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BACKGROUND: Methane is a major greenhouse gas at-tributed to global warming partly contributed by agricul-tural activities from ruminant fermentation and rice pad-dy fields. Methanotrophs are microorganisms that utilize methane. Their unique metabolic lifestyle is enabled by enzymes known as methane monooxygenases (MMOs) catalyzing the oxidation of methane to methanol. Rice ab-sorbs, transports, and releases methane directly from soil water to its stems and the micropores and stomata of the plant epidermis. Methylobacterium species associated with rice are dependent on their host for metabolic sub-strates including methane. METHODS AND RESULTS: Methylobacterium spp. isolated from rice were evaluated for methane oxidation activities and screened for the presence of sMMO mmoCgenes. Qualitatively, the soluble methane mono-oxygenase (sMMO) activities of the selected strains of Methylobacterium spp. were confirmed by the naphthalene oxidation assay. Quantitatively, the sMMO activity ranged from 41.3 to 159.4 nmol min--1 mg of protein-1. PCR-based amplification and sequencing confirmed the presence and identity of 314 bp size fragment of the mmoC gene showing over 97% similarity to the CBMB27 mmoC gene indicating that Methylobacterium strains be-long to a similar group. CONCLUSION(S): Selected Methylobacterium spp. contained the sMMO mmoC gene and possessed methane oxidation activity. As the putative methane oxidizing strains were isolated from rice and have PGP properties, they could be used to simultaneously reduce paddy field methane emission and promote rice growth.
Phosphorus is one of the major plant growth limiting nutrients, despite being abundant in soils in both inorganic and organic forms. Phosphobioinoculants in the form of microorganisms can help in increasing the availability of accumulated phosphates for plant growth by solubilization. Penicillium ocalicum CBPS Tsa, isolated from paddy rhizosphere, was studied for its phosphate solubilization. The influence of various carbon sources Like glucose, sucrose, mannitol and sorbitol and nitrogen sources Like arginine, sodium nitrate, potassium nitrate, ammonium chloride and ammonium sulphate were evaluated using liquid media with tricalcium phosphate (Ca-P), femc phosphate (Fe-P) and aluminium phosphate (Al-P). Maximum soluble phosphate of 824 ㎎/L was found in the amendment of sucrose-sodium nitrate from 5g/L of Ca-P. Mannitol, sorbitol, and ariginine were poor in phosphate solubilization. While sucrose was better carbon source in solubilization of Ca-P and ALP, glucose fared better in solubilization of Fe-P. Though all the nitrogen sources enhanced P solubilization, nitrates were better than ammonium. In the amendments of ammonium chloride and ammonium sulphate, higher uptake of available phosphates by the fungus was found, and this resulted in depletion of available P in Fe-P amendment. Phosphate solubilization was accompanied by acidification of the media, and the highest pH decrease was observed in glucose amendment. Among the nitrogen sources, ammonium chloride favored greater pH decrease.
In this study, we compared the levels of methylotrophic bacterial community diversity in the leaf, stem, grain, root and rhizosphere soil samples of four rice cultivars collected from three regions of Korea. Thirty‐five pigmented and five non‐pigmented isolates showing characteristic growth on methanol were obtained. When phylotypes were defined by performing numerical analysis of 42 characteristics, four distinct clusters were formed. While two clusters, I and IV diverged on the basis of nitrate and nitrite reduction, other two clusters, comprising only pink‐pigmented colonies, diverged on the basis of cellulase activity. Out of the two reference strains used in the analysis, Methylobacterium extorquens AM1 diverged from all the clusters and M. fujisawaense KACC 10744 grouped under cluster III. All the isolates were positive for urease, oxidase, catalase and pectinase activity and negative for indole production, MR and VP test, H2S production, starch, and casein hydrolysis. No clusters were found to possess thermo tolerant isolates, as no growth of the isolates was observed at 45°C. Two strains in cluster I were found to possess gelatin hydrolysis and methane utilizing properties respectively. Most of the isolates in all the four clusters utilized monosaccharides, disaccharide and polyols as carbon source. Six isolates showed considerable nitrogenase activity ranging from 86.2 to 809.9 nmole C2H4 h‐1 mg‐1 protein. 벼(Oryza sativa L.)에 서식하고 있는 메탄올 자화세균(methylotrophic bacteria)의 군집구조를 분석하기 위하여, 국내 3지역(청원, 익산, 밀양)의 경작지 논에서 재배되고 있는 4품종(일미, 동진, 남평, 오대) 벼의 잎, 줄기, 낟알, 뿌리 및 근권토양을 수집하였다. Methanol이 유일한 탄소원으로 첨가된 선택배지를 이용하여, 분홍색 색소체를 갖는35균주와 무색소체의 5균주를 선별하였으며, 선별균주들의 형태학적, 생리.생화학적 특성을 조사하여 4개의 군집으로 구분하였다. 군집 I 및 IV 는 각각 nitrate 와 nitrite reduction 특성에 의해 구별되었으며, pink pigment colony 를 형성하는 또 다른 두 개의 군집들은 cellulase 생성유무에 의하여 구분되었다. 표준균주인Methylobacterium extorquens AM1은 분리균주들과는 다른 군집으로 구분되었으며, M. fujisawaense KACC10744는 III 군집에 속하는 것으로 분석되었다. 분리된 모든 균주들은 urease, oxidase, catalase, pectinase 활성시험에서 양성반응을 나타냈으며, indole, MR‐VP, H2S, starch, casein 시험에서는 음성반응을 나타내었다. 또한, 모든 분리 균주들의 열 내성은 없었으며, 45℃ 이상에서는 성장하지 못하였다. 군집 I에서 두개의 분리균주가 각각 gelatin 가수분해와 methane 이용능을 나타내었으며, 대부분의 균주들은 탄소원으로 monosaccharides, disaccharide, polyols를 이용하여 성장하였다. 분리 및 선별되어진 균주들 중 6 균주만이 86.2‐809.9 nmoles C2H4 h‐1 mg‐1 protein범위의 질소고정능을 나타내었다.
Islam, Rashedul,Trivedi, Pankaj,Madhaiyan, Munusamy,Seshadri, Sundaram,Lee, Gillseung,Yang, Jinchul,Kim, Yoohak,Kim, Myungsook,Han, Gwanghyun,Singh Chauhan, Puneet,Sa, Tongmin Springer-Verlag 2010 BIOLOGY AND FERTILITY OF SOILS - Vol.46 No.3