| Abstract: | Abstract On the action of some nucleosides and related bases on some physiologiacal aspects of RHIZOBIUM LEGUMINOSARUM Frank. — Research was carried out on the action of some nucleosides and related bases on some physiological aspects of Rhizobium leguminosarum Frank. The compounds tested were: adenine, adenosine, cytosine, guanine, guanosine, hypoxantine, inosine, thymine, thymidine, uracil, uridine. Pyrimidinic nucleosides, apart from the disappearance of ribose, behave similarly to their bases. The bases and nucleosides tested stimulate changes in the respiration of R. leguminosarum. Remarkably different values are observed in the endogenous respiration when compared to the control, and a remarkable delay in the beginning of respiration in the case of cells precultivated in presence of cytidine, uridine and thymidine. A number of these cells were later found to have an anaerobic metabolism, at least in the starting period. These findings may be explained admitting that the regulatory system of Rhizobium, with regard to oxygen uptake, are dependent on the presence of certain compunds, including some nucleosides, which the microorganism is in contact with within the nodule. Apart from cytidine sulphate, there is a fundamental stimulatory effect on the growth of R. leguminosarum. After 24 hours incubation, purinic bases and their nucleosides are not detectable in cultural media. Thymine and cytosine, however, are still present in the medium, or have been transforned into uracil; the latter undergoes no transformation in the medium |
