Rhizobacterium-derived diacetyl modulates plant immunity in a phosphate-dependent manner.

Plants establish mutualistic associations with beneficial microbes while deploying the immune system to defend against pathogenic ones. Little is known about the interplay between mutualism and immunity and the mediator molecules enabling such crosstalk. Here, we show that plants respond differentially to a volatile bacterial compound through integral modulation of the immune system and the phosphate-starvation response (PSR) system, resulting in either mutualism or immunity. We found that exposure of Arabidopsis thaliana to a known plant growth-promoting rhizobacterium can unexpectedly have either beneficial or deleterious effects to plants. The beneficial-to-deleterious transition is dependent on availability of phosphate to the plants and is mediated by diacetyl, a bacterial volatile compound. Under phosphate-sufficient conditions, diacetyl partially suppresses plant production of reactive oxygen species (ROS) and enhances symbiont colonization without compromising disease resistance. Under phosphate-deficient conditions, diacetyl enhances phytohormone-mediated immunity and consequently causes plant hyper-sensitivity to phosphate deficiency. Therefore, diacetyl affects the type of relation between plant hosts and certain rhizobacteria in a way that depends on the plant's phosphate-starvation response system and phytohormone-mediated immunity.

Bacterial diacetyl suppresses abiotic stress-induced senescence in Arabidopsis.

Premature plant senescence induced by abiotic stresses is a major cause of agricultural losses worldwide. Tools for suppressing stress-induced plant senescence are limited. Here, we report that diacetyl, a natural compound emitted by the plant-beneficial bacterium Bacillus amyloliquefaciens, suppresses abscisic acid -mediated foliar senescence in Arabidopsis thaliana under various abiotic stress conditions. Our results establish diacetyl as an effective protector against stress-induced plant senescence and reveal a molecular mechanism for bacteria-enhanced plant stress resistance.

Effects of extended pharmacological disruption of zebrafish embryonic heart biomechanical environment on cardiac function, morphology, and gene expression.

BACKGROUND: Biomechanical stimuli are known to be important to cardiac development, but the mechanisms are not fully understood. Here, we pharmacologically disrupted the biomechanical environment of wild-type zebrafish embryonic hearts for an extended duration and investigated the consequent effects on cardiac function, morphological development, and gene expression. RESULTS: Myocardial contractility was significantly diminished or abolished in zebrafish embryonic hearts treated for 72 hours from 2 dpf with 2,3-butanedione monoxime (BDM). Image-based flow simulations showed that flow wall shear stresses were abolished or significantly reduced with high oscillatory shear indices. At 5 dpf, after removal of BDM, treated embryonic hearts were maldeveloped, having disrupted cardiac looping, smaller ventricles, and poor cardiac function (lower ejected flow, bulboventricular regurgitation, lower contractility, and slower heart rate). RNA sequencing of cardiomyocytes of treated hearts revealed 922 significantly up-regulated genes and 1,698 significantly down-regulated genes. RNA analysis and subsequent qPCR and histology validation suggested that biomechanical disruption led to an up-regulation of inflammatory and apoptotic genes and down-regulation of ECM remodeling and ECM-receptor interaction genes. Biomechanics disruption also prevented the formation of ventricular trabeculation along with notch1 and erbb4a down-regulation. CONCLUSIONS: Extended disruption of biomechanical stimuli caused maldevelopment, and potential genes responsible for this are identified.

NPY/NPF-Related Neuropeptide FLP-34 Signals from Serotonergic Neurons to Modulate Aversive Olfactory Learning in Caenorhabditis elegans.

Aversive learning is fundamental for animals to increase chances of survival. In addition to classical neurotransmitters, neuropeptides have emerged to modulate such complex behaviors. Among them, neuropeptide Y (NPY) is well known to promote aversive memory acquisition in mammals. Here we identify an NPY/neuropeptide F (NPF)-related neuropeptide system in Caenorhabditis elegans and show that this FLP-34/NPR-11 system is required for learning negative associations, a process that is reminiscent of NPY signaling in mammals. The Caenorhabditis elegans NPY/NPF ortholog FLP-34 displays conserved structural hallmarks of bilaterian-wide NPY/NPF neuropeptides. We show that it is required for aversive olfactory learning after pairing diacetyl with the absence of food, but not for appetitive olfactory learning in response to butanone. To mediate diacetyl learning and thus integrate the aversive food context with the diacetyl odor, FLP-34 is released from serotonergic neurons and signals through its evolutionarily conserved NPY/NPF GPCR, NPR-11, in downstream AIA interneurons. NPR-11 activation in the AIA integration center results in avoidance of a previously attractive stimulus. This study opens perspectives for a deeper understanding of stress conditions in which aversive learning results in excessive avoidance.SIGNIFICANCE STATEMENT Aversive learning evolved early in evolution to promote avoidance of dangerous and stressful situations. In addition to classical neurotransmitters, neuropeptides are emerging as modulators of complex behaviors, including learning and memory. Here, we identified the evolutionary ortholog of neuropeptide Y/neuropeptide F in the nematode Caenorhabditis elegans, and we discovered that it is required for olfactory aversive learning. In addition, we elucidated the neural circuit underlying this avoidance behavior, and we discovered a novel coordinated action of Caenorhabditis elegans neuropeptide Y/neuropeptide F and serotonin that could aid in our understanding of the molecular mechanisms underlying stress disorders in which excessive avoidance results in maladaptive behaviors.

The Amyloid Aggregation Accelerator Diacetyl Prevents Cognitive Decline in Alzheimer's Mouse Models.

Diacetyl (DA), a food flavorant, is linked with occupational lung disease. Our in vitro experiments described the formation of a covalent adduct by DA with Arg5 of the Aß1-42 peptide, which resulted in only a transient increase in neurotoxicity in SH-SY5Y cells. However, in vivo implications of these effects on Alzheimer's disease (AD) pathogenesis and the underlying mechanisms remain poorly understood. In the APP/PS1 transgenic AD mouse model, DA treatment did not exacerbate learning and memory deficits in the Morris water maze test. Moreover, DA increased the Aß1-42 plaque burden and decreased neuronal inflammation in the transgenic AD mice. Additionally, cognitive impairment induced by intracerebroventricular Aß1-42 was restored by the DA treatment, as assessed by the T-maze test. A corresponding mitigation of neuronal inflammation was also observed in the hippocampus of these nontransgenic mice due to the acceleration of Aß1-42 aggregation by DA into nontoxic plaques. The data from SDS-PAGE, dot-blot, and TEM in vitro experiments corroborated the acceleration of the Aß1-42 aggregation observed in vivo in AD animal models and characterized the DA-induced formation of Aß1-42 fibrils. Such Aß1-42-DA fibrils were unstable in the presence of detergent and amenable to detection by the thioflavin T reagent, thus underscoring the distinct assembly of these fibrils compared to that of the fibrils of the native Aß1-42. Taken together, the results of this study present for the first time the in vivo implications of the DA-induced acceleration of Aß1-42 and may provide a strategy for the rational design of Aß1-42 aggregation accelerators as AD therapeutics that promote oligomer-free Aß1-42 fibril formation.

The inhibitory effect of volatile organic compounds produced by Bacillus subtilis CL2 on pathogenic fungi of wolfberry.

Bacillus subtilis strain CL2 is antagonistic to wolfberry postharvest pathogenic fungi. In this study, we isolated and screened this strain for in vitro experiments. The result of the two-sealed-base-plates method revealed that volatile organic compounds (VOCs) emitted from the strain CL2 inhibited the hyphal growth of four pathogenic fungi Mucor circinelloides LB1, Fusarium arcuatisporum LB5, Alternaria iridiaustralis LB7, and Colletotrichum fioriniae LB8. After exposure to VOCs for 5 days, the hyphal growth of the pathogen C. fioriniae LB8 was inhibited by 73%. Scanning electron microscopy revealed that the VOCs produced by B. subtilis CL2 caused the mycelium morphology of the pathogenic fungi to deform, twist, fold, and shrink. In the in vivo experiments, we noticed that VOCs could significantly reduce the weight loss rate of wolfberry fruits caused by the pathogenic fungus M. circinelloides LB1 and that the decay incidence rate were caused by the pathogenic fungi F. arcuatisporum LB5, A. iridiaustralis LB7, and C. fioriniae LB8. On the basis of the headspace-gas chromatography-ion mobility spectrometry analysis, seven VOCs produced by strain CL2 were identified. Among them, 2,3-butanedione and 3-methylbutyric acid are the main antifungal active substances. This study investigated the antifungal properties of VOCs produced by the strain CL2 on postharvest pathogenic fungi isolated from wolfberry fruits both in vivo and in vitro, thereby providing the theoretical basis for its future applications.

Inhibition of Mitochondrial Complex II by the Anticancer Agent Lonidamine.

The antitumor agent lonidamine (LND; 1-(2,4-dichlorobenzyl)-1H-indazole-3-carboxylic acid) is known to interfere with energy-yielding processes in cancer cells. However, the effect of LND on central energy metabolism has never been fully characterized. In this study, we report that a significant amount of succinate is accumulated in LND-treated cells. LND inhibits the formation of fumarate and malate and suppresses succinate-induced respiration of isolated mitochondria. Utilizing biochemical assays, we determined that LND inhibits the succinate-ubiquinone reductase activity of respiratory complex II without fully blocking succinate dehydrogenase activity. LND also induces cellular reactive oxygen species through complex II, which reduced the viability of the DB-1 melanoma cell line. The ability of LND to promote cell death was potentiated by its suppression of the pentose phosphate pathway, which resulted in inhibition of NADPH and glutathione generation. Using stable isotope tracers in combination with isotopologue analysis, we showed that LND increased glutaminolysis but decreased reductive carboxylation of glutamine-derived α-ketoglutarate. Our findings on the previously uncharacterized effects of LND may provide potential combinational therapeutic approaches for targeting cancer metabolism.

The Broadly Tuned Odorant Receptor OR1A1 is Highly Selective for 3-Methyl-2,4-nonanedione, a Key Food Odorant in Aged Wines, Tea, and Other Foods.

Key food odorants are the most relevant determinants by which we detect, recognize, and hedonically evaluate the aroma of foods and beverages. Odorants are detected by our chemical sense of olfaction, comprising a set of approximately 400 different odorant receptor types. However, the specific receptor activity patterns representing the aroma percepts of foods or beverages, as well as the key food odorant agonist profiles of single-odorant receptors, are largely unknown. We aimed to establish comprehensive key food odorant agonist profiles of 2 unrelated, broadly tuned receptors, OR1A1 and OR2W1, that had been associated thus far with mostly non-key food odorants and shared some of these agonists. By screening both receptors against 190 key food odorants in a cell-based luminescence assay, we identified 14 and 18 new key food odorant agonists for OR1A1 and OR2W1, respectively, with 3-methyl-2,4-nonanedione emerging as the most potent agonist for OR1A1 by 3 orders of magnitude, with a submicromolar half maximal effective concentration. 3-Methyl-2,4-nonanedione has been associated with a prune note in oxidized wine and is an aroma determinant in tea and apricots. Further screening against the entire set of 391 human odorant receptors revealed that 30 or 300 µmol/L 3-methyl-2,4-nonanedione activated only 1 receptor, OR1A1, suggesting a unique role of OR1A1 for the most sensitive detection of this key food odorant in wine, tea, and other food matrices.

X-ray diffraction analysis of the effects of myosin regulatory light chain phosphorylation and butanedione monoxime on skinned skeletal muscle fibers.

The phosphorylation of the myosin regulatory light chain (RLC) is an important modulator of skeletal muscle performance and plays a key role in posttetanic potentiation and staircase potentiation of twitch contractions. The structural basis for these phenomena within the filament lattice has not been thoroughly investigated. Using a synchrotron radiation source at SPring8, we obtained X-ray diffraction patterns from skinned rabbit psoas muscle fibers before and after phosphorylation of myosin RLC in the presence of myosin light chain kinase, calmodulin, and calcium at a concentration below the threshold for tension development ([Ca(2+)] = 10(-6.8)M). After phosphorylation, the first myosin layer line slightly decreased in intensity at ∼0.05 nm(-1)along the equatorial axis, indicating a partial loss of the helical order of myosin heads along the thick filament. Concomitantly, the (1,1/1,0) intensity ratio of the equatorial reflections increased. These results provide a firm structural basis for the hypothesis that phosphorylation of myosin RLC caused the myosin heads to move away from the thick filaments towards the thin filaments, thereby enhancing the probability of interaction with actin. In contrast, 2,3-butanedione monoxime (BDM), known to inhibit contraction by impeding phosphate release from myosin, had exactly the opposite effects on meridional and equatorial reflections to those of phosphorylation. We hypothesize that these antagonistic effects are due to the acceleration of phosphate release from myosin by phosphorylation and its inhibition by BDM, the consequent shifts in crossbridge equilibria leading to opposite changes in abundance of the myosin-ADP-inorganic phosphate complex state associated with helical order of thick filaments.

Rapid severing and motility of chloroplast-actin filaments are required for the chloroplast avoidance response in Arabidopsis.

Phototropins (phot1 and phot2 in Arabidopsis thaliana) relay blue light intensity information to the chloroplasts, which move toward weak light (the accumulation response) and away from strong light (the avoidance response). Chloroplast-actin (cp-actin) filaments are vital for mediating these chloroplast photorelocation movements. In this report, we examine in detail the cp-actin filament dynamics by which the chloroplast avoidance response is regulated. Although stochastic dynamics of cortical actin fragments are observed on the chloroplasts, the basic mechanisms underlying the disappearance (including severing and turnover) of the cp-actin filaments are regulated differently from those of cortical actin filaments. phot2 plays a pivotal role in the strong blue light-induced severing and random motility of cp-actin filaments, processes that are therefore essential for asymmetric cp-actin formation for the avoidance response. In addition, phot2 functions in the bundling of cp-actin filaments that is induced by dark incubation. By contrast, the function of phot1 is dispensable for these responses. Our findings suggest that phot2 is the primary photoreceptor involved in the rapid reorganization of cp-actin filaments that allows chloroplasts to change direction rapidly and control the velocity of the avoidance movement according to the light's intensity and position.

Chloroplast and oxygen evolution changes in Symbiodinium sp. as a response to latrunculin and butanedione monoxime treatments under various light conditions.

The actin cytoskeleton is a dynamic structure that provides an interactive platform for organelles and cellular components. It also serves as track for membranes and vesicles that move via myosin. The actin cytoskeleton of Symbiodinium is a well-organized reticular structure suggestive of multiple membrane interactions, very likely including those of the chloroplast. The Symbiodinium chloroplast membrane network is, in turn, a highly organized structure, suggestive of being under the control of an organizing network. We visualized the chloroplast membranes of cultured Symbiodinium sp. under various light conditions and observed changes dependent on illumination intensity. Since we suspected interaction between these two organelles, and we knew that the Symbiodinium actin cytoskeleton collapses upon treatment with either latrunculin B, an actin microfilament-disrupting agent, or butanedione monoxime, a myosin function inhibitor, we tested the Symbiodinium sp. oxygen evolution in their presence. Upon latrunculin B addition, the oxygen production decreased compared to non-treated cells; however, this was not observed after a 24 h latrunculin treatment. On the contrary, butanedione monoxime treatment caused a non-recoverable dysfunction of the chloroplast causing a severe loss in oxygen production even after long-term exposure. Using electron microscopy, we observed an alteration of the Symbiodinium sp. chloroplast distribution after latrunculin B treatment, with respect to untreated cells. Furthermore, a thorough disorganization of the chloroplast grana was observed after butanedione monoxime treatment. These data suggest that an actomyosin system would be important for chloroplast organization and distribution, and critical for normal photosynthetic function of Symbiodinium sp.

Modification of CO2 avoidance behaviour in Drosophila by inhibitory odorants.

The fruitfly Drosophila melanogaster exhibits a robust and innate olfactory-based avoidance behaviour to CO(2), a component of odour emitted from stressed flies. Specialized neurons in the antenna and a dedicated neuronal circuit in the higher olfactory system mediate CO(2) detection and avoidance. However, fruitflies need to overcome this avoidance response in some environments that contain CO(2) such as ripening fruits and fermenting yeast, which are essential food sources. Very little is known about the molecular and neuronal basis of this unique, context-dependent modification of innate olfactory avoidance behaviour. Here we identify a new class of odorants present in food that directly inhibit CO(2)-sensitive neurons in the antenna. Using an in vivo expression system we establish that the odorants act on the Gr21a/Gr63a CO(2) receptor. The presence of these odorants significantly and specifically reduces CO(2)-mediated avoidance behaviour, as well as avoidance mediated by 'Drosophila stress odour'. We propose a model in which behavioural avoidance to CO(2) is directly influenced by inhibitory interactions of the novel odours with CO(2) receptors. Furthermore, we observe differences in the temporal dynamics of inhibition: the effect of one of these odorants lasts several minutes beyond the initial exposure. Notably, animals that have been briefly pre-exposed to this odorant do not respond to the CO(2) avoidance cue even after the odorant is no longer present. We also show that related odorants are effective inhibitors of the CO(2) response in Culex mosquitoes that transmit West Nile fever and filariasis. Our findings have broader implications in highlighting the important role of inhibitory odorants in olfactory coding, and in their potential to disrupt CO(2)-mediated host-seeking behaviour in disease-carrying insects like mosquitoes.

Short communication: Combined antimicrobial activity of reuterin and diacetyl against foodborne pathogens.

Reuterin (ß-hydroxypropionialdehyde) is a broad-spectrum antimicrobial substance produced by some strains of Lactobacillus reuteri during anaerobic fermentation of glycerol. Some of these strains are able to survive and produce reuterin in cheese and yogurt when added as adjuncts to the starter. Similarly, in fermented dairy foods, other inhibitory compounds such as lactic acid and diacetyl are produced during fermentation. In this work, we studied the combined effect of reuterin and diacetyl under different pH conditions against Escherichia coli O157:H7, Salmonella Enteritidis, and Listeria monocytogenes. Results from agar spot assays showed that the antimicrobial activity of reuterin-producing strains against the gram-negative bacteria tested was enhanced as the concentration of diacetyl increased to 50 mg/kg, and was higher under acidic conditions (pH 5.0) for the 3 pathogenic strains. The combination of reuterin and diacetyl had an additive effect against L. monocytogenes only at diacetyl concentrations of 50 mg/kg and pH 5.0. In addition, growth kinetics studies showed that the combination of 1 activity unit (AU)/mL of reuterin with 100mg/kg diacetyl increased the lag time of the 3 pathogens. In milk, synergistic antimicrobial activity was observed with the combination of 1 AU/mL reuterin and 50 or 100 mg/kg of diacetyl on the gram-negative strains tested, and with 1 AU/mL reuterin and 100 mg/kg of diacetyl on L. monocytogenes. The greatest inhibition of the 3 pathogens was achieved in acidified milk at pH 5.0 with reuterin (1 AU/mL) and diacetyl (100 mg/kg). Based on these results, the combination of reuterin and diacetyl in acidified dairy products could be a promising strategy to control food pathogens in these products.

Increased passive stiffness of cardiomyocytes in the transverse direction and residual actin and myosin cross-bridge formation in hypertrophied rat hearts induced by chronic ß-adrenergic stimulation.

BACKGROUND: Left ventricular (LV) hypertrophy is often present in patients with diastolic heart failure. However, stiffness of hypertrophied cardiomyocytes in the transverse direction has not been fully elucidated. The aim of this study was to assess passive cardiomyocyte stiffness of hypertrophied hearts in the transverse direction and the influence of actin-myosin cross-bridge formation on the stiffness. METHODS AND RESULTS: Wistar rats received a vehicle (control) or isoproterenol (ISO) subcutaneously. After 7 days, compared with the controls, ISO administration had significantly increased heart weight and LV wall thickness and had decreased peak early annular relaxation velocity (e') assessed by echocardiography. Elastic modulus of living cardiomyocytes in the transverse direction assessed by an atomic force microscope was significantly higher in the ISO group than in controls. We added butanedione monoxime (BDM), an inhibitor of actin-myosin interaction, and blebbistatin, a specific myosin II inhibitor, to the medium. BDM and blebbistatin significantly reduced the elastic modulus of cardiomyocytes in the ISO group. X-ray diffraction analysis showed that the reflection intensity ratio (I((1,0))/I((1,1))) at diastole was not different before and after treatment with BDM, which induces complete relaxation, in control hearts, but that I((1,0))/I((1,1)) was significantly increased after BDM treatment in the ISO group, indicating residual cross-bridge formation in hypertrophied hearts. CONCLUSIONS: Passive cardiomyocyte stiffness in the transverse direction is increased in hearts with ISO-induced hypertrophy and this is caused by residual actin-myosin cross-bridge formation.

Bioactives from probiotics for dermal health: functions and benefits.

Probiotics have been extensively reviewed for decades, emphasizing on improving general gut health. Recently, more studies showed that probiotics may exert other health-promoting effects beyond gut well-being, attributed to the rise of the gut-brain axis correlations. Some of these new benefits include skin health such as improving atopic eczema, atopic dermatitis, healing of burn and scars, skin-rejuvenating properties and improving skin innate immunity. Increasing evidence has also showed that bacterial compounds such as cell wall fragments, their metabolites and dead bacteria can elicit certain immune responses on the skin and improve skin barrier functions. This review aimed to underline the mechanisms or the exact compounds underlying the benefits of bacterial extract on the skin based on evidences from in vivo and in vitro studies. This review could be of help in screening of probiotic strains with potential dermal enhancing properties for topical applications.

The role of dynamic instability and wavelength in arrhythmia maintenance as revealed by panoramic imaging with blebbistatin vs. 2,3-butanedione monoxime.

Unlike other excitation-contraction uncouplers, blebbistatin has few electrophysiological side effects and has gained increasing acceptance as an excitation-contraction uncoupler in optical mapping experiments. However, the possible role of blebbistatin in ventricular arrhythmia has hitherto been unknown. Furthermore, experiments with blebbistatin and 2,3-butanedione monoxime (BDM) offer an opportunity to assess the contribution of dynamic instability and wavelength of impulse propagation to the induction and maintenance of ventricular arrhythmia. Recordings of monophasic action potentials were used to assess effects of blebbistatin in Langendorff-perfused rabbit hearts (n = 5). Additionally, panoramic optical mapping experiments were conducted in rabbit hearts (n = 7) that were sequentially perfused with BDM, then washed out, and subsequently perfused with blebbistatin. The susceptibility to arrhythmia was investigated using a shock-on-T protocol. We found that 1) application of blebbistatin did not change action potential duration (APD) restitution; 2) in contrast to blebbistatin, BDM flattened APD restitution curve and reduced the wavelength; and 3) incidence of sustained arrhythmia was much lower under blebbistatin than under BDM (2/123 vs. 23/99). While arrhythmias under BDM were able to stabilize, the arrhythmias under blebbistatin were unstable and terminated spontaneously. In conclusion, the lower susceptibility to arrhythmia under blebbistatin than under BDM indicates that blebbistatin has less effects on arrhythmia dynamics. A steep restitution slope under blebbistatin is associated with higher dynamic instability, manifested by the higher incidence of not only wave breaks but also wave extinctions. This relatively high dynamic instability leads to the self-termination of arrhythmia because of the sufficiently long wavelength under blebbistatin.

Enhanced Ca2+ binding of cardiac troponin reduces sarcomere length dependence of contractile activation independently of strong crossbridges.

Calcium sensitivity of the force-pCa relationship depends strongly on sarcomere length (SL) in cardiac muscle and is considered to be the cellular basis of the Frank-Starling law of the heart. SL dependence may involve changes in myofilament lattice spacing and/or myosin crossbridge orientation to increase probability of binding to actin at longer SLs. We used the L48Q cardiac troponin C (cTnC) variant, which has enhanced Ca(2+) binding affinity, to test the hypotheses that the intrinsic properties of cTnC are important in determining 1) thin filament binding site availability and responsiveness to crossbridge activation and 2) SL dependence of force in cardiac muscle. Trabeculae containing L48Q cTnC-cTn lost SL dependence of the Ca(2+) sensitivity of force. This occurred despite maintaining the typical SL-dependent changes in maximal force (F(max)). Osmotic compression of preparations at SL 2.0 µm with 3% dextran increased F(max) but not pCa(50) in L48Q cTnC-cTn exchanged trabeculae, whereas wild-type (WT)-cTnC-cTn exchanged trabeculae exhibited increases in both F(max) and pCa(50). Furthermore, crossbridge inhibition with 2,3-butanedione monoxime at SL 2.3 µm decreased F(max) and pCa(50) in WT cTnC-cTn trabeculae to levels measured at SL 2.0 µm, whereas only F(max) was decreased with L48Q cTnC-cTn. Overall, these results suggest that L48Q cTnC confers reduced crossbridge dependence of thin filament activation in cardiac muscle and that changes in the Ca(2+) sensitivity of force in response to changes in SL are at least partially dependent on properties of thin filament troponin.

Phylogenetic analysis, molecular modeling, substrate-inhibitor specificity, and active site comparison of bacterial, fungal, and plant heme peroxidases.

Phylogenetic analysis of 40 heme peroxidases, belonging to both prokaryotes and eukaryotes, revealed their clustering into three major classes. Class I represented sequences from plants, bacteria, fungi, and algae, whereas classes II and III exclusively represented plant and fungal peroxidases, respectively. Modeling of three representative classes of peroxidases, belonging to each of bacterial, plant, and fungal categories, revealed a similar kind of folding; however, superimposition analysis revealed relatively more closeness between plant and fungal peroxidases than that of the bacterial peroxidase. The docking analysis of three representative modeled peroxidases with three common substrates, namely, H2O2, guaiacol, and ascorbate, and three arginine-specific inhibitors, namely, phenylglyoxal, 1,2-cyclohexanedione, and 2,3-butanedione, revealed that all three inhibitors competed for guaiacol- and ascorbate-binding sites of peroxidases, except for phenylglyoxal binding in the case of plant peroxidase. Phenylglyoxal, 1,2-cyclohexanedione, and 2,3-butanedione were found to be most potent inhibitors of bacterial, fungal, and plant peroxidases, respectively.

[Influence of bacteria of Bacillus genus on the causative agent of bacterial cancer of tomatoes].

It has been shown that bacteria of the genus Bacillus inhibited the development of infection caused by Clavibacter michiganensis subsp. michiganensis, in tomatoes. Pre-sowing seed treatment with suspensions of Bacillus subtilis IMV B-7023 and Bacillus pumilus 3 enhanced resistance of plants to bacterial disease of cancer, probably due to the synthesis of biologically active substances with antimicrobial properties by these bacteria. Of the two strains of bacillus, differing by antagonist properties to C. michiganensis subsp. michiganensis, a significant stimulating effect on the growth and development of tomatoes was provided by the strain B. subtilis IMV B-7023, which is part of the bacterial preparations for crop production.