Acid-Tolerant Moderately Thermophilic Methanotrophs of the Class Gammaproteobacteria Isolated From Tropical Topsoil with Methane Seeps

作者：Islam Tajul^*; Torsvik Vigdis; Larsen Oivind; Bodrossy Levente; Ovreas Lise; Birkeland Nils Kare

来源：Frontiers in Microbiology, 2016, 7: 851.

DOI：10.3389/fmicb.2016.00851

• terrestrial
• Gammaproteobacteria
• methanotroph
• acid-tolerant
• moderately thermophilic
• pMMO

Terrestrial tropical methane seep habitats are important ecosystems in the methane cycle. Methane oxidizing bacteria play a key role in these ecosystems as they reduce methane emissions to the atmosphere. Here, we describe the isolation and initial characterization of two novel moderately thermophilic and acid-tolerant obligate methanotrophs, assigned BFH1 and BFH2 recovered from a tropical methane seep topsoil habitat. The new isolates were strictly aerobic, non-motile, coccus-shaped and utilized methane and methanol as sole carbon and energy source. Isolates grew at pH range 4.2-7.5 (optimal 5.5-6.0) and at a temperature range of 30-60 degrees C (optimal 51-55 degrees C). 16S rRNA gene phylogeny placed them in a well-separated branch forming a cluster together with the genus Methylocaldum as the closest relatives (93.1-94.1% sequence similarity). The genes prmoA, mxaF and cbbL were detected, but mmoX was absent. Strains BFH1 and BFH2 are, to our knowledge, the first isolated acid-tolerant moderately thermophilic methane oxidizers of the class Gammaproteobactena. Each strain probably denotes a novel species and they most likely represent a novel genus within the family Methylococcaceae of type I methanotrophs. Furthermore, the isolates increase our knowledge of acid-tolerant aerobic methanotrophs and signify a previously unrecognized biological methane sink in tropical ecosystems.

• 出版日期2016-6-15