1、菌株名称：苜蓿中华根瘤菌Sinorhizobium meliloti
3、其它中心编号：ATCC9930
4、主要用途：研究；教学
斜面菌种和冻干菌种应在2~8℃保存。
1. 培养基名称：根瘤菌琼脂-1
2. 培养基成分：Sucrose (or Mannitol) 10.0 g，MgSO4·7H2O 0.2 g，K2HPO4 0.5 g,CaSO4 0.2 g，NaCl 0.1 g, NaMoO4(1%) 1.0 ml, MnSO4(1% ) 1.0 ml, Yeast extract 1.0 g, Iron citrate(1%) 1.0 ml, Boric acid (1%) 1.0 ml, Agar 15.0 g, Distilled water 1.0 L, pH 6.8-7.0
3. 培养温度：28-30℃
4. 培养时间：24-48h
1、复苏后，微生物菌种应保藏于建议的温度、清洁和干燥的地方，室温放置时间过长会导致菌种衰退。
2、初次使用时请按照本说明书推荐条件进行复活培养，如使用其它类型培养基或培养条件造成菌种不活等损失，泰斯拓生物不负责任。
3、使用者应保证菌种的安全存储和操作，带菌废弃物应高压灭菌处理后丢弃。
Ensifer meliloti (formerly Rhizobium meliloti and Sinorhizobium meliloti) are an aerobic, Gram-negative, and diazotrophic species of bacteria. S. meliloti are motile and possess a cluster of peritrichous flagella. S. meliloti fix atmospheric nitrogen into ammonia for their legume symbionts, such as alfalfa. S. meliloti forms a symbiotic relationship with legumes from the genera Medicago, Melilotus and Trigonella, including the model legume Medicago truncatula. This symbiosis promotes the development of a plant organ, termed a root nodule. Because soil often contains a limited amount of nitrogen for plant use, the symbiotic relationship between S. meliloti and their legume hosts has agricultural applications. These techniques reduce the need for inorganic nitrogenous fertilizers.
Symbiosis between S. meliloti and its legume hosts begins when the plant secretes an array of betaines and flavonoids into the rhizosphere: 4,4′-dihydroxy-2′-methoxychalcone, chrysoeriol, cynaroside, 4′,7-dihydroxyflavone, 6′′-O-malonylononin, liquiritigenin, luteolin, 3′,5-dimethoxyluteolin, 5-methoxyluteolin, medicarpin, stachydrine, and trigonelline. These compounds attract S. meliloti to the surface of the root hairs of the plant where the bacteria begin secreting nod factors. This initiates root hair curling. The rhizobia then penetrate the root hairs and proliferate to form an infection thread. Through the infection thread, the bacteria move toward the main root. The bacteria develop into bacteroids within newly formed root nodules and perform nitrogen fixation for the plant. A S. meliloti bacterium does not perform nitrogen fixation until it differentiates into a endosymbiotic bacteroid. A bacteroid depends on the plant for survival.
Leghemoglobin, produced by leguminous plants after colonization of S. meliloti, interacts with the free oxygen in the root nodule where the rhizobia reside. Rhizobia are contained within symbiosomes in the root nodules of leguminous plants. The leghemoglobin reduces the amount of free oxygen present. Oxygen disrupts the function of the nitrogenase enzyme in the rhizobia, which is responsible for nitrogen fixation.
The S. meliloti genome contains four genes coding for flagellin. These include fliC1C2–fliC3C4.The genome contains three replicons: a chromosome (~3.7 megabases), a chromid (pSymB; ~1.7 megabases), and a plasmid (pSymA; ~1.4 megabases). Individual strains may possess additional, accessory plasmids. Five S. meliloti genomes have been sequenced to date: Rm1021,AK83,BL225C, Rm41,and SM11with 1021 considered to be the wild type. Indeterminate nodule symbiosis by S. meliloti is conferred by genes residing on pSymA.
The proteins encoded by E. meliloti genes uvrA, uvrB and uvrC are employed in the repair of DNA damages by the process of nucleotide excision repair. E. meliloti is a desiccation tolerant bacterium. However, E. meliloti mutants defective in either genes uvrA, uvrB or uvrC are sensitive to desiccation, as well as to UV light. This finding indicates that the desiccation tolerance of wild-type E. meliloti depends on the repair of DNA damages that can be caused by desiccation.
