Govindarajan Munusamy, Balandreau Jacques, Kwon Soon-Wo, Weon Hang-Yeon, Lakshminarasimhan Cunthipuram
Postgraduate and Research Department of Microbiology and Botany, AVVM Sri Pushpam College, Bharathidasan University, Trichy, Tanjore 613503, South India.
Microb Ecol. 2008 Jan;55(1):21-37. doi: 10.1007/s00248-007-9247-9. Epub 2007 Apr 4.
During a survey of endophytic diazotrophic bacteria associated with different rice varieties in Tamilnadu, some "endophytes" were obtained. Thirteen bacterial isolates from surface-sterilized roots and shoots were obtained in pure culture, which produced indole acetic acid (IAA) and reduced acetylene to ethylene. Polymerase chain reaction (PCR) amplification confirmed the presence of nif-H gene in all the isolates. Morphological, biochemical, and molecular characteristics indicated that all of them belonged to the genus Burkholderia One of them, MGK3, was consistently more active in reducing acetylene, and 16S rDNA sequences of isolate MGK3 confirmed its identification as Burkholderia vietnamiensis. Colonization of rice root was confirmed by strain MGK3 marked with gusA gene. The inoculated roots showed a blue color, which was most intense at the points of lateral root emergence and at the root tip. Transverse sections of roots, 15 days after inoculation, revealed beta-glucuronidase (GUS) activity within many of the cortical intercellular spaces next to the stele and within the aerenchyma. Nitrogen fixation was quantified by using (15)N isotope dilution method with two different cultivars grown in pot and field experiments. Higher nitrogen fixation was observed in variety Ponni than in ADT-43, where nearly 42% (field) and 40% (pot) of the nitrogen was derived from the atmosphere (% Ndfa). Isolate MGK3 was used to inoculate rice seedlings in a comparison with four other diazotrophs, viz., Gluconacetobacter diazotrophicus LMG7603, Herbaspirillum seropedicae LMG6513, Azospirillum lipoferum 4B LMG4348, and B. vietnamiensis LMG10929. They were used to conduct two pot and four field inoculation experiments. MGK3 alone, and combined with other diazotrophs, performed best under both pot and field conditions: combined inoculation produced yield increases between 9.5 and 23.6%, while MGK3 alone increased yield by 5.6 to 12.16% over the uninoculated control treatment.
在对泰米尔纳德邦不同水稻品种相关的内生固氮细菌进行调查期间，获得了一些“内生菌”。从表面消毒的根和茎中获得了13株细菌分离株，它们在纯培养物中产生吲哚乙酸（IAA）并将乙炔还原为乙烯。聚合酶链反应（PCR）扩增证实所有分离株中均存在nif-H基因。形态学、生化和分子特征表明它们都属于伯克霍尔德氏菌属。其中之一MGK3在乙炔还原方面始终更具活性，分离株MGK3的16S rDNA序列证实其鉴定为越南伯克霍尔德氏菌。用携带gusA基因的菌株MGK3证实了水稻根的定殖。接种的根呈现蓝色，在侧根出现点和根尖处颜色最深。接种15天后根的横切面显示，在紧邻中柱的许多皮层细胞间隙内以及通气组织中有β-葡萄糖醛酸酶（GUS）活性。通过在盆栽和田间试验中种植的两个不同品种，使用（15）N同位素稀释法对固氮进行了定量。在Ponni品种中观察到的固氮量高于ADT-43，其中近42%（田间）和40%（盆栽）的氮来自大气（%Ndfa）。将分离株MGK3与其他四种固氮菌，即固氮葡糖醋杆菌LMG7603、巴西固氮螺菌LMG6513、脂环酸芽孢杆菌4B LMG4348和越南伯克霍尔德氏菌LMG10929进行比较，用于接种水稻幼苗。它们被用于进行两个盆栽和四个田间接种试验。单独使用MGK3以及与其他固氮菌组合使用，在盆栽和田间条件下表现最佳：联合接种使产量提高了9.5%至23.6%，而单独使用MGK3比未接种的对照处理使产量提高了5.6%至12.16%。
