Spore and crystal formation inBacillus thuringiensis var.thuringiensis during growth in cystine and cysteine

The effect of the addition of different concentratons of cystine and cysteine on sporulation and parasporal crystal formation inBacillus thuringiensis var.thuringiensis was studied. The effect was well pronounced when the cystine/cysteine additions were made after the stationary phase. Heat stable spores and crystals were formed when the culture was provided with a low concentration of cystine/cysteine (0.05 per cent w/v). At a moderate concentration of cystine or cysteine (0.15%), only heat labile spores were formed without the production of the crystal. When the cystine/cysteine concentration was high (0.25%), spore and crystal formation were completely inhibited. Partial reversal of inhibition of sporulation was brought about by sodium sulphate or Zinc sulphate and lead, copper, cadmium or cobalt acetate at 0.2 mM or at 0.2% of sodium or potassium pyruvate, citrate, cisaconitate, oxalosuccinate, ∞ -keto-glutarate, succinate, fumarate, malate, or oxalacetate. Glutamate (0.2%) overcame the inhibitory effect of cystine/cysteine completely. The structural changes observed using phase contrast microscopy were dependent upon the concentration of cystine/cysteine.     

Regulation of sulfate assimilation in Cytophaga johnsonae

We have studied the regulation of sulfate assimilation by the gliding bacterium Cytophaga johnsonae in which 20% of the total sulfur is in the sulfornate moiety of sulfonolipid. Added cystine inhibited sulfate uptake and growth with cystine as sulfur source resulted in a repression of sulfate uptake. However, low concentrations of cystine preferentially repressed the terminal reactions of sulfate assimilation responsible for cysteine synthesis while allowing the transport and activation of sulfate for sulfonolipid synthesis. The significance of this novel pattern of regulation in bacteria is discussed.     

Edeine inhibition and resistance in Neurospora

To obtain data on the biochemical effects of edeine in the fungus Neurospora crassa, in vivo protein synthesis, in vitro protein synthesis, as well as in vivo RNA and DNA synthesis of the wildtype and an edeine resistant mutant were measured.—Incorporation of ³H leucine into conidia of both strains, which served as a measure for in vivo protein synthesis, was inhibited by 200 g edeine/ml as follows: Wildtype approx. 40%, mutant approx. 6%.—Incorporation of ¹⁴C phenylalanine into polyphenylalanine in a cell free system with ribosomes from either the wildtype or the mutant, was inhibited between 74 and 95% by edeine at a ratio of 2 molecules edeine per ribosome.—Incorporation of ³H adenosine into conidia, serving as a measure for in vivo RNA synthesis, was inhibited in the wild-type (approx. 30% inhibition by 200 g edeine/ml). It was, however, not influenced in the ed ^r mutant. Similarly, in vivo DNA synthesis was decreased in the wildtype, but not in the mutant.—These results suggest that edeine acts at more than one site. The resistance of the mutant ed ^r -29 (ed ^r -2 locus) is tentatively interpreted as due to a block in edeine uptake.     

Effects of protein inhibitors and auxin on nucleic Acid metabolism in peanut cotyledons

The accumulation of labeled phosphorus into newly synthesized nucleic acids or peanut cotyledon slices incubated with chloramphenicol, puromycin, or 2,4-dichlorophenoxyacetic acid (2,4-D) was reduced. Promotion of nucleic acid synthesis was not noted by any of these chemicals. Chloramphenicol completely inhibited the synthesis of the DNA-RNA fraction at 1.25 × 10⁻³ m while soluble and ribosomal RNA was inhibited by 70% and 80%, respectively. At the same concentration messenger RNA was inhibited by only 40%. These effects suggest that chloramphenicol inhibit nucleic acid synthesis in peanut cotyledons in a differential manner. Similar results were noted for DNA at low concentrations of 2,4-D. However, at high concentrations of 2,4-D, DNA as well as RNA fractions were inhibited in a similar manner at a given concentration. Puromycin did not differentially inhibit nucleic acid synthesis except at 2 × 10⁻³ m where DNA was least inhibited.     

Role of N-acetylcysteine and cystine in glutathione synthesis in human erythrocytes

Abstract

Glutathione is an intracellular antioxidant that often becomes depleted in pathologies with high oxidative loads. We investigated the provision of cysteine for glutathione synthesis to the human erythrocyte (red blood cell; RBC). Almost all plasma cysteine exists as cystine, its oxidized form. In vitro, extracellular cystine at 1.0 mM sustained glutathione synthesis in glutathione-depleted RBCs, at a rate of 0.206 ± 0.036 μmol (L RBC)^?1min^?1 only 20% of the maximum rate obtained with cysteine or N-acetylcysteine. In plasma-free solutions, N-acetylcysteine provides cysteine by intracellular deacetylation but to achieve maximum rates of glutathione synthesis by this process in vivo, plasma N-acetylcysteine concentrations would have to exceed 1.0 mM, which is therapeutically unattainable. ¹H-NMR experiments demonstrated that redox exchange reactions between NAC and cystine produce NAC-cysteine, NAC-NAC and cysteine. Calculations using a mathematical model based on these results showed that plasma concentrations of N-acetylcysteine as low as 100 μM, that are attainable therapeutically, could potentially react with plasma cystine to produce ～50 μM cysteine, that is sufficient to produce maximal rates of glutathione synthesis. We conclude that the mechanism of action of therapeutically administered N-acetylcysteine is to reduce plasma cystine to cysteine that then enters the RBC and sustains glutathione synthesis.     

Phytotoxicity of iron in relation to its solubility conditions and the effect of ionic strength

The effect of iron on root elongation and seed germination of Lactuca sativa was investigated within the limits of the plant's sensitivity to an acidic environment and iron solubility under experimental conditions. Because ionic strength was found to have phytotoxic effects, the same pH and ionic strength conditions were kept constant over the entire iron concentration range, so as to evaluate solely the effect of iron. 0.14 mM Fe³⁺ was found to be the lowest effective concentration inhibiting root elongation. The low solubility of iron at a pH of 3 (the lowest value which could be applied for root elongation) excluded the testing of higher iron concentrations. Due to the lower sensitivity of seed germination to acidity, a pH of 2.6 could be applied in this case. The lowest effective iron concentration (the lowest applied concentration causing a significant decrease in germination as compared to the control, P < 0.05), EC50 (the concentration at which germination was 50% of that of the control specimens) and the completely effective iron concentration (the concentration that completely inhibited seed germination) were 0.6, 0.92 and 2.0 mM, respectively.     

Aspartate kinase and the synthesis of aspartate-derived amino acids in wheat

Aspartate kinase (EC 2.7.2.4.) has been purified from 7 day etiolated wheat (Triticum aestivum L. var. Maris Freeman) seedlings and from embryos imbibed for 8 h. The enzyme was 50% inhibited by 0.25 mM lysine. In this study wheat aspartate kinase was not inhibited by threonine alone or cooperatively with lysine; these results contrast with those published previously. In vivo regulation of the synthesis of aspartate-derived amino acids was examined by feeding [¹⁴C]acetate and [³⁵S]sulphate to 2–3 day germinating wheat embryos in culture in the presence of exogenous amino acids. Lysine (1 mM) inhibited lysine synthesis by 86%. Threonine (1 mM) inhibited threonine synthesis by 79%. Lysine (1 mM) plus threonine (1 mM) inhibited threonine synthesis by 97%. Methionine synthesis was relatively unaffected by these amino acids, suggesting that there are important regulatory sites other than aspartate kinase and homoserine dehydrogenase. [³⁵S]sulphate incorporation into methionine was inhibited 50% by lysine (2 mM) plus threonine (2 mM) correlating with the reported 50% inhibition of growth by these amino acids in this system. The synergistic inhibition of growth, methionine synthesis and threonine synthesis by lysine plus threonine is discussed in terms of lysine inhibition of aspartate kinase and threonine inhibition of homoserine dehydrogenase.Abbreviations AEC S-(2-aminoethyl) cysteine     

Effects of various compounds on growth of yeast cells of Histoplasma capsulatum

Summary A number of compounds were screened for their effects on growth of the yeast cells ofHistoplasma capsulatum. Included were penicillin and related compounds, sulfhydryl inhibitors, various organic sulfur compounds recently synthesized for the first time, and compounds structurally related to the required metabolites, thiamine and cystine or cysteine. Cephalothin was the only one of the penicillin related compounds which inhibited growth. This occurred only when a high concentration (8.3 × 10^–4 M) was used. Of the analogues of cystine tested, allylglycine had the greatest inhibitory effect on growth of the yeast cells in the synthetic medium, but it failed to inhibit growth in a complex medium containing peptones and plasma. Among the sulfhydryl inhibitors, the maleimides were the most effective, producing complete inhibition of growth in the peptone medium at 10µg/ml or less. At subinhibitory concentrations the cultures tended to become mycelial. The action of the maleimides was reversed by cystine over a range of concentrations. At low concentrations, some of the disulfide derivatives of thiamine stimulated growth equally as well as thiamine, but at concentrations of 100 to 150µg/ml, they completely inhibited growth. On the basis of results obtained to date, three classes of the new organic sulfur compounds being tested offer promise as sources of potentially useful chemotherapeutic agents. These classes, which differ widely in structure, are as follows: the benzyl decylaminoethyl disulfides, the acyl disulfides, and the trithiopercarbamates.This investigation was supported by Public Health Service Research Grant AI-03524 from the National Institute of Allergy and Infectious Diseases.     

Cystine catabolism in mycelia of Microsporum gypseum,a dermatophytic fungus

The fate of ³⁵S label was studied during cystine degradation by mycelia of the dermatophytic fungus Microsporum gypseum. Excess free cystine in the medium was readily taken up and its sulfur moiety excreted as inorganic sulfate and sulfite. At intervals after 3–60 min of incubation with ³⁵S cystine the products of cystine catabolism were extracted from the mycelia by boiling water and separated by thin layer chromatography and electrophoresis. A total of 10 sulfur-containing compounds were identified, and their relative radioactivity was assessed. After 3 min the mycelia contained, in addition to cystine, labeled cysteine and particularly cysteine sulfinic acid which was accompanied by a smaller amount of cysteic acid. Later on, oxidized and reduced glutathione, inorganic sulfate and taurine appeared consecutively. In all extracts, small amounts of labeled S-sulfocysteine were found, not, however, sulfite.The results suggest that the intermediates of cysteine degradation in the fungal mycelia are cysteine, cysteine sulfinate, unstable sulfinylpyruvate, sulfite and sulfate, i.e., that the catabolic pattern is similar to that of higher organisms.The formation and the role of S-sulfocysteine, cysteic acid, and of taurine is not yet completely understood, although certainly autoxidative processes are involved in the formation of the latter two compounds, and sulfitolysis in that of the former compound.     

Effect of calcium on synthesis of dipicolinic acid inPenicillium citreoviride and its feedback resistant mutant

Dipicolinic acid synthesis inPenicillium citreoviride strain 3114 was inhibited by Ca²⁺ ions, but not by Ba²⁺, Cu²⁺or Fe²⁺. Among the metals tested, only Zn²⁺ inhibited the synthesis of dipicolinic acid and promoted sporulation. None of these metals reversed the inhibition by Ca²⁺ or Zn²⁺. A mutant 27133-dpa-ca selected for resistance to feedback inhibition by dipicolinic acid: Ca²⁺ complex showed cross-resistance to inhibition by dipicolinic acid: Zn²⁺. Both 3114 and271 33-dpa-ca excreted a number of aliphatic and amino acids during secondary metabolism of dipicolinic acid. In the presence of 1000 ppm of Ca²⁺, accumulation of citric acid and α-aminoadipic acid was completely inhibited under conditions of inhibition of dipicolinic acid in parent strain 3114 but not in the mutant. Citric acid with or without Ca²⁺ did not inhibit thede novo synthesis of dipicolinic acid in the strain 3114. In fact, citric acid in the presence of Ca²⁺ improved significantly rate of dipicolinic acid synthesis. Apart from resistance to feed back inhibition by dipicolinic acid: Ca²⁺ complex, mutant differed from the parent in three other aspectsviz. (i) dipicolinic acid synthesis was not subject to catabolite repression by glucose, (ii) sporulation as well as dipicolinic acid synthesis was dependent on the presence of Ca²⁺ ions in the medium and (iii) Mg²⁺ requirement for the mutant increased three fold. Higher requirement of the Mg²⁺ could be partially relieved by Ca²⁺ during secondary metabolism. The results support the inference thatde novo synthesis of dipicolinic acid is regulated through feedback inhibition by dipicolinic acid: Ca²⁺complex.     

λ-Glutamylcysteine synthetase in higher plants: catalytic properties and subcellular localization

λ-Glutamylcysteine synthetase activity (EC 6.3.2.2) was analysed in Sephacryl S-200 eluents of extracts from cell suspension cultures ofNicotiana tabacum L. cv. Samsun by determination of λ-glutamylcysteine as its monobromobimane derivative. The enzyme has a relative molecular mass (M_r) of 60000 and exhibits maximal activity at pH 8 (50% at pH 7.0 and pH9.0) and an absolute requirement for Mg²⁺. With 0.2mM Cd²⁺ or Zn²⁺, enzyme activity was reduced by 35% and 19%, respectively. Treatment with 5 mM dithioerythritol led to a heavy loss of activity and to dissociation into subunits (M_r 34000). Buthionine sulfoximine andl-methionine-sulfoximine, known as potent inhibitors of λ-glutamylcysteine synthetase from mammalian cells, were found to be effective inhibitors of the plant enzyme too. The apparent K_m values forl-glutamate,l-cysteine, and α-aminobutyrate were, respectively, 10.4mM, 0.19 mM, and 6.36 mM. The enzyme was completely inhibited by glutathione (K_i=0.42 mM). The data indicate that the rate of glutathione synthesis in vivo may be influenced substantially by the concentration of cysteine and glutamate and may be further regulated by feedback inhibition of λ-glutamylcysteine synthetase by glutathione itself. λ-Glutamylcysteine synthetase is, like glutathione synthetase, localized in chloroplasts as well as in the cytoplasm. Chloroplasts fromPisum sativum L. isolated on a Percoll gradient contained about 72% of the λ-glutamylcysteine synthetase activity in leaf cells and 48% of the total glutathione synthetase activity. In chloroplasts ofSpinacia oleracea L. about 61% of the total λ-glutamylcysteine synthetase activity of the cells were found and 58% of the total glutathione synthetase activity. These results indicate that glutathione synthesis can take place in at least two compartments of the plant cell. Dedicated to Professor A. Prison on the occasion of his 80th birthday     

Relationships between nitrogenase,glutamine synthetase,glutamine, and energy charge in Azotobacter vinelandii

When continuous cultures of Azotobacter vinelandii were supplied with ammonium or nitrate in amounts, which just repressed nitrogenase synthesis completely, both the intracellular glutamine level and the degree of adenylylation of the glutamine synthetase (GS) increased only slightly (from 0.45–0.50 mM and from 2 to 3 respectively), while the total GS level remained unaffected. Higher amounts of ammonium additionally inhibited the nitrogenase activity, caused a strong rise in the intracellular glutamine concentration and adenylylation of the GS, but caused no change in the ATP/ADP ratio. These results are considered as evidence that in A. vinelandii the regulation of nitrogenase synthesis is not linked to the adenylylation state of the GS and to the intracellular glutamine level, and that the inhibition of the nitrogenase activity as a consequence of a high extracellular ammonium level is not mediated via a change in the energy charge.Abbreviations GS glutamine synthetase - GS-S(Mg) Mg²⁺ dependent synthetic activity of GS - GS-T(Mn) Mn²⁺ dependent transferase activity of GS     

Isolation of antifouling compounds from the marine bacterium, <Emphasis Type="Italic">Shewanella oneidensis</Emphasis> SCH0402

Two compounds, 2-hydroxymyristic acid (HMA) and cis-9-oleic acid (COA), were isolated from a chloroform extract of the marine bacterium, Shewanella oneidensis SCH0402. In a spectrophotometer-based chemotaxis assay, HMA completely eliminated the optical density (OD) of Alteromonas marina SCH0401 and Bacillus atrophaeus SCH0408, motile, fouling bacteria, at 100 and 1000 μg ml⁻¹, respectively. COA similarly decreased the OD of A. marina and B. atrophaeus by 100% at 1000 μg ml⁻¹. The commercially available, highly toxic anti-fouling compound, tributyltin oxide (TBTO) never reduced the OD of the target bacteria by 100% even at higher concentration. Instead, all the test bacterial cells were killed at higher than 1000 μg ml⁻¹ of concentration. Both HMA and COA inhibited germination of Ulva pertusa spores completely at 10 and 100 μg ml⁻¹, respectively, while TBTO inhibited germination at 0.01 μg ml⁻¹. However, in field assays, both HMA and COA showed anti-fouling activities as potent as TBTO against a wide range of fouling organisms, including micro- and macro-algae, barnacles, and mussels. The average fouling coverage on the surface of the control panel was 93 ± 6% after 1.5 years but no fouling was observed on the surface of the test panel onto which each compound was applied separately. Thus, bacterial repellent compounds can be used as substitutes for potent toxic anti-fouling compounds, resulting in higher standards of environmental safety without loss of anti-fouling performance.     

Acetate synthesis from 2 CO2 in acetogenic bacteria: is carbon monoxide an intermediate?

Cultures of Acetobacterium woodii and Clostridium thermoaceticum growing on fructose or glucose, respectively, were found to produce small, but significant amounts of carbon monoxide. In the gas phase of the cultures up to 53 ppm CO were determined. The carbon monoxide production was completely inhibited by 1 mM cyanide. Cultures and cell suspensions of both acetogens incorporated ¹⁴CO specifically into the carboxyl group of acetate. This CO fixation into C₁ of acetate was unaffected by cyanide (1 mM). The findings are taken to indicate that CO (in a bound form) is the physiological precursor of the C₁ of acetate in acetate synthesis from CO₂. The cyanide inhibition experiments support the hypothesis that the cyanide-sensitive carbon monoxide dehydrogenase may serve to reduce CO₂ to CO rather than to incorporate the carbonyl into C₁ of acetate.     

Selective control of cyanobacteria by surfactin-containing culture broth of Bacillus subtilis C1

Of several types of chemical surfactants and biosurfactants, only the culture broth of Bacillus subtilis C1 containing surfactin at 10 mg l^–1 completely inhibited the growth of Microcystis aeruginosa, a bloom-forming cyanobacterium in highly eutrophic lakes. The broth with 10 mg surfactin l^–1 also removed 85% of the maximally grown M. aeruginosa (chlorophyll-a concentration, 1000 g l^–1) within 2 d, and the removal efficiency was enhanced by Ca²⁺ over 1 mM. The growth of Anabaena affinis, another bloom-forming cyanobacterium, was also inhibited about 70% with surfactin at 10 mg l^–1 broth. However, the effect of the broth was delayed over 3 d in the green algae, Chlorella vulgaris and Scenedesmus sp., and was negligible in a diatom, Navicula sp., indicating the potential for the selective control of cyanobacterial blooms.     

Contrasting responses of sulphate and phosphate transport in barley (Hordeum vulgare L.) roots to protein-modifying reagents and inhibition of protein synthesis

The uptake of sulphate into roots of barley seedlings is highly sensitive to phenylglyoxal (PhG), an arginine-binding reagent. Uptake was inhibited by >80% by a 1-h pre-treatment of roots with 0.45 mol · m^–3 PhG. Inhibition was maximal in pre-treatment solutions buffered between pH 4.5 and 6.5. Phosphate uptake, measured simultaneously by double-labelling uptake solutions with ³²P and ³⁵S, was less susceptible to inhibition by PhG, particularly at pH <6.5, and was completely insensitive to the less permeant reagent p-hydroxyphenylglyoxal (OH-PhG) administered at 1 mol · m^–3 at pH at 5.0 or 8.2; sulphate uptake was inhibited in -S plants by 90% by OH-PhG-treatment. Root respiration in young root segments was unaffected by OH-PhG pre-treatment for 1 h and inhibited by only 17% after 90 min pre-treatment. The uptake of both ions was inhibited by the dithiol-specific reagent, phenylarsine oxide even after short exposures (0.5–5.0 min). Sulphate uptake was more severely inhibited than that of phosphate, but in both cases inhibition could be substantially reversed by 5 min washing of treated roots by 5 mol · m^–3 dithioerythritol. After longer pre-treatment (50 min) with phenylarsine oxide, inhibition of the ion fluxes was not relieved by washing with dithioerythritol. Inhibition of sulphate influx by PhG was completely reversed by washing the roots for 24 h with culture solution lacking the inhibitor. The reversal was dependent on protein synthesis; less than 20% recovery was seen in the presence of 50 mmol · m^–3 cycloheximide. Sulphate uptake declined rapidly when -S roots were treated with cycloheximide. In the same roots the phosphate influx was little affected, small significant inhibitions being seen only after 4 h of treatment. Respiration was depressed by only 20% in apical and by 31% in basal root segments by cycloheximide pre-treatment for 2 h. Similar rates of collapse of the sulphate uptake and insensitivity of phosphate uptake were seen when protein synthesis was inhibited by azetidine carboxylic acid, p-fluorophenylalanine and puromycin. Considering the effects of all of the protein-synthesis inhibitors together leads to the conclusion that the sulphate transporter itself, or some essential sub-component of the uptake system, turns over rapidly with a half-time of about 2.5 h. The turnover of the phosphate transporter is evidently much slower. The results are discussed in relation to strategies for identifying the transport proteins and to the regulation of transporter activity during nutrient stress.Abbreviations CAP chloramphenicol - CHM cycloheximide - DTE dithioerythritol - OH-PhG p-hydroxyphenylglyoxal - PhAsO phenylarsine - PhG phenylglyoxal Paper dedicated to the memory of the late Ken Treharne who did much to encourage this collaboration.D.T.C. gratefully acknowledges a fellowship provided by Le Ministére des Etrangers during his stay in Montpellier.     

Individual and combined effects of physicochemical parameters on ellagitannin acyl hydrolase and ellagic acid production from ellagitannin by <Emphasis Type="Italic">Aspergillus oryzae</Emphasis>

The individual and interactive effects of physicochemical parameters on ellagitannin acyl hydrolase activity and ellagic acid production by Aspergillus oryzae using ellagitannins from acorn fringe of oak as substrate were studied. Ellagitannins concentration, incubation time were identified as important physicochemical parameters influencing the enzyme synthesis and the production accumulation, and the substrate concentration with initial pH was determined to has an interactive effect on the enzyme synthesis, while ellagitannins concentration and initial pH with incubation time were found to have interactions on the production accumulation. Furthermore, the parameters were optimized by quadratic programming. Under optimum condition, the fermentation run lasted 84 h with 4 g L⁻¹ ellagitannins concentration, yielding 17.7% ellagic acid. However, the maximum enzyme activity was obtained in 96 h with 5 g L⁻¹ substrate concentration. The research demonstrated a possible way to develop an efficient approach for recovery of higher added-value product (ellagic acid) from forestry byproduct (acorn fringe of oak).     

Shikonin isovalerate: An inhibitor of photosystem II in Chlorogloeopsis fritschi

Shikonin isovalerate, extracted from the roots of the desert plant Arnebia decumbens, was tested for its effect on photosynthetic electron transport system of Chlorogloeopsis fritschii. The ferricyanide-Hill reaction with water and DPC as electron donors was inhibited completely with 10^-5 M shikonin isovalerate. The photoreduction of DCPIP through photosystem II was only slightly inhibited. Photosystem I from durohydroquinone to methyl viologen was not affected using 10^-6 M shikonin isovalerate. The same concentration caused 49% inhibition of cyclic photophosphorylation. These results suggest that shikonin isovalerate inhibits photosynthetic electron flow at the plastoquinone pool.Abbreviations DCMU 3-(3,4-dichlorophenyl)-N,N-dimethyl urea - DBMIB 2,5-dibromo-3-methyl-6-isopropyl-P-benzoquinone - DCPIP 2–6-dichlorophenolindophenol - DPC Diphenylcarbazide - Tricine N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine     

γ -Ray-Induced DNA Damage and Repair in Methanosarcina barkeri

The capacity of the mesophilic archaeon, Methanosarcina barkeri (DSM 804) for DNA double strand break repair following⁶⁰Co- γ irradiation was investigated. The genome (1.9 Mb) of Methanosarcina barkeri was largely fragmented and was found to be repaired on incubation in medium under anaerobic conditions at 37°C for 4 h. To get an insight into its repair process a set of inhibitors were used. The methanogenesis inhibitor, bromoethanesulfonate showed partial inhibition of repair in Methanosarcina barkeri but not in Escherichia coli or human peripheral blood mononuclear cells. The Methanosarcina barkeri cells could also partially repair the DNA damage in a non-nutrient medium. Arabinosine-CTP, a nucleoside analogue and a polymerase inhibitor, completely inhibited repair in this archaeon. Arabinosine-CTP did not affect DSB (double-strand break) repair in human peripheral blood mononuclear cells but completely inhibited repair in Escherichia coli (a bacterium). The involvement of polymerase indicates recombination to be the underlying mechanism in DSB repair of Methanosarcina barkeri. 3-Aminobenzamide, a poly (ADP-ribose) polymerase inhibitor, completely inhibited repair in this archaeon as well as in eukarya but not in Escherichia coli showing the involvement of poly (ADP-ribose) polymerase in the DSB repair of Methanosarcina barkeri.     

Evaluation of Bacillus thuringiensis bioinsecticidal protein effects on soil microorganisms

The effect of B. thuringiensis and its crystal protein on plant growth and on functional groups of microorganisms is not well understood. Soybean (Glycine max) var. Br 322 was grown in non-sterile soil infested with three B. thuringiensis (Bt) inocula: insecticidal crystal protein producer (Cry+), a mutant non-producer (Cry–), or insecticidal crystal protein (ICP), at a rate of 10⁷ cells g^–1 dry soil or 1.25 mg of protein g^–1 dry soil. Non-inoculated plants were maintained as control. Measurements were carried out on soil samples before sowing (time zero) and after sowing and inoculation (5, 15, 25, 35 and 45 d) on samples of rhizosphere soil. The effect of spore and crystal protein produced by B. thuringiensis on the populations of functional groups of microorganisms (bacteria including actinomycetes and fungi) involved in the biogeochemical cycling of carbon (cellulolytic, amylolytic and proteolytic), phosphorus (arbuscular mycorrhizal fungi), and nitrogen (number of nodules and proteolytic) were evaluated. Population sizes of culturable heterotrophic bacteria and saprophytic fungi were also evaluated. No difference was found in heterotrophic bacterial populations inoculated with B. thuringiensis. Difference was observed in functional groups of C-cycling microorganisms. Nodule formation and plant growth were increased by Cry+ strain and ICP when compared with uninoculated plants. Crystal protein did not show any effect on arbuscular mycorrhiza (AM) colonization. However, a deleterious effect was observed with Cry+ and Cry– strains that inhibited colonization of AM fungi when compared with uninoculated plants.