[Screening of potential antibiotics, inhibitors of the nonmevalonate pathway of isoprenoid biosynthesis--2-C-methyl-D-erythritol-2,4-cyclodiphosphate derivatives].

The recently discovered nonmevalonate pathway of isoprenoid biosynthesis is a prospective target in screening of new antibiotics. Because of the absence of the pathway in the animal cells, the specific inhibitors of the pathway will be a new class of antibiotics against many pathogens (which cause, e.g., malaria, tuberculosis, etc), combining high efficiency and low toxicity. Several derivatives of 2-C-methyl-D-erythritol-2,4-cyclodiphosphate (MEC) were synthesized. 4-Phospho-methyl-D-erythritol-1,2-cyclophosphate, benzyl ether and benzyliden derivative of MEC inhibited the 14C-MEC incorporation into isoprenoids of chromoplasts from red pepper with IC50 of 1.7-5 MM. Some inhibition (about 10%) was also observed with the use of dimethyl ether and isopropyliden derivative of MEC.

[2-(14)C-Methylerythritol 2,4-cyclodiphosphate incorporation into bacterial and plant isoprenoids].

To work out a test system for studying the inhibition of isoprenoid biosynthesis through non-mevalonate pathway, the conversion of 2-(14)C-methylerythritol 2,4-cyclodiphosphate (14C-MEC) into isoprenoids of three bacteria species and into plastids of 11 higher plant species was studied. The highest efficiency (up to 63%) of the process was observed with chromoplasts from narcissus (Narcissus pseudonarcissus L.) and celandine (Chelidonium majus L.). Twenty five percent of added 14C-MEC was recovered in an isoprenoid fraction of red pepper (Capsicum annuum L.) chromoplasts. Thus, these three models can be used to test antibiotic inhibitors of isoprenoid biosynthesis.

[Interrelation between the pathways of isoprenoid biosynthesis and carbon source catabolism in anaerobic and facultatively anaerobic bacteria].

Data on the interrelation between the pathways of the carbon source catabolism and isoprenoid biosynthesis in anaerobic and facultatively anaerobic bacteria were obtained. Two pathways of isoprenoid biosynthesis (nonmevalonate and mevalonate) were revealed in the representatives of the genus Clostridium. The non-mevalonate pathway of isoprenoid biosynthesis and the glycolytic pathway of substrate oxidation are typical of glucose-grown bacteria, whereas the pentose phosphate cycle operates in xylose-grown bacteria. The mevalonate pathway of isoprenoid biosynthesis was revealed in strain Clostridium thermosaccharolyticum DSM 571 grown in the presence of mevinolin, as well as in a number of lactic acid bacteria. Mevinolin is known to react with the lactate dehydrogenase complex, preventing reduction of pyruvate. The nonmevalonate pathway of isoprenoid biosynthesis was revealed in Bifidobacterium bifidum. The role of different metabolic pathways in isoprenoid biosynthesis is discussed.

[The role of 2-C-methylerythritol-2,4-cyclopyrophosphate in the resuscitation of the "nonculturable" forms of Mycobacterium smegmatis].

2-C-Methyl-D-erythritol-2,4-cyclopyrophosphate (MEC), an intermediate of the biosynthesis of isoprenoid compounds in bacteria, was found to be capable of exerting a resuscitating effect on resting Mycobacterium smegmatis cells. The introduction of an additional copy of the ispE gene encoding cytidyl-methylerythritol kinase, an enzyme involved in MEC synthesis in M. smegmatis, resulted in the emergence of a capacity for spontaneous reactivation of "nonculturable" M. smegmatis cells, which is not characteristic of the wild-type cells of this species. The involvement of MEC in the transition from the "nonculturable" state to the state of active growth is indicative of a previously unknown function of MEC, assumed to consist in regulation of the bacterial genome activity.

[Evaluation of in vitro antibacterial activity of fosmidomycin and its derivatives].

Unlike the mammals, some species of pathogenic microorganisms synthesize isoprenoids by the mevalonate-independent pathway known as the methyl-erythritol phosphate pathway (MEP). The macromolecules of the polyprenyl compounds play an essential role in the metabolism of the microbial cell. Therefore, the MEP enzymes can be targets for new antibiotics. Antibacterial activity of fosmidomycin, an inhibitor of 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), the key enzyme of MEP in isoprenoid biosynthesis was estimated. By the results of the in vitro experiments the tested microorganisms were divided into susceptible and resistant to fosmidomycin. Vaccinal strains of B. anthracis and practically all the strains of P. aeruginosa were included into the first group. The minimum inhibitory concentrations of fosmidomycin for them determined by the method of serial dilutions were 1-8 mcg/ml. The second group for which the MICs were 16-64 mcg/ml included representatives of Listeria, Yersinia and Burkholderia. The tested species of enteric bacteria, Mycobacterium, Corynebacterium, Campylobacterium and the tularemia vaccinal strain were fosmidomycin resistant. The MICs for them varied from 128 to 512 mcg/ml. Since all the above mentioned bacteria have DXR, resistance to fosmidomycin was conjectured with the difficulty of its delivery to the target in the microbial cell. To increase penetrability of fosmidomycin, various functional groups modifing its hydrophoby were added to the antibiotic molecule. However, no expected increase of the susceptibility to the derivatives was achieved probably because their affinity to DXR lowered. Penetrability of fosmidomycin to the cell was facilitated by using its combinations with compounds influencing the integrity of the bacterial cell membrane. Combined use of fosmidomycin with polymyxin B, chlorhexidine and cetrimide 4-64 times lowered its MICs for the strains of Listeria, Burkholderia and Yersinia.

[Isoprenoid pigments in representatives of the family Microbacteriaceae].

By using fosmidomycin and mevinolin (inhibitors of the synthesis of isoprenoid pigments), spectrophotometry, and mass spectrometry, the presence of isoprenoid pigments is shown in 71 of the 78 strains under study. All of these strains belong to 11 genera of the family Microbacteriaceae. Yellow, orange, and red pigments are found to have absorption spectra typical of C40-carotenoids. Eight out of the sixteen strains of the genus Microbacterium are able to synthesize neurosporene, a precursor of lycopene and beta-carotene. The biosynthesis of carotenoids in some representatives of the genera Agromyces, Leifsonia, and Microbacterium is induced by light. Inhibition of the biosynthesis of isoprenoid pigments by fosmidomycin suggests that they are synthesized via the nonmevalonate pathway. Twelve strains are found to exhibit both the nonmevalonate and mevalonate pathways of isoprenoid synthesis. These data, together with the difference in the inhibitory concentration of fosmidomycin, can be used for differentiating various taxa within the family Microbacteriaceae.

[Prevalence of nonmevalonate and mevalonate pathways for isoprenoid biosynthesis among bacteria of different systematic groups].

The effect of fosmidomycin and mevinoline, inhibitors of the nonmevalonate and the mevalonate pathway of isoprenoid biosynthesis, respectively, on the growth of 34 anaerobic and 10 aerobic prokaryotic strains was studied. Fosmidomycin at the concentrations used was shown to inhibit the growth of 9 (of 10) representatives of the family Microbacteriaceae, 4 (of 5) strains of Thermoanaerobacter, and 11 (of 12) strains of Clostridium, whereas mevinoline inhibited the growth of lactobacilli (Carnobacterium), methanogenic and sulfate-reducing bacteria insensitive to fosmidomycin. During the late growth phase, four strains of actinobacteria (of nine) accumulate the compound, which, upon oxidation, generates a long-lived free radical; three strains synthesize 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEC). It was concluded that the difference in the sensitivity of the organisms to fosmidomycin and mevinoline might serve as a test to differentiate several representatives of the family Microbacteriaceae. The use of mevinoline for inhibiting methanogens in ecological investigations seems to be promising.

[Free radicals in mercury-resistant bacteria indicate a novel metabolic pathway]. / Svobodnye radikaly u rtut'-rezistentnykh bakterii kak indikatory novogo metabolicheskogo puti.

A mercury resistant-soil bacterium P.10.15, identified as a close relative of Pseudomonas veronii, was shown to accumulate a specific compound in the stationary phase of growth. This compound is converted to a long-lived free radical under oxidizing conditions, as registered by its EPR signal at room temperature. The compound was purified by ion-exchange and gel-filtration chromatography and identified by mass spectroscopy, 2D NMR, and EPR as a trisaccharide beta-D-GlcpNOH,CH3-(1-->6)-alpha-D-Glcp-(1-->1)-alpha-D-Glcp, or, in other words, as 6-O-(2-deoxy-2-[N-methyl]hydroxylamino-beta-D- glucopyranosyl)-alpha-alpha-trehalose, previously discovered in Micrococcus luteus (lysodeikticus) and named lysodektose. The compound is suggested to be a novel intermediate of a previously unknown basic metabolic pathway of trehalose transformation in bacteria, a potential target for antibacterial drug development.

[Properties of 2-C-methyl-D-erythritol 2,4-cyclopyrophosphate--an intermediate in the non-mevalonate isoprenoid biosynthesis]. / Nekotorye svoistva 2-C-metil-D-éritritol-2,4-tsiklopirofosfata--intermediata bezmevalonatnogo puti biosinteza izoprenoidov.

Extraction and purification from the biomass of Corynebacterium ammoniagenes of 2-C-methyl-D-erhythritol 2,4-cyclopyrophosphate (MEC) was associated with its spontaneous transformation into a number of derivatives (which was due to pyrophosphate bond lability and the formation of complexes with metals). These derivatives included 1,2-cyclophospho-4-phosphate, 2,4-diphosphate, 2,3-cyclophosphate, 1,4-diphosphate, and 3,5-diphosphate (identified by 1H, 31P, and 13C NMR spectroscopy) and accounted for about 10% MEC. When added to a solution of DNA in the presence of the Fenton reagent, MEC prevented DNA decomposition. In addition, MEC slowed down the interaction of the reagent with tempol radicals, which indicates that complexation of ferrous ions by MEC attenuates their ability to catalyze the formation of hydroxyl radicals from hydrogen peroxide. In the presence of 0.23 mM MEC, the rate of respiration of rat liver mitochondria increased 1.8 times. At 0.1-1.0 mM, MEC activated in vitro proliferation of human Vgamma9 T-cells. It is suggested that MEC acts as an endogenous stabilizing agent for bacterial cells subjected to oxidative stress and as an immunomodulator for eukaryotic hosts.

[Effect of fosfidomycin on development of various infections in mice]. / Deistvie fosmidomitsina na razvitie nekotorykh infektsii u myshei.

Antibiotic fosmidomycin will know as inhibitor of the nonmevalonate pathway of isoprenoid biosynthesis and as possible antimalarial drug, was shown to possess a certain protective effect on mice experimentally infected with tularemia, tiphus or coli-septicemia. Positive effect on mice with chronic form of tuberculosis was not observed when the animals were given 1 mg of fosmidomycin per capita twice a day. Under oxidative conditions an ESR signal of long living nitroxil free radicals were registered in the water solution of fosmidomycin. The radicals are supposed to be involved in the therapeutic effect of the antibiotic.

[Immunomodulatory properties of 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate and search for its new derivatives]. / Immunomoduliatornye svoistva i poisk novykh proizvodnykh 2-C-Metil-D-éritriol-2,4-tsiklopirofosfata.

A strong immunomodulatory effect of 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEC) responsible for the survival of bacteria was shown on isolated macrophages and in experimental infections in mice (typhoid and tularemia). Derivatives of MEC were found by 1H-NMR spectroscopy under stress conditions in colorless mutants of the bacteria and isolated to be subsequently purified and used for modulation of the immune system of animals.

[Interaction of bacteria with mercuric compounds]. / Vzaimodeistvie bakterii s rtutnymi soedineniiami.

We investigated the interaction of mercuric compounds with the bacteria Corynebacterium ammoniagenes, Micrococcus luteus, and Mycobacterium smegmatus capable of producing hydroxylamines (R-NOH) and 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MECP), which are prone to form free radicals. The interaction of these substances with Hg2+ ions and their dynamics during the mercuric poisoning of bacteria was studied by EPR and NMR. Under stress conditions induced by lowering pH or generation of active oxygen species, the bacteria and, especially, their mutants with enhanced sensitivity to oxidative stress, were found to respond to exposure to 1-3 micrograms/ml HgCl2 and p-chloromercuribenzoate by a several-fold increase in their viability. The data obtained were interpreted in terms of the involvement of the sulfhydryl groups of bacterial surface proteins in this phenomenon. The interaction of bacteria with mercuric compounds may affect the pathogenesis of tuberculosis and other diseases.

[Participation of 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate in reactions of bacteria on oxidative stress and their persistence in macrophages]. / Uchstie 2-C-metil-D-éritritol-2,4-tsiklopirofosfata v reaktsii bakterii na okislitel'nyi stress i v ikh persistentsii v makrofagakh.

In aerated medium, Corynebacterium ammoniagenes cells accumulate 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEC) during heat shock and in the presence of O2--generating compounds or ozone. The ability to accumulate MEC was genetically transformed from C. ammoniagenes to E. coli XL-1; transformed E. coli (2-31 clone) accumulates MEC in the presence of glucose and glucose oxidase (generation of H2O2) or benzylviologen (generation of O2-); the viability of transformed bacteria inside the murine peritoneal macrophages also significantly increases. However, model conditions of phagosomes of warm-blooded animals (NO + H2O2 + O2-) did not cause MEC accumulation by C. ammoniagenes but increased the formation of polyphosphate which can be due to selective oxidative aberration of biosynthetic processes. Growth rate of Acanthamoeba castellanii on solid medium with bacterial lawn was not significantly different in C. ammoniagenes, C. ammoniagenes with preaccumulated MEC, E. coli XL-1, and E. coli 2-31 and did not depend on the accumulation of MEC by bacteria. Unlike the recipient E. coli strain, the transformed 2-31 clone synthesizes two nonpolar lipids (Rf = = 0.85 and 0.75; TCL on Silufol in hexane) and carotinoid pigments; this can be due to changes in metabolic pathways of isopentenylpyrophosphate that can be a precursor of MEC biosynthesis. Thus, MEC is involved in bacterial responses to certain components of oxidative stress and in bacterial persistence inside the macrophages.

[Relationship between the synthesis of a new stress response component and bacterial cell metabolism]. / Sviaz' sinteza novogo komponenta stressornoi reaktsii s metabolizmom bakterial'noi kletki.

Various stress factors (incubation with redox-cycling agents, ozonization, heat shock) that induced accumulation of 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEC) were also shown to induce various alterations of the phospholipid composition in three microbial species: Corynebacterium ammoniagenes, Micrococcus luteus, and Staphylococcus aureus. The influence of adding 10 carbohydrates to the growth medium on MEC accumulation by C. ammoniagenes cells was tested. Only glucose and mannose exerted a pronounced stimulatory effect on the MEC synthesis under oxidative stress. The target of oxidative attack whose transformation causes MEC synthesis is suggested to be located near or on the bacterial cytoplasmic membrane.

[Stability of a new product of oxidative stress in bacterial cells]. / Stabil'nost' novogo produkta okislitel'nogo stress v kletkakh bakterii.

Data on 32P-label incorporation with subsequent addition of non-radiolabelled o-phosphate suggest that the new phosphorus compound, 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEC), accumulated in the cells of some bacterial species in response to oxidative stress does not rapidly exchange phosphorus with external o-phosphate 3 hours after the introduction of its synthesis inducers into the Corynebacterium ammoniagenes culture. The accumulated MEC is retained in the cells despite the action of the cell wall synthesis inhibitor, chloramphenicol, or the energetic poisons, KCN and iodoacetate and also under anaerobic conditions. It has been shown that incubation of the cell-free lysate of a non-induced culture, Micrococcus luteus, with MEC does not result in MEC hydrolysis; therefore, MEC accumulation after the redox-mediator addition is hardly due to the hydrolase inactivation but, rather, is due to the activation of the MEC-synthesizing enzyme. The cells of C. ammoniagenes incorporate 32P from [32P]MEC but not 14C from [14C]MEC. This points to MEC hydrolysis prior to the uptake of its phosphoryl fragment by the cells. In this case 32P is found in the fractions differing by their position from MEC fractions. Experiments with sheep erythrocytes and mouse splenocytes revealed that MEC (10-100 micrograms per 1,000,000 splenocytes) does not influence the antibody production by these cells, whereas used at concentrations of 200-550 micrograms per 1,000,000 cells, MEC enhances the antibody production. However, while doing so, MEC causes the destruction of a considerable portion of splenocytes and sheep erythrocytes.

[Oxidative stress and organic cyclopyrophosphates in bacteria]. / Okislitel'nyi stress i organicheskii tsiklopirofosfat u bakterii.

Oxidative stress in nocardioform bacteria--Corynebacterium (Brevibacterium) ammoniagenes, Micrococcus luteus and Mycobacterium smegmatis--is accompanied by a significant accumulation of 2-C-methyl-D-erythrol-2,4-cyclopyrophosphate (MEC), which is correlated with the ability of the producer to grow under stress. Metabolic stability of MEC in bacterial cells, its spontaneous isomerization into 1,2-cyclophospho-4-phosphate and the possibility of a genetic transfer of the MEC-synthesizing capacity from Corynebacterium to E. coli have been demonstrated. The involvement of MEC in the response to oxidative stress via the complex formation between MEC and bivalent cations has been postulated.

[Effect of antiseptics and redox-cycling agents on Corynebacterium ammoniagenes and related microorganisms in relation to synthesis of a new macroergic compound]. / Deistvie antisepticheskikh sredstv i redokstsikliruiushchikh agentov na Corynebacterium ammoniagenes i rodstvennye mikroorganizmy v sviazi s sintezom novogo makroérga.

Sublethal concentration of the antiseptic composition Desoxon-1 was shown to provoke in cells of Corinebacterium ammoniagenes in a liquid medium the biosynthesis and accumulation of a novel macroergic 2-methylbutane-1,2,3,4-tetraol-2,4-cyclopyrophosphate. This substance is also synthesized when C. ammoniagenes is cultivated in a solid agar medium supplemented with benzylviologen. Cells preloaded with the new cyclopyrophosphate maintain its content when treated with 4% phenol, DP-2, Desoxon-1 or boiled and heated in an autoclave. Experiments with Mycobacterium tuberculosis and BCG revealed the ability of these bacteria to grow in a medium supplemented with BV++ possibly due to ability of synthesis of a new cyclopyrophosphate which was shown to correlate with resistance toward redox-cycling drugs. Accumulation of polyphosphates in the control cells of M. tuberculosis was illustrated by 31P-NMR spectroscopy and disappearance of the polyphosphates during cultivation in a BV(++)-supplemented medium. No signal of the new cyclopyrophosphate was yet registered in cells of M. tuberculosis by 31P-NMR.