrelated; they are influenced by the initial bacterial population density but not by the in situ and the final population densities. Knowledge of disease-inducing characters of P. polymyxa GBR-1 can be used in the development of biocontrol strategies.
ISSN:1364-5072
1365-2672
DOI:10.1111/j.1365-2672.2010.04674.x