Complexing agents from microorganisms

Summary The majority of extracellular complexing ligands produced by microorganisms are summarized as being of low molecular mass (<10,000 daltons) and are usually released as part of metal detoxification processes. These exudates appear to exhibit strong metal-binding characteristics, often reducing metal toxicity. Under certain conditions microbes produce metal-specific compounds of low molecular mass called siderophores; although these are normally specific for iron they also have relatively high affinities for radionuclides such as Pu and facilitate their uptake into cells. The occurrence of specific actinide complexing agents has been recorded.The breakdown of lignins and cellulosic material produces large macromolecular compounds called humates. These contain multiligand sites and display a wide range of complexing abilities. They form both soluble and insoluble complexes with toxic elements with various results. Humates also considerably influence adsorption of metals to substrate surfaces and at high pH may compete with OH-ions for metal binding.As well as with extracellular ligands, metals can interact directly with microorganisms by accumulation in subcellular compartments or by adsorption on bacterial surfaces.     

Epithelial antimicrobial peptides: innate local host response elements

Multicellular organisms have to survive in an environment laden with numerous microorganisms, which represent a potential hazard to life. Different strategies have been developed to ward off infections by preventing microorganisms from entering surfaces and by preventing the attack of microorganisms that have already entered the epithelia. Therefore, it is not surprising that epithelia are equipped with various antimicrobial substances that act rapidly to kill a broad range of microorganisms. This review summarizes our present knowledge about epithelial peptide antibiotics produced in plants, invertebrates, and vertebrates including humans. There is now strong evidence that in addition to constitutively secreted peptide antibiotics, others are induced upon contact with microorganisms or by proinflammatory cytokines. beta-Defensins represent one family of vertebrate antimicrobial peptides, members of which are inducible and have recently been identified in humans. The defensin-characteristic local expression pattern may indicate that specialized surfaces express a characteristic surface antimicrobial peptide pattern that might define the characteristic microflora as well as the density of microorganisms present on the surface.     

Microbial energetics applied to waste repositories

Summary Through their catalytic abilities microbes can increase rates of chemical reactions which would take a very long time to reach equilibrium under abiotic conditions. Microbes also alter the concentration and composition of chemicals in the environment, thereby creating new conditions for further biological and chemical reactions. Rates of degradation and possible indirect consequences on leaching rates in waste repositories are a function of the presence or absence of microbes and of the conditions which allow them to become catalytically active.Microbially mediated reactions are no exception to the rule that all chemical processes are basically governed by thermodynamic laws. Naturally occurring processes proceed in the direction that leads to the minimal potential energy level attained when equilibrium is reached. A continuous supply of energy to an ecosystem in the form of biochemically unstable compounds maintains non-equilibrium conditions, a prerequisite for all chemotrophic life. Energy is released as a chemical reaction progresses towards equilibrium. Microbes scavenge that portion of the free energy of reaction (G_r) which can be converted into biochemically usable forms during the chemical oxidation processes. As electrontransfer catalysts, the microorganisms mediate reactions which are thermodynamically possible thereby stimulating reaction rates. Decomposition and mineralization in systems without a continuous supply of substrates and oxidants will lead to equilibria with minimal free energy levels at which point further microbial action would cease. The differences in the free energy levels of reactions (G_r), represent the maximal energy which is available to microorganisms for maintenance and growth. How much of the released free energy will be conserved in energy-rich bonds, compounds (e.g. ATP), and chemical potentials (e.g. emf) useful for biosynthesis and biological work is characteristic for the microbes involved and the processes and metabolic routes employed.Materials whose elements are not present in the most oxidized form attainable in the oxic environment of our planet are potentially reactive. Microbial activities are associated only with chemical reactions whose free energy changes are exergonic. This should be kept in mind for all investigations related to the role of microbes in repositories or in the layout of proper waste storage conditions. Rigorous application of thermodynamic concepts to environmental microbiology allows one to develop models and design experiments which are often difficult to conceive of in complex natural systems from physiological information alone. Thermodynamic considerations also aid in selecting proper deposition conditions and in carrying out thoughtful experiments in areas related to microbial ecology of waste repositories.     

Intorno alle attività biochimiche deiFlavobacterium

Summary A fewFlavobacterium, among themFlav. dehydrogenans, present oxidative activities upon sterins from the serie of sexual hormons, acting in a selective manner. These microorganisms have a scarce fermentative capacity against carbohydrates and an eminent oxidative action upon hydrocarbures and their derivatives as toluol, xylol, paraphine, benzoic acid, salicylic acid, phenol.The pigment ofFlav. dehydrogenans, which is exclusively elaborated at diffusive light, is straightly fixed at oxidative processes determined by the bacterium.     

Soluble polysialylated NCAM: a novel player of the innate immune system in the lung

Posttranslational modification of the neural cell adhesion molecule (NCAM) by polysialic acid (polySia) is well studied in the nervous system and described as a dynamic modulator of plastic processes like precursor cell migration, axon fasciculation, and synaptic plasticity. Here, we describe a novel function of polysialylated NCAM (polySia-NCAM) in innate immunity of the lung. In mature lung tissue of healthy donors, polySia was exclusively attached to the transmembrane isoform NCAM-140 and located to intracellular compartments of epithelial cells. In patients with chronic obstructive pulmonary disease, however, increased polySia levels and processing of the NCAM carrier were observed. Processing of polysialylated NCAM was reproduced in a mouse model by bleomycin administration leading to an activation of the inflammasome and secretion of interleukin (IL)-1β. As shown in a cell culture model, polySia-NCAM-140 was kept in the late trans-Golgi apparatus of lung epithelial cells and stimulation by IL-1β or lipopolysaccharide induced metalloprotease-mediated ectodomain shedding, resulting in the secretion of soluble polySia-NCAM. Interestingly, polySia chains of secreted NCAM neutralized the cytotoxic activity of extracellular histones as well as DNA/histone-network-containing “neutrophil extracellular traps”, which are formed during invasion of microorganisms. Thus, shedding of polySia-NCAM by lung epithelial cells may provide a host-protective mechanism to reduce tissue damage during inflammatory processes.     

Molecular dialogue between the human gut microbiota and the host: a Lactobacillus and Bifidobacterium perspective

The human gut represents a highly complex ecosystem, which is densely colonized by a myriad of microorganisms that influence the physiology, immune function and health status of the host. Among the many members of the human gut microbiota, there are microorganisms that have co-evolved with their host and that are believed to exert health-promoting or probiotic effects. Probiotic bacteria isolated from the gut and other environments are commercially exploited, and although there is a growing list of health benefits provided by the consumption of such probiotics, their precise mechanisms of action have essentially remained elusive. Genomics approaches have provided exciting new opportunities for the identification of probiotic effector molecules that elicit specific responses to influence the physiology and immune function of their human host. In this review, we describe the current understanding of the intriguing relationships that exist between the human gut and key members of the gut microbiota such as bifidobacteria and lactobacilli, discussed here as prototypical groups of probiotic microorganisms.     

Microbiology of subteranean waste sites

Summary Excavated repositories for radioactive waste in deep and shallow geological formations will be subject to microbial contamination; therefore, a number of groundwater environments have been examined in Europe for the presence and activity of microorganisms. Common soil bacterial isolates were found to predominate in the groundwaters. Their activity is curtailed by the oligotrophic conditions encountered. It still remains to be demonstrated whether waste and waste isolation materials such as cellulose and bitumen will provide an exogenous nutrient source for the microorganisms and whether microbial activity will compromise nuclear waste immobilisation. A further constraint to the microorganisms is the high pH near-field environment generated by cement/concrete barriers.     

Laccases of prokaryotic origin: enzymes at the interface of protein science and protein technology

The ubiquitous members of the multicopper oxidase family of enzymes oxidize a range of aromatic substrates such as polyphenols, methoxy-substituted phenols, amines and inorganic compounds, concomitantly with the reduction of molecular dioxygen to water. This family of enzymes can be broadly divided into two functional classes: metalloxidases and laccases. Several prokaryotic metalloxidases have been described in the last decade showing a robust activity towards metals, such as Cu(I), Fe(II) or Mn(II) and have been implicated in the metal metabolism of the corresponding microorganisms. Many laccases, with a superior efficiency for oxidation of organic compounds when compared with metals, have also been identified and characterized from prokaryotes, playing roles that more closely conform to those of intermediary metabolism. This review aims to present an update of current knowledge on prokaryotic multicopper oxidases, with a special emphasis on laccases, anticipating their enormous potential for industrial and environmental applications.     

The effect of adhesion on survival and growth of microorganisms

Summary Adhesion of microorganisms to solid surfaces or water/air interfaces can significantly influence cellular metabolic activity, development and viability. Attachment is of advantage particularly for organisms growing under oligotrophic or otherwise extreme conditions. However, the ability to detach and migrate is of vital importance when prevailing conditions become too harsh or in situations of population explosion.Adhesion can cause alterations in the physical and chemical properties of substratum surfaces as well, by means of degradation, aggregation, emulsification etc.     

Microorganisms seen by scanning and transmission electron microscopy in Legionnaires' disease from human lung

Summary In addition to several anomalous structures, other general forms of definitely rod-shaped microorganisms have been found by scanning and transmission electron microscopy in the lung tissue taken at autopsy from a patient who succumbed to confirmed Legionnaires' disease with extensive necrotizing lobar pneumonia. The microorganisms were greatly varied in size and shape. They were micrographed in the act of fission. These forms have been found to some extent throughout the tissue. No nickel was demonstrated, either in the lung tissue or in the microorganisms.This work has been supported in part by a Henry Ford Hospital institutional grant from the Ford Foundation and in part by the Veterans Administration Medical Center Research Funds.     

Nutzung der Sonnenenergie-Möglichkeiten mit Mikroorganismen

From numerous possibilities of biological energy conversion 3 examples with photoautotrophic microorganisms are discussed:Dunaliella producing glycerol,Botryococcus synthesizing hydrocarbons and photosynthetic bacteria evolving hydrogen in the light. These processes are initiated by environmental stress and lead to a single high energy product with a quantum yield comparable to the solar energy conversion in plants in general. However not enough is known on the regulatory aspects and the, biotechnological problems of such large scale photobiological processes are not yet solved.     

Photon emission of phagocytes in relation to stress and disease.

Phagocytes, the first-line cells of the body's defence mechanisms against invading pathogens, kill microorganisms by means of lysosomal degradative enzymes and highly toxic reactive oxygen intermediates. The reactive oxygen compounds are produced, in a process called the 'respiratory burst', by the NADPH oxidase complex in plasma membranes, and by myeloperoxidase in phagolysosomes after degranulation. These processes generate electronically excited states which, on relaxation, emit photons, giving rise to phagocyte chemiluminescence (CL). This paper describes the conditions for the measurement of CL, and reviews the activity of phagocytes from individuals undergoing stress or disease. The capability of phagocytes to emit photons reflects remarkably well the pathophysiological state of the host. In many cases even the magnitude of the stress, the presence of a pathogen in the body, or the activity of the disease can be estimated. Physiological changes, e.g. in the reproductive cycle, can also be predicted.     

Microorganisms seen by scanning and transmission electron microscopy in Legionnaires' disease from human lung.

In addition to several anomalous structures, other general forms of definitely rod-shaped microorganisms have been found by scanning and transmission electron microscopy in the lung tissue taken at autopsy from a patient who succumbed to confirmed Legionnaires' disease with extensive necrotizing lobar pneumonia. The microorganisms were greatly varied in size and shape. They were micrographed in the act of fission. These forms have been found to some extent throughout the tissue. No nickel was demonstrated, either in the lung tissue or in the microorganisms.     

Photon emission of phagocytes in relation to stress and disease

Phagocytes, the first-line cells of the body's defence mechanisms against invading pathogens, kill microorganisms by means of lysosomal degradative enzymes and highly toxic reactive oxygen intermediates. The reactive oxygen compounds are produced, in a process called the ‘respiratory burst’, by the NADPH oxidase complex in plasma membranes, and by myeloperoxidase in phagolysosomes after degranulation. These processes generate electronically excited states which, on relaxation, emit photons, giving rise to phagocyte chemiluminescence (CL). This paper describes the conditions for the measurement of CL, and reviews the activity of phagocytes from individuals undergoing stress or disease. The capability of phagocytes to emit photons reflects remarkably well the pathophysiological state of the host. In many cases even the magnitude of the stress, the presence of a pathogen in the body, or the activity of the disease can be estimated. Physiological changes, e.g. in the reproductive cycle, can also be predicted.     

Sexual reproduction in the Candida clade: cryptic cycles, diverse mechanisms, and alternative functions

To have sex, or not to have sex, is a question posed by many microorganisms. In favor of a sexual lifestyle is the associated rearrangement of genetic material that confers potential fitness advantages, including resistance to antimicrobial agents. The asexual lifestyle also has benefits, as it preserves complex combinations of genes that may be optimal for pathogenesis. For this reason, it was thought that several pathogenic fungi favored strictly asexual modes of reproduction. Recent approaches using genome sequencing, population analysis, and experimental techniques have now revised this simplistic picture. It is now apparent that many pathogenic fungi have retained the ability to undergo sexual reproduction, although reproduction is primarily clonal in origin. In this review, we highlight the current understanding of sexual programs in the Candida clade of species. We also examine evidence that sexual-related processes can be used for functions in addition to mating and recombination in these organisms.     

Formation of ethanol by bacteria. A pledge for the use of extreme thermophilic anaerobic bacteria in industrial ethanol fermentation processes

Summary Many anaerobic, facultatively anaerobic and even some strictly aerobic microorganisms form various amounts of ethanol from glucose. Only few mesophilic and extreme thermophilic bacteria ferment glucose stoichiometrically to 2 ethanol and 2 carbondioxid. Biotechnological processes at elevated temperatures seem advantageous in many respects. Hence, thermophiles and extreme thermophiles can potentially substitute for yeast in ethanol production on an industrial scale. Advantages and disadvantages of thermophilic mixed cultures and of potentially useful organisms are discussed.Acknowledgment. This work was partly supported by Energy and Research Development Administration contract number EY-76-509-0888-M003 and by the Deutsche Forschungsgemeinschaft.     

Lebensverlängernde Wirkung von γ-Strahlen auf Männchen des LärchenwicklersZeiraphera diniana (Lepidoptera; Tortricidae)

Summary Males of the larch bud mothZeiraphera diniana live longer when irradiated with 20–40 kR of⁶⁰Co-rays than non-irradiated males. The prolongation of life in the irradiated males is probably neither a consequence of reduced fertility nor due to a hygienic effect, i.e. destruction of parasitic microorganisms. It seems probable that irradiation with the above mentioned doses stimulates certain regenerative processes.     

Evaluating the fate of genetically modified microorganisms in the environment: Are they inherently less fit?

Genetically modified microorganisms hold great promise for environmental applications. Nonetheless, some may have unintended adverse effects. Of particular concern for risk assessment is the simple fact that microorganisms are self-replicating entities, so that it may be impossible to control an adverse effect simply by discontinuing further releases of the organism. It has been suggested, however, that genetically modified microorganisms will be poor competitors and therefore unable to persist in the wild due to energetic inefficiency, disruption of genomic coadaptation, or domestication. Many studies support the hypothesis that genetically modified microorganisms are less fit than their progenitors, but there are a few noteworthy counter-examples in which genetic modifications unexpectedly enhance competitive fitness. Furthermore, subsequent evolution may eliminate the maladaptive effects of some genes, increasing the likelihood that a modified organism or its engineered genes will persist. Evaluating the likelihood that a genetically modified microorganism or its engineered genes will persist is a complex ecological and evolutionary problem. Therefore, an efficient regulatory framework would require such evaluations only when there are plausible scenarios for significant adverse environmental effects.     

Light metal compound casting

Compound castingsimplifies joining processes by directly casting a metallic melt onto a solid metal substrate.A continuously metallurgic transition is very important for industrial applications,such as joint structures of spaceframe constructions in transport industry.In this project,compound castingof light metals is investigated,aiming at weight-saving.The substrate used is a wrought aluminium alloy of type AA5xxx,containing magnesium as main alloying element. The melts are aluminium alloys,containing var...     

Biological weapons

Bioterrorism is defined by the intentional or threatened of microorganisms or toxins derived from living organisms to cause death or diseases in humans, animals or plants on which we depend. The other major point is to generate fear in the population. More than 180 pathogens have been reported to be potential agents for bioterrorism. The following is an overview of several agents that could be involved in a biological attack.