Effect of coliform and Proteus bacteria on growth of Staphylococcus aureus

Cultures of coliform and Proteus bacteria, mostly from foods, were tested for their effect on growth of Staphylococcus aureus in Trypticase Soy Broth. Inhibition of the staphylococcus by these competitors increased with increasing proportions of inhibiting (effector) bacteria in the inoculum and decreasing incubation temperatures (37 to 10 C). Time required for 2 × 10⁴ staphylococci to increase to 5 × 10⁶ cells per milliliter, the minimal number assumed to be necessary for food poisoning, varied with the species of effector, the original ratio of effector bacteria to staphylococci in the medium, and the incubation temperature. When the original ratio was 100:1, the staphylococci did not reach 5 × 10⁶ cells per milliliter at 10, 15, 22, or 30 C (with one exception), when growing with cultures representing six species of coliform bacteria and two of Proteus. When the ratio was 1:1, all effectors either greatly delayed the staphylococcus or prevented it from reaching hazardous numbers at 15 C, six of the eight caused a delay of 2 to 3 hr at 22 C, and only Escherichia coli delayed the coccus at 30 C. All effectors were ineffective at 22 and 30 C when original numbers of effectors and staphylococci were in the ratio 1:100. Greatest overall inhibition was by E. coli, E. freundii, and Proteus vulgaris, and these species were more effective than the others at 22 and 30 C. Aerobacter cloacae and Paracolobactrum aerogenoides were more effective at 15 C. In general, results were similar with different strains of a species. Except for Aerobacter aerogenes, Klebsiella sp., and P. aerogenoides, which apparently did not compete for nutrients, inhibition of the staphylococcus was by a combination of antibiotic substances and competition for nutrients.     

Fate of Staphylococci and Enteric Microorganisms Introduced into Slurry of Frozen Pot Pies

A slurry was prepared from six frozen pot pies diluted 1:5 with distilled water, two chicken, two turkey, and two beef pies of different brands. This slurry formed a reference sample and was placed in sterilized jars, frozen, and used as needed throughout the experiments. A second slurry was prepared in a similar manner from a frozen beef pot pie and a chicken pot pie, and was used as a control in only one experiment. The total count of microorganisms and the number of coliforms, Escherichia coli, salmonellae, and coagulase-positive staphylococci per gram were determined. Samples of slurry were inoculated in decimal dilutions with one or more of the following: Salmonella typhimurium, E. coli, and a strain of staphylococcus that causes food poisoning. The natural flora was found to exert an inhibitory effect upon the growth of the added microorganisms after incubation at 35 C for 18 hr. The inhibitory effect on growth was in part due to pH. The predominating organism isolated from the natural flora after incubation was a lactobacillus, which, when added in mixture with the test organisms in sterilized slurry, did not exert the profound inhibitory effect observed in the case of the natural flora. Some factors which may be concerned with the inhibition were investigated.     

Variations in leaf and root stoichiometry of Nitraria tangutorum along aridity gradients in the Hexi Corridor,northwest China

Nitrogen (N) and phosphorus (P) concentrations and N: P ratios between leaves and roots of Nitraria tangutorum along aridity gradients were studied. N. tangutorum was relatively limited by N in April (mean leaf N: P ratio = 11.13) and by P in August (mean leaf N: P ratio = 38.78). N and P in both leaves and roots were highly correlated across sampling sites. In April both leaf and root N and P concentrations increased along aridity gradients. Mean leaf N: P ratios changed slightly, but mean root N: P ratios increased with increasing aridity gradients. We suggest that leaf N: P ratios can indicate nutrient status at different plant growth stages, and root N: P ratios can signify if the amount of soil nutrients is insufficient.     

Rapid acquisition of preference in concurrent schedules: Effects of d-amphetamine on sensitivity to reinforcement amount

In the present study, effects of d-amphetamine on sensitivity to reinforcement amount under concurrent schedules were examined using a rapid-acquisition procedure. Four pigeons key pecked under single concurrent variable-interval 30-s schedules of grain presentation. Two different reinforcer-amount ratios (7:1 and 1:7) changed across sessions according to a 31-step pseudo-random binary sequence (PRBS). After at least four times through the PRBS, response ratios generally tracked the session-to-session changes in amount ratios; estimates of sensitivity ranged from 0.26 to 0.31 across the four pigeons. Effects of a range of doses of d-amphetamine (0.3-5.6 mg/kg) then were determined. For 3 of 4 pigeons, at least one dose, which did not dramatically alter overall response output or bias, decreased sensitivity to reinforcement amount. These results suggest that reducing sensitivity of responding to reinforcement amount may be one behavioral mechanism of stimulants, which may have implications for interpreting drug effects on self-control.     

Susceptibility of Agrobacterium tumefaciens Strains to Two Agrocin-Producing Agrobacterium Strains

Sixty-five strains and isolates of Agrobacterium tumefaciens representing each of the known biotypes, were tested for in vitro and in vivo susceptibility to the agrocin-producing strains Agrobacterium radiobacter 84 and A. tumefaciens D286. No biotype 3 strain was susceptible to the effects of either of the agrocinogenic strains in vitro. On datura and tobacco, the best inhibition of tumor formation was obtained when the agrocinogenic strains were applied to wounds 24 h before the pathogens and by the concomitant application of agrocin producer and pathogen at cell ratios of 10:1 or 3:1; inhibition of infection tended to decrease progressively as the cell ratio decreased from 10:1 to 3:1 to 1:1. Generally, strain 84 was superior to D286 in inhibiting tumor formation. A combined cell suspension of 84 and D286 was as effective as 84 alone. The overall pattern of inhibition of tumor formation by biotype 1 and 2 pathogens resistant to the agrocinogenic strains in vitro was similar to that obtained with strains that were susceptible in vitro.     

西瓜藤提取物的抑菌作用研究

采用琼脂稀释法研究西瓜藤提取物的体外抑菌作用,用小鼠腹腔注射金黄色葡萄球菌法研究80%醇提物的体内抑菌作用。结果表明:西瓜藤提取物对金黄色葡萄球菌、大肠埃希氏菌、铜绿假单胞菌、伤寒沙门氏菌、枯草芽孢杆菌和肺炎克雷伯氏菌均有不同程度的抑制作用,但对链球菌作用不明显。其中80%醇提取物和乙酸乙酯萃取物抑制金黄色葡萄球菌活性最好,其最低抑菌浓度(MIC)分别为4.2、8.4mg.mL-1。体内实验也表明,乙醇提取物具有较好的抑菌作用。西瓜藤提取物具有抑菌活性,在抑菌方面有一定开发前景。     

Glutathione turnover in human cell lines in the presence of agents with glutathione influencing potential with and without acivicin inhibition of γ-glutamyltranspeptidase

Background: We have previously shown that there were great discrepancies between different agents regarding their glutathione stimulating potential and that agents with mainly oxidative effects did not increase concentrations of glutathione in human cell cultures, in contrast to other thiol reactive agents. In order to evaluate whether increased glutathione degradation might be one reason for these discrepancies, we have investigated the effect of different agents with potential influence on glutathione metabolism in human cell cultures with or without acivicin inhibition of γ-glutamyltranspeptidase (GT), since GT is responsible for the initial degradation of glutathione. Methods: Intra- and extracellular concentrations of glutathione were investigated in HeLa and hepatoma cell cultures, with and without acivicin inhibition of GT, in the presence of oxidative and electrophilic agents (copper ions, hydrogen peroxide and N-ethylmaleimide), hydroquinone, reducing agents (lipoic acid and N-acetylcysteine), and a thiol reactive metal (mercury ions). Results: There were great discrepancies between the different agents regarding their maximal glutathione response (the sum of the intracellular and the extracellular amount of glutathione) in cell cultures. There was only a small increase in total glutathione in the presence of hydrogen peroxide or N-ethylmaleimide before the cell protein decreased compared to findings with mercury ions, lipoic acid or hydroquinone. In both HeLa and hepatoma cell cultures, there were correlations between the original glutathione amount and the total glutathione amount observed after acivicin inhibition. Conclusion: The relatively small increase of glutathione amount in the presence of oxidative and electrophilic agents compared to other thiol reactive agents is not due to increased GT degradation of glutathione.     

Dietary protein:carbohydrate balance is a critical modulator of lifespan and reproduction in Drosophila melanogaster: A test using a chemically defined diet

Macronutrient balance is an important determinant of fitness in many animals, including insects. Previous studies have shown that altering the concentrations of yeast and sugar in the semi-synthetic media has a profound impact on lifespan in Drosophila melanogaster, suggesting that dietary protein:carbohydrate (P:C) balance is the main driver of lifespan and ageing processes. However, since yeast is rich in multiple nutrients other than proteins, this lifespan-determining role of dietary P:C balance needs to be further substantiated through trials using a chemically-defined, synthetic diet. In the present study, the effects of dietary P:C balance on lifespan and fecundity were investigated in female D. melanogaster flies fed on one of eight isocaloric synthetic diets differing in P:C ratio (0:1, 1:16, 1:8, 1:4, 1:2, 1:1, 2:1 or 4:1). Lifespan and dietary P:C ratio were related in a convex manner, with lifespan increasing to a peak at the two intermediate P:C ratios (1:2 and 1:4) and falling at the imbalanced ratios (0:1 and 4:1). Ingesting nutritionally imbalanced diets not only caused an earlier onset of senescence but also accelerated the age-dependent increase in mortality. Egg production was suppressed when flies were fed on a protein-deficient food (0:1), but increased with increasing dietary P:C ratio. Long-lived flies at the intermediate P:C ratios (1:2 and 1:4) stored a greater amount of lipids than those short-lived ones at the two imbalanced ratios (0:1 and 4:1). These findings provide a strong support to the notion that adequate dietary P:C balance is crucial for extending lifespan in D. melanogaster and offer new insights into how dietary P:C balance affects lifespan and ageing through its impacts on body composition.     

Effects of male-female rations on mating and egg production in Octomyomermis muspratti (Mermithidae: Nematoda)

Octomyomermis muspratti, a mermithid parasite of mosquito larvae, molted to the adult stage in 4–16 days. When male-female ratios were relatively high (1:2), mating and oviposition began soon after maturation, and oviposition was completed in 21–40 days. The number of females developing eggs increased with a corresponding increase in the male-female ratio. About 60% of the females completed oviposition at male-female ratios of 1:20, and about 100% completed oviposition as the male-female ratios were increased to 1:2. No egg development was observed in the absence of males. Male O. muspratti were capable of mating with a number of females and remained reproductively active for at least 50 days after a maturation at 26–28°C.     

Tannins as gibberellin antagonists

Fourteen chemically defined hydrolyzable tannins and six impure mixtures of either condensed or hydrolyzable tannins were found to inhibit the gibberellin-induced growth of light-grown dwarf pea seedlings. The highest ratio of tannins to gibberellic acid tested (1000: 1 by weight) inhibited from 80 to 95% of the induced growth for all tannins tested except for two monogalloyl glucose tannins which inhibited only 50% of the induced growth. The lowest ratio tested (10: 1) inhibited the induced growth by less than 25% except for the case of terchebin where 50% inhibition was found. The inhibition of gibberellin-induced growth was found to be completely reversed by increasing the amount of gibberellin in three cases tested. Tannins alone did not inhibit endogenous growth of either dwarf or nondwarf pea seedlings. Eight compounds related to tannins, including coumarin, trans-cinnamic acid, and a number of phenolic compounds were also tested as gibberellin antagonists. Most of these compounds showed some inhibition of gibberellin-induced growth, but less than that of the tannins. At the highest ratio (1000: 1) the greatest inhibition was 55%; at the lowest ratio (10: 1) no more than 17% was observed. These compounds did not inhibit endogenous growth, and the inhibition of gibberellin-induced growth could be reversed by increasing the amount of gibberellin in two cases tested.     

Streptomycin induced changes in growth and metabolism of etiolated seedlings

Effects of various concentrations of streptomycin sulphate either alone or in combination with different cations and hormones on mungbean (Phaseolus aureus L.) seedling growth were studied. The relative inhibition of root growth was stronger than that of hypocotyl growth. Root growth inhibition was completely overcome by calcium, while other cations were ineffective. Inhibition of hypocotyl elongation could not be prevented by cations. IAA and GA₃ were capable of relieving streptomycin inhibition but kinetin was ineffective. In the coleoptiles of streptomycin-treated rice (Oryza sativa L.) seedlings, there were accumulation of nucleic acids and decline in protein content resulting in increased RNA/protein and DNA/protein ratios. High nucleic acid content induced by streptomycin could be correlated with reduced activity of the nucleases.     

Improvement of protein bait produced from beer yeast waste for controlling Bactrocera dorsalis (Diptera: Tephritidae) in China

In the present study, preservatives and antibiotics were applied in a variety of doses to assess their effects on the beer waste-based protein bait, a product widely used to control populations of Bactrocera dorsalis (Diptera: Tephritidae). Screening was performed using the inhibition zone method against the dominant bacteria in deteriorated protein bait. Additionally, the attractiveness of the bait was assessed after respectively adding different doses of methyl eugenol, brown sugar solution, ammonium acetate, and guava essence, as determined by bio-cage tests. The results showed that the four selected preservatives had different inhibition effects at different dose levels, and that the level of inhibition increased with dose: at the highest dose of 1:1 (v:v), sodium benzoate can significantly inhibit Staphylococcus spp., potassium sorbate can significantly inhibit Lactobacillus spp., sodium nitrite can significantly inhibit Escherichia spp. and ethyl p-hydroxybenzoate can significantly inhibit Staphylococcus spp. and Xanthomonas spp. Among three antibiotics, kanamycin was the most effective in suppressing a mix of all four bacteria for all tested doses. In terms of lure performance, the addition of four substances in various ratios into the protein bait were found to have varying effects on its attractiveness to B. dorsalis females and males. Specifically, the addition of a high-dose of guava essence could significantly enhance the attractiveness of the bait. Our findings will help to enhance the effectiveness of protein bait applications by prolonging the quality guarantee period and improving its attractiveness toward both female and male B. dorsalis.     

Monoclonal antibodies as reversible equilibrium carriers of radiopharmaceuticals

We have prepared monoclonal antibodies (MoAbs) with the specific ability to bind metal chelates such as ¹¹¹In benzyl EDTA. One, 10, 50 and 100 μg MoAb CHA255 K_b = 4 × 10E9 was complexed with ¹¹¹In BLEDTA II, BLEDTA IV, and benzyl EDTA and injected i.v. in Balb/c mice with KHJJ tumor. The biological half-life by whole body counting was profoundly altered for all three compounds; from minutes to hours with 10 μg; to days with 100 μg. Tumor uptake increased 50 fold at 24 h with increasing MoAb but satisfactory tumor concentrations (3% per g) and tumor/blood ratios (1.8:1) were obtained with an amount equivalent to 7 mg for a human. Blood level and whole body activity were decreased 30–50% within 3 h or i.v. injection of a “flushing” dose of unlabeled indium benzyl EDTA, increasing tumor/blood ratios to 50:1.     

我院医务人员手部葡萄球菌携带调查及增多原因分析

目的调查我院医务人员手部葡萄球菌携带情况,查明其增多原因。方法将医务人员手部携带的部分金黄色葡萄球菌、凝固酶阴性葡萄球菌做了“８４”消毒剂定性杀菌试验、ＭＩＣ检测、β－内酰胺酶、耐甲氧西林检测,抗菌药物耐药谱、质粒酶切谱分型。结果发现我院医务人员手部金黄葡萄球菌、葡萄球菌携带率已分别从１９９２年的８７０％（１０／１１５）、３２１７％（３７／１１５）上升至１９９７年的３４０６％（７８／２２９）、６５９４％（１５１／２２９）,且７７９７％的菌株为ＭＲＳＡ（或ＭＲＣＮＳ）,各科室之间无同源菌株。全部试验菌株在“８４”消毒剂有效氯的含量为１００ｐｐｍ浓度时,１分钟内可将其全部杀灭。结论我院医务人员手部葡萄球菌及金黄色葡萄球菌逐年上升的因素为：①长时间使用“８４”消毒剂,导致了部分菌株对“８４”消毒剂敏感性降低;②医务人员不常洗手;③采用“８４”消毒剂洗手致手部粗糙,难以洗净。     

Microbial profiles, in vitro gas production and dry matter digestibility based on various ratios of roughage to concentrate

The study assessed the effects of different roughage to concentrate ratios on enteric methane production, rumen fermentation and microbial counts. These ratios were 80:20, 50:50, and 20:80 for diets 1, 2, and 3, respectively. No significant differences were observed in total gas production among diets; however, methane emissions increased (P?<?0.05) with increased roughage in diet. The pH was greater (P?<?0.05) in diet 1 compared to diets 2 and 3 (6.38 vs 6.17 and 6.07). In vitro dry matter digestibility increased with decreased roughage ratios (47.67, 61.67, 67.33 % for diets 1, 2 and 3, respectively). Similarly, total volatile fatty acids (mM/100 mL) also increased with decreased roughage ratios [diet 1 (5.38); diet 2 (6.30); diet 3 (7.37)]. Methanogen counts, total bacterial counts and protozoal counts were lower (P?<?0.05) in diet 3 compared to diet 1 and 2. However, total fungal counts were higher in diet 1 compared to diet 2 and 3. The results indicate that methane emission, enteric fermentation patterns, and change in methanogens population appear only with higher level of roughage. These findings are important for reducing methane without any impact on rumen performance.     

The relationship between absorption of sulfur dioxide (SO2) and inhibition of photosynthesis in several plants

Photosynthetic rate, transpiration rate and SO₂ absorption rate were simultaneously measured under exposure to SO₂ (0.1–1.0 μl l ^?1) for 5 or 8 hr in six species belonging to C₄ or C₃ plants (Zea mays, Sorghum vulgare, Amaranthus tricolor, Oryza sativa, Avena sativa andHelianthus annuus). Distinct interspecific differences were found as to the extent of inhibition of photosynthetic rate. Calculation of diffusive resistance to H₂O(r) and SO₂(r′) showed that the ratio of r′/r was 1.9 irrespective of species and coincided well with the theoretical value based on molecular diffusion. Thus it was made clear that the absorption of SO₂ was dependent upon the gas exchange capacity of leaf blade. Using the ratio of r′/r the rate of SO₂ absorption could be calculated from transpiration rate and was compared with the inhibition rate of photosynthesis. In three C₄ species, the inhibition of photosynthesis increased linearly with the amount of SO₂ absorbed during a 5-hour period. The pattern of inhibition of photosynthesis inA. sativa andH. annuus among C₃ species was similar to that of C₄ species until the amount of SO₂ absorbed reached 60 mg-SO₂ m^?2 above which the inhibition abruptly increased. The inhibition of photosynthesis inO. sativa was exceptionally severe even with only a small amount of SO₂ absorbed.     

The effect of dietary restriction on longevity,fecundity, and antioxidant responses in the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

Recent studies in fruit flies have imposed dietary restriction (DR) by diluting yeast and have reported increased lifespan as the yeast-to-sugar ratio decreased. In this study, the effects of DR on the lifespan of Bactrocera dorsalis were investigated using constant-feeding diets with different yeast:sugar ratios and an intermittent-feeding diet in which flies ate every sixth day. Antioxidant enzyme activities and the malondialdehyde concentration were also measured in virgin females under constant-feeding DR protocols to investigate their relationships with lifespan. The results showed that B. dorsalis lifespan was significantly extended by DR, and carbohydrate-enriched diet may be important for lifespan-extension. Female flies lived significantly longer than males at all dietary levels under both feeding regimes, indicating no interaction between diet and sex in determining lifespan. Antioxidant enzyme activities increased with the amount of yeast increased in the diets (0–4.76%) between starvation and DR treatments, indicating that the antioxidants may have influences in determining lifespan in B. dorsalis under starvation and DR treatments. However, antioxidants cannot keep up with increased oxidative damage induced by the high yeast diet (25%). These results revealed that the extension of lifespan by DR is evolutionarily conserved in B. dorsalis and that yeast:sugar ratios significantly modulate lifespan in this species.     

Effect of N:K supply ratios on the performance of three grass species from herbaceous wetlands

Shifts from N limitation to P or K limitation in wetlands (e.g. due to mowing and high atmospheric N deposition) are reflected by increased N:P and N:K ratios of plant biomass and changes in species composition. So far, the implications of increased N:K ratios for wetland vegetation have hardly been investigated. We examined how the supply of N and K influences the growth of three wetland grass species (Holcus lanatus, Anthoxanthum odoratum, Deschampsia caespitosa) to determine at what N:K ratios growth is likely to be K limited, how N:K ratios influence biomass allocation and nutrient uptake, and whether the responses to high N:K ratios vary among species. Plants were grown in sand at six N:K supply ratios ranging from 0.17 to 40.5 and combined with two levels of fertility in a factorial design. In 15 weeks of growth, plant biomass increased with increasing N:K supply ratios, indicating that growth was mostly limited by N and not by K across the entire range of N:K ratios. However, there were indications of K deficiency at the highest N:K supply ratio, such as increased leaf mortality and strong reduction of K concentrations during leaf senescence. The response of total plant biomass to nutrient treatments did not differ among the three species. However, other plant traits, such as biomass allocation to roots, leaf senescence and N concentrations, suggested that D. caespitosa is better adapted to extremely low K availability than the other two species.The short-term responses of the three wetland grass species to N and K supply were similar to those found in previous experiments testing different N:P supply ratios. In both cases, growth depended mainly on N supply, despite high N:K or N:P supply ratios and very low K or P concentrations in plant biomass. In those previous experiments, P supply became more important in the second year. There are indications that the same could also be true for K in a longer-term experiment. Hence, the so-called ‘critical’ values for N:K ratios of plant biomass in the field might be lower than indicated by our short-term experiment.     

Effects of nitrogen on growth and carbohydrate formation in Porphyridium cruentum

The microalga Porphyridium cruentum (Rhodophyta) has several industrial and pharmaceutical uses, especially for its polysaccharide production. This study aimed to investigate the influence of nitrogen levels as reflected by altered N:P ratios on the production and content of biomass and carbohydrate. N:P molar ratios were altered in batch cultures to range from 1.6 to 50 using the Redfield ratio of 1:16 as reference. Algal growth (estimated as final cell number, biomass concentration and maximum specific growth rate) was negatively affected at low N:P ratios. The optimal N:P ratio for growth was identified at 35–50, with specific growth rates of 0.19 day^?1 and maximum cell concentrations of 59·10⁸ cells L^?1 and 1.2 g dry weight of biomass L^?1. In addition, variation in cell size was seen. Cells with larger diameters were at higher N:P ratios and smaller cells at lower ratios. The cellular carbohydrate content increased under reduced nitrogen availability. However, because accumulation was moderate at the lowest N:P ratio, 0.4 g per g dry weight biomass compared to 0.24 at the Redfield ratio of 16:1, conditions for increased total carbohydrate formation were identified at the N:P ratios optimal for growth. Additionally, carbohydrates were largely accumulated in late exponential to stationary phase.     

响应面法优化波赛链霉菌JMC 06001发酵培养基

采用响应面法对产生抑菌活性物质的波赛链霉菌（Streptomyces peucetius）菌株JMC 06001的发酵培养基进行优化。首先采用Minnimum Run Equireplicated Res IV设计对初始发酵培养基的8个营养因素进行筛选,获得影响产生抑菌活性物质的3个主要影响因素：葡萄糖、大豆粉和NaCI;然后用最陡爬坡实验快速逼近最大响应区域;最后,结合Box-Behnken设计及响应面分析,确定主要影响因素的最佳浓度,得出该菌株产抑菌活性物质的最优发酵培养基配方为：葡萄糖1．2％,麦芽糖0．7％,蛋白胨0．9％,大豆粉1．4％,NaCl3．7％,CaCO3 0．1％,复合盐A液2．0％,复合盐B液0．1％,起始pH值7．0。用优化后的培养基发酵所得发酵液对敏感指示菌藤黄八叠球菌的抑菌圈直径达31．5mm,与预测值的相对偏差仅为1．59％,与用初始发酵培养基发酵所得发酵液的抑菌效果（抑菌圈直径26．5mm）相比提高了18．9％。