Liu Xuming, Zhao Hongxing, Chen Sanfeng
State Key Laboratory for Agrobiotechnology and College of Biological Sciences, China Agricultural University, Beijing, 100094, P. R. China.
Curr Microbiol. 2006 Mar;52(3):186-90. doi: 10.1007/s00284-005-0162-3. Epub 2006 Feb 18.
Bacillus megaterium C4, a nitrogen-fixing bacterium, was marked with the gfp gene. Maize and rice seedlings were inoculated with the, GFP-labeled B. megaterium C4 and then grown in gnotobiotic condition. Observation by confocal laser scanning microscope showed that the GFP-labeled bacterial cells infected the maize roots through the cracks formed at the lateral root junctions and then penetrated into cortex, xylem, and pith, and that the bacteria migrated slowly from roots to stems and leaves. The bacteria were mainly located in the intercellular spaces, although a few bacterial cells were also present within the xylem vessels, root hair cells, epidermis, cortical parenchyma, and pith cells. In addition, microscopic observation also revealed clearly that the root tip in the zone of elongation and differentiation and the junction between the primary and the lateral roots were the two sites for the bacteria entry into rice root. Therefore, we conclude that this Gram-positive nitrogen-fixer has a colonization pattern similar to those of many Gram-negative diazotrophs, such as Azospirillun brasilense Yu62 and Azoarcus sp. As far as we know, this is the first detailed report of the colonization pattern for Gram-positive diazotrophic Bacillus.
巨大芽孢杆菌C4是一种固氮细菌，用绿色荧光蛋白（gfp）基因进行了标记。将绿色荧光蛋白标记的巨大芽孢杆菌C4接种到玉米和水稻幼苗上，然后在无菌条件下培养。共聚焦激光扫描显微镜观察表明，绿色荧光蛋白标记的细菌细胞通过侧根连接处形成的裂缝感染玉米根，然后穿透到皮层、木质部和髓部，并且细菌从根缓慢迁移到茎和叶。细菌主要位于细胞间隙，尽管也有一些细菌细胞存在于木质部导管、根毛细胞、表皮、皮层薄壁细胞和髓细胞内。此外，显微镜观察还清楚地显示，伸长和分化区的根尖以及主根与侧根的连接处是细菌进入水稻根的两个部位。因此，我们得出结论，这种革兰氏阳性固氮菌具有与许多革兰氏阴性固氮菌类似的定殖模式，如巴西固氮螺菌Yu62和食氮菌属。据我们所知，这是关于革兰氏阳性固氮芽孢杆菌定殖模式的第一份详细报告。
