An ad hoc committee for the re-evaluation of the species definition in bacteriology met in Gent, Belgium, in February 2002. The committee made various recommendations regarding the species definition in the light of developments in methodologies available to systematists.

The organization of the ribosomal genes is unique in Borrelia burgdogeri in that the rrl (23s) and rrf (5s) genes are tandemly duplicated. We took advantage of this uniqueness to assess the restriction polymorphism of PCR products obtained with primers at the 3' end of the first rrfgene and at the 5' end of the second rrl gene. An amplicon that was 226 to 266 bp long was generated from 99 of 100 B. burgdorferi sensu lato strains. The nuclease MseI restriction polymorphism of the amplicons provided a useful tool for identifying B. burgdorferi sensu stricto, Borrelia garinii, Borrelia afielii (formerly group VS461), and Borrelia japonica (formerly group F63B). Furthermore, it allowed us to recognize four new genomic groups, which were confirmed by DNA-DNA hybridization data. Two of these genomic groups comprised European strains, and the other two groups contained American strains. The American genomic groups involved vectors with enzootic cycles quite different from those of B. burgdorferi sensu stricto, which previously was the only Lyme disease Borrelia species known to occur in the United States. Our method could be used for rapid screening of strain collections and for epidemiological and medical purposes.

The seventh cholera pandemic has heavily affected Africa, although the origin and continental spread of the disease remain undefined. We used genomic data from 1070 Vibrio cholerae O1 isolates, across 45 African countries and over a 49-year period, to show that past epidemics were attributable to a single expanded lineage. This lineage was introduced at least 11 times since 1970, into two main regions, West Africa and East/Southern Africa, causing epidemics that lasted up to 28 years. The last five introductions into Africa, all from Asia, involved multidrug-resistant sublineages that replaced antibiotic-susceptible sublineages after 2000. This phylogenetic framework describes the periodicity of lineage introduction and the stable routes of cholera spread, which should inform the rational design of control measures for cholera in Africa

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