Physiological characteristics and primary identification of a methane-fed bacterium from a natural gasfield in China

Abstract

A methane-fed bacterium was enriched, isolated and purified from soil of Dagang gasfield, Tianjin, China. It was a Gram-negative coccus. The biochemical characteristics and morphology of the strain were investigated. The total DNA was extracted, and its 16S rDNA was amplified. The GenBank accession number was JN616389. The bacterium has the highest similarity to Pseudoxanthomonas mexicana with almost 100%. The strain showed a good property of methane utilization when methane was added as a sole carbon source.

Introduction

Natural gas is an important source of energy, methane accounts for about 90% of its content. In the region of natural gas reservoir, light hydrocarbons seep and rise to the ground from subterranean oil and gas deposits (Saunders et al., 1999; Prasanna et al., 2010; Spulber et al., 2010). Some bacteria grow with light hydrocarbons as the carbon source in the soil of oil and gas reservoirs (Sleat and Vonderdick, 1990; Voordouw, 2011; Liu et al., 2011). Therefore, the detecting of the anomalous distribution and the characteristic of special types of bacteria in soil can be used to forecast the existence of oil and gas deposits (Larter et al., 2003; Rasheed et al., 2009). As a representative of these special bacteria, the methanotrophs can be used as the indicator bacteria in microbial prospecting of oil and gas (MPOG) (Kim et al., 2004; Wendlandt et al., 2010; Zhang et al., 2010). Additionally, methanotrophs are widely existed in nature (Liebner and Wagner, 2007; Overland et al., 2010; Kip et al., 2010). However, a number of non-methane-oxidizing bacteria are generally engaged in methane oxidation (Nakamura et al., 2007; Alperin and Hoehler, 2009). They play important roles in the carbon cycle (Delsontro et al., 2010). Until now, MPOG techniques involving the isolation of hydrocarbon-oxidizing bacteria (Sleat and Vonderdick, 1990) and molecular biology techniques (Zhang et al., 2010), but the second method is costly and indirectly. And the traditional isolation of bacteria can provide a direct study of MPOG. The types of methane-feeding bacteria are different from methanotrophs greatly. As they all can use methane as the carbon source. However, methanotrophs only survive with methane as the sole carbon source. But methane-feeding bacteria can grow with other carbon sources.

The main objectives of this study were to isolate a methane-feeding bacterium and analyze its characteristics, then identify the bacterium and construct the phylogenetic tree. The existence of the methane-feeding bacterium proves not only methanotrophs but also methane-feeding bacterium survive in soil above the natural gas reservoir. It confirms the theory and applies microbial prospecting of oil and gas (MPOG).