Abstract：
Methanotrophs of the genus Methylocystis are frequently found in rice paddies. Although more than ten facultative methanotrophs have been reported since 2005, none of these strains was isolated from paddy soil. Here, a facultative methane-oxidizing bacterium, Methylocystis iwaonis SD4, was isolated and characterized from rhizosphere samples of rice plants in Nanjing, China. This strain grew well on methane or methanol but was able to grow slowly using acetate or ethanol. Moreover, strain SD4 showed sustained growth at low concentrations of methane (100 and 500 ppmv). M. iwaonis SD4 could utilize diverse nitrogen sources, including nitrate, urea, ammonium as well as dinitrogen. Strain SD4 possessed genes encoding both the particulate methane monooxygenase and the soluble methane monooxygenase. Simple and rapid genetic manipulation methods were established for this strain, enabling vector transformation and unmarked genetic manipulation. Fast growth rate and efficient genetic tools make M. iwaonis SD4 an ideal model to study facultative methanotrophs, and the ability to grow on low concentration of methane implies its potential in methane removal.
摘要：
甲基囊藻属的甲烷营养菌常见于稻田中。尽管自2005年以来已报道了十多种兼性甲烷营养菌，但这些菌株均未从稻田土壤中分离出来。这里,兼性甲烷氧化细菌，从南京水稻植物的根际样品中分离并鉴定了methylocystisiwaonisSD4，中国。该菌株在甲烷或甲醇上生长良好,但能够使用乙酸盐或乙醇缓慢生长。此外，菌株SD4在低浓度的甲烷（100和500ppmv）下显示出持续的生长。M.iwaonisSD4可以利用多种氮源，包括硝酸盐,尿素,铵和氮。菌株SD4具有编码颗粒甲烷单加氧酶和可溶性甲烷单加氧酶的基因。建立了该菌株简单快速的遗传操作方法,实现载体转化和无标记的遗传操作。快速的生长速度和高效的遗传工具使M.iwaonisSD4成为研究兼性甲烷营养菌的理想模型，并且在低浓度甲烷下生长的能力意味着其在甲烷去除方面的潜力。
