ATP oscillation inPhysarum plasmodium

Summary Using bioluminescence of luciferin-luciferase, we showed that ATP leaked out rhythmically from a strand segment ofPhysarum plasmodium made permeable with caffeine-arsenate. With simultaneous measurement of isometric tension rhythm of the strand, it was revealed that the period and phase of oscillation in ATP leakage correspond well with those of tension production. Further, microinjection of luciferin-luciferase into the plasmodial strand indicated that the intracellular luminescence of luciferin-luciferase also oscillates with the same period and in the same phase as the tension rhythm.The free ATP concentration in a homogenate ofPhysarum plasmodium was of the order of 10 M, but if the homogenate was heated in boiling water, the intensity of luminescence suddenly increased 10–100 fold. ATP available for mechanical workin vivo is thus supposed to be at a much lower level than the total average, which was found in the range of 0.2–0.7 mM.     

Untersuchungen an Archangium violaceum

Ohne ZusammenfassungGekürzte Fassung einer Dissertation der Fakultät für Natur-und Geisteswissenschaften der Technischen Hochschule Karlsruhe.     

Klonkulturen von Archangium violaceum

Ohne Zusammenfassung     

Denitrification by Chromobacterium violaceum

One host (Rana catesbiana)-associated and two free-living mesophilic strains of bacteria with violet pigmentation and biochemical characteristics of Chromobacterium violaceum were isolated from freshwater habitats. Cells of each freshly isolated strain and of strain ATCC 12472 (the neotype strain) grew anaerobically with glucose as the sole carbon and energy source. The major fermentation products of cells grown in Trypticase soy broth (BBL Microbiology Systems, Cockeysville, Md.) supplemented with glucose included acetate, small amounts of propionate, lactate, and pyruvate. The final cell yield and culture growth rate of each strain cultured anaerobically in this medium increased approximately twofold with the addition of 2 mM NaNO₃. Final growth yields increased in direct proportion to the quantity of added NaNO₃ over the range of 0.5 to 5 mM. Each strain reduced NO₃⁻, producing NO₂⁻, NO, and N₂O. NO₂⁻ accumulated transiently. With 2 mM NaNO₃ in the medium, N₂O made up 85 to 98% of the N product recovered with each strain. N-oxides were recovered in the same quantity and distribution whether 0.01 atm (ca. 1 kPa) of C₂H₂ (added to block N₂O reduction) was present or not. Neither N₂ production nor gas accumulation was detected during NO₃⁻ reduction by growing cells. Cell growth in media containing 0.5 to 5 mM NaNO₂ in lieu of NaNO₃ was delayed, and although N₂O was produced by the end of growth, NO₂⁻ -containing media did not support growth to an extent greater than did medium lacking NO₃⁻ or NO₂⁻. The data indicate that C. violaceum cells ferment glucose or denitrify, terminating denitrification with the production of N₂O, and that NO₂⁻ reduction to N₂O is not coupled to growth but may serve as a detoxification mechanism. No strain detectably fixed N₂ (reduced C₂H₂).     

Effect of Cold Temperatures on the Viability of Chromobacterium violaceum

The effect of low, nonfreezing temperatures on the viability of five strains of Chromobacterium violaceum was studied. The viability of cultures grown at 30 C was determined after exposure to various diluents held at 0 to 2 C. A culture diluted at its growth temperature served as the control. Cells of strain N were most sensitive in the early part of the exponential phase of growth. Cells of strains 252 and 341 were most sensitive in the late exponential, early stationary phase of growth. Cells of strain 9 showed greatest loss of viability during the maximal stationary phase. Strain 69 was completely resistant throughout its growth cycle to cold injury. Cell viability was much greater in buffered salts solution than in distilled water, broth, or physiological saline, whether cultures were diluted at room temperature or in the cold. The proportion of cells surviving after exposure to cold, however, was the same regardless of the composition of the diluent. Loss of viability was progressive at 0 to 2 C and reached a maximum after 2 hr. There was no loss of viability of cells exposed to 20 C, but there was some loss at 12 C. Strain 341 cultivated at 15 C was much less sensitive to 0 to 2 C than when it was cultivated at 30 C. The composition of the growth medium seemed to have no effect on the survival of cells exposed to cold. The polyamines, spermine and trimethylenediamine, as well as erythritol and sucrose, exerted some protective action against the effects of cold but not uniformly for all strains studied.     

Merozoite surface antigen-I of plasmodium

The merozoite is the invasive form of the asexual stage of Plasmodium species. At least two polymorphic glycoproteins have been found on its surface in the human malaria parasite Plasmodium falciparum. The best-characterized of these is known as merozoite surface antigen-1 (MSA1) (185-200 kDa) (Ref. 1). Similar molecules are found in other malaria species. The other merozoite surface antigen, MSA2 (35-48 kDa) (Ref. 2), is distinct from MSA1 but is equally polymorphic. In this review, Juan Cooper condenses the body of structural information on MSA1 known to date. A database compiled from MSA1 sequences from several species used together with sequence comparisons and predicted secondary structure reveals interesting features of this molecule.     

Dynamic organization of Physarum plasmodium

Birefringent fibrils (BRFs) with a positive sign composed of bundles of F-actin were found throughout the Physarum plasmodium with the mode of existence differing regionally. In the zone behind the leading edge of an advancing plasmodium, where cytoplasmic sol and gel were still not well differentiated, more BRFs came to the foreground when the endoplasm flowed backward (emptying phase), and a substantial portion disappeared when the endoplasm flowed forward (filling phase), except for nodes, from which BRFs were reorganized in the early emptying phase of each cycle. BRFs found in the wall of the streaming channel in the posterior network and the branched vein section ran in parallel to or helically around the channel. They were much more stable and maintained strong birefringence irrespective of the direction of the cytoplasmic flow. When the fan-like expanse ceased moving forward, the BRFs no longer appeared and disappeared cyclically but persisted in the area which had previously been the front. We concluded that the site of the active contraction-relaxation rhythm in an advancing plasmodium with antero-posterior polarity is restricted to its frontal zone and that the rest of the plasmodium is in a state of "tonus" which continuously imparts a certain level of hydrostatic pressure to the interior. The meaning of the tonus and the mechanics of tensile force production in the plasmodium are discussed in terms of a working hypothesis arrived at from the phase relationship between isometric and isotonic contraction waves.     

Mesosome Structure in Chromobacterium violaceum

Exponentially growing cells of the gram-negative bacterium Chromobacterium violaceum demonstrate invaginations of the cytoplasmic membrane with a high frequency. These invaginations conform to the ultrastructural appearance of mesosomes of gram-positive bacteria. As many as four mesosomes are observed per cell, each of which may increase the total membrane surface of the cell by 30%. Washing of cells in dilute tris(hydroxymethyl)aminomethane buffer effects a distension of the mesosome "neck" and/or cytoplasmic membrane clarifying the association of the mesosome to the cytoplasmic membrane. Plasmolysis effects an eversion of the mesosome into the plasmolysis vacuole.     

Drug resistance in Chromobacterium violaceum

Chromobacterium violaceum is a free-living bacterium commonly found in aquatic habitats of tropical and subtropical regions of the world. This bacterium is able to produce a large variety of products of biotechnological and pharmacological use. Although C. violaceum is considered to be non-pathogenic, some cases of severe infections in humans and other animals have been reported. Genomic data on the type strain ATCC 12472(T) has provided a comprehensive basis for detailed studies of pathogenicity, virulence and drug resistance genes. A large number of open reading frames associated with various mechanisms of drug resistance were found, comprising a remarkable feature of this organism. Amongst these, beta-lactam (penicillin and cephalosporin) and multidrug resistance genes (drug efflux pumps) were the most numerous. In addition, genes associated with bacitracin, bicyclomycin, chloramphenicol, kasugamycin, and methylenomycin were also found. It is postulated that these genes contribute to the ability of C. violaceum to compete with other bacteria in the environment, and also may help to explain the common drug resistance phenotypes observed in infections caused by this bacterium.     

DNA repair in Chromobacterium violaceum

Chromobacterium violaceum is a Gram-negative beta-proteobacterium that inhabits a variety of ecosystems in tropical and subtropical regions, including the water and banks of the Negro River in the Brazilian Amazon. This bacterium has been the subject of extensive study over the last three decades, due to its biotechnological properties, including the characteristic violacein pigment, which has antimicrobial and anti-tumoral activities. C. violaceum promotes the solubilization of gold in a mercury-free process, and has been used in the synthesis of homopolyesters suitable for the production of biodegradable polymers. The complete genome sequence of this organism has been completed by the Brazilian National Genome Project Consortium. The aim of our group was to study the DNA repair genes in this organism, due to their importance in the maintenance of genomic integrity. We identified DNA repair genes involved in different pathways in C. violaceum through a similarity search against known sequences deposited in databases. The phylogenetic analyses were done using programs of the PHILYP package. This analysis revealed various metabolic pathways, including photoreactivation, base excision repair, nucleotide excision repair, mismatch repair, recombinational repair, and the SOS system. The similarity between the C. violaceum sequences and those of Neisserie miningitidis and Ralstonia solanacearum was greater than that between the C. violaceum and Escherichia coli sequences. The peculiarities found in the C. violaceum genome were the absence of LexA, some horizontal transfer events and a large number of repair genes involved with alkyl and oxidative DNA damage.     

Energetic metabolism of Chromobacterium violaceum

Chromobacterium violaceum is a free-living microorganism, normally exposed to diverse environmental conditions; it has a versatile energy-generating metabolism. This bacterium is capable of exploiting a wide range of energy resources by using appropriate oxidases and reductases. This allows C. violaceum to live in both aerobic and anaerobic conditions. In aerobic conditions, C. violaceum is able to grow in a minimal medium with simple sugars, such as glucose, fructose, galactose, and ribose; both Embden-Meyerhoff, tricarboxylic acid and glyoxylate cycles are used. The respiratory chain supplies energy, as well as substrates for other metabolic pathways. Under anaerobic conditions, C. violaceum metabolizes glucose, producing acetic and formic acid, but not lactic acid or ethanol. C. violaceum is also able to use amino acids and lipids as an energy supply.     

Syngamy and plasmodium formation in the MyxomyceteDidymium iridis

Summary Cell and nuclear behavior during syngamy in the MyxomyceteDidymium iridis and the development of zygotes into plasmodia by both synchronous mitoses and by coalescence with other zygotes and plasmodia are described. Various aspects of cell and nuclear behavior are discussed in relation to the induction of syngamy and the trigger mechanisms responsible for switching the course of development from one pathway to another.     

Studies on the velocity distribution of the protoplasmic streaming in the myxomycete plasmodium

Summary It was shown that the velocity distribution of the intracapillary streaming of protoplasm in a plasmodium ofPhysarum polycephalum is the same no matter whether the flow is spontaneous or whether it is induced artificially by external local air pressure applied to the plasmodium. Thus we conclude that the protoplasmic flow in the plasmodium is caused by local difference in endoplasm pressure. The view that the seat of the motive force responsible for the flow is located in the streaming protoplasm itself is untenable for this type of streaming.