Growth ofM Research Articles

Microcystin production by Microcystis aeruginosa in a phosphorus-limited chemostat.

The production of microcystins (MC) from Microcystis aeruginosa UTEX 2388 was investigated in a P-limited continuous culture. MC (MC-LR, MC-RR, and MC-YR) from lyophilized M. aeruginosa were extracted with 5% acetic acid, purified by a Sep-Pak C(18) cartridge, and then analyzed by high-performance liquid chromatography with a UV detector and Nucleosil C(18) reverse-phase column. The specific growth rate (mu) of M. aeruginosa was within the range of 0.1 to 0.8/day and was a function of the cellular P content under a P limitation. The N/P atomic ratio of steady-state cells in a P-limited medium varied from 24 to 15 with an increasing mu. The MC-LR and MC-RR contents on a dry weight basis were highest at mu of 0.1/day at 339 and 774 microg g(-1), respectively, while MC-YR was not detected. The MC content of M. aeruginosa was higher at a lower mu, whereas the MC-producing rate was linearly proportional to mu. The C fixation rate at an ambient irradiance (160 microeinsteins m(-2) s(-1)) increased with mu. The ratios of the MC-producing rate to the C fixation rate were higher at a lower mu. Accordingly, the growth of M. aeruginosa was reduced under a P limitation due to a low C fixation rate, whereas the MC content was higher. Consequently, increases in the MC content per dry weight along with the production of the more toxic form, MC-LR, were observed under more P-limited conditions.

Effects of growth conditions on expression of mycobacterial murA and tyrS genes and contributions of their transcripts to precursor rRNA synthesis.

All mycobacteria studied to date have an rRNA operon, designated rrnA, located downstream from a single copy of the murA gene, which encodes an enzyme (EC 2.5.1.7) important for peptidoglycan synthesis. The rrnA operon has a promoter, P1(A), located within the coding region of murA, near the 3' end. Samples of RNA were isolated from Mycobacterium tuberculosis at different stages of the growth cycle and from Mycobacterium smegmatis grown under different conditions. RNase protection assays were used to investigate transcripts of both murA and rrnA. Transcription of murA was found to continue into the 16S rRNA gene, as if murA and rrnA form a hybrid (protein coding-rRNA coding) operon. During the growth of M. tuberculosis, the hybrid operon contributed approximately 2% to total pre-rRNA. Analysis of M. smegmatis RNA revealed that the level of murA RNA depended on the growth rate and that the patterns of expression during the growth cycle were different for murA and rrnA. M. smegmatis has a second rRNA operon, rrnB, located downstream from a single copy of the tyrS gene, encoding tyrosyl-tRNA synthetase. Transcription of tyrS was found to continue into the 16S rRNA gene rrnB. The hybrid tyrS-rrnB operon contributed 0.2 to 0.6% to rrnB transcripts. The pattern of tyrS expression during the growth cycle matched the pattern of rrnB expression, reflecting the essential role of TyrS and rRNA in protein biosynthesis.

Antitubercular activity of garlic (allium sativum) extract on combination with conventional antitubercular drugs in tubercular lymphadenitis

Based on our demonstration earlier that ethanol extract, water extract and a compound purified from garlic possessedin vitro antitubercular activity against drug resistant and susceptibleMycobacterium tuberculosis, we tried the effect of garlic extract in 30 patients of tubercular lymphadenitis. For ethical considerations, two groups of patients, 30 each, were given antitubercular therapy (ATT) consisting of isoniazid, rifampicin, ethambutol and pyrazinamide for 30 days. For the next 15 days (31 to 45 days) group 1 patients received 3-6 garlic pearls per day in addition to ATT while group 2 patients received ATT only. From 46th day onwards both the groups received ATT only for 6-8 months. Antitubercular activity of the serum samples collected on 45th day was assessed by its effect on the growth ofM. tuberculois. The serum of group 1 patients showed significantly much higher antitubercular activity than that of group 2 patients. Further, there was relief of dyspeptic symptoms caused by ATT therapy in patients of group 1 with garlic plus ATT therapy but no change in group 2 patients with ATT only. Liver function and hematological tests were normal in both the groups after 6 months of therapy. Garlic extracts or compounds have a good potential as antitubercular(s) drug if given as a supplement to ATT.

Inhibition of development of Myxococcus xanthus by eukaryotic protein kinase inhibitors.

Myxococcus xanthus is a social bacterium that lives in the soil and undergoes spectacular development to form multicellular fruiting bodies. It contains a large family of eukaryote-like serine/threonine protein kinases. We found that a number of inhibitors for eukaryotic protein serine, threonine, and tyrosine kinases could inhibit the development and sporulation of M. xanthus to various degrees. These results suggest that serine/threonine and tyrosine phosphorylation may be involved in development of M. xanthus. None of the inhibitors tested had any effect on vegetative growth of M. xanthus. Most of them seemed to act during the early stages of development. However, the expression of a very early development-specific gene, Omega4521, was not significantly affected by the inhibitors. The patterns of protein phosphorylation during development were also not significantly altered by the inhibitors, suggesting that the targets of the inhibitors are minor or unstable phosphoproteins but play key roles in fruiting-body formation in M. xanthus.

Multinucleated Giant Cell Formation Induced by IFN-γ/IL-3 Is Associated with Restriction of VirulentMycobacterium tuberculosisCell to Cell Invasion in Human Monocyte Monolayers

One of the hallmarks of an effective immune response againstMycobacterium tuberculosisis the formation of granulomas containing multinucleated giant cells. IFN-γ and interleukin-3 (IL-3) promote Langhans-type multinucleated giant cell formation and have been identified in T cell clones reacting toM. tuberculosisantigens. The ability of human monocytes treated with IFN-γ and IL-3 to limit the spread ofM. tuberculosisin anin vitroinfection assay was examined. Monocytes were incubated with control medium, IFN-γ, TNF-α, and calcitriol, a combination permissive toM. tuberculosisgrowth, or IFN-γ and IL-3 and infected with a low inoculum ofM. tuberculosis(Erdman). IFN-γ/IL-3 treatment reducedM. tuberculosisCFU relative to both untreated and IFN-γ/TNF-α/calcitriol-treated monocytes. Specifically, CFU were reduced by 79% at 14 days in the IFN-γ/IL-3 treatment group relative to the IFN-γ/TNF-α/calcitriol treatment group, an effect that was not due to toxic monocyte metabolites.M. tuberculosisgrowth restriction by IFN-γ/IL-3-treated monocyte monolayers was associated with the development of Langhans-type multinucleated giant cells. At the light microscope level, dense growth ofM. tuberculosissurrounded by a ring of nuclei localized to the center of individual cells. The intracellular location ofM. tuberculosiswas confirmed by electron microscopy. In contrast, monocyte monolayers treated with IFN-γ/TNF-α/calcitriol consisted of a syncitium of cells containing monocyte aggregates. Nonlocalized linear arrays ofM. tuberculosiswere observed to be growing throughout such aggregates. These results suggest that physical sequestration ofM. tuberculosisby Langhans-type multinucleated giant cells may limit cell to cell spread of this pathogen, thereby restricting growth.

Site-directed mutagenesis of the 19-kilodalton lipoprotein antigen reveals No essential role for the protein in the growth and virulence of Mycobacterium intracellulare.

The mycobacterial 19-kilodalton antigen (19Ag) is a highly expressed, surface-associated glycolipoprotein which is immunodominant in infected patients and has little homology with other known proteins. To investigate the pathogenic significance of the 19Ag, site-directed mutagenesis of the Mycobacterium intracellulare 19Ag gene was carried out by using a suicide vector-based strategy. Allelic replacement of the 19Ag gene of a mouse-avirulent M. intracellulare strain, 1403, was achieved by double-crossover homologous recombination with a gentamicin resistance gene-mutated allele. Unfortunately, an isogenic 19Ag was not achievable in the mouse-virulent strain, D673. However, a 19Ag mutant was successfully constructed in M. intracellulare FM1, a chemically mutagenized derivative of strain D673. FM1 was more amenable to genetic manipulation and susceptible to site-directed mutagenesis of the 19Ag gene yet retained the virulent phenotype of the parental strain. No deleterious effects of 19Ag gene mutation were observed during in vitro growth of M. intracellulare. Virulence assessment of the isogenic 19Ag mutants in a mouse infection model demonstrated that the antigen plays no essential role in the growth of M. intracellulare in vivo. Site-directed mutagenesis of the 19Ag gene demonstrated that it plays no essential role in growth and pathogenicity of M. intracellulare; however, the exact nature of its biological function remains unknown.

High level expression of theMagnaporthe griseamitochondrial small sub-unit rRNA during rice leaf colonization and rapid down-regulation prior to the onset of disease symptoms

Differential cDNA screening identified aMagnaporthe griseagene which is highly expressed during rice leaf colonization by the fungus. The transcript accumulatd 72 h after plant inoculation, just before symptom expression by the pathogen, but rapidly decreased in abundance after this time. DNA sequence analysis showed that the cDNA has homology to mitochondrial small sub-unit rRNAs. Consistent with this, the cDNA hybridized to purified mitochondrial DNA but did not hybridize to nuclear genomic DNA or chromosomal-sized DNA molecules. The corresponding gene also failed to segregate as a nuclear-encoded marker. To investigate expression of theM. griseasmall sub-unit mitochondrial rRNA during growth ofM. griseain axenic culture, experiments were carried out which showed that the transcript is constitutively expressed during active fungal growth but down-regulated by oxidative stress or prolonged nutrient starvation. The mitochondrial rRNA was also down-regulated developmentally during conidiation. The data are consistent with very active mitochondrial protein synthesis during colonization of rice tissue byM. grisea, followed by rapid down-regulation of mitochondrial activity prior to disease symptom outbreak and the onset of conidiogenesis.

Effects of decontamination methods and culture conditions on viability of Mycobacterium ulcerans in the BACTEC system.

We used the BACTEC system to evaluate the effects of several decontamination methods and the addition of antibiotics on the viability of Mycobacterium ulcerans. The effects of polyoxyethylene stearate or egg yolk as supplements were also evaluated to determine their impact on the growth of M. ulcerans. Strains of different geographic origins were subjected to Petroff, reversed Petroff, oxalic acid, and mild HCI treatments. After treatment, the viability of each strain was assessed in the BACTEC system. All of the decontamination methods tested adversely affected bacterial viability. Treatment with mild HCl gave the best results, allowing better growth rates with some strains and causing a delay in growth with others, depending on the geographic origin of the strain. A mixture of polymyxin B, amphotericin B, nalidixic acid, trimethoprim, and azlocillin did not significantly inhibit growth. Supplementing BACTEC medium with egg yolk markedly improved the recovery of M. ulcerans following the use of each of the decontamination methods. Our findings demonstrate a detrimental impact on the viability of M. ulcerans by all of the decontamination methods currently in common use. This explains, at least in part, the difficulty often experienced in cultivating this organism from clinical specimens. Egg yolk should be added to enhance the rate of successful primary cultivation of M. ulcerans in the BACTEC system.

A Comparative Study ofMiscanthus floridulus(Labill) Warb andM. transmorrisonensisHayata: Photosynthetic Gas Exchange, Leaf Characteristics and Growth in Controlled Environments

Abstract The relationship between temperature and the distribution ofMiscanthus floridulus(Labill) Warb andM. transmorrisonensisHayata along altitudinal gradients in central Taiwan was examined. Responses of biomass accumulation, leaf characteristics and photosynthetic gas exchange to growth temperature (from 10 to 30 °C) ofM. floridulusfrom an altitude of 390 m and ofM. transmorrisonensisfrom 2700 m were determined. There were differences between the two species in above-ground biomass, CO2uptake characteristics and leaf chlorophyll contents in response to growth temperature. The optimal temperatures for biomass accumulation were 30/25 (day/night temperature) and 25/20 °C forM. floridulusandM. transmorrisonensis,respectively. Light saturated photosynthetic rates (Amax) were largest in plants grown at the optimal temperature. Growth at 15/10 and 10/10 °C compared to the optima reduced accumulated biomass, leaf chlorophyll content and photosynthetic rate in both species with a greater reduction inM. floridulusthan inM. transmorrisonensis.We concluded that growth ofM. floridulusat high altitude is limited by an inability to grow at temperatures lower than 15 °C, whileM. transmorrisonensisis able to grow in chilling temperatures at higher altitudes.

Virulence ofMetarhizium anisopliaeto Embryos of the Grass ShrimpPalaemonetes pugio

Experiments were performed in which developing embryos of the grass shrimp,Palaemonetes pugio,were exposed to conidiospores of the insect pathogenic fungus,Metarhizium anisopliae.Responses were variable, with significant (P≤0.05) adverse effects observed in five of six experiments conducted. Dead embryos and larvae with visible growth ofM. anisopliaewere observed in all experiments. Growth ofM. anisopliaewas occasionally observed on embryos and larvae prior to death. Delayed hatch was also observed. In one of the initial experiments, an increase inN-acetyl-β-d-glucosaminidase, EC 3.2.1.30 (NAGase), activity accompanied by an increase in virulence toward shrimp embryos was observed. Additional experiments in which conidiospores were produced on homogenized caterpillars suggested a positive correlation between virulence ofM. anisopliaetoP. pugioembryos and activity of spore-associated NAGase. Under these laboratory conditionsM. anisopliaewas an invasive pathogen of grass shrimp embryos, and the growth substrates on which their spores develop can influence the severity of effects on these nontarget arthropods.

Inhibition of the Trehalose-P Synthase of Mycobacteria by Various Antibiotics

A number of antibiotics were tested as potential inhibitors of the purified trehalose-P synthase ofMycobacterium smegmatis.Of about 30 compounds tested, 4 (cathomycin, circulin, diumycin, and moenomycin) were active against this enzyme. Thus each of these compounds inhibited the formation of trehalose-P by the purified trehalose-P synthase when either UDP-glucose or GDP-glucose was used as the glucosyl donor. However, preincubation of the synthase with heparin, a polyanion activator of the enzyme when UDP-glucose is used as the substrate, prevented the inhibition by these various antibiotics. Fifty percent inhibition by diumycin and moenomycin occurred at a concentration of about 50 μg/ml (Kiof about 1 × 10−5M), but 50% inhibition by cathomycin and circulin required substantially higher concentrations (about 50 to 200 μg/ml). The inhibition by cathomycin, diumycin, and moenomycin was of the competitive type, whereas that by circulin was noncompetitive in nature. However, the inhibition was of a complex nature and the data suggest two different binding sites for these inhibitors. Photoaffinity labeling of the synthase with an azido-UDP-[32P]glucose probe was effectively blocked by diumycin, moenomycin, or cathomycin indicating that these inhibitors do interact at the substrate binding site. These antibiotics also inhibited the growth ofM. smegmatiswhen added to cells innoculated into trypticase soy broth. The inhibition of growth was concentration-dependent and directly proportional to the size of the bacterial innoculum. These antibiotics, however, did not inhibit protein synthesis nor did they inhibit the incorporation of mannose into lipid-linked saccharides.

Metabolic Pathways in Methanococcus jannaschii and Other Methanogenic Bacteria

Eleven strains of methanogenic bacteria were divided into two groups on the basis of the directionality (oxidative or reductive) of their citric acid pathways. These pathways were readily identified for most methanogens from the patterns of carbon atom labeling in glutamate, following growth in the presence of [2-C]acetate. All used noncyclic pathways, but members of the family Methanosarcinaceae were the only methanogens found to use the oxidative direction. Methanococcus jannaschii failed to incorporate carbon from acetate despite transmembrane equilibration comparable to other weak acids. This organism was devoid of detectable activities of the acetate-incorporating enzymes acetyl coenzyme A synthetase, acetate kinase, and phosphotransacetylase. However, incorporation of [1-C]-, [2-C]-, or [3-C]pyruvate during the growth of M. jannaschii was possible and resulted in labeling patterns indicative of a noncyclic citric acid pathway operating in the reductive direction to synthesize amino acids. Carbohydrates were labeled consistent with glucogenesis from pyruvate. Leucine, isoleucine, phenylalanine, lysine, formate, glycerol, and mevalonate were incorporated when supplied to the growth medium. Lysine was preferentially incorporated into the lipid fraction, suggesting a role as a phytanyl chain precursor.

Cephalopod prey of the grey-headed albatrossDiomedea chrysostoma

Cephalopod remains were collected, at regular intervals throughout the fledging period, from the stomach contents of chicks of the grey-headed albatrossDiomedea chrysostoma at Bird Island, South Georgia, in 1984 and 1986 and from regurgitations of adults at the nest in 1986. The 1984 sample was taken during a season characterised by abnormal local oceanographic conditions in which the breeding success was very low; in 1986 conditions were normal and breeding success was high. Cephalopod beaks (289 from adults; 5 651 from chicks) were identified, and allometric equations were used to estimate the biomass represented. Five cephalopod species belonging to five families (Gonatidae, Onychoteuthidae, Psychroteuthidae, Ommastrephidae and Cranchiidae) contributed 98% by number and 97% of the biomass fed to chicks. The most important species was the ommastrephidMartialia hyadesi, contributing 68.9 to 77.4% by number and 72.5 to 79.3% of the total biomass fed to chicks. The relative proportions of cephalopod species in the chicks' diet were similar between 1984 and 1986, but the total number and biomass was significantly less in 1984. There is evidence of growth ofM. hyadesi between January and June.

Application of growth substances and mineral nutrition affecting disease development and glyceollin production of soybean

The effects of foliar application of growth substances and mineral nutrition of the host on the development of charcoal rot disease of soybean caused byMacrophomina phaseolina was tested. Among the eight growth substances examined, gibberellic acid was most successful in reducing the disease severity, followed by 3-indoleacetic acid and 2,3,5-triiodobenzoic acid. Low concentrations of these compounds stimulated while high concentrations inhibited the mycelial growth ofM. phaseolina in vitro. Substrate supplementation with different doses of N, P, K and Ca had varying effects on disease development. Disease increased considerably by both excess and defficient N and also by deficient Ca, while excess Ca conferred partial resistance. Glyceollin contents of host roots before and after excess Ca and gibberellic acid (10 mg/L) treatments were estimated. Both compounds significantly increased glyceollin production in infected roots. However, gibberellic acid induced glyceollin synthesis even in uninoculated roots. Changes in the host reaction towards increased resistance was correlated with increased phytoalexin production.

Reversal of cerulenin inhibition ofMycobacterium avium by octanoate

Mycobacterium avium is an opportunistic pathogen that may cause either localized or, in persons with acquired immune deficiency syndrome (AIDS), disseminated disease. Under certain conditionsM. avium exhibits a requirement for fatty acid for maximum production of colony-forming units (CFU). However, cerulenin, a drug that inhibits fatty acid synthetase, inhibited the growth ofM. avium LM1 (serovar 1) with a minimal inhibitory concentration of 10 μg/ml regardless of oleic acid supplementation at 50 μg/ml. Cerulenin at 10 μg/ml also inhibited the growth of five other strains ofM. avium isolated from AIDS patients. Octanoate, oleate, and palmitate, individually or in two-way combinations, were tested for ability to reverse the effect of cerulenin. Octanoate at 50 μg/ml could reverse the bactericidal effect of cerulenin at 10 μg/ml and the bacteriostatic effect of the drug at 5 μg/ml. Because cerulenin when effectively inhibiting production of CFU also prevented cell elongation, the data suggest that octanoate, or a metabolic product, is critical to cell division ofM. avium.

Role of Amino Acids and Vitamins in Nutrition of Mesophilic Methanococcus spp

In this study we found that autotrophic methanococci similar to Methanococcus maripaludis obtained up to 57% of their cellular carbon from exogenous amino acids. About 85% of the incorporation was into protein. Primarily nonpolar and basic amino acids and glycine were incorporated; only small amounts of acidic and some polar amino acids were taken up. An additional 10% of the incorporation was into the nucleic acid fraction. Because little CO(2) was formed from the C-amino acids, little metabolism of the amino acids occurred. Therefore the growth stimulation by amino acids was probably due to the sparing of anabolic energy requirements. Of the amino acids incorporated, only alanine was also a sole nitrogen source for these methanococci. In contrast, Methanococcus vannielii and "Methanococcus aeolicus" are autotrophic methanococci which did not incorporate amino acids and did not utilize alanine as a sole nitrogen source. Although glutamine served as a sole nitrogen source for the autotrophic methanococci and Methanococcus voltae, a heterotrophic methanococcus, growth was due to chemical deamination in the medium. M. voltae requires leucine and isoleucine for growth. However, these amino acids were not significant nitrogen sources, and alanine was not a sole nitrogen source for the growth of M. voltae. The branched-chain amino acids were not extensively metabolized by M. voltae. Pantoyl lactone and pantoic acid were readily incorporated by M. voltae. The intact vitamin pantothenate was neither stimulatory to growth nor incorporated. In conclusion, although amino acids and vitamins are nutritionally important to both autotrophic and heterotrophic methanococci, generally they are not subject to extensive catabolism.

Incorporation of Exogenous Purines and Pyrimidines by Methanococcus voltae and Isolation of Analog-Resistant Mutants

Methanococcus voltae incorporated exogenous adenine, guanine, hypoxanthine, and uracil, but not thymine. Growth of M. voltae was also sensitive to purine and pyrimidine analogs. Of the 20 analogs tested, 12 were inhibitory at 1 mg/ml. The most effective inhibitors were purine analogs with endocyclic substitutions. Nucleoside analogs and analogs with exocyclic substitutions or additions were less effective. Four purine analogs, 8-aza-2,6-diaminopurine, 8-azaguanine, 8-azahypoxanthine, and 6-mercaptopurine and one pyrimidine analog, 6-azauracil, were especially toxic. The MICs were 20, 0.5, 2.0, 80, and 10 mug/ml, respectively. Spontaneous resistance mutants were isolated for these five analogs. The MICs for these mutants were 20.5, 8.2, >65, >41, and 20.5 mg/ml, respectively. These concentrations far exceeded the solubilities of the analogs and represented an increase in resistance of at least three orders of magnitude. In addition to demonstrating cross resistance to several of the analogs, four of these mutants lost the ability to incorporate exogenous bases. These appeared to be mutations in the salvage pathways for purines and pyrimidines. In contrast, the mutant resistant to 6-mercaptopurine was not defective in purine uptake. Instead, it degraded 6-mercaptopurine. In the presence or absence of high concentrations of the analogs, the growth rates of the resistant mutants were no less than one-half of the growth rate of the wild type in the absence of the analog. The high level of resistance and rapid growth are very desirable properties for the application of the mutants in genetic experiments.

Utilization of Methanol plus Hydrogen by Methanosarcina barkeri for Methanogenesis and Growth

Methanosarcina barkeri grew on methanol plus H(2). Both substrates were consumed in equimolar amounts. Growth was strictly dependent on the presence of acetate, which was required for the biosynthesis of cellular constituents. Only about 0.4% of the methane produced originated from acetate. By using deuterated methanol, it was demonstrated that methanogenesis from this compound under H(2) did not occur via oxidation of methanol to CO(2) and subsequent reduction but by direct reduction with H(2). Growth yields with methanol plus H(2) and with methanol alone were not significantly different: 2.8 g of cells per mol of methanol in mineral medium and 4.6 g of cells per mol of methanol in complex medium, respectively. Growth of M. barkeri on methanol plus H(2) depended strictly on the presence of sodium ions in the medium. In the presence of 50 mM K the K(s) for Na was 5 mM.

Uncoupling of Methanogenesis from Growth of Methanosarcina barkeri by Phosphate Limitation

Production of methane by Methanosarcina barkeri from H(2)-CO(2) was studied in fed-batch culture under phosphate-limiting conditions. A transition in the kinetics of methanogenesis from an exponentially increasing rate to a constant rate was due to depletion of phosphate from the medium. The period of exponentially increasing rate of methanogenesis was extended by increasing the initial concentration of phosphate in the medium. Addition of phosphate during the constant period changed the kinetics to an exponentially increasing rate of methanogenesis, indicating the reversibility of phosphate depletion. The relation between methanogenesis and growth of M. barkeri was investigated by measuring the incorporation of phosphorus, supplied as KH(2)PO(4), in the medium. At a low (1 muM) initial concentration of phosphate in the medium and during the constant period of methanogenesis, there was no net cell growth. At a higher (10 muM) initial concentration of phosphate, cell growth proceeded linearly with time after phosphate had been removed from the medium by uptake into cells.

Effect of 2,4-dinitrophenol and ionophores on growth and methanogenesis inMethanobacterium thermoautotrophicum

2,4-Dinitrophenol and gramicidin D completely inhibited growth and methanogenesis inMethanobacterium thermoautotrophicum. At low K+ concentrations valinomycin inhibited growth and methanogenesis relatively slightly, at high K+ concentrations (0.1m KCl) growth was inhibited completely and methanogenesis by about 50%. Monensin and nigericin inhibited growth completely; methanogenesis was inhibited like with valinomycin at high K+ concentrations. The results can be interpreted in terms of Mitchell’s chemiosmotic theory as follows. The protonmotive force inM. thermoautotrophicum is the basic source of energy for endergonic processes. Dissipation of the electrical component of protonmotive force may probably be compensated by an increased generation of the proton gradient. However, the osmotic component is essential for growth ofM. thermoautotrophicum.