Genome-scale analysis of gene function in the hydrogenotrophic methanogenic archaeon Methanococcus maripaludis

A comprehensive whole-genome analysis of gene function by transposon mutagenesis and deep sequencing methodology has been implemented successfully in a representative of the Archaea domain. Libraries of transposon mutants were generated for the hydrogenotrophic, methanogenic archaeon Methanococcus maripaludis S2 using a derivative of the Tn5 transposon. About 89,000 unique insertions were mapped to the genome, which allowed for the classification of 526 genes or about 30% of the genome as possibly essential or strongly advantageous for growth in rich medium. Many of these genes were homologous to eukaryotic genes that encode fundamental processes in replication, transcription, and translation, providing direct evidence for their importance in Archaea. Some genes classified as possibly essential were unique to the archaeal or methanococcal lineages, such as that encoding DNA polymerase PolD. In contrast, the archaeal homolog to the gene encoding DNA polymerase B was not essential for growth, a conclusion confirmed by construction of an independent deletion mutation. Thus PolD, and not PolB, likely plays a fundamental role in DNA replication in methanococci. Similarly, 121 hypothetical ORFs were classified as possibly essential and likely play fundamental roles in methanococcal information processing or metabolism that are not established outside this group of prokaryotes.