Abstract
Pathogens and parasites, like all other forms of life, have evolutionary histories. Elucidating these histories using phylogenetic methods is of immense importance as it provides knowledge concerning the mechanisms of infectious disease pathogenesis and how diseases might be controlled or ideally prevented. Changes in genome structure and gene content also have the potential to reveal when and how pathogens arose and perhaps even to predict future evolutionary events related to disease. Recent phylogenetic studies of Yersinia pestis, Salmonella typhi, Bordetella species have established the importance of gene gain, displacement and loss mediated by horizontal gene transfer (HGT) in pathogen evolution (Achtman & Wagner, 2008). These changes in genotype however invariably involve changes in components of the so - called pan genome that encode ancillary rather than core elements. The genus Neisseria comprises gram-negative, oxidase-positive diplococci that are frequently isolated from the mucosal surfaces of humans and animals. Two species of Neisseria, N. gonorrhoeae and N. meningitidis are important pathogens of man. Gonorrhea remains one of the most common sexually transmitted diseases contributing to worldwide morbidity, mortality and infertility. Although treatable with antibiotics, no vaccine is available. N. meningitidis is a commensal of the human oropharynx that under as yet poorly understood circumstances causes invasive disease and meningitis. Despite there differing host interactions, they show very high (98 %) sequence identity in house-keeping genes and would normally normally be included in a single species. Current dogma suggests that the evolution of these species which has occurred in - host is due to gain and loss of ancillary genes as shown for other pathogens. In contrast, we have now identified two rare genetic changes in a component of cytochrome cbb3 oxidase that are associated with macroevolution of these agents.
Norway