Energy coupling mechanisms in host-grown Mycobacterium lepraemurium

Energy coupling mechanisms of Mycobacterium lepraemurium isolated from Sprague-Dawley rats lepromata were investigated. Cell-free extracts catalyzed phosphorylation coupled to the oxidation of generated NADH, added NADH, and succinate yielding P/O ratios of approximately 0.8, 0.6, and 0.4, respectively. Ascorbate oxidation alone or in the presence of cytochrome c or N,N,N',N'-tetramethyl-p-phenylenediamine was not coupled to ATP synthesis. The oxidative phosphorylation was completely uncoupled by 2,4-dinitrophenol, 2,6-dibromophenol, pentachlorophenol, m-chlorocarbonylcyanide phenylhydrazone, dicumarol, and gramicidin at concentrations which did not cause any inhibition of oxygen uptake. While the NADH oxidation and associated phosphate esterification was markedly sensitive to rotenone and other flavoprotein inhibitors, these inhibitors had no effect, however, on the phosphorylation coupled to succinate oxidation. The respiratory chain inhibitors such as antimycin A or 2-n-heptyl-4-hydroxyquinoline-N-oxide, and cyanide were the potent inhibitors of the phosphorylation associated with the oxidation of NADH and succinate. The ATP formation coupled to the oxidation of NADH and succinate was also inhibited by oligomycin as well as by the thiol-binding agents, p-hydroxymercuribenzoate and N-ethylmaleimide. The results indicated that NADH and succinate oxidation by in vivo grown M. lepraemurium was mediated by oxidative enzymes involving first and second energy coupling sites.

[Oxidative phosphorylation in Mycobacterium lepraemurium]

The generation of ATP by cell-free extracts of Mycobacterium lepraemurium isolated from Sprague-Dawley rats was investigated. Cell-free preparations catalyzed phosphorylation coupled to the oxidation of NADH and succinate yielding P/O ratios of 0.6 and 0.4, respectively. Ascorbate oxidation did not result in ATP formation. The oxidative phosphorylation was uncoupled by 2,4- dinitrophenol and pentachlorophenol. Phosphate esterification coupled to NADH oxidation was inhibited by rotenone which had no effect on ATP synthesis associated with succinate oxidation. Antimycin A and cyanide completely inhibited phosphorylation coupled to the oxidation of NADH or succinate.

[A model for growing mycobacteria from leprous tissues placed in aliphatic hydrocarbons, tetradecane, a preliminary report]

Strains of Mycobacteria were regularly cultured from human and armadillo lepromata in liquid media, supplemented with tetradecane and dimethylsulfoxide. These substances had to be emulsified with heavy inoculum in order to obtain positive subcultures in the tetradecane-DMSO media. The use of nonpurified suspension of host-grown cells was advantageous for the primary cultivation. Subcultures were grown in the inorganic salt-tetradecane-dimethyl-sulfoxide liquid media. Strains did not grown on Löwenstein or Dubos medium. There is indication that the obtained cultures might be identical to M. leprae since the strongly acid-fast strains were obtained only in dimethylsulfoxide media. They were cultivated from a high proportion of human and armadillo lepromata collected from distant geographical locations. Cultures did not grow on any other media used for the cultivation of mycobacteria.

Cholesterol dynamics in macrophages implication for the bacteriology and pathology of leprosy

M. leprae in the host multiplies abundantly in macrophages rich in cholesterol. Host-grown leprosy bacilli have an extremely high cholesterol content and in this respect they occupy a unique place among procariotic cells. M. leprae takes up cholesterol from the environment and it is not clear whether it can synthesize cholesterol and if so from which precursors. Mycobacteria can be grown from leprous tissues in primary cultures only in the presence of cholesterol. These strains quickly adapt to in vitro substrates and are able to synthesize cholesterol from still-unknown chemical entities, which are also sources of carbon and energy. These still unknown substrates will probably have to be discovered before cultivation of these elusive microorganisms is achieved and we approach a better understanding of the chemical mediators in the cellular defence and/or pathology of leprosy.

Mycobacterium leprae: atypical and unclassified

Once M. leprae is grown on artificial media in the test tube, it might prove to have a great variety of characteristics quite different to those expected from our knowledge of M. leprae isolated from the susceptible host. The cultures might be slow or fast growing, pigmented or colorless, pathogenic for the armadillo, or not; they might produce limited disease in the foot pad of mice, or the contrary. The in vitro M. leprae culture might or might not provoke a lepromine reaction; the culture might grow at a lower or higher temperature. It is well documented that mycobacteria show great differences in elasticity and adaptability to cultivation conditions. It is absolutely certain that once grown in a test tube, M. leprae will behave as an atypical species. However, each individual culture of M. leprae obtained in vitro will have the same drug sensitivity pattern as in the lepromatous leprosy patient from whom it was cultivated.

Oxidation of formate by mycobacteria of the scrofulaceum group

Intact cells obtained from Mycobacterium scrofulaceum as well as from mycobacterial strains M.A6 and M.R56 isolated respectively from leprous tissues of armadillo and rat leproma and grown with glycerol as the oxidizable substrate catalyzed complete oxidation of formate. The stoichiometry of formate oxidase system yielded a value of 2 mol of CO2 produced per mole of O2 or per 2 moles of formate consumed. Cell-free preparations from these three strains of mycobacteria contained formate dehydrogenase which was associated exclusively in the particulate fraction. Formate oxidation was markedly stimulated by small amounts of selenite and molybdate added together. Formate-reduced minus oxidized difference spectra disclosed cytochromes of the b type while spectral evidence did not suggest the existence of cytochromes a or c components. The effect of 2-N-heptyl-4-hydroxyquinoline-N-oxide on the redox state of cytochromes indicated that formate oxidation was mediated by cytochrome b with absorption maximum of 556 nm and not of 562 nm.

An approach for the in vitro screening of drugs for activity against leprosy

Slow growing strains of mycobacteria isolated from leprous tissues present a characteristic resistance pattern to antibacterial agents that is comparable to drug sensitivity of M. leprae in man.

In vitro cultivation of mycobacteria in cholesterol lecithin media from lepromas of rats infected with Mycobacterium lepraemurium

In vivo grown M. lepraemurium suspensions were inoculated into a basal medium containing cholesterol and lecithin. Slow growing strains of mycobacteria were cultured regularly in these media. The presence of free cholesterol or cholesterol in serum or cholesterol in trypsin-digested egg yolk was essential for growth. The primary cultures were difficult to obtain, but the strains were easily subcultured. A heavy inoculum was necessary to obtain primary cultures in the liquid media, no growth occurred on semisolid agar slants. Similarly slow-growing primary cultures were obtained on Ogawa egg yolk media. Growth developed in a considerably shorter time if Ogawa's medium was enriched with 0.4% yeast extract (Difco). The cultures obtained on Ogawa egg yolk media were successfully subcultered in liquid cholesterol-lecithin media. The relation of the cultured strains of mycobacteria to the pathology of murine leprosy is not yet clear. The dynamics of cholesterol metabolism in the macrophages related to murine leprosy is discussed.

Cholesterol, a factor which is required for growth of mycobacteria from leprous tissues

In a yeast extract, glycerol and sheep serum containing medium, slow but abundant growth of mycobacteria occurred when media were inoculated with M. leprae isolated from leprous tissues of armadillos (Dasypus novemcinctus Linn.). The lipid fraction of the serum was the essential factor for growth. Cholesterol not only replaced, but surpassed the growth promoting effect of the lipid fraction. However, growth of mycobacteria was observed only when media were enriched with serum. The relationship of the obtained strains of mycobacteria to leprosy is not yet clear. The following cholesterol medium, stabilized with lecithin, is proposed for primary cultivation of mycobacteria from leprous tissues: KH2PO4-8.2 gm, Na2HPO4-0.5 gm, yeast extract (Difco)-4 gm, and glycerol 30 gm, dissolved to make one liter basal medium in distilled water. Cholesterol (200 mg) dissolved in 4 ml warm acetone is injected with a syringe into the basal medium. The solution is autoclaved for ten minutes to evaporate the acetone. Lecithin, 200 mg dissolved in 20 ml of the basal medium is mixed to the medium cooled to room temperature. Nine milliliter aliquots are distributed into each of a series of 50 ml screw cap tubes and autoclaved for 25 minutes. One milliliter of filter sterilized sheep serum is added to each of the tubes containing 9 ml of the cholesterol-lecithin medium. Semisolid media are prepared the same way but 1.5% agar w/v is added to the cholesterol-lecithin medium before autoclaving. When cooled to 56 degrees C, 10% w/v sheep serum is mixed to the liquid. The medium is distributed into screw cap tubes and agar slants are poured and allowed to solidify in the inclined tubes at room temperature. Macrophages contain considerable amounts of cholesterol. Cholesterol is proposed as a possible growth factor for host grown M. leprae in the macrophages of the susceptible host and the same sterol as a growth factor for primary cultivation of mycobacteria from leprous tissues.

Oxidation of various substrates by host grown Mycobacteria leprae and M. lepraemurium

Oxidation of various substrates by whole cell suspensions of M. Lepraemurium and M. leprae was investigated using manometric techniques. Yeast extract, L-cysteine, dithioerythritol, and DL-penicillamine were oxidized by both M. lepraemurium as well as by M. leprae. Although tween 80 was oxidized by M. lepraemurium cell suspensions, it was not by M. leprae. Succinate was readily oxidized by whole cells of M. leprae (without being frozen) whereas it was oxidized only by M. lepraemurium cells frozen at -40 degrees C for one minute. The results indicate that M. leprae and M. lepraemurium are capable of oxidizing some substrates without requiring any cofactor and are not dependent upon host cells for respiration.

Oxidation of 3,4-dihydroxyphenylalanine by connective tissue constituents. Identification of Mycobacterium leprae not related to phenolase activity

The oxidation of 3,4-dihydroxyphenylalanine (DOPA) was studied by spectrophotometric methods at pH 6.8. In the presence of L- or D-DOPA, a color development occurred in the presence of the following substances as measured by increase in absorption both at 540 nm and 480 nm: hyaluronic acid, trypsinized human skin and umbilical cord extract, trypsin treated rat tissue from subcutaneous rat leproma, trypsin treated M. lepraemurium isolated from rat lepromata, and trypsinized M. leprae isolated from non-treated lepromatous leprosy cases. Normal human skin and connective tissue extract and nontrypsinized connective tissue of rat leprosy granuloma did not oxidize DOPA. While the trypsin-treated partially purified M. leprae suspension oxidized DOPA at both wave-lengths, the hyaluronidase-treated same suspension of M. leprae failed to oxidize these phenolic compounds. Mushroom tyrosinase oxidized D-DOPA, L-DOPA, epinephrine and norepinephrine at 480 nm. Hyaluronic acid also oxidized epinephrine and norepinephrine at both wave-lengths. Since it is known that M. leprae in the human host is closely associated with the presence of the acid mucopolysaccharides of the skin, and since acid mucopolysaccharides and skin constituents strongly oxidized DOPA, and since the hyaluronidase treated M. leprae failed to oxidize DOPA, it became evident that hyaluronic acid and not M. leprae is responsible for DOPA oxidation, and phenolase activity is not associated with the metabolism of M. leprae. Evidence is presented that DOPA is not a unique characteristic of the human leprosy bacillus. For instance, trypsin-treated murine leprosy bacilli from the rat strongly oxidized DOPA. The reaction of DOPA oxidation, therefore, must be rejected as a test for the identification of M. leprae. The obtained results confirmed the pertinent findings of Skinsnes and his co-workers.

A simplified hyaluronic acid based culture medium for mycobacteria isolated from human lepromata

Acid-fast bacilli multiplied in liquid culture media containing hyaluronic acid when inoculated with mycobacteria from a lepromatous leprosy nodule. The culture was readily subcultured at ten day intervals in the homologue media, but failed to grow in the Dubos, Middlebrook and Lowenstein media. These findings confirm the results of Skinsnes et al (1975). Identification of this culture is not yet available, however it gives positive immunofluorescence with authentic anti-M. leprae serum. The obtained culture also grows as a chromogenic culture at 34 degrees C on a simple medium prepared from trypsin digested human umbilical cord, yeast extract powder and glycerol. This medium can be sterilized in an autoclave, but filter sterilized sheep, bovine or horse serum must be added aseptically as an essential ingredient. The medium does not differ considerably from the hyaluronic acid medium proposed by Skinsnes et al, but it is easier to prepare, it is inexpensive and permits a logarithmic growth within seven days of the so far unidentified culture isolated from leprotic nodules.

The respiratory metabolism of Mycobacterium lepraemurium

The respiratory metabolism of Mycobacterium lepraemurium isolated from Sprague-Dawley rats lepromata using several substrates was investigated. None of the intermediates of the glycolysis cycle as well as of the tricarboxylic acid cycle except succinate was oxidized by purified whole suspensions of M. lepraemurium. Likewise, many sulfur compounds such as cystine, thiourea, thioacetate, thiodiglycol, mercaptoact and some sulfhydryl compounds, e.g., cysteine, dithioerythritol, dithiorthritol, and penicillamine were readily oxidized by murine bacillary suspensions, whereas thioglycolate, thioglucose, and reduced glutathione were oxidized at a slow rate. Succinate was not or was very poorly oxidized by normal cells probably because of impermeability of the cell wall but the addition of succinate to the cell suspensions frozen for 1 min at -40 degrees C considerably enhanced oxygen uptake over the endogenous value. The oxidation of succinate was unaffected by inhibitors rotenone, atabrine, and amytal but was markedly inhibited by thenoyltrifluoroacetone, antimycin A, 2-N-heptyl-4-hydroxyquinoline-N-oxide, and cyanide. The thiol-binding agents, p-hydroxymercuribenzoate and N-ethylmaleimide were also effective inhibitors of succinate oxidation but the process was not affected by uncouplers dinitrophenol, dibromophenol, pentachlorophenol, and carbonyl-cyanide-m-chlorophenylhydrazone. The results indicated that succinate oxidation by M. lepraemurium was mediated by oxidative enzymes involving an electron transport chain with oxygen as the terminal electron acceptor.

Leprosy: "loathsome disease in Tracadie, New Brunswick"--a flimpse into the past century

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Separation of Mycobacterium lepraemurium from the subcutaneous tissues of the rat

In an effort to obtain cell suspensions free from blood cells which interfere in spectrophotometric studies, a method was devised by which relatively large quantities of whole cell suspensions of M. lepraemurium are obtained for experimental purposes. We have routinely employed this procedure which is quite reliable, technically simple, moderate in equipment requirements, and in a matter of five minutes it can be ascertained whether or not the preparations are free from contaminants which render the purified bacillary suspensions unsuitable for studies involving spectrophotometric technics. However, in this procedure, certain points are essential in order to obtain large quantities of purified bacillary suspensions. It is important to homogenize the lepromata for only a few seconds at brief intervals. Excessive homogenization may cause considerable damage to the bacilli and it may be difficult to separate the bacilli from the host tissues. It is also important to use transparent bottles and tubes during centrifugation as the material can be seen and thus each fraction can be separated easily. Very few bacilli are lost in the discarded material and we have repeatedly obtained 2.5 to 3 gm wet weight of M. lepraemurium from one leproma weighing 25 gm to 30 gm.

Occurrence of c-type cytochrome in Mycobacterium lepraemurium

The existence of c-type cytochrome in Mycobacterium lepraemurium was examined. The dithionite-treated cell-free extracts exhibited absorption peaks of cytochromes a + a3 and b, whereas the alpha band of c-type cytochrome at 552 nm was obscured by the large absorption peak of cytochrome b at 560 nm. The addition of NADH, NADPH, or succinate to cell-free extracts caused the reduction of b- and c-type cytochromes to nearly the same extent and thus the difference spectra displayed distinct separate peaks of b- and c-type cytochromes at 562 and 552 nm, respectively. The cell-free extracts treated with ascorbate showed absorption bands of cytochrome types c and a + a3, whereas the addition of succinate to a system preinhibited by antimycin A revealed the absorption bands of cytochrome b only. The absorption spectrum of the pyridine hemochromogens of M. lepraemurium was similar to that of mammalian cytochrome c. The results clearly indicated that, in addition to cytochromes of the a + a3 and b type, c-type cytochrome is also present in M. lepraemurium.

The cytochrome system in Mycobacterium lepraemurium

The respiratory chain system of cell suspensions of Mycobacterium lepraemurium was investigated spectrophotometrically. The results obtained indicated that whole cell preparations contained flavins, cytochromes of the a + a3 and b type, as well as two CO-binding pigments; cytochromes a3–CO and a second pigment similar to cytochrome o. The cytochromes were found to be in the reduced form. The presence of cytochrome systems could only be shown after the cell suspensions in the reference cuvette were exposed to oxygen. The positions of the peaks in the difference spectra were similar when the cell suspensions were reduced anaerobically without added substrate or treated with dithionite. The whole cell suspensions of M. lepraemurium were not found to contain detectable quantities of cytochrome c.