(vitamin B12) can be complexed with metal via the ATP-dependent reactions (aerobic pathway) (e.g., in P. denitrificans) or via ATP-independent reactions (anaerobic pathway) (e.g., in Salmonella typhimurium ). [ 8 ] [ 9 ] The corresponding cobalt chelatases are not homologous . However, aerobic cobalt chelatase subunits CobN and CobS are homologous