Histochemical localization of phosphatases in Mycoplasma gallisepticum

Enzymatic activities in cell fractions of mycoplasmalike organisms purified from aster yellows-infected plants

Mycoplasmalike organisms (MLOs), purified from aster yellows-infected plants were osmotically lysed, and the membranes were separated from the cytoplasmic fraction through differential centrifugation. Electron microscopic examinations of sections of the purified MLOs and the isolated membranes showed pleomorphic bodies and unit membranous empty vesicles, respectively. Cell fractions were tested for NADH oxidase, NADPH oxidase, ATPase, RNase, DNase, and p-nitrophenyl phosphatase activity. NADH oxidase and ATPase were confined to the membrane fraction and NADPH oxidase to the cytoplasmic fraction of the MLOs. para-Nitrophenyl phosphatase, RNase, and DNase activities were detected in both membrane and cytoplasmic fractions, but p-nitrophenyl phosphatase and RNase appeared to be associated with membranes and DNase with the cytoplasmic fraction. Glucose-6-phosphate dehydrogenase was found in the cytoplasmic fraction of the MLO cells. Our findings on the distribution of enzymes in MLO cells and cell fractions are the first basic documentation on nonhelical, nonculturable microbes parasitic to plants.

Analysis of membrane fractions from Mycoplasma gallisepticum

Membrane fractions have been isolated from Mycoplasma gallisepticum following a procedure derived from that described by Maniloff, J. and Quinlan, D.C. (J. Bacteriol. (1974) 120, 495-501). A light fraction F1 was obtained which contained structures resembling the bleb-infrableb apparatus characteristic of M. gallisepticum. It was enriched in DNA and had an electrophoretic profile different from that of unfractionated membranes. Cholesterol-to-phospholipid ratios higher than two and elevated values of the ratio of saturated to unsaturated fatty acids were other characteristics of this fraction. The two other fractions isolated (FII and FIV) also differed from intact membranes by their cholesterol and phospholipid content as well as by their saturation ratios. The membrane fluidity of FII and FIV, estimated by fluorescence polarization, was similar to that of unfractionated membranes while a slight but significant difference was recorded for the light fraction. Possible relationships between the lateral heterogeneity of the M. gallisepticum membrane and the obtainment of fractions are discussed.

Mode of action of the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline on Mycoplasma gallisepticum

Various physiological important activities of Mycoplasma gallisepticum were inhibited by the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline [Cu(DMP)2NO3]. The energy-yielding metabolism was inhibited because the conversion of pyruvate into lactate was found to be blocked by Cu(DMP)2NO3, indicating a selective inhibition of lactate dehydrogenase. Also, the production rate of acetate and the rate of oxygen uptake by whole cells of M. gallisepticum appeared to be strongly decreased. Experiments with crude cell extracts showed an inhibition of reduced nicotinamide adenine dinucleotide (NADH) oxidase by Cu(DMP)2NO3 and an even stronger inhibition of NADH oxidase and lactate dehydrogenase by CuSO4. No preferential inhibition of adenosine 5'-triphosphatase and pyruvate kinase was found. Investigations on the influence of Cu(DMP)2NO3 on deoxyribonucleic acid, ribonucleic acid, and protein synthesis with growing cells of M. gallisepticum showed a selective inhibition of the incorporation of [14C]thymidine into deoxyribonucleic acid. Cu(DMP)2NO3 induced a decrease in the total amount of accessible sulfhydryl groups of whole cells of M. gallisepticum, indicating that the observed diverse toxicity of Cu(DMP)2NO3 may be associated with the interaction of copper ions with protein sulfhydryl groups.

Electron microscopical study of antibody binding to Mycoplasma gallisepticum: indirect immunoferritin labelling

The ultrastructural aspects of the interaction of Mycoplasma gallisepticum with specific rabbit antibody have been studied. In particular, fixation conditions which allow the simultaneous preservation of cellular fine structure and membrane antigenicity have been established and applied in a procedure of indirect immunological labelling of the antibody-coated organisms with ferritin conjugated sheep anti-rabbit IgG. The advantages of working with agar embedded organisms in a multistep labelling procedure are discussed. In membrane fractions of M. gallisepticum, prepared by osmolysis and freeze-thawing, only sealed membranes retained their antibody-binding capacity. Electron microscopical examination of "break-through" colonies from immune growth inhibition zones revealed that the majority of cells in these colonies were destroyed, sometimes limited only by a single-layered membrane and without extracellular antibody coat. An exception from this was the presumedly young cells in the periphery of colonies and in microcolonies which appeared to be intact and had a heavy antibody layer surrounding the cells. Based on these characteristics, a possible sequence of events is suggested eventually leading to destruction of mycoplasma organisms in immune growth inhibition zones.

Electron microscope histochemical localization of alkaline phosphatase(s) in Bacillus licheniformis

Sites of alkaline phosphatase (APase) activity in a facultative thermophilic strain of Bacillus licheniformis MC14 have been localized by electron microscope histochemistry, using a lead capture method. The effects of 3% glutaraldehyde and 3.0 mM lead on APase activity were investigated, and these compounds were found to significantly inhibit enzyme activity, 68 and 18%, respectively. A number of parameters were varied in studies to localize APase activity, including: growth temperature (55 and 37 degrees C); substrate concentration in the histochemical mixture (0.06, 0.15, 0.30, 1.00 mM); fixatives; protoplast preparations and whole cells; phosphate-repressed and -derepressed cells; and age of vegetative cells (mid-log and late log). These variations affected the number but not the location of lead phosphate deposits, which appeared at discrete sites along the inner side of the cytoplasmic membrane. Control cells incubated in histochemical mixtures lacking substrate, lead, or both exhibited no lead phosphate depositis. The histochemical localization at membrane sites correlated well with biochemical localization data, which indicated that greater than 80% of the APase activity was associated with the membrane fraction in logarithmically growing cells.

Characterization of the mycoplasma membrane proteins. V. Release and localization of membrane-bound enzymes in Acholeplasma laidlawii

The peripheral membrane protein fraction released by washing Acholeplasma laidlawii membranes with low-ionic strength buffers contained about 50% of the total membrane-bound ribonuclease and deoxyribonuclease activities. The ATPase, NADH oxidase and p-nitrophenylphosphatase activities remained bound to the membrane even when EDTA was added to the wash fluids, and thus appear to belong to the integral membrane protein group. Serving as a marker for peripheral membrane proteins, the membrane-bound ribonuclease activity was solubilized by bile salts much more effectively than the integral membrane-bound enzymes. On the other hand, the solubilized ribonuclease showed a much lower capacity to reaggregate with other solubilized membrane components to membranous structures. Yet, most of the ribonuclease molecules which were bound to the reaggregated membranes could not be released by low-ionic strength buffer. The reaggregated membranes differed from the native membranes in the absence of particles on their fracture faces obtained by freeze cleaving, and by their much higher labeling by the [125-I]lactoperoxidase iodination system. These results suggest that most of the proteins are exposed on the reaggregated membrane surfaces, with very little, if any, protein embedded in its lipid bilayer core. Enzyme disposition in the A. laidlawii membrane was studied by comparing the activity of isolated membranes with that of membranes of intact cells after treatment with pronase or with an antiserum to membranes. The data indicate the asymmetrical disposition of these activities, the ATPase and NADH oxidase being localized on the inner membrane surface, while the nucleases are exposed on the external membrane surface.

Partial purification of a membrane-associated deoxyribonucleic acid complex from Mycoplasma gallisepticum

A Mycoplasma gallisepticum subcellular fraction (P2), which contains the deoxyribonucleic acid replication complex, can be isolated by differential centrifugation of freeze-thaw-lysed cells. The nascent deoxyribonucleic acid is released from P2 by Lubrol-WX, sodium dodecyl sulfate, Pronase, and deoxyribonuclease, but not by saponin, ribonuclease, phospholipase C, or high-frequency sonic treatment. Sonic treatment further fractionates the cell ghost and allows partial purification, on sucrose density gradients, of a deoxyribonucleic acid replication complex attached to the cells' polar membrane-bleb-infrableb structures.

Membrane association of the deoxyribonucleic acid growing-point region in Mycoplasma gallisepticum

Newly replicated deoxyribonucleic acid (DNA) in Mycoplasma gallisepticum A5969 is membrane associated. Cells pulse-labeled 1 to 3 min with (3)H-thymidine are lysed by a freeze-thaw procedure. After brief sonic treatment to shear the DNA, differential centrifugation gives a cell fraction (P2) that is enriched sevenfold for pulse-labeled DNA. P2 contains 80% of the total adenosine triphosphatase activity, 65% of the total cholesterol, and morphologically intact terminal bleb structures. Three to four minutes are needed to fully label the DNA growing-point region, whereas 7 to 8 min are required to "chase" 50% of the (3)H-labeled DNA. This pulse-chase removes 80 to 85% of the nascent DNA from the P2 fraction.

Cell biology of the mycoplasmas

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Distribution of the sites of alkaline phosphatase(s) activity in vegetative cells of Bacillus subtilis

Sites of alkaline phosphatase activity have been located by an electron microscopic histochemical (Gomori) technique in vegetative cells of a repressible strain SB15 of Bacillus subtilis, derepressed and repressed by inorganic phosphate, and in a mutant SB1004 which forms alkaline phosphatase in a medium high in phosphate. The sites of enzyme activity were revealed as discrete, dense, and largely spherical bodies of varying sizes (20 to 150 nm). Cells of both repressible and repression-resistant strains acted on a wide variety of phosphate esters (p-nitrophenylphosphate, beta-glycerophosphate, adenosine-5'-phosphate, glucose-6-phosphate, glucose-l-phosphate, adenosine triphosphate, and sodium pyrophosphate) to produce inorganic phosphorus under conditions of alkaline phosphatase assay [0.05 m tris(hydroxymethyl)aminomethane buffer (pH 8.4) containing 2 mm MgCl(2)]. The purified alkaline phosphatase also acted on all these esters, although much less effectively on adenosine triphosphate and sodium pyrophosphate than did the cells. Comparison of the relative utilization of the various substrates by repressed and derepressed cells and purified enzyme suggested the presence of multiple enzymes in the cells. Thus, the cytochemical method of trapping the newly generated inorganic phosphorus determines the location of an alkaline phosphatase of broad substrate profile, and in addition locates the sites of other enzymes generating inorganic phosphorus under identical conditions of assay. It is intriguing that all of these enzymes usually exist in a few clusters attached to the peripheral plasma membrane. In addition to this predominant location, there were a few sites of enzyme activity in the cytoplasm unattached to any discernible structure, and also in the cell wall of the repression-resistant and of the derepressed, repressible strains.

Cytochemistry of phosphatases in Myxococcus xanthus

An Mg(2+)-dependent and a K(+)-stimulated adenosine triphosphatase were localized by cytochemistry at or near both surfaces of the cytoplasmic membrane of Myxococcus xanthus. An alkaline and an acid phosphatase resided at the external surface of the membrane or in the periplasm. All enzymes could be extracted from partially fixed cells with Mg(2+)-deficient buffers. Suboptimal external phosphate elicited dissociation of adenosine triphosphatase from the membrane but not that of the unspecific phosphatases. The dissociated enzymes migrated into the cytoplasm where they were associated mainly with cytoplasmic aggregates.