Department of Agricultural Biotechnology, Seoul National University, Seoul, Korea.
KT&G Central Research Institute, Daejeon, Korea.
J Appl Microbiol. 2010 Aug;109(2):461-470. doi: 10.1111/j.1365-2672.2010.04674.x. Epub 2010 Jan 11.
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 10(8) colony-forming units (CFU) ml(-1)] and low (1 x 10(6) 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 degrees 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 beta-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.
研究植物促生根瘤菌多粘类芽孢杆菌 GBR-1 的种群增长与生物学特性之间的关系。
在体外和体内，分别用高（1×10(8)cfu/ml）和低（1×10(6)cfu/ml）初始接种密度，检测了从腐烂人参根中分离出的多粘类芽孢杆菌 GBR-1 的种群增长、菌落形成、淀粉水解活性以及对人参根腐病的影响。多粘类芽孢杆菌 GBR-1 在淀粉含量相对较低的改良淀粉琼脂上具有较强的淀粉水解活性，但仅在一定的培养温度（18 和 23℃）下才有此活性；高密度接种可产生比低接种密度形成的菌落厚约 9 倍的细菌菌落。通过光镜、扫描电镜和透射电镜观察发现，高密度接种形成的厚菌落充满了胞外聚合物（EPS），其中分布着相对较少的椭圆形-杆状细菌细胞（主要是带芽孢的细胞）。相比之下，低密度接种形成的薄菌落由大量的杆状营养细胞组成，且 EPS 最少。荧光原位杂交（FISH）显示，只有在高密度接种形成的厚菌落中的细菌细胞中表达了β-淀粉酶基因，而在低密度接种形成的薄菌落中则没有表达。厚菌落的培养液滤液在改良淀粉琼脂上产生水解透明带，以各种方式降解淀粉颗粒，并在人参根组织上产生腐烂症状。
多粘类芽孢杆菌 GBR-1 的菌落形成、淀粉水解和人参组织腐烂等生物学特性相互关联；它们受初始细菌种群密度的影响，但不受原位和最终种群密度的影响。
了解多粘类芽孢杆菌 GBR-1 的致病特性可用于开发生物防治策略。
