Studies of the Effect of Sodium Azide on Microbic Growth and Respiration

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Abstract
The technics involved in the quantitative determination of the gas exchange of microorganisms were the ones described by Novy, Roehm, and Soule. Actively proliferating cells in nutrient broth were used in all studies, and the cultures were incubated at about 37[degree]C for 96 hrs. At the end of this time the amt. of O2 consumed and of CO2 produced was determined, converted to standard conditions, and the R. Q. calculated. The influence of NaN3 on the gas exchange of Bacillus subtilis and Pseudomonas aeruginosa under aerobic conditions showed that for both organisms there was a marked inhibition in the O2 consumption of the germs and a reduction in growth in the presence of critical conc. of the chemical. This conc. was about 0.05% (M/130) for P. aeruginosa and only about 0.003% (M/2167) for B. subtilis. The resulting R. Q. at critical conc. were markedly increased and suggested that the respiration of the germs was almost entirely anaerobic. The high sensitivity of B. subtilis to NaN3 may be explained by its strong aerobic tendencies; the resistance of P. aeruginosa may be due to the fact that it grows well in the absence of free O2 and possesses a good anaerobic respiratory mechanism. In the expt. with pyocyanine, the pigment was added to NaN3 media in a conc. of M/2500. In the absence of pyocyanine there was an inhibition of O2 consumption amounting to 70%; in the presence of the pigment, normal respiration occurred. This is apparently due to the fact that the pyocyanine was able to exercise the role of an O2 transfer catalyst in the place of NaN3 sensitive heme-containing respiratory enzymes.

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