Effect of lowered incubation temperatures on nucleic acid and protein synthesis by a mesophilic and a psychrophilic bacterium

The authors studied changes in the synthesis of nucleic acids (RNA, DNA) and protein by a mesophilic strain ofEscherichia coli B and a psychrophilic strain ofPseudomonas fluorescens at a low incubation temperature giving tenfold prolongation of the generation time. It was found that lowering the incubation temperature was followed by an increase in the intracellular nucleic acid content during the lag phase and the phase of accelerated growth, in which maximum nucleic acid (NA) values were reached. As a result, the total NA level in the cell also remained relatively high during further proliferation, when the increase in NA (particularly RNA) slows down at low incubation temperatures. Proteosynthesis, however, fell in the mesophilic culture. The smaller effect of a lowered temperature on DNA biosynthesis was manifested specifically in the lag phase ofEscherichia coli, in which disproportion developed between the amount of DNA (which was synthesized at a relatively higher rate) and RNA; this was afterwards equalized by a temporary break in DNA production. Pronounced differences in the given types of biosynthesis were found only in the mesophilic culture, while at suboptimal temperatures the metabolism of the psychrophilic strain slowed down but no marked changes occurred.     

Olfactory response of four aphidophagous insects to aphid- and caterpillar-induced plant volatiles

Plants damaged by herbivores emit blends of volatile organic compounds (VOCs) that attract the herbivore’s natural enemies. Most work has focussed on systems involving one plant, one herbivore and one natural enemy, though, in nature, plants support multiple herbivores and multiple natural enemies of these herbivores. Our study aimed to understand how different aphid natural enemies respond to aphid-induced VOCs, and whether attraction of the natural enemies that responded to aphid-induced VOCs was altered by simultaneous damage by a chewing herbivore. We used a model system based on Brassica juncea (Brassicaceae), Myzus persicae (Hemiptera: Aphididae) and Plutella xylostella (Lepidoptera: Plutellidae). Ceraeochrysa cubana (Neuroptera: Chrysopidae) did not show preferences for any plant odour, while Cycloneda sanguinea (Coleoptera: Coccinellidae) responded to undamaged plants over air but not to aphid-damaged plants over undamaged plants. Therefore, no further tests were carried out with these two species. Chrysoperla externa (Neuroptera: Chrysopidae) preferred aphid-damaged plants, but not caterpillar-damaged plants, over undamaged plants, and preferred plants damaged by both herbivores over both undamaged plants and aphid-damaged plants. When tested for responses against undamaged plants, Aphidius colemani (Hymenoptera: Braconidae) preferred aphid-damaged plants but not plants damaged by caterpillars. Plants damaged by both herbivores attracted more parasitoids than undamaged plants, but not more than aphid-damaged plants. Thus, multiply damaged plants were equally attractive to A. colemani and more attractive to C. externa than aphid-damaged plants, while C. cubana and C. sanguinea did not respond to aphid-induced VOCs, highlighting how different natural enemies can have different responses to herbivore-damaged plants.     

Attraction of <Emphasis Type="Italic">Telenomus podisi</Emphasis> to volatiles induced by <Emphasis Type="Italic">Euschistus heros</Emphasis> in three different plant species

Specialized natural enemies that forage for polyphagous hosts need to locate hosts on different plants. Telenomus podisi (Hymenoptera: Platygastridae) is a stink bug egg parasitoid with a preference for Euschistus heros (Hemiptera, Pentatomidae), a polyphagous species. The aim of this study was to evaluate the induction of defences in three E. heros host plants: maize (Zea mays), sunflower (Helianthus annuus) and pigeon pea (Cajanus cajan). We hypothesized that E. heros damage to these three plants enhances the attraction of the parasitoid T. podisi as has been observed in other systems. Using Y-tube olfactometer bioassays, we tested parasitoid responses to combinations of the following odour sources: clean air, undamaged plants and plants damaged by stink bug feeding. Volatiles were collected by means of dynamic headspace collection and analysed by gas chromatography coupled to mass spectrometry. T. podisi did not distinguish odours from undamaged plants against air for any of the three plant species. For maize, the parasitoid preferred the odour from herbivore-damaged plants over both clean air and undamaged plants. For sunflower, the parasitoid only preferred the odour of herbivore-damaged plants over the odour of undamaged plants. For pigeon pea, no preferences were observed. Quantitative differences in the volatile profile of damaged and undamaged plants were observed in each plant species. We conclude that sunflower and maize plants, when damaged by E. heros, release volatiles that attract the parasitoid T. podisi; the parasitoid appears to use a different blend composition to distinguish herbivore-damaged plants of each species.     

Effect of indoleacetic acid on the growth ofRhizobium in culture

After inoculation ofRhizobium lupini strain A98 andR. leguminosarum strain PRE into a medium containing IAA, growth was initially suppressed. However, when IAA was added in the course of the logarithmic phase, growth was not inhibited. Apparently, IAA affects primarily the lag phase cells.Neither adaptation ofRhizobium to IAA was observed, nor spontaneous breakdown or biological degradation of IAA.The lag phase prolongation depended on the ratio: amount of IA A/number of cells.The authors wish to thank Professor Dr. A. Quispel for his interest and valuable discussions.     

The effect of galling aphids feeding on photosynthesis photochemistry of elm trees (<Emphasis Type="Italic">Ulmus</Emphasis> sp.)

Changes of chlorophyll (Chl) a fluorescence and photosynthetic pigment contents were analysed in galled leaves (visibly damaged and undamaged parts) and intact leaves. The values of minimal fluorescence of the dark-adapted state, maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemical conversion, and photochemical quenching coefficient decreased in Ulmus pumila L. leaves galled by Tetraneura ulmi (L.) and in U. glabra Huds. galled by Eriosoma ulmi (L.). Colopha compressa (Koch.) feeding affected these parameters only in damaged parts of U. laevis Pall. galled leaves. The increasing number of T. ulmi galls progressively decreased photosynthetic performance. In gall tissues of all analysed aphid species, the lowest photosynthetic pigment content was found, indicating that the photosynthetic capacity must have been low in galls. Significant reduction of Chl and carotenoid contents were observed in damaged and undamaged portions of galled leaves only in the case of T. ulmi feeding.     

Significance of different inoculum sources for the Fusarium infection of wheat ears

From 1997 to 1999 the occurrence ofFusarium spp. on wheat grain and its contamination with the mycotoxins deoxynivalenol and invalenol were investigated under organic farming conditions in the Rhineland, Germany. For comparison, some trials were also run under integrated farming conditions. The importance of the seed contamination withFusarium spp. as well as the impact of farming system, previous crop and soil preparation on the inoculum sources ofFusarium spp. in the soil were investigated. The data on the inoculum sources was compared to the Fusarium infection of grains and their content of DON and NIV. The crop residues in the soil were the most important inoculum source for the Fusarium species infecting wheat ears and grains. The amount of potential inoculum in the soil largely depended on the previous crop and the system of soil preparation.     

Behavior in two-phase aqueous polymer systems of L5178Y mouse leukemic cells : II. The lag and exponential phases of growth

The behavior of lag and exponential growth phase L5178Y mouse leukemic cells under normal and prolonged lag phase conditions with respect to partition in aqueous dextran — polyethylene glycol polymer systems has been studied. ‘Backculture’ of early stationary cells into fresh growth medium is accompanied by a decrease in partition ratio from 0.52 to 0.11. The partition ratio remains depressed for a time considerably longer than the duration of lag phase but rises rapidly and returns to its former value as the cells reach late exponential/early stationary phase. If lag phase is prolonged, the time for which the partition ratio remains depressed is also prolonged. In the exponential phase following a prolonged lag phase, the partition ratio rises at a rate slower than during a normal exponential phase and does not reach the same magnitude for the same position in the cycle. Net negative surface charge as measured by particle microelectrophoresis does not change appreciably throughout the growth cycle. The results suggest that the sequence of events at the cell surface on a populational basis which contribute to the partitioning behavior is possibly predetermined or programmed at the time of transfer into fresh medium. The results further substantiate the technique of aqueous polymer partitioning as being the most sensitive method available for monitoring subtle changes in plasma membrane properties during the cell growth cycle.     

Adaptation of aerobic methylobacteria to dichloromethane degradation

A shortening of the lag phase in dichloromethane (DCM) consumption was observed in the methylobacteria Methylopila helvetica DM6 and Albibacter methylovorans DM10 after prior growth on methanol with the presence of 1.5% NaCl. Neither heat nor acid stress accelerated methylobacterium adaptation to DCM consumption. Sodium azide (1 mM) and potassium cyanide (1 mM) inhibited consumption of DCM by these degraders but not by transconjugants Methylobacterium extorquens AM1, expressing DCM dehalogenase but unable to grow on DCM. This indicates that the degrader strains possess energy-dependent systems of transport of DCM or chloride anions produced during DCM dehalogenation. Inducible proteins were found in the membrane fraction of A. methylovorans DM10 cells adapted to DCM and elevated NaCl concentration.     

Oviposition Preferences of <Emphasis Type="Italic">Plutella xylostella</Emphasis> are Influenced by the Type of Plant Induction and Glucosinolate Hydrolysis Profiles

Effects of inducing plants by exposing them to insect herbivory, mechanical damage or damaged neighboring plants were evaluated on the oviposition preferences of Plutella xylostella. The role of plant genotypes differing in their glucosinolate hydrolysis profiles was also evaluated using a wild ecotype (Col-0) and a genetically modified line (tgg1tgg2) of Arabidopsis thaliana. While the Col-0 line has normal production of glucosinolate hydrolysis products, the double myrosinase knockout (tgg1tgg2) is defective in the production of these volatiles. Dual choice oviposition assays were performed using naïve P. xylostella females, and the two A. thaliana lines, which were exposed to the three types of induction treatments. Female oviposition preferences were significantly influenced by both the type of plant induction and the plant genotypes differing in their volatile profiles. Plutella xylostella females significantly preferred to oviposit on herbivore-damaged plants (versus undamaged controls) when Col-0 plants were used, but chose control plants over the double myrosinase knockout tgg1tgg2. However, plant genotype did not influence oviposition choices between plant-plant primed or mechanically damaged plants and paired undamaged controls. Given the prevalent use of genetically modified plants and the potential differences in their responses to different types of induction, these factors may be important to consider in the management of specialist pests such as the diamondback moth P. xylostella.     

„Kragen” an Atrypiden aus Schillen des Unteren Plattenkalkes (Givet) von Bergisch Gladbach (Rheinisches Schiefergebirge)

In the Lower Plattenkalk of Bergisch Gladbach occur, besides the well known?Hians”-beds, polymictic accumulations of shell material. Together with the valves ofMartinia inflata (Schnur),Uncinulus parallelepipedus (Br.) andIsopoma brachyptyctum (Schnur) are great numbers ofSpinatrypa tubaecostata (Paeck.) andAtrypa prisca gladbachensis n. subsp. In spite of the fact that the host rock was deposited as shell debris, in particular the rhynchonellids and atrypids are easily separated from it in a well preserved state. Atrypa (Desquamatia) prisca gladbachensis n. subsp. is commonly found with its alations intact. This subspecies, which is here described in some detail, fluorisched on a marly ooze bottom. The expanded valves increased the food gathering field, while the alations, surrounding the shell margin almost like a flange, functioned as effective particle filters. Because of this, the free valves floated under wave attack and became fossilized almost undamaged. The brachiopod shells and the organoplastic debris were washed on to discontinuity surfaces which probably had already been lithified by algal growth.     

Cell Aggregation in Cultures of <Emphasis Type="Italic">Micrococcus luteus</Emphasis>, Studied by Dynamic Light Scattering

Cell aggregation was studied using the method of dynamic light scattering in the course of growth of Micrococcus luteus cultures in a liquid medium. The method detects particles ranging in size from 0.5 to 1000 μm in samples containing no more than 10⁵ cells/ml. When grown in liquid media, M. luteus forms aggregates; during the lag phase, 80% of the cells are found in aggregates of 10–1000 μm, only minor amounts being represented by single cells. With the onset of exponential growth, the aggregates were decomposed and single cells became prevalent in the culture liquid. This observation confirms that the aggregation of the cells during the lag phase is prerequisite to the initiation of bacterial growth. The method may be used in biotechnology for monitoring the state of bacterial cultures. __________ Translated from Prikladnaya Biokhimiya i Mikrobiologiya, Vol. 41, No. 6, 2005, pp. 647–651. Original Russian Text Copyright ? 2005 by Voloshin, Kaprelyants.     

Cassava leaf protein

Crude protein content of the leaf of cultivars ofManihot esculenta is very high. There are no analyses of nutritionally essential ami no acids, but certain evidence indicates that cassava leaf may be of value in protein-rich diets.     

Degradation of wyerone,the phytoalexin of faba beans byRhizobium leguminosarum

Wyerone is the predominant phytoalexin produced byVicia faba. At a concentration of 100 µM, wyerone prolonged the lag phase before the onset of exponential growth of different strains ofRhizobium leguminosarum andBradyrhizobium japonicum. The response to wyerone was dose dependent, with a shorter lag phase occurring at lower concentrations. Wyerone was only moderately inhibitory towards the phytopathogenic bacteriumErwinia carotovora cv. atroseptica. HPLC analysis of the medium during bacterial growth indicated thatRhizobium leguminosarum was able to metabolize wyerone. The identification of the product as hydroxyester wyerol was confirmed by GC/MS analysis.     

GenusCandida berkhout

The authors describe a study of the pathogenicity of 95 strains ofCandida albicans, the typing of which was described in the previous paper. Mortality among mice after intravenous administration was not related to the sex of the mice or the age of the strain in the artificial culture, but to the number of yeast-like microorganism cells in the dose of inoculum. All the strains ofCandida albicans were to some extent pathogenic. The most pathogenic strains had tufts of small, spherical blastospores on the pseudomycelium, while the least pathogenic had large, elongated spores arranged on the pseudomycelium in whorls.     

Growth Stimulating Substance for Microorganisms Produced by Escherichia coli Causing the Reduction of the Lag Phase in Microbial Growth and Identity of the Substance with Pyrroloquinoline Quinone

The finding that most strains of microbes produce a growth stimulating substance for microorganisms was demonstrated and confirmed with the culture broth of Escherichia coli grown on a glucose-mineral medium. Addition of culture broth of E. coli to the culture media of the others markedly reduced the lag phase in microbial growth but not growth rate in the subsequent exponential phase nor the total cell yield in the stationary phase. The growth stimulation causing reduction of the lag phase was dependent on the amount of culture broth added. Occurrence of cell growth was essential for the excretion of the growth stimulating substance by E. coli. Under identical inoculum size, even with a heavy inoculum, a further reduction of the lag phase was observed by the addition of culture broth of E. coli. The substance was only effective at the initial growth phase but inert when the substance was added to a growing culture at the exponential phase. Finally, the substance was identified as pyrroloquinoline quinone, a newly established coenzyme, through chromatographic, spectroscopic and enzymatic criteria.     

Long-term H<Subscript>2</Subscript> photoproduction from starch by co-culture of <Emphasis Type="Italic">Clostridium butyricum</Emphasis> and <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis> in a repeated batch process

Objectives

To prove the possibility of efficient starch photofermentation in co-culture of heterotrophic and phototrophic bacteria over prolonged period.

Results

Repeated batch photofermentation of starch was demonstrated in co-culture Clostridium butyricum and Rhodobacter sphaeroides under microaerobic conditions. It continued 15 months without addition of new inoculum or pH regulation when using 4–5 g starch l^?1 and 0.04 g yeast extract l^?1. The complete degradation of starch without volatile fatty acids accumulation was shown in this co-culture. The average H₂ yield of 5.2 mol/mol glucose was much higher than that in Clostridium monoculture. The species composition of co-culture was studied by q-PCR assay. The concentration of Clostridium cells in prolonged co-culture was lower than in monoculture and even in a single batch co-culture. This means that Clostridia growth was significantly limited whereas starch hydrolysis still took place.

Conclusion

The prolonged repeated batch photofermentation of starch by co-culture C. butyricum and R. sphaeroides provided efficient H₂ production without accumulation of organic acids under conditions of Clostridia limitation.

     

The determination of the activity of some enzymes of carbon-metabolism in extracts ofEuglena gracilis cells

The activity of aldolase, glyceraldehyde-3-phosphate dehydrogenase, 3-phospho-glycerate kinase, pyruvate phosphokinase, malic dehydrogenase, glutamic-oxalacetic transaminase was studied in extracts of green and streptomycin- or erythromycin-depigmented cells ofEuglena gracilis var.bacillaris obtained by the freezing technique. The presence of lactic dehydrogenase acting with DPN, of glutamic dehydrogenase and of glutamicpyruic-transaminase was not demonstrated.     

The effect of culture medium and aeration on growth of Listeria monocytogenes at pH 4.5

Listeria monocytogenes multiplied at 20°C in medium adjusted to pH 4.5 with HCl, and the lag before growth was eliminated when the inoculum was grown to log phase in the same medium. In a tryptone soya medium with yeast extract and added glucose, growth at pH 4.5 was more rapid than in a tryptose phosphate medium, and this difference was greater in air than under nitrogen. The results show that the bacterium was capable of more rapid growth in air than under nitrogen at this pH and suggest that the tryptose phosphate medium was nutritionally limiting for growth.     

The adaptation ofCandida utilis to dense recycled molasses mashes under continuous cultivation

A two-phase metabolism ofCandida utilis occurred during batch cultivation in a molasses mash. It was characterized by intensive accumulation of biomass without a lag, utilization of glucose, formation of acetate and ethanol and their conversion to ethyl acetate during the first phase. In the second phase the accumulation of biomass continued and was accompanied by simultaneous utilization of ethyl acetate or amino acids, contained in molasses or produced by the culture during the first phase. A content of betaine, ash, non-assimilable nitrogen and reducing compounds as well as osmotic pressure increased with increasing density in separated mashes. The culture adapted to this medium during a two-stage continuous cultivation divided according to the two-phase nature of the metabolism. In the course of the adaptation the culture developed the ability to utilize succinate, glutamate, citrate and other originally non-assimilable compounds. A specific growth rate and productivity of the system increased proportionally with the increased concentration of assimilable substrates during a transition from one steady state to another. The adaptation in batch culture was not successful.     

Serologic characteristics of certain root-nodule bacteria of legumes

Rhizobium trifolii organisms associated with eleven species ofTrifolium were isolated and studied by means of antigen-antibody agglutination and immune diffusion techniques. Ten serologic types were differentiated from the eleven species of nativeTrifolium. Certain serologic types of rhizobia were widely distributed among the native species ofTrifolium, whereas other rhizobial types were found only on one or two species. The distribution pattern appears to be independent of the proportion of each type present in the soil population. This may indicate specificity of selection between a host legume and serologic types of rhizobia.