Kinetics and strain specificity of rhizosphere and endophytic colonization by enteric bacteria on seedlings of Medicago sativa and Medicago truncatula
Kinetics and strain specificity of rhizosphere and endophytic colonization by enteric bacteria on seedlings of Medicago sativa and Medicago truncatula
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DOI：
10.1128/aem.69.3.1783-1790.2003
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发表时间：
2003-03-01
影响因子：
4.4
通讯作者：
Triplett, EW
中科院分区：
文献类型：
--
作者：
Dong, YM;Iniguez, AL;Triplett, EW
生农产品表面和内部存在人类致病的肠道细菌是一个重大的健康问题。这里讨论了这些细菌与紫花苜蓿(Medicago Sativa)幼苗之间相互作用的生物学方面的几个方面。用绿色荧光蛋白标记了与紫花苜蓿芽污染相关的肠杆菌、大肠杆菌K-12、鼠伤寒沙门氏菌atcc 14028和玉米内生菌肺炎克雷伯氏菌342，并比较了它们在根际和植株内部定植的能力。这些菌株的内生定植能力差异很大，肺炎克雷伯菌342和大肠杆菌K-12分别是最好和最差的定殖菌。病原菌的能力介于肺炎克雷伯菌342和大肠杆菌K-12之间。所有沙门氏菌都在苗木内部大量定植，接种量为10(2)cfu，尽管每个菌株的感染特征不同。对大多数菌株而言，内生定殖率与根际定殖率有很强的相关性。这些结果表明，这些菌株对进入植物具有显著的菌株特异性。观察到侧根裂缝的显著定植，表明这可能是这些细菌进入植物的场所。在低接种量条件下，根际共生突变体dmil在根际和内生沙门氏菌体内的定殖量均高于野生型寄主。元宝菇的内生侵入似乎是通过一种独立于苜蓿中华根瘤菌或菌根真菌共生侵染的机制发生的。
The presence of human-pathogenic, enteric bacteria on the surface and in the interior of raw produce is a significant health concern. Several aspects of the biology of the interaction between these bacteria and alfalfa (Medicago sativa) seedlings are addressed here. A collection of enteric bacteria associated with alfalfa sprout contaminations, along with Escherichia coli K-12, Salmonella enterica serotype Typhimurium strain ATCC 14028, and an endophyte of maize, Klebsiella pneumoniae 342, were labeled with green fluorescent protein, and their abilities to colonize the rhizosphere and the interior of the plant were compared. These strains differed widely in their endophytic colonization abilities, with K. pneumoniae 342 and E. coli K-12 being the best and worst colonizers, respectively. The abilities of the pathogens were between those of K. pneumoniae 342 and E. coli K-12. All Salmonella bacteria colonized the interiors of the seedlings in high numbers with an inoculum of 10(2) CFU, although infection characteristics were different for each strain. For most strains, a strong correlation between endophytic colonization and rhizosphere colonization was observed. These results show significant strain specificity for plant entry by these strains. Significant colonization of lateral root cracks was observed, suggesting that this may be the site of entry into the plant for these bacteria. At low inoculum levels, a symbiosis mutant of Medicago truncatula, dmil, was colonized in higher numbers on the rhizosphere and in the interior by a Salmonella endophyte than was the wild-type host. Endophytic entry of M. truncatula appears to occur by a mechanism independent of the symbiotic infections by Sinorhizobium meliloti or mycorrhizal fungi.