Studying the Diversity of Methanotrophic Bacteria Using FISH Probes.

Methane (CH₄) is a potent greenhouse gas that is found at lower concentrations in the atmosphere than CO₂ but, on a similar mass basis, has a global warming potential23 times greater than CO₂.Agriculture, amongst other land-use practices, impacts the rate of CH₄ oxidation, with a number of studies indicating that varying tillage practices, undisturbed grasslands and pristine forests have different rates of CH₄ oxidation. 

Methanotrophs, or methane-oxidizing bacteria (MOB) present in aerobic soil, serve as the only known biological sink for atmospheric  CH₄. Methanotrophs in soil use methane monooxygenases to catalyze the oxidation of CH₄ and are grouped into Type I and Type II categories based on the oxidation pathway followed. The pmoA gene sequences can be used as phylogenetic markers to characterize the nature and abundance of methanotrophic communities in different soils.

The objective of the current study is to determine diversity methanotrophic bacteria in different soil types under long-term (48-50 years) no-tillage, plow tillage, grasslands and forests. A total of 18 samples were collected.  The DNA was extracted from these soil samples and the methane monooxygenase gene (pmoA), and the 16S rRNA genes for both type-1 and type-2 methanotrophs were amplified. The DNA amplicons were then separated using denaturing gradient electrophoresis (DGGE) and unique bands were sequenced. The sequences will be used to develop fluorescent probes which will be used for FISH experiments.

The significance of this study is that it represents a rapid method for determining the presence of methanotrophic bacteria in soils under contrasting tillage/management systems, and will lead to a better understanding of how these systems affect the concentration of CH₄ in the atmosphere.