Skin Commensal Staphylococci May Act as Reservoir for Fusidic Acid Resistance Genes

We analyzed the occurrence and mechanisms of fusidic acid resistance present in staphylococci isolated from 59 healthy volunteers. The fingers of the volunteers were screened for the presence of staphylococci, and the collected isolates were tested for resistance to fusidic acid. A total of 34 fusidic acid resistant staphylococcal strains (all were coagulase-negative) were isolated from 22 individuals (22/59, 37.3%). Examination of the resistance genes revealed that acquired fusB or fusC was present in Staphylococcus epidermidis, Staphylococcus capitis subsp. urealyticus, Staphylococcus hominis subsp. hominis, Staphylococcus warneri and Staphylococcus haemolyticus. Resistance islands (RIs) carrying fusB were found in S. epidermidis and S. capitis subsp. urealyticus, while staphylococcal chromosome cassette (SCC)-related structures harboring fusC were found in S. hominis subsp. hominis. Genotypic analysis of S. epidermidis and S. hominis subsp. hominis indicated that the fus elements were disseminated in diverse genetic strain backgrounds. The fusC elements in S. hominis subsp. hominis strains were highly homologous to SCCfusC in the epidemic sequence type (ST) 239/SCCmecIII methicillin-resistant S. aureus (MRSA) or the pseudo SCCmec in ST779 MRSA. The presence of acquired fusidic acid resistance genes and their genetic environment in commensal staphylococci suggested that the skin commensal staphylococci may act as reservoir for fusidic acid resistance genes.     

Evolutionary Changes in the Content of Dehydrogenase System Metabolites as a Mechanism of Adaptation to Cold in Higher Vertebrates

It has been found that the optimal body balance control under the conditions of the adaptation to cold is mostly determined by the ratio of the blood concentrations of endogenous ethanol and acetaldehyde related to the activities of liver alcohol dehydrogenase and aldehyde dehydrogenase in the order of increasing level of adaptation: higher vertebrates unadapted to cold, including human → small animals adapted to cold → large animals adapted to cold native to the North → hibernators, regardless of the species specificity and the environment.     

Copepods as environmental indicator in lakes: special focus on changes in the proportion of calanoids along nutrient and pH gradients

Copepods are important contributors to the zooplankton community in lakes. Being “sandwiched” between predators and resources, they are sensitive to changes in the environment. It has been proposed that the proportion of calanoids of total copepod abundance or biomass could be a valuable indicator of eutrophication. We investigated relationships between environmental factors and the abundance, biomass and size of calanoid and cyclopoid copepods as well as their proportions in summer in 68 Danish freshwater lakes (587 lake years) with contrasting nutrient levels and pH. When lake pH was?<?6.0, mean lake depth and trophic state were the most important factors and calanoids completely dominated the copepod community. In shallow lakes with a mean depth?<?2.5 m and with pH?>?6.0, the proportion of calanoids in terms of biomass decreased substantially with increasing phosphorus and chlorophyll a concentrations but stayed around 50% at?>?2.5 m depth irrespective of nutrient level. Time series of the lakes, recovering from eutrophication, confirmed this multi-lake pattern although the trajectory varied from lake to lake. We conclude that the proportion of calanoids in terms of biomass might be a valuable indicator of trophic state in shallow but not deep lakes and only when pH?>?6.

     

Seed Dispersal as a Maternally Influenced Character: Mechanistic Basis of Maternal Effects and Selection on Maternal Characters in an Annual Plant

Maternal influences on progeny characters affect phenotypic correlations between characters expressed in maternal and progeny generations and consequently influence evolutionary responses to selection. Net selection on maternally influenced characters depends on selection both on the progeny character and on the maternal characters that influence it. I used seed dispersal in Cakile edentula as a system in which to identify the mechanisms of environmentally mediated maternal effects and to determine how selection on maternal characters alters the adaptive value of dispersal. In C. edentula, maternal morphology responds to conspecific density experienced by the mother. Maternal morphology in turn affects offspring (seed) dispersal and density and thereby offspring morphology and fitness. I estimated the magnitude of density-mediated maternal effects on dispersal and identified their mechanism by characterizing the plasticity of maternal morphology to density. I also measured density-dependent selection on maternal characters that influence dispersal. Maternal plasticity to density was caused by both allometric and nonallometric variation in morphology, and this plasticity resulted in a negative correlation between maternal and progeny density. Such negative maternal effects are expected to retard responses to selection. Maternal morphology influenced maternal fitness, in part through the relationship of fitness to maternal plant size and in part through size-independent fitness effects. Maternal phenotypes that promote dispersal, and thereby increase progeny fitness, were associated with decreased maternal fitness. Selection on dispersal at the level of progeny favors increased dispersal; maternal influences on dispersal, however, not only cause a greatly reduced adaptive value of dispersal but lead to the prediction of a slower response to selection.     

Effects of Temperature, pH, and Organic Phosphates on Fish Hemoglobins

This review presents data on effects of temperature, pH, and organic phosphates on structural-functional characteristics of fish hemoglobins. Special attention is paid to the structure of pigments insensitive to pH as well as those that have the reverse Bohr effect in alkaline range of pH. The role of surface -adrenoreceptors and activity of Na⁺/H⁺ exchanger in regulation of the acid-base equilibrium of intraerythrocyte medium are considered. There are compared characteristics of participation of nucleotide triphosphates, 2,3-DPG, and other organic phosphates in correction of fish hemoglobin affinity to oxygen. The values of H for fish respiratory pigments are presented, and their dependence on conditions of erythrocyte microsurrounding is discussed.     

黑玛丽精子包特性及pH和温度对其精子活力的影响

通过研究黑玛丽Poecilia latipinna精子包破裂的过程和影响因素、精子运动的情况及影响因素,结果发现,当精液用Hank’s平衡盐溶液(HBSS)稀释约5 min后精子包开始破裂,约12 min后全部破裂。释放出的精子暂时处于休眠状态,约50 min后,处于HBSS稀释液中的精子会被激活。应用计算机辅助精子分析系统对黑玛丽精子在不同pH和不同温度下HBSS中的精子运动百分数、运动时间和平均运动速率进行观察。在pH7~8的中性或弱碱性溶液中,精子运动活力较强;而在酸性(pH<7)或碱性较强(pH>9)的溶液中,精子的运动活力都会降低。在不同温度下的HBSS中精子的活力不同,精子在低温(4℃)条件下的运动时间显著长于在室温(20℃)条件下,但运动速度较慢。本研究初步探讨了黑玛丽的精子包特性以及pH和温度对精子运动活力的影响,旨在对黑玛丽等卵胎生鱼类的人工授精,以及生殖生物学特性等的研究提供更丰富的基础资料。     

Effects of pH Changes on Ion and 2,4-D Uptake of Wheat Roots

The quantitative relationships between pH-dependent ion and 2,4-D uptake in winter wheat seedlings (Triticum aestivum L. cv. Yubileynaya 50) have been investigated. The movement of various ions (potassium, phosphate, nitrate and ammonium) and 2,4-D across the root membranes was monitored with radioactive and stable isotope tracer methods. It was found that the H₊ ion concentration of the absorption solution strongly influences the 2,4-D uptake of the roots. Simultaneously, the 2,4-D uptake stimulates secretion of H⁺ into the absorption solution, that is, a H⁺ efflux can accompany the uptake of 2,4-D. This finding is consistent with the acid secretion theory of auxin and fusicoccin action. At pH 4 the 2,4-D uptake was much higher than at pH 6, thereby inhibiting the ion uptake and increasing the phytotoxicity in the plant. The results indicate that 2,4-D enters the root cells rapidly at the lower pH, mostly as undissociated molecules. With reference to the 2,4-D concentration in the roots at pH 4, a possible transport mechanism of the auxin herbicide is briefly discussed.     

Variability of Temperature, pH, and Moisture in an Aerobic Composting Process

This study measured the environmental variability which exists in a commercial aerobic composting process. The specific process studied is carried out in six decomposition cells which present six different phases of the process. Temperature, pH, and moisture content were determined in several randomly chosen sample sites in each cell, both at the beginning and at the end of the time the material was left in the cell. Temperature and pH varied greatly from one sample site to another in each cell, whereas moisture content was less varied. A significant rise in both temperature and pH was observed at two stages of degradation.     

Effects of Light, Temperature, and pH Value on Aflatoxin Production In Vitro

In the complete absence of light, an isolate of Aspergillus flavus produced up to 170,000 pg aflatoxin per g, whereas the incubation of the fungus in light caused a reduction (35,000 pg/g) of the toxin synthesis.     

Effects of Temperature and pH on Survival of Free Nuclear Polyhedrosis Virus of Autographa californica

The effects of temperature and low pH on replication and survival of nonoccluded Autographa californica nuclear polyhedrosis virus were investigated. No virus replication or formation of polynuclear inclusion bodies occurred at 37°C. The virus was immediately inactivated upon exposure to pH 2.0 and was inactivated within 1 h at pH 4.0. The virus titer slowly declined, a 3-orders of magnitude reduction in virus titer, at pH 5.0 during a 4-h exposure. Virus survival at pH 6.0 was equal to that of the control in cell culture medium 199 MK (pH 7.12).     

Operating Mechanism and Molecular Dynamics of Pheromone-Binding Protein ASP1 as Influenced by pH

Odorant binding protein (OBP) is a vital component of the olfactory sensation system. It performs the specific role of ferrying odorant molecules to odorant receptors. OBP helps insects and types of animal to sense and transport stimuli molecules. However, the molecular details about how OBPs bind or release its odorant ligands are unclear. For some OBPs, the systems'' pH level is reported to impact on the ligands'' binding or unbinding capability. In this work we investigated the operating mechanism and molecular dynamics in bee antennal pheromone-binding protein ASP1 under varying pH conditions. We found that conformational flexibility is the key factor for regulating the interaction of ASP1 and its ligands, and the odorant binds to ASP1 at low pH conditions. Dynamics, once triggered by pH changes, play the key roles in coupling the global conformational changes with the odorant release. In ASP1, the C-terminus, the N-terminus, helix α2 and the region ranging from helices α4 to α5 form a cavity with a novel ‘entrance’ of binding. These are the major regions that respond to pH change and regulate the ligand release. Clearly there are processes of dynamics and hydrogen bond network propagation in ASP1 in response to pH stimuli. These findings lead to an understanding of the mechanism and dynamics of odorant-OBP interaction in OBP, and will benefit chemsensory-related biotech and agriculture research and development.     

Evolution of Stability in a Cold-Active Enzyme Elicits Specificity Relaxation and Highlights Substrate-Related Effects on Temperature Adaptation

Molecular aspects of thermal adaptation of proteins were studied by following the co-evolution of temperature dependence, conformational stability, and substrate specificity in a cold-active lipase modified via directed evolution. We found that the evolution of kinetic stability was accompanied by a relaxation in substrate specificity. Moreover, temperature dependence and selectivity turned out to be mutually dependent. While the wild-type protein was strictly specific for short-chain triglycerides (C4) in the temperature range 10-50 °C and displayed highest activity in the cold, its stabilized variant was able to accept C8 and C12 molecules and its selectivity was temperature dependent. We could not detect any improvement in the overall structural robustness of the mutant when the structure was challenged by temperature or chemical denaturants. There is, however, strong evidence for local stabilization effects in the active-site region provided by two independent approaches. Differential scanning fluorimetry revealed that the exposure of hydrophobic patches (as the active site is) precedes denaturation, and molecular dynamics simulations confirmed that stability was obtained by restriction of the mobility of the lid, a flexible structure that regulates the access to the enzyme active site and influences its stability. This reduction of lid movements is suggested to be accompanied by a concomitant increase in the mobility of other protein regions, thus accounting for the observed broadening of substrate specificity.     

Effects of Temperature and pH on Reduction of Bacteria in a Point-of-Use Drinking Water Treatment Product for Emergency Relief

The effects of temperature and pH on the water treatment performance of a point-of-use (POU) coagulant/disinfectant product were evaluated. Cold temperatures (∼5°C) reduced the bactericidal efficiency of the product with regard to Escherichia coli and total coliform log₁₀ reductions.     

Effects of Temperature, pH, and NaCl on Growth and Pectinolytic Activity of Pseudomonas marginalis

The interaction of temperature (4, 10, 18, and 30°C), pH (6, 7, and 8), and NaCl (0, 2.5, and 5%) and their effects on specific growth rate, lag phase, and pectinolytic enzymes of Pseudomonas marginalis were evaluated. Response surface methodology was adapted to describe the response of growth parameters to environmental changes. To obtain good conditions of storage, the combined action of salt and temperature is necessary. At 4°C with an NaCl concentration of 5% and a pH of 7, the lag time was 8 days and no growth was observed at 4°C with 5% NaCl and a pH of 6. In the absence of salt, P. marginalis could grow regardless of temperature and pH. Pectate lyase and pectin lyase were produced by P. marginalis, while pectin methyl esterase activity was not observed in our culture conditions. The enzyme production depended on temperature, pH, and salt concentration but also on the age of the culture. Pectinolytic enzymes were abundantly excreted during the stationary phase, and even at 4°C, after 2 weeks of storage, enzyme activities in supernatant culture were sufficient to damage vegetables. Both bacterial growth and enzymatic production have to be taken into account in order to estimate correctly the shelf life of vegetables.     

Pupil Size Changes as an Active Information Channel for Biofeedback Applications

Pupil size is usually regarded as a passive information channel that provides insight into cognitive and affective states but defies any further control. However, in a recent study (Ehlers et al. 2015) we demonstrate that sympathetic activity indexed by pupil dynamics allows strategic interference by means of simple cognitive techniques. Utilizing positive/negative imaginings, subjects were able to expand pupil diameter beyond baseline variations; albeit with varying degrees of success and only over brief periods. The current study provides a comprehensive replication on the basis of considerable changes to the experimental set-up. Results show that stricter methodological conditions (controlled baseline settings and specified user instructions) strengthen the reported effect, whereas overall performance increases by one standard deviation. Effects are thereby not restricted to pupillary level. Parallel recordings of skin conductance changes prove a general enhancement of induced autonomic arousal. Considering the stability of the results across studies, we conclude that pupil size information exceeds affective monitoring and may constitute an active input channel in human–computer interaction. Furthermore, since variations in pupil diameter reliably display self-induced changes in sympathetic arousal, the relevance of this parameter is strongly indicated for future approaches in clinical biofeedback.     

盐分胁迫对大叶藻某些胞内酶耐盐性及其生理功能的影响

分别以3个盐度（100％、150％和200％人工海水）处理大叶藻（Zostera marina L.)植株5d,然后在体外测定了大叶藻叶片中两个胞内酶（PEP羧化酶和苹果酸脱氢酶）的耐盐性和在不同盐度介质中（100％、150％、200％、300％人工海水）经不同盐度（100％、150％和200％人工海水）海水预处理的大叶藻叶片光合速率以及一些生理指标的改变。结果表明在高于海水的盐度下,大叶藻叶片中丙二醛（MDA）、还原性糖和Na^ ,Cl^-含量及渗透势（绝对值）均随海水盐度的提高而增加,但K^ 和游离氨基酸的含量均降低。从处理5d的植株中提取的苹果酸脱氢酶在体外每一盐度下,其活性（A）大小依次为：A100％ASW＞A150％ASW＞A200％ASW（artificial seawater),并且其活性对盐度敏感（低盐度激活高盐度抑制）;但从100％及200％人工海水（ASW）处理的植株中提取的PEP羧化酶的活性在体外对盐度不敏感,而从150％人工海水处理的植株中提取的PEP羧化酶的活性对盐度具有很高的抗性。实验结果显示由150％人工海水处理的植株,在每一特定的盐度下其光合速率均高于另外两组处理（100％ASW和200％ASW）,并且3个处理的光合速率均与其PEPC在不同盐度下的活性表现相一致。但是,经150％ASW处理的大叶藻植株是否受到盐害还有待于进一步探讨。实验表明“大叶藻耐盐性在一定程度上是由于其代谢酶对盐度的耐性造成的”这一说法是不合适的;不存在蒸腾作用可能是大叶藻耐盐机理的重要组成部分。     

Effects of pH, Temperature, and Nutrients on Propionate Degradation by a Methanogenic Enrichment Culture

Enrichment cultures were used to determine the conditions promoting fastest methanogenic propionate degradation and growth by adapting the cultures to various physical and chemical conditions and measuring the specific growth rate. We found that the fastest growth of propionate oxidizers occurred at pH 6.8 to 8.5 and 32 to 45°C. Acetate-degrading populations showed narrower optima for fastest growth (pH 6.8 to 7.2 and 37 to 43°C). Enrichment cultures grew as well in minimal medium as in complex medium, although individual microbial populations appeared to require growth factors which could be met by cross-feeding.     

Environmental pH as an important factor for the distribution of urease positive ammonia-oxidizing bacteria

The effect of pH on ureolytic activity of a number of chemolithotrophic ammonia-oxidizing bacteria (AOB) has been studied in context with distribution patterns of these species. The pH-optima for urea-based nitrification were found to differ clearly among the examined species. Pronounced optima ranged between pH 5.0 and 8.0. Urease is an intracytoplasmic enzyme and should therefore be independent of the external pH. Our first results indicated the presence of a pH-dependent uptake system for urea. Simultaneous oxidation of free ammonia, possible only at high pH values, led to a strong intensification of ureolysis. The lag-phase of growth on urea as the sole energy source was clearly prolonged compared to free ammonia. Our results point on the existence of an active, most likely energy-linked urea-uptake system in addition to a possible passive diffusion of urea. The different pH-optima of urea-uptake agree with known distribution patterns of distinct AOB. It might be a reason for the shift of dominant Nitrosospira populations along pH gradients in acid soils as observed by others in molecular analyses of natural AOB populations.