The resultant binary matrix is used to produce a dendrogram and to measure the fit of the dendrogram to the data. DNA relatedness among strains is estimated with DNA reassociation analysis. DNA homology is an attempt to answer whether the DNA of two organisms have a base sequence sufficiently similar to allow the formation of DNA heteroduplexes. DNA homology values are measurements of similarity in which the entire genome of one organism is compared with that of another. DNA homology values are used to detect similarities between closely related organisms and to conclude whether two strains belong to the same species.
Microbial phylogeny is estimated from sequencing analysis of the ribosomal genes.
The Rhizobiaceae do not form a branch, which is distinctly different than the other genera in the alpha subdivision of the Purple Bacteria, and therefore they constitute several lineages evident as separate genera. The effort with ribosomal gene sequencing is focused on identification of the genera of accessions, preliminary estimation of speciation, and the uncovering of novel nucleotide sequences for use in strain and species identification. The training period was usually 12 months. These visitors were from Iraq, Spain, Thailand, Tanzania, the People's Republic of China, Mali, Egypt, Kenya, Zambia, and Pakistan. Three visitors were accommodated who received Fulbright Scholarships and who chose to participate in the activities associated with the collection.