Pathways of Nucleotide Biosynthesis in Mycoplasma mycoides subsp. mycoides

Abstract

By measuring the specific activity of nucleotides isolated from ribonucleic acid after the incorporation of 14 C-labeled precursors under various conditions of growth, we have defined the major pathways of ribonucleotide synthesis in Mycoplasma mycoides subsp. mycoides. M. mycoides did not possess pathways for the de novo synthesis of nucleotides but was capable of interconversion of nucleotides. Thus, uracil provided the requirement for both pyrimidine ribonucleotides. Thymine is also required, suggesting that the methylation step is unavailable. No use was made of cytosine. Uridine was rapidly degraded to uracil. Cytidine competed effectively with uracil to provide most of the cytidine nucleotide and also provided an appreciable proportion of uridine nucleotide. In keeping with these results, there was a slow deamination of cytidine to uridine with further degradation to uracil in cultures of M. mycoides . Guanine was capable of meeting the full requirement of the organism for purine nucleotide, presumably by conversion of guanosine 5′-monophosphate to adenosine 5′-monophosphate via the intermediate inosine 5′-monophosphate. When available with guanine, adenine effectively gave a complete provision of adenine nucleotide, whereas hypoxanthine gave a partial provision. Neither adenine nor hypoxanthine was able to act as a precursor for the synthesis of guanine nucleotide. Exogenous guanosine, inosine, and adenosine underwent rapid cleavage to the corresponding bases and so show a pattern of utilization similar to that of the latter.

Quantifying biosynthetic network robustness across the human oral microbiome

“…Furthermore, a set of three nucleotides: dGTP, GTP, and TTP, have high PM values for TM7 and PM values of zero for Mycoplasma organisms (Figure 4 II). This pattern of nucleotide biosynthesis deficiency in Mycoplasma is consistent with the observation that some strains have been shown to be dependent on supplementation of thymidine and guanosine but not adenine or cytosine nucleobases for growth 94 . Finally, the cofactors acyl carrier protein (ACP) and flavin adenine dinucleotide (FAD) had high PM values in Mycoplasma and PM values of zero in TM7 organisms (Figure 4 III).…”

A simple and reliable method of producing in vitro infections of cryptosporidium parvum (apicomplexa)

“…Cells were tested monthly for contamination with Mycoplasma spp. using 4',6-diamidino-2-phenylindole (DAPI) stain [7][8][9]. To lift cells from the surface of flasks, a 0.25% (w/v) trypsin/0.53 mM ethylenediamine tetraacetic acid (EDTA) in phosphate-buffered saline (PBS) solution was used.…”

Purine and pyrimidine metabolism in parasitic protozoa

“…Most organisms are 'prototrophic' for purines, i.e., capable of synthesising purines de novo and therefore not dependent upon exogenous sources of these compounds [6]. In contrast, some microorganisms, including Mycoplasma [7,8] and most parasitic protozoa are incapable of de novo synthesis of purines and therefore are obligate 'auxotrophs' for them [2]. Indeed, not all mammalian cells are capable of de novo synthesis of purine nucleotides; mature erythrocytes [9,10] and lymphocytes [11,12] are totally dependent on the salvage of preformed purines.…”