Microbial genomics

Abstract

Hot on the heels of the Neisseria meningitidis serogroup B genome sequence comes publication of a second complete meningococcal genome sequence, this time from a serogroup A strain, Z2491. Although not common in the UK, serogroup A strains are responsible for most meningococal disease and death on a global basis. Julian Parkhill and others at the Sanger Centre, with collaborators from Oxford and Berlin, thanks to funding from the Wellcome Trust have recently described the 2.18-Mb genome sequence 1 Parkhill J. et al. Complete DNA sequence of a serogroup A strain of Neisseria menigitidis Z2491. Nature. 2000; 404: 502-506 Crossref PubMed Scopus (614) Google Scholar . Two notable discoveries were the presence of many hundreds of repetitive elements and of at least 60 coding regions (nearly 5% in total) with a lower than average G+C content (i.e. probably representing recently acquired DNA). Detailed analysis of the genome suggested three mechanisms of repeat-mediated antigenic variation: on/off switching by slipped-strand mispairing; intragenomic recombination leading to the use of different carboxy termini for surface-exposed proteins; and intergenomic gene conversion of surface-protein-encoding genes associated with large arrays of repeats, mediated by the internalization of related DNA through a DNA uptake sequence. Work is already underway at the Sanger Centre on a third meningococcal genome sequence, of a serogroup C strain. The genome sequences and associated information are accessible through the Sanger web site: (http://www.sanger.ac.uk/ Projects/N_meningitidis/).