The inoculated plates were incubated overnight, and the MIC was defined as the amount of nitrofurantoin needed in the plate to completely inhibit the growth of the organisms in 24 hours. Spontaneous mutation frequency determination Cultures of GC were grown in GCP broth + 0.42% NaHCO3 and Kellogg’s supplement to exponential growth phase, and aliquots (~1 × 108 cfu) plated onto GCK plates containing 3:g/ml nitrofurantoin. Viable counts were determined by plating cells onto GCK agar plates. Mutation frequencies were defined as the number of colonies obtained on nitrofurantoin-containing media divided by the

number of colonies obtained on GCK media. Nitroreductase assay Nitroreductase activity was measured by a modification of the method of Whiteway et al. [24]. Cultures (100 ml) of GC were grown in GCP broth + 0.42% NaHCO3 and Kellogg’s supplement at 37°C find more with shaking to a turbidity of 100 klett units. Cells were collected by centrifugation (~4,000 rpm

for 10 min in a Sorvall GSA rotor), washed with PBS, and resuspended in 5 ml 100 mM Tris-HCl, pH 7.5. Cells were TGF-beta inhibitor lysed by sonication using a Branson sonicator with the microprobe, set on full power, using 5 10 sec pulses (Suspensions were incubated on ice for 1 min between pulses). The sonicates were clarified by centrifugation (~10,000 rpm for 30 min in a Sorvall SS-34 rotor) and the supernatants collected. Protein concentrations of each sample were measured with the BioRad protein assay (Hercules, CA) using check details BSA as a standard, and samples were normalized to the same protein concentration in 100 mM Tris-HCl, pH 7.5. Samples containing 800:l lysate and 0.1 mM nitrofurazone were 4-Hydroxytamoxifen mw placed in a quartz cuvette, and the reaction initiated by adding 100:l NADPH (2 mM stock). A control reaction was performed using water instead of nitrofurazone. Reactions were incubated at room temperature and absorbance was measured every 30 sec at 400 nm. Bioinformatics A homolog of E. coli nfsB in the gonococcus was identified by submitting the entire E. coli nfsB protein sequence to http://​blast.​ncbi.​nlm.​nih.​gov/​Blast.​cgi using the tblastn program. The database

option was set to “”nucleotide collection,”" and limited to Neisseria gonorrhoeae. The database option was set to “”bacteria,”" and the number of best-scoring sequences to show was set to 250. The top scoring hits from unique genera were aligned using ClustalW http://​www.​ebi.​ac.​uk/​Tools/​clustalw/​. Results MIC/Spontaneous Mutation Frequency Studies If N. gonorrhoeae possesses a nitroreductase, it should be sensitive to antimicrobial agents that are activated by nitroreductases and it should be possible to isolate mutants that become resistant to these activated antimicrobials due to the organism’s loss of nitroreductase activity. We determined the MIC for nitrofurantoin, an antimicrobial agent that is activated by nitroreductases, for several different gonococcal strains.