Genetics of methane and methanol oxidation in Gram-negative methylotrophic bacteria

Within the past few years, considerable progress has been made in the understanding of the molecular genetics of methane and methanol oxidation. In order to summarize this progress and to illustrate the important genetic methods employed, this review will focus on several well-studied organisms. These organisms include the gramnegative faculative methylotrophsMethylobacterium extorquens, Methylobacterium organophilum andParacoccus denitrificans. In addition, the obligate methanotrophsMethylococcus capsulatus andMethylosinus trichosporium are discussed. We have chosen not to discuss the genetics of methanol oxidation in the yeasts or in gram-positive bacteria. Likewise, the genetics of related topics (for example, methylamine oxidation and carbon assimilation pathways) are not reviewed here. Broad host range conjugatable plasmids have enabled researchers to complement mutations and clone genes from gram-negative methylotrophic bacteria. More recently, ‘promoter probe’ derivative plasmids have been used to elucidate aspects of gene regulation. Also, alternative gene-cloning techniques are proving useful in circumventing problems in the genetic studies of the obligate methanotrophs, the group of bacteria that is the most refractory to traditional methods.