GROWTH AND MOVEMENT OF SPOT INOCULATED RHIZOBIUM-MELILOTI ON THE ROOT SURFACE OF ALFALFA
GROWTH AND MOVEMENT OF SPOT INOCULATED RHIZOBIUM-MELILOTI ON THE ROOT SURFACE OF ALFALFA
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DOI：
10.1104/pp.98.3.1181
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发表时间：
1992-03-01
期刊：
影响因子：
7.4
通讯作者：
BAUER, WD
中科院分区：
文献类型：
--
作者：
CAETANOANOLLES, G;WROBELBOERNER, E;BAUER, WD
将体积约为10纳升的接种液滴和含有约10个梅利洛蒂根瘤菌细胞的接种液滴放在苜蓿幼苗的根表面的塑料生长袋中，分别放在根尖、最小的露出根毛的位置，或在这些点之间的中间位置。液滴最初被限制在大约0.2平方毫米的区域内。接种后48和96 h，接种菌及其子代分布在初始沉积部位和生长根尖之间数厘米的根内，在初始沉积部位附近密度达到每厘米10(3)~ 10(4)个细菌，从初始沉积部位向根尖方向呈指数递减。沉积在根表面靠近生长尖端的石墨颗粒在48和96 h时沿根长分布相似，表明根细胞伸长的被动位移是细菌传播的主要原因。一个非运动突变体在苜蓿根部的定殖程度与野生型相同，并且通常以相同的方式分布，这表明在这些条件下细菌的运动性对细菌的长距离传播贡献不大。然而，当少量施用时，在移动性或趋化性方面有缺陷的R. meliloti突变体在接种点附近形成根瘤的效率明显低于野生型。这意味着运动性和/或趋化性对局部寻找合适的感染部位有重要贡献。初生根上几乎所有的根瘤都是在离接种点几毫米的范围内形成的，这表明在我们的实验条件下，在根生长过程中，根表面的移动和繁殖不足以在根感染区维持足够的种群。
Inoculum droplets of approximately 10 nanoliter volume and containing about 10 Rhizobium meliloti cells were placed onto the root surface of alfalfa seedlings in plastic growth pouches at either the root tip, the position of the smallest emergent root hairs, or at a site midway between these points. The droplets were initially confined to an area of about 0.2 square millimeter at the point of application. By 48 and 96 hours after inoculation, the inoculum bacteria and their progeny were distributed over several centimeters of the root between the initial site of deposition and the growing root tip, reaching densities of 10(3) to 10(4) bacteria per centimeter near the site of initial deposition and decreasing exponentially from that point toward the root tip. Graphite particles deposited on the root surface close to the growing tip were similarly distributed along the root length by 48 and 96 hours, suggesting that passive displacement by root cell elongation was primarily responsible for the spread of bacteria. A nonmotile mutant of R. meliloti colonized alfalfa roots to the same extent as the wild type and was usually distributed in the same manner, indicating that bacterial motility contributed little under these conditions to long distance spread of the bacteria. However, when applied in low numbers, R. meliloti mutants defective in motility or chemotaxis were considerably less efficient in initiating nodules near the point of inoculation than the wild type. This implies that motility and/or chemotaxis contribute significantly to local exploration for suitable infection sites. Almost all nodules on the primary root formed within a few millimeters of the spot-inoculation site, indicating that, under our experimental conditions, movement and multiplication of R. meliloti on the root surface were not sufficient to maintain an adequate population in the infectible region of the root during root growth.