The distribution and evolution of C1 transfer enzymes and evolution of the planctomycetes

Abstract

When the first genome sequence of a Planctomycete became available (in 2003), it revealed the presence of genes encoding a pathway for a tetrahydromethanopterin-mediated transfer of C1 units between the oxidation levels of formaldehyde and formate, resembling a pathway for methanogenesis being carried out by a specialized group of Archaea and a pathway for formaldehyde oxidation employed by some methylotrophic bacteria, the latter pathway acting in reverse to methanogenesis. This discovery was of importance as the presence of the genes in question in the Planctomycetes has challenged the assumption of a limited distribution of these genes/pathways in the microbial world, at the same time suggesting novel scenarios for the evolution of C1 transfer pathways in microbes and providing support for the potential antiquity of these pathways. In this chapter, I review the early work on the discovery and analysis of the genetic determinants of C1 functions in Planctomycetes and the significance of these discoveries in interpreting the emergence and the evolution of C1 metabolism in Prokaryotes. This is followed by a review of the continuously emerging new genomic data suggesting a much wider distribution of the tetrahydromethanopterin-linked functions in Prokaryotes, further supporting the hypothesis of the long evolution for these functions. While the Planctomycetes provide these important insights into the evolution of specific biochemical pathways as well as the evolution of Prokaryotes in general, the exact function of the tetrahydromethanopterin-linked C1 transfer pathway in Planctomycetes and in many other phyla remains unknown.