Why Sequence Type I and II Methanotrophs?

Methanotrophic bacteria are absolutely vital for the global carbon cycle and to carbon sequestration, as they constitute the largest known biological methane sink. Methanotrophs are also central to the bioremediation and biofuel development goals of the DOE. To date, only two methanotrophic bacteria have undergone complete genome sequencing, and only one sequence is available to the public.

Methanotrophs are distinguished from other microorganisms by their ability to utilize methane as a sole carbon and energy source, yet they are physiologically and phylogenetically diverse, affiliating with both Gammaproteobacteria (type I methanotrophs) and Alphaproteobacteria (type II methanotrophs). Methanotrophs are ubiquitous and play a major role in the global cycling of carbon and nitrogen as well as in the degradation of hazardous organic materials. Furthermore, recent results suggest that methanotrophs play a role in either solubilization or immobilization of a variety of metals in situ. Ecophysiological data have revealed niche differentiation of type I and type II methanotrophs; however, the mechanisms for adaptation of distinct methanotrophic communities to different environments are not understood.

JGI will sequence the genomes of the methanotrophs Methylomicrobium album BG8 (type I) and Methylosinus trichosporium OB3b (type II), for which a large body of ecophysiological, biochemical, and molecular genetic information has already been generated. The genome sequences will be used to compare methane oxidation, carbon fixation, inorganic nitrogen metabolism, metal acquisition, and other pathways between type I and type II methanotrophs. They will also enable comparison with the complete genome sequence of Methylococcus capsulatus Bath, which has similarities to both type I and type II methanotrophs. Comparisons of the genome sequences of these representative obligate methanotrophic bacteria with the genome sequence of the facultative methanotroph Methylocella silvestris BL2 and with the facultative methylotrophs Methylobacterium extorques and Methylibium petroleiphilum will reveal the basis of obligate methanotrophy, a key scientific question for the last 35 years. Sequence information will also allow researchers to create transcriptome arrays for global gene expression studies and to identify targets for molecular genetic analysis of key pathways of methylotrophy, central carbon and nitrogen metabolism, and metal ion sequestration and uptake.

Principal Investigators: Lisa Y. Stein (Univ. of California, Riverside), Alan A. DiSpirito (Iowa State Univ.), Martin G. Klotz (Univ. of Louisville), and J. Colin Murrell (Univ. of Warwick)