Neisseria species colonizing the human nasopharynx ( N. meningitidis and N. lactamica ), but not N. gonorrhoeae , which colonizes the genital tract, have a complete metabolic pathway potentially involved in sulfate reduction. (a) Genomic context of the genes likely to be involved in sulfate reduction in N. meningitidis (identical in N. lactamica) and in N. gonorrhoeae. Genes of the same color encode orthologous proteins. cysI and cysJ in the gonococcus are pseudogenes and the frameshifts are represented by horizontal lines within the CDS. All the genes are drawn to scale. (b) Predicted biochemical pathway for sulfate reduction in N. meningitidis. APS: adenosine 5'-phosphosulfate.