Published: Sulfate-reducing bacteria (SRBs) gain their energy by coupling the oxidation of organic substrate to the reduction of sulfate to sulfide. Several SRBs are able to use alternative terminal electron acceptors to sulfate such as nitrate. Nitrate-reducing SRBs have been isolated from a diverse range of environments.
An investigation of the molecular basis of the switch between aerobic and anaerobic growth was initiated by the cloning of the genes encoding the respiratory nitrate reductase from B. subtilis. Oligonucleotides deduced from conserved amino acid sequence regions of eubacterial respiratory nitrate reductases and related enzymes were used for the Citrate Negative: Escherichia coli ATCC 25922 (no growth or trace of growth) Limitations of Citrate Utilization Test. Some organisms are capable of growth on citrate and do not produce a color change. Growth is considered a positive citrate utilization test, even in the absence of a color change. Tests with equivocal results should be repeated. 338 When nitrate concentration dropped below our limit of detection (0.5 mM) at 8.5 h, the current 15 339 remained at ~ -0.5 mA, most likely due to the commencement of nitrite reduction. E. coli is 340 known to preferentially reduce nitrate with the stoichiometry 1MKH2 + 1NO3− → 1MK + 1NO2−, 341 followed by a switch to nitrite reduction Nitrate Reduction test. Mycobacterium tuberculosis is a strongly nitrate-positive organism. This test is valuable for the identification of M. tuberculosis, M. kansasii, M. szulgai and M. fortuitum. Rapid growers such as M. fortuitum can be tested within 2 weeks, but slow growers should be tested after 3-4 weeks of luxuriant growth. kNx14.