Adenosine phosphorylase activity as a technique for detection of mycoplasmas in biological media

Rapid and sensitive detection of Mollicutes in cell culture by polymerase chain reaction

Infections with Mollicutes species (such as Mycoplasma, Acholeplasma, and Ureaplasma) can induce a variety of problems in living organisms and laboratory cell cultures. Therefore, it is necessary to establish a routine diagnostic protocol for Mycoplasma infection in order to ensure reliable research results, as well as the safety of commercial biological products. For that purpose a novel PCR-based procedure using specific designed primers complementary to 16S rRNA genome region of mollicute species was evaluated. PCR was optimized and sensitivity and specificity was evaluated by defined cell count concentrations (2-31250 CFU/ml) of different strains of Mycoplasma, Acholeplasma and Ureaplasma. Amplicon (272 bp) was cloned by PCR-cloning and sequenced by dideoxy chain termination. PCR, was found to be able to detect 10 copies of mollicute target DNA. No cross-reactivity with genomic DNA of non-mollicute bacteria or human cell lines was observed. Forty seven human and animal cell lines were evaluated for mollicute contamination. Twenty five cell lines (53%) were correctly identified as contaminated by this molecular approach. The results of this study demonstrated that this PCR-based method is not only fast and reproducible, but also highly sensitive and specific for detecting contaminant mycoplasmas in cell cultures.

Methods for reducing the ammonia in hybridoma cell cultures

The factors which limit the proliferation of eukaryotic cells in vitro are still not well known. Ammonia is believed to be toxic for mammalian cell proliferation and secretion. We have tried two approaches to reducing the ammonia in the medium. We first limited the ammonia produced by the cells by replacing glutamine by glutamate. Then, we used two chemical engineering methods to eliminate accumulated ammonia. In one the used medium was passed through a natural cation exchanger: the clinoptilolite. In the other, the culture medium was passed through a hydrophobic microporous hollow fiber module. Replacing the glutamine by glutamate reduced the medium ammonia concentration. The physicochemical removal of ammonia induced a better cell growth, but not a better specific antibody secretion.

Rapid, sensitive PCR-based detection of mycoplasmas in simulated samples of animal sera

A fast and simple method to detect mycoplasmal contamination in simulated samples of animal sera by using a PCR was developed. The following five mycoplasma species that are major cell culture contaminants belonging to the class Mollicutes were investigated: Mycoplasma arginini, Acholeplasma laidlawii, Mycoplasma hyorhinis, Mycoplasma orale, and Mycoplasma fermentans. After a concentration step involving seeded sera, genus-specific primers were used to amplify a 717-bp DNA fragment within the 16S rRNA gene of mycoplasmas. In a second step, the universal PCR was followed by amplification of variable regions of the 16S rRNA gene by using species-specific primers, which allowed identification of contaminant mycoplasmas. With this method, 10 fg of purified DNA and 1 to 10 color-changing units of mycoplasmas could be detected. Since the sensitivity of the assay was increased 10-fold when the amplification products were hybridized with an internal mycoplasma-specific 32P-labelled oligonucleotide probe, a detection limit of 1 to 10 genome copies per PCR sample was obtained. This highly sensitive, specific, and simple assay may be a useful alternative to methods currently used to detect mycoplasmas in animal sera.

Assay for detection of adenosine phosphorylase from mycoplasmas

A microtechnique is described which permits simple evaluation of the activity of the enzyme adenosine phosphorylase (AdoP), present in all mycoplasmas tested thus far. The good solubility and stability of AdoP and the sensitivity of the assay should be advantageous in detecting mycoplasmas in biological samples such as animal sera, cell cultures and vaccines.

Synthesis of deoxyribomononucleotides in Mollicutes: dependence on deoxyribose-1-phosphate and PPi

Cell extracts of Acholeplasma laidlawii B-PG9, Acholeplasma morum S2, Mycoplasma capricolum 14, and Mycoplasma gallisepticum S6 were examined for 37 cytoplasmic enzyme activities involved in the salvage and biosynthesis of purines. All of these organisms had adenine phosphoribosyltransferase activity (EC 2.4.2.7) and hypoxanthine phosphoribosyltransferase activity (EC 2.4.2.8). All of these organisms had purine-nucleoside phosphorylase activity (EC 2.4.2.1) in the synthetic direction using ribose-1-phosphate (R-1-P) or deoxyribose-1-phosphate (dR-1-P); this activity generated ribonucleosides or deoxyribonucleosides, respectively. The pyrimidine nucleobase uracil could also be ribosylated by using either R-1-P or dR-1-P as a donor. The synthesis of deoxyribonucleosides from nucleobases and dR-1-P has been reported from only one other procaryote, Escherichia coli (L. A. Mason and J. O. Lampen, J. Biol. Chem. 193:539-547, 1951). The reverse of this phosphorylase reaction is more widely known, and we found such activity in all mollicutes studied. Some Acholeplasma species but not the Mycoplasma species can phosphorylate deoxyribonucleosides to deoxyribomononucleotides by a PPi-dependent deoxyribonucleoside kinase activity, which was first reported in this group for the ribose analogs (V. V. Tryon and J. D. Pollack, Int. J. Syst. Bacteriol. 35:497-501, 1985). This is the first report of PPi-dependent purine deoxyribonucleoside kinase activity. An ATP-dependent purine deoxyribonucleoside kinase activity is known only in salmon milt extracts (H. L. A. Tarr, Can. J. Biochem. 42:1535-1545, 1964). Deoxyribomononucleotidase activity was also found in cytoplasmic extracts of these mollicutes. This is the first report of deoxyribomononucleotidase activity.