Complete genome sequence of the genetically tractable hydrogenotrophic methanogen Methanococcus maripaludis.

The genome sequence of the genetically tractable, mesophilic, hydrogenotrophic methanogen Methanococcus maripaludis contains 1,722 protein-coding genes in a single circular chromosome of 1,661,137 bp. Of the protein-coding genes (open reading frames [ORFs]), 44% were assigned a function, 48% were conserved but had unknown or uncertain functions, and 7.5% (129 ORFs) were unique to M. maripaludis. Of the unique ORFs, 27 were confirmed to encode proteins by the mass spectrometric identification of unique peptides. Genes for most known functions and pathways were identified. For example, a full complement of hydrogenases and methanogenesis enzymes was identified, including eight selenocysteine-containing proteins, with each being paralogous to a cysteine-containing counterpart. At least 59 proteins were predicted to contain iron-sulfur centers, including ferredoxins, polyferredoxins, and subunits of enzymes with various redox functions. Unusual features included the absence of a Cdc6 homolog, implying a variation in replication initiation, and the presence of a bacterial-like RNase HI as well as an RNase HII typical of the Archaea. The presence of alanine dehydrogenase and alanine racemase, which are uniquely present among the Archaea, explained the ability of the organism to use L- and D-alanine as nitrogen sources. Features that contrasted with the related organism Methanocaldococcus jannaschii included the absence of inteins, even though close homologs of most intein-containing proteins were encoded. Although two-thirds of the ORFs had their highest Blastp hits in Methanocaldococcus jannaschii, lateral gene transfer or gene loss has apparently resulted in genes, which are often clustered, with top Blastp hits in more distantly related groups.

Molecular characterization of Haemophilus ducreyi strains from Jackson, Mississippi, and New Orleans, Louisiana.

Chancroid, a sexually transmitted disease caused by Haemophilus ducreyi, is one of the most common genital ulcer diseases in developing countries. In the United States, while less common, the disease has been associated with outbreaks in inner cities, particularly among persons who engage in sex for drugs or money. Two outbreaks of chancroid were recently studied in the United States, one in New Orleans (from 1990 to 1992) and one in Jackson, Mississippi (from 1994 to 1995). By use of ribotyping, plasmid content, and antibiotic susceptibility, the chancroid cases in New Orleans were found to be due to a limited number of strains, consistent with a limited introduction of H. ducreyi into this community. The H. ducreyi isolates from New Orleans and Jackson had different ribotype patterns, suggesting that the two outbreaks were probably not linked.