NifD: Its Evolution and Phylogenetic Use in Cyanobacteria
Nitrogen fixation is randomly dispersed throughout prokaryotic lineages, raising the question of its evolution by vertical descent vs. lateral transfer. In this study, the nitrogen fixation gene, nifD, was examined for cyanobacteria. Nucleotide sequence data of nifD from nitrogen-fixing nonheterocystous and heterocystous cyanobacteria was used to generate a phylogenetic tree. The nifD phylogeny was visually compared to 16s ribosomal DNA phylogenies to elucidate the evolution of nifD within the cyanobacteria. It appears that the inheritance of nifD is through vertical descent for most cyanobacteria, with the exception of a possible lateral transfer in Anabaena variabilis. The phylogeny of nifD also provided additional insight into the evolution of the cyanobacteria, supporting previous suggestions that the heterocystous lineage arose from within the nonheterocystous cyanobacteria. The data further corroborates previous data that the nonheterocystous cyanobacteria subsections and genera are polyphyletic suggesting the need for the possible revision of the current classification.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:cyanobacterial evolution nitrogen fixation nifd cyanobacteria
Date of Publication:01/01/2007