Effect of Carbon Source on the Antimicrobial Activity of the Air Flora

Summary In an attempt to screen for air flora producing new potent antimicrobial substances, Bacillus megaterium NB-3, Bacillus cereus NB-4, Bacillus cereus NB-5, Bacillus subtilis NB-6 and Bacillus circulans NB-7, were isolated and were found to be antagonistic to bacteria and/or fungi. Production of antimicrobial substances by the bacterial strains was greatly influenced by variation of carbon sources. Glycerol strongly enhanced the antimicrobial activity of strains NB-3 and NB-6, whereas glucose increased the antimicrobial activity of strains NB-4 and NB-5. The maximum antibiotic yield of NB-7 was achieved with fructose as a carbon source. Starch (Bacillus megaterium NB-3), maltose (Bacillus cereus NB-5), glycerol (Bacillus circulans NB-7), arabinose, ribose (Bacillus cereus NB-4) and arabinose, fructose, glucose, ribose and sucrose (Bacillus subtilis NB-6) repressed the production of antimicrobial substances by the respective bacterial strains.     

Effect of plant population on the production and distribution of dry matter in maize

Grain and total dry weight of maize (Zea mays L.) at final harvest increased by about 50% and 30%, respectively, when the population was increased from 23000 to 48000 plants/ha, but did not increase further with population up to 74000/ha. Between 6 and 10 weeks after sowing, crop growth rate (C) increased by about 40% with increase in leaf-area index (L) from 2 to 5·5, despite a concomitant increase in moisture stress. Immediately after flowering, which occurred at 10–11 weeks, C increased up to the greatest L attained, 6·7, and would probably have reached a maximum, with L about 7, when nearly all the incident light would be intercepted by foliage. Later, the L at which C was maximal decreased, probably because the photosyhthetic efficiency of leaves decreased faster with time as L increased; 18 weeks after sowing, when L varied between 3 and 5·5, C was maximal when L was 5. The proportion of grain in the dry matter accumulated after flowering increased from 73% when population was 23000/ha to 82% when it was 60000–74000/ha. Stem weight increased until 3–4 weeks after flowering, then remained constant when population was 23000/ha, but decreased in denser populations. The fraction of the ear consisting of grain increased with population.     

Effect of Abscisic Acid on the Transpiration of Zea mays

Intact plants of Zea mays L. were treated with foliar sprays of cis-trans-abscisic acid (ABA) at concentrations from 10⁻⁹ to 10⁻⁴M. Even the lowest concentration caused a reduction of the transpiration rate as measured between 1 and 33 h after spraying. With increasing ABA concentrations, there was a nearly linear relationship between the logarithm of the ABA concentration and the (decreasing) transpiration rate within that period. Subsequently a partial recovery of the transpiration rate set in, beginning progressively later as the ABA concentration was increased. After 5 1/2 days the transpiration rate of plants treated with 10⁻⁹ and 10⁻⁸M was nearly back to normal, whereas plants treated with 10⁻⁴M transpiration at only about 2/3 their normal rate. In experiments with detached maize leaves supplied with water or ABA solutions (10⁻⁸ to 10⁻⁵M) through their cut bases, the transpiration of control leaves decreased gradually to a low level in 24 h. ABA caused a marked and rapid reduction of the transpiration rate compared to that of the controls. After a few hours, the transpiration of the treated leaves decreased at a slower rate than that of the controls, thus approaching the control values. After 35 h, the transpiration of leaves treated with 10⁻⁵M ABA was nearly the same as in untreated leaves. Exchanging the ABA solution for distilled water after 24 h had little effect on the subsequent course of the transpiration rate.     

Effect of neem on the growth and development of the obliquebanded leafroller, Choristoneura rosaceana

Neem, Azadirachta indica A. Juss. (Meliaceae), seed oil (NSO) added to meridic diet at concentrations as low as 0.016% reduced pupation and prevented adult eclosion of obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). At a rate of 0.0016%, NSO reduced the fitness of C. rosaceana, resulting in longer developmental times, lower adult eclosion rates, and reduced egg production compared with controls. The neem insecticide Margosan-O ^TM produced comparable results based on concentrations of the most biologically active constituent, azadirachtin. Pupation was completely inhibited at concentrations of 0.25% and 1.0% for larvae exposed at 5th or 6th instar, respectively; rates as low as 0.016% reduced pupal weights and adult eclosion rates. For larvae transferred to treated diet at 5th instar, physical abnormalities in the wings of adults occurred at a rate of 0.004% NSO and increased with increasing treatment rates. NSO at concentrations as high as 2.0% was not antifeedant to neonate larvae, based on 24 and 48 h choice test bioassays, when incorporated into a meridic diet.     

Effect of sequential deletion of extra N-terminal residues on the structure and stability of yeast iso-1-cytochrome-c

A sequence alignment of yeast cytochrome-c (y-cyt-c) with mammalian cyts-c shows that the yeast protein has a five residue long N-terminal extension. A question arises: Does this N-terminal extension play any roles in the stability, structure, and folding of the yeast protein? To answer this question, in silico and in vitro studies were carried out on the wild type (WT) protein and its five deletants (Δ(?5/?5), Δ(?5/?4), Δ(?5/?3), Δ(?5/?2), and Δ(?5/?1) where Δ denotes the deletion and the numbers refer to the residues deleted, e.g. Δ(?5/?1) denotes the deletion of residues numbered from ?5 to ?1 (TEFKA), while Δ(?5/?2) denotes the deletion of resides numbered from ?5 to ?2 (TEFK) and so on). The main conclusion of the in silico study is that the order of stability of deletants and WT protein is Δ(?5/?4) > WT > Δ(?5/?3) > Δ(?5/?5) > Δ(?5/?1) ~ Δ(?5/?2). In vitro studies involved (i) measurements of thermodynamic stability of all proteins by differential scanning calorimetry and from sigmoidal curves of two different structural properties ([θ]₂₂₂, a probe for detecting change in secondary structure, and Δε₄₀₅, a probe for detecting alteration in the heme environment), and (ii) characterization of all proteins by various spectral properties. The main conclusions of the in vitro studies are as follows: (i) The order of thermodynamic stability of all proteins is in excellent agreement with that predicted by in silico studies, and (ii) A sequential deletion of the N-terminal extension has no effects on protein structure and folding.     

Conformational studies on pyrimidine 5'-monophosphates and 3',5'-diphosphates. Effect of the phosphate groups on the backbone conformation of polynucleotides

In continuation of our studies on the effect of the base and the phosphate groups on the glycosyl and the sugar-phosphate backbone conformation, we have carried out semi-empirical potential energy calculations on the common 5′- and 3′5′-ribopyrimidine mono- and diphosphates by considering simultaneous rotations about the glycosyl (χ) and the C(4′)–C(5′) (ψ) bonds. This calculation provides an assessment of the nature and orientation of the base on the sugar–phosphate backbone conformation of nucleotides and polynucleotides. It is found that the attractive inetractions between the 5′-phosphate group and the base mutually stabilize the antiand the gauche-gauche (gg) conformations about χ and ψ, respectively, in 5′-ribopyrimidine nucleotides. The introduction of the 3′-phosphate group as in 3′,5′-ribopyrimidine diphosphates, still leaves the anti-gg as the most favored conformation with the important difference that the probability of occurrence of the anti, gauche-trans (gt) is how substantially increased. This is dependent to a large extent on the sugar conformation and to a lesser extent on the base. Uracil and thymine show a greater probability for the anti-gt than cytosine. The syn conformation is considerably less likely and its occurrence is also dependent on the base type, cytosine showing a lesser tendency than uracil and thymine. For the syn base, the most favourec conformation for ψ is gt, since gg is sterically disallowed and tg is destabilized by electrostatic repulsive interactions between the 3′ and 5′-phosphate groups. Thus, there is a striking correlation between the glycoysl and the backbone C(4′)–C(5′) bond conformations. The rest of the bonds of the backbone are considerable less dependent on the glycosyl conformation. These studies reveal that in poly-ribopyrimidine nucletides the majority of the nucleotide residues are expected to occur in the anti-gg conformation.     

Effect of ionic strength on the pKa of ligands bound to DNA

The pK_a of 3,8-diamino-6-phenyl-phenanthridine (DAPP), a nonquaternary analog of ethidium bromide, has been determined spectrophotometrically as a function of sodium ion concentration both free in solution and complexed to DNA. Unwinding angle determinations with this compound were determined with Col El DNA using ethidium bromide as a standard. The unwinding angle for DAPP was 24 ± 2° relative to 26° for ethidium, and this suggests that DAPP binds in a manner quite similar to ethidium and with no significant outside bound DAPP under these experimental conditions. Isobestic behavior was obtained on spectrophotometric pH titration above pH 5 as long as the ratio of DNA-phosphate to ligand was between 100 and 300 and the DNA phosphate concentration was approximately 0.01M or greater. The loss of isosbestic behavior which occurred below pH 5 is probably due to titration of the 8 amino group of the ligand complexed to DNA. To circumvent this problem, pK_a values and the extinction coefficient of the acidic species were both determined by a computer program using experimental data obtained above pH 5. The pK_a of the free compound has only a minor dependence on ionic strength, while the pK_a of the ligand bound to DNA in an intercalated complex depends strongly on the sodium ion concentration. The pK_a of the DAPP-DNA complex is a linear function of –log[Na⁺] as predicted by the ion-condensation theory of polyelectrolytes. It was determined that DAPP is essentially completely bound to DNA under the conditions of these experiments by (1) determination of apparent pK_a values as a function of total DNA concentration, (2) calculation of binding constants for the neutral species of DAPP, and (3) spectral analysis of the protonated and neutral species of DAPP bound to DNA relative to DAPP free in solution. These results support the ion-condensation theory; provide an independent method for measuring ψ*, the average number of counterions associated per phosphate of DNA in the intercalated conformation; and illustrate that there are no specific pH effects or absolute pK_a values for ligands bound to DNA, but only ionic-strength-dependent results.     

The Effect of Calcium and Magnesium on the Activity of Bovicin HC5 and Nisin

Some Gram-positive bacteria produce small peptides (bacteriocins) that have antimicrobial activity, but many bacteria can become bacteriocin resistant. Bovicin HC5, a lantibiotic produced by Streptococcus bovis HC5, has the ability to inhibit nisin-resistant bacteria. Because nisin resistance has in many cases been correlated with an alteration of lipoteichoic acids or the polar head groups of membrane phospholipids, we decided to examine the effect of divalent cations on nisin and bovicin HC5 activity. Both bacteriocins catalyzed potassium efflux from S. bovis JB1, a non–bacteriocin-producing strain. The addition of large amounts (100 mM) of calcium or magnesium increased the ability of S. bovis JB1 to bind Congo red (an anionic dye) and counteracted bacteriocin-mediated potassium loss. Calcium was more effective than magnesium in decreasing nisin activity, but the reverse was observed with bovicin HC5. Nisin-resistant S. bovis JB1 cells bound three times as much Congo red as nisin-sensitive cells, and this result is consistent with the idea that changes in cell surface charge can be a mechanism of bacteriocin resistance. The nisin-resistant cells were less susceptible to bovicin HC5, but bovicin HC5 still caused a 50% depletion of intracellular potassium. These results indicate that nisin and bovicin HC5 react differently with the cell surfaces of Gram-positive bacteria. Proprietary or names are necessary to report factually on available data; however, the United States Department of Agriculture (USDA) neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product, and exclusion of others that may be suitable.     

Effect of ortho-dihydroxyphenols on growth and protein pattern of callus cultures from Prunus avium

Excised shoot discs from Prunus avium L. were cultivated on a modified Murashige and Skoog medium for 4 weeks under long day conditions. The basal medium was supplemented with IAA and benzylaminopurine. Further addition of 5.7 × 10^?5 resp, 11.4 × 10^?5M catechin and 4.25 × 10^?5 resp. 8.5 × 10^?5M chlorogenic acid resulted in a highly significant promotion of callus proliferation. Proteins and enzymes were separated by isoelectric focusing. The supply of both polyphenols resulted in a higher number and intensity of protein bands including esterases as compared to controls.     

Effect of some Cardiac and Respiratory Drugs on Succinate-Cytochrome c Reductase

Succinate-cytochrome c reductase was inhibited in vitro and in vivo by phenobarbitone, aminophylline and neostigmine using both 2,6-dichlorophenolindophenol (DCIP) and cytochrome c (cyt c) as substrates. The enzyme was also activated by gallamine towards both substrates. In vitro, phenobarbitone and aminophylline inhibited the enzyme with respect to the reduction of DCIP and cyt c in a non-competitive manner with K_i values of 1.5 × 10^?5 and 5.7 × 10^?5 M, respectively. Moreover, neostigmine competitively inhibited the enzyme towards both substrates with K_i values of 1.36 × 10^?5 and 1.50 × 10^?5 M, respectively.     

Effect of trace elements and vitamins on the growth of Methanosarcina barkeri

Growth of Methanosarcina barkeri on methanol as energy source was found to be dependent on cobalt and molybdenum. In the presence of 10^?6 M Co and 5 × 10^?7M Mo optimal growth occurred. Furthermore it could be demonstrated that nickel and selenium each in a concentration of 10^?7 M stimulated the growth of this methanogenic bacterium while the following elements tested in the range of 10^?7 M to 10^?3 had no influence: B, Cr, Cu, Mn, Pb. The requirement of Co and Ni for optimal growth are in accordance with the results that the cells contain the Co containing corrinoid Factor III (0.1 – 0.2 mg 5-hydroxylbenzimidazolylcyanocobamide per g wet cells) and Factor F₄₃₀, a nickel component. Studies on the vitamin dependency of M. barkeri showed that this strain needs only the vitamin riboflavin for the growth in a defined medium. Under these conditions a cell density of 2.6 g dry cells/l could be obtained in a fed batch culture.     

Effect of Anabaena flos-aquae on the abilities of Daphnia and Keratella to feed and reproduce on unicellular algae

SUMMARY.

• 1 This study tests the hypothesis that the filamentous cyanobacterium, Anabaena flos-aquae, inhibits Daphnia's ability to feed and reproduce on unicellular algae more than it does Keratella's. Double-label radiotracer experiments using whole and sonieally disrupted Anabaena filaments showed that even low concentrations of Anabaena (5 × 10³ cells ml^?1) inhibited the abilities of Daphnia pulex and D. galeata mendotae to feed on Chlamydomonas and that this inhibition was due to both mechanical interference with feeding and increased food availability. A single-label radiotracer experiment showed that Anabaena (5 × 10³ and 2 × 10⁴ cells ml^?l) reduced the abilities of neonate, juvenile, and adult D. pulex to feed on Chlamydomonas but had a much more pronounced effect on adults.
• 2 Single-label radiotracer experiments using screened (25 μm mesh) and unscreened suspensions of whole Anabaena filaments showed that only very high concentrations of Anabaena (10⁵ cells ml^?1) reduced the ability of Keratella cochlearis to feed on Cryptomonas and that this inhibition probably was due to mechanical interference with feeding, since Keratella ate Anabaena extremely inefficiently - especially when single cells and short filaments were removed by screening.
• 3 Experiments comparing the survivorship and fecundity of individuals fed Anabaena, Chlamydomonas, or no food showed that the Anabaena was not toxic to either Keratella or D. galeata mendotae, was not utilized by Keratella, and was utilized by Daphnia, although not as well as Chlamydomonas was.
• 4 Anabaena (5 × 10³ or 10⁴ cells ml^?1) did not affect, or slightly increased, the population growth rate (r_m) of K. cochlearis on Cryptomonas, while it substantially increased that of D. pulex, Duphnia's ability to utilize Anabaena probably more than offset its reduced ability to feed on Cryptomonas. The presence of cyanobacterial filaments in natural plankton communities could adversely affect Daphnia and decrease its ability to competitively suppress Keratella and other rotifers if the filaments were of little nutritional value to the Daphnia, greatly interfered

     

Effect of Bacteria on Survival and Growth of Acanthamoeba castellanii

The growth and survival of Acanthamoeba castellanii in the presence of Gram-negative bacteria such as Pseudomonas aeruginosa, Escherichia coli, Serratia marcescens, and Stenotrophomonas maltophilia varied with the densities and species of bacteria. All species of bacteria suspended in a buffered saline at densities of 10⁵ to 10⁶/ml supported the growth and survival of 10⁶/ml trophozoites of Acanthamoeba castellanii in a buffered saline solution. At densities of bacteria to amoebae of 100:1 or greater, growth and survival of A. castellanii were suppressed, particularly by P. aeruginosa. In an enrichment medium, the rapid growth of most co-inoculated bacteria inhibited the growth and survival of the amoeba. Received: 12 September 1996 / Accepted: 20 September 1996     

Effect of DNA Local Conformation on the Affinity and Binding Specificity of bis-Netropsins to DNA

The interaction of short nucleotide duplexes with bis-netropsins, in which netropsin fragments are linked tail-to-tail via cis-diammineplatinum group (Nt–Pt(NH ₃ )–Nt) or aliphatic pentamethylene chain (Nt–(CH ₂ ) ₅ –Nt), has been studied. Both bis-netropsins have been shown to bind to DNA oligomer 5"-CCTATATCC-3" (I) as a hairpin with parallel orientation of netropsin fragments in 1:1 stoichiometry. Monodentate binding has been detected upon binding of bis-netropsins to other duplexes of sequences 5"-CCXCC-3" [where X = TTATT (II), TTAT (III), TTTTT (IV), and AATTT (V)] along with the binding of bis-netropsins as a hairpin. The formation of dimeric antiparallel motif between the halves of two bound bis-netropsin molecules has been observed in the complexes of Nt–(CH ₂ ) ₅ –Nt with DNA oligomers IV and V. The ratio of binding constant of bis-netropsin as a hairpin ( ₂) to monodentate binding constant ( ₁) has been shown to correlate with the width and/or conformational lability of DNA in the binding site. The share of bis-netropsin bound as a hairpin decreases in the order: TATAT > TTATT > TTAAT > TTTTT > AATTT, whereas the contribution of monodentate binding rises. The minimal strong binding site for Nt–Pt(NH ₃ )–Nt and Nt–(CH ₂ ) ₅ –Nt binding as a hairpin has been found to be DNA duplex 5"-CGTATACG-3".     

Effect of Foliar Application of Chitin and Chitosan Oligosaccharides on Photosynthesis of Maize and Soybean

On the first day after foliar application, chitosan pentamer (CH5) and chitin pentamer (CHIT5) decreased net photosynthetic rate (P _N) of soybean and maize, however, on subsequent days there was an increase in P _N in some treatments. CH5 caused an increase in maize P _N on day 3 at 10^–5 and 10^–7 M; the increases were 18 and 10 % over the control plants. This increase was correlated with increases in stomatal conductance (g _s) and transpiration rate (E), while the intercellular CO₂ concentration (C _i) was not different from the control plants. P _N of soybean plants did not differ from the control plants except for treatment CH5 (10^–7 M) which caused an 8 % increase on day 2, along with increased g _s, E, and C _i. On days 5 and 6 the CHIT5 treatment caused a 6–8 % increase in P _N of maize, which was accompanied by increases in g _s, E, and C _i. However, there was no such increase for soybean plants treated with CHIT5. In general, foliar application of high molecular mass chitin (CHH) resulted in decreased P _N, particularly for 0.010 % treated plants, both in maize and soybean. Foliar applications of chitosan and chitin oligomers did not affect (p > 0.05) maize or soybean height, root length, leaf area, shoot or root or total dry mass.     

Effect of the hydrophile-lipophile balance of non-ionic detergents (Triton X-series) on the solubilization of biological membranes and their integral b-type cytochromes

The solubilization of four integral membrane proteins (i.e. cytochrome b-561 of the chromaffin granule membrane, cytochrome b₅ of the endoplasmic reticulum and the mitochondrial b-type cytochrome(s) as well as cytochrome c oxidase) has been studied at 0 °C using the non-ionic detergents of the Triton X-series having the common hydrophobic 4(1,1,3,3-tetramethylbutyl)phenoxy (t-octyl-phenoxy) group and a variable average number ( ) of polar ethylene oxide units added. Following a pre-extraction of peripheral membrane and matrix proteins with low and high salt concentration and a weak non-ionic detergent (Tween 20, average hydrophile-lipophile balance ( ), the amount of heme proteins solubilized by subsequent Triton X-solutions was measured. With the detergents tested the degree of solubilization decreased in the sequence cytochrome b-561 >cytochrome b₅ >mitochondrial cytochrome(s) b and parallelled the effect of the detergents on light scattering and the phospholipid to protein ratio of the three membranes. For all the b-cytochromes, the solubilizing power of the detergent increased with decreasing average length of the polar ethylene oxide chain and the hydrophile-lipophile balance as long as clouding did not occur (e.g. Triton X-114, and ). Thus, the greatest difference in the degree of solubilization of the three cytochromes was observed with Triton X-405 ( and ). All the cytochromes were most efficiently solubilized (i.e. approx. 90%) by Triton X-100 ( and ).     

Effect of temperature on development, overwintering and establishment potential of Franklinothrips vespiformis in the UK

This study investigated the effect of temperature on the development and overwintering potential of the predatory thrips Franklinothrips vespiformis (Crawford) (Thysanoptera: Aeolothripidae), a biological control agent used against glasshouse pests in continental Europe and Israel. Developmental rates increased linearly with rearing temperatures. It was estimated that 304.9 degree days, above a lower threshold temperature of 11.9 °C, were required for F. vespiformis to complete development from egg to adult eclosion. The effect of low temperatures (–5, 0, and 5 °C) was examined on adult female and larval survival. Subsequent reproductive and developmental attributes of survivors were also investigated. Lethal time experiments indicated that larval stages are more cold tolerant than adult F. vespiformis females. Surviving larvae increased their developmental times to adults with decreasing temperature and increasing exposure periods and second instars were significantly more successful than first instars in reaching adulthood. Surviving adult females decreased their oviposition rate with decreasing temperature and increasing exposure periods, and exposures to low temperatures affected the number of viable eggs produced. The results are discussed in the context of overwintering and establishment potential of F. vespiformis in the UK in the event of introducing the predatory thrips as a biological control agent against glasshouse pests.     

Effect of Different Gibberellins on the Growth of the Hypocotyl

It has been stated earlier that hypocotyls of different plants show different growth response to added GA₃. It was suggested that this difference may be due to the requirement of some specific gibberellin. Hence hypocotyl growth response of three groups of plants has been studied with different gibberellins: group one showing no or insignificant growth response, group two showing 150–200 per cent growth response and group three showing 300–500 per cent growth response to added GA₃. Eight gibberellins were used, viz., GA₁, GA₂, GA₃, GA₄, GA₅, GA₇, GA₈ and GA₉, to test if this varying response is connected with the requirement of some specific gibberellin. In general, the results obtained do not favour this view. Iberis amara, a plant showing no response to added GA₃, Dianthus sp., a plant showing 150 to 200 per cent response and Lactuca satwa, Antirrhinum majus and Nicotiana tabacum, plants showing 300 to 500 per cent response, were promoted by all the gibberellins tested to a similar extent as by GA₃, with the exception of GA₈ which was inactive in most of the cases.     

Effect of mating frequency and brood cell infestation rate on the reproductive success of the honeybee parasite Varroa jacobsoni

Abstract.

• 1 The reproductve biology of Varroa jacobsoni, whose females infest honeybee brood, was studied in natural and transparent artificial brood cells. These investigations were made under the headings of maturation behaviour and fertilization, and the influence of infestation rate of brood cells on the number of mated females produced per infesting Varroa.
• 2 Mating of Varroa daughters, observed in the transparent brood cells with time-lapse video, occurs just after ecdysis and as soon as they arrive on the faecal accumulation prepared by the mother. Such females are remated for as long as no other freshly moulted daughter arrives on the faecal accumulation.
• 3 The number of spermatozoa stocked in the spermatheca increases with remating, a strong indication for sperm mixing in this species when brood cells contain more than one Varroa foundress.
• 4 The number of daughters per infesting mother decreases at higher rates of infestation per cell, but the proportion of such daughters with a mate rises sharply due to the higher probability of finding a male within multi-infested cells. The number of mated daughters per mother is maximal in cells with two foundress Varroa females.
• 5 The frequency distributions of infesting mites in drone cells are aggregated, and approximate to negative binomial distributions.
• 6 We postulate from the above that the observed non-random infestation by Varroa in drone brood augments the mite's mean reproductive success through the production of a higher number of mated daughters than the corresponding Poisson distributions would.