Althabegoiti María Julia, López-García Silvina L, Piccinetti Carlos, Mongiardini Elías J, Pérez-Giménez Julieta, Quelas Juan Ignacio, Perticari Alejandro, Lodeiro Aníbal R
Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET, La Plata, Argentina.
FEMS Microbiol Lett. 2008 May;282(1):115-23. doi: 10.1111/j.1574-6968.2008.01114.x. Epub 2008 Mar 10.
A Bradyrhizobium japonicum USDA 110-derived strain able to produce wider halos in soft-agar medium than its parental strain was obtained by recurrent selection. It was more chemotactic than the wild type towards mannitol and three amino acids. When cultured in minimal medium with mannitol as a single carbon-source, it had one thick subpolar flagellum as the wild type, plus several other flagella that were thinner and sinusoidal. Root adsorption and infectivity in liquid media were 50-100% higher for the selected strain, but root colonization in water-unsaturated vermiculite was similar to the wild type. A field experiment was then carried out in a soil with a naturalized population of 1.8 x 10(5) soybean-nodulating rhizobia g of soil(-1). Bradyrhizobium japonicum strains were inoculated either on the soybean seeds or in the sowing furrows. Nodule occupation was doubled when the strains were inoculated in the sowing furrows with respect to seed inoculation (significant with P<0.05). On comparing strains, nodule occupation with seed inoculation was 6% or 10% for the wild type or selected strains, respectively, without a statistically significant difference, while when inoculated in the sowing furrows, nodule occupation increased to 12% and 22%, respectively (differences significant with P<0.05).
通过轮回选择获得了一株源自慢生根瘤菌日本种USDA 110的菌株，该菌株在软琼脂培养基中产生的晕圈比其亲本菌株更宽。与野生型相比，它对甘露醇和三种氨基酸的趋化性更强。当在以甘露醇作为单一碳源的基本培养基中培养时，它与野生型一样有一根粗壮的亚极鞭毛，另外还有几根更细且呈正弦状的鞭毛。所选菌株在液体培养基中的根吸附和感染性比野生型高50 - 100%，但在水分不饱和的蛭石中的根定殖情况与野生型相似。然后在每克土壤中天然存在1.8×10⁵个大豆根瘤菌种群的土壤中进行了田间试验。慢生根瘤菌日本种菌株分别接种在大豆种子上或播种沟中。与种子接种相比，当菌株接种在播种沟中时，根瘤占有率翻倍（P<0.05，差异显著）。比较各菌株时，野生型或所选菌株通过种子接种的根瘤占有率分别为6%或10%，无统计学显著差异，而接种在播种沟中时，根瘤占有率分别增至12%和22%（差异显著，P<0.05）。
