Journal Article An acid-tolerant ammonia-oxidizing γ-proteobacterium from soil

早津, 雅仁  ,  多胡, 香奈子  ,  内山, 郁夫  ,  豊田, 敦  ,  王, 勇  ,  下村, 有美  ,  大久保, 拓  ,  栗栖, 太  ,  廣野, 祐平  ,  野中, 邦彦  ,  秋山, 博子  ,  伊藤, 武彦  ,  高見, 英人  ,  HAYATSU, Masahito  ,  TAGO, Kanako  ,  UCHIYAMA, Ikuo  ,  TOYODA, Atsushi  ,  WANG, Yong  ,  SHIMOMURA, Yumi  ,  OKUBO, Takashi  ,  KURISU, Futoshi  ,  HIRONO, Yuhei  ,  NONAKA, Kunihiko  ,  AKIYAMA, Hiroko  ,  ITOH, Takehiko  ,  TAKAMI, Hideto

11pp.1130 - 1141 , 2017-01-10 , Nature Publishing Group
Nitrification, the microbial oxidation of ammonia to nitrate via nitrite, occurs in a wide range of acidic soils with widely varying pH values (3-5.5). However, the ammonia-oxidizing bacteria (AOB) and archaea (AOA) that have been isolated from soil to date are acid-sensitive, except for Candidatus ‘Nitrosotalea devanaterra’. Therefore, the microbiological basis for ammonia oxidation in highly acidic soils has been poorly understood. Here we report the isolation and characterization of acid adapted AOB from an acidic agricultural soil. The isolated AOB, strain TAO100, is classified within Gammaproteobacteria based on phylogenetic characteristics. TAO100 can grow in the pH range of 5-7 and survive in highly acidic conditions until pH 2 by forming cell aggregates. The ammonia monooxygenase subunit A gene and its transcript of TAO100 is higher abundant than those of AOA and betaproteobacterial AOB in the strongly acidic soil. These results indicate that TAO100 plays an important role in nitrification of acidic soils. The TAO100 genome, which is composed of a 2.01-Mb chromosome and a 6.4-kb plasmid, is considerably smaller than other gammaproteobacterial AOB (γ-AOB). All known γ-AOB species are halophiles that exclusively thrive in marine and saline aquatic environments. However, TAO100 is not phenotypically halophilic, and several genes associated with salt tolerance unnecessary for survival in soil are absent from the genome. Based on these results, TAO100 is proposed as a novel species of a new genus, Candidatus Nitrosoglobus terrae.

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