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21.
Emily H Alexander F Andrea Rivera Ian Marriott Juan Anguita Kenneth L Bost Michael C Hudson 《BMC microbiology》2003,3(1):1-11
Background
Bacterial mercury resistance is based on enzymatic reduction of ionic mercury to elemental mercury and has recently been demonstrated to be applicable for industrial wastewater clean-up. The long-term monitoring of such biocatalyser systems requires a cultivation independent functional community profiling method targeting the key enzyme of the process, themerAgene coding for the mercuric reductase. We report on the development of a profiling method formerAand its application to monitor changes in the functional diversity of the biofilm community of a technical scale biocatalyzer over 8 months of on-site operation.Results
Based on an alignment of 30merAsequences from Gram negative bacteria, conserved primers were designed for amplification ofmerAfragments with an optimized PCR protocol. The resulting amplicons of approximately 280 bp were separated by thermogradient gelelectrophoresis (TGGE), resulting in strain specific fingerprints for mercury resistant Gram negative isolates with differentmerAsequences. ThemerAprofiling of the biofilm community from a technical biocatalyzer showed persistence of some and loss of other inoculum strains as well as the appearance of new bands, resulting in an overall increase of the functional diversity of the biofilm community. One predominant new band of themerAcommunity profile was also detected in a biocatalyzer effluent isolate, which was identified asPseudomonas aeruginosa. The isolated strain showed lower mercury reduction rates in liquid culture than the inoculum strains but was apparently highly competitive in the biofilm environment of the biocatalyzer where moderate mercury levels were prevailing.Conclusions
ThemerAprofiling technique allowed to monitor the ongoing selection for better adapted strains during the operation of a biocatalyzer and to direct their subsequent isolation. In such a way, a predominant mercury reducingPs. aeruginosastrain was identified by its unique mercuric reductase gene. 相似文献22.
A chimeric protein containing the uncleaved signal sequence of plasminogen activators inhibitor-2 (PAI2) fused to alkaline phosphatase (AP) interferes with Escherichia coli protein export and arrests growth. Suppressors of this toxicity include secG mutations that define the Thr-41-Leu-42-Phe-43 (TLF) domain of SecG. These mutations slow down the export of PAI2-AP. Another construct encoding a truncated PAI2 signal sequence (hB-AP) is also toxic. Most suppressors exert their effect on both chimeric proteins. We describe here five secG suppressors that only suppress the toxicity of hB-AP and selectively slow down its export. These mutations do not alter the TLF domain: three encode truncated SecG, whereas two introduce Arg residues in the transmembrane domains of SecG. The shortest truncated protein only contains 13 residues of SecG, suggesting that the mutation is equivalent to a null allele. Indeed, a secG disruption selectively suppresses the toxicity of hB-AP. However, the missense mutations are not null alleles. They allow SecG binding to SecYE, although with reduced affinity. Furthermore, these mutated SecG are functional, as they facilitate the export of endogenous proteins. Thus, SecG participates in signal sequence recognition, and both transmembrane domains of SecG contribute to ensure normal signal sequence recognition by the translocase. 相似文献
23.
Gregory CA Amos Emma Gozzard Charlotte E Carter Andrew Mead Mike J Bowes Peter M Hawkey Lihong Zhang Andrew C Singer William H Gaze Elizabeth M H Wellington 《The ISME journal》2015,9(6):1467-1476
Multi-drug-resistant bacteria pose a significant threat to public health. The role of the environment in the overall rise in antibiotic-resistant infections and risk to humans is largely unknown. This study aimed to evaluate drivers of antibiotic-resistance levels across the River Thames catchment, model key biotic, spatial and chemical variables and produce predictive models for future risk assessment. Sediment samples from 13 sites across the River Thames basin were taken at four time points across 2011 and 2012. Samples were analysed for class 1 integron prevalence and enumeration of third-generation cephalosporin-resistant bacteria. Class 1 integron prevalence was validated as a molecular marker of antibiotic resistance; levels of resistance showed significant geospatial and temporal variation. The main explanatory variables of resistance levels at each sample site were the number, proximity, size and type of surrounding wastewater-treatment plants. Model 1 revealed treatment plants accounted for 49.5% of the variance in resistance levels. Other contributing factors were extent of different surrounding land cover types (for example, Neutral Grassland), temporal patterns and prior rainfall; when modelling all variables the resulting model (Model 2) could explain 82.9% of variations in resistance levels in the whole catchment. Chemical analyses correlated with key indicators of treatment plant effluent and a model (Model 3) was generated based on water quality parameters (contaminant and macro- and micro-nutrient levels). Model 2 was beta tested on independent sites and explained over 78% of the variation in integron prevalence showing a significant predictive ability. We believe all models in this study are highly useful tools for informing and prioritising mitigation strategies to reduce the environmental resistome. 相似文献
24.
Jean‐Baptiste Thiebot Yves Cherel Manon Acqueberge Aurélien Prudor Philip N. Trathan Charles‐André Bost 《Ibis》2014,156(3):511-522
The annual moult creates the highest physiological stress during a penguin's breeding‐cycle and is preceded by a period of hyperphagia at sea. Although crucial to individual survival, foraging strategies before moult have been little investigated in keystone marine consumers in the Southern Ocean. The Macaroni Penguin Eudyptes chrysolophus demonstrates how individuals may adjust their foraging strategies during this period in line with constraints such as potential intraspecific competition between localities, foraging ability between dimorphic sexes and timing at sea between breeding and non‐breeding population components. We recorded pre‐moult behaviour at sea for 22 Macaroni Penguins from Crozet and Kerguelen Islands (southern Indian Ocean) during 2009 and 2011, using light‐based geolocation and stable isotope analysis. Penguins were distributed in population‐specific oceanic areas with similar surface temperatures (3.5 °C) south of the archipelagos, where they foraged at comparable trophic levels based on stable isotopes of their blood. Bayesian ‘broken stick’ modelling with concurrent analysis of seawater temperature records from the animal‐borne devices showed that within each population, females remained 6 days longer than males in the colder waters before heading back towards their colonies. Finally, 17 other non‐breeding individuals that moulted earlier had a higher mean blood δ15N value than did post‐breeding birds, meaning that early moulters probably fed more on fish than did late moulters. Our findings of such adjustments in foraging strategies developed across locality, sex and breeding status help understanding of the species' contrasted pre‐moult biology across its range and its ecology in the non‐breeding period. 相似文献
25.
Does prey capture induce area-restricted search? A fine-scale study using GPS in a marine predator, the wandering albatross 总被引:1,自引:0,他引:1
In a patchy environment, predators are expected to increase turning rate and start an area-restricted search (ARS) when prey have been encountered, but few empirical data exist for large predators. By using GPS loggers with devices measuring prey capture, we studied how a marine predator adjusts foraging movements at various scales in relation to prey capture. Wandering albatrosses use two tactics, sit and wait and foraging in flight, the former tactic being three times less efficient than the latter. During flight foraging, birds caught large isolated prey and used ARS at scales varying from 5 to 90 km, with large-scale ARS being used only by young animals. Birds did not show strong responses to prey capture at a large scale, few ARS events occurred after prey capture, and birds did not have high rates of prey capture in ARS. Only at small scales did birds increase sinuosity after prey captures for a limited time period, and this occurred only after they had caught a large prey item within an ARS zone. When this species searches over a large scale, the most effective search rule was to follow a nearly straight path. ARS may be used to restrict search to a particular environment where prey capture is more predictable and profitable. 相似文献
26.
CA Kalva-Filho EZ Campos VL Andrade ASR Silva AM Zagatto MCS Lima M Papoti 《Biology of sport / Institute of Sport》2015,32(4):333-337
The aims of the present study were to investigate the relationship of aerobic and anaerobic parameters with 400 m performance, and establish which variable better explains long distance performance in swimming. Twenty-two swimmers (19.1±1.5 years, height 173.9±10.0 cm, body mass 71.2±10.2 kg; 76.6±5.3% of 400 m world record) underwent a lactate minimum test to determine lactate minimum speed (LMS) (i.e., aerobic capacity index). Moreover, the swimmers performed a 400 m maximal effort to determine mean speed (S400m), peak oxygen uptake () and total anaerobic contribution (CANA). The CANA was assumed as the sum of alactic and lactic contributions. Physiological parameters of 400 m were determined using the backward extrapolation technique ( and alactic contributions of CANA) and blood lactate concentration analysis (lactic anaerobic contributions of CANA). The Pearson correlation test and backward multiple regression analysis were used to verify the possible correlations between the physiological indices (predictor factors) and S400m (independent variable) (p < 0.05). Values are presented as mean ± standard deviation. Significant correlations were observed between S400m (1.4±0.1 m·s-1) and LMS (1.3±0.1 m·s-1; r = 0.80), (4.5±3.9 L·min-1; r = 0.72) and CANA (4.7±1.5 L·O2; r= 0.44). The best model constructed using multiple regression analysis demonstrated that LMS and explained 85% of the 400 m performance variance. When backward multiple regression analysis was performed, CANA lost significance. Thus, the results demonstrated that both aerobic parameters (capacity and power) can be used to predict 400 m swimming performance. 相似文献
27.
Polyana C Tizioto Jeremy F Taylor Jared E Decker Caio F Gromboni Mauricio A Mudadu Robert D Schnabel Luiz L Coutinho Gerson B Mour?o Priscila SN Oliveira Marcela M Souza James M Reecy Renata T Nassu Flavia A Bressani Patricia Tholon Tad S Sonstegard Mauricio M Alencar Rymer R Tullio Ana RA Nogueira Luciana CA Regitano 《遗传、选种与进化》2015,47(1)
28.
29.
Rasley A Marriott I Halberstadt CR Bost KL Anguita J 《Journal of immunology (Baltimore, Md. : 1950)》2004,172(9):5707-5713
Substance P is a ubiquitous CNS neuropeptide and has recently been demonstrated to augment immune cell function during inflammatory events. Central to the ability of substance P to modulate immune cell function is the interaction of substance P with the substance P neurokinin-1 receptor expressed by a variety of immune cells, including microglia. CNS involvement during Lyme disease can occur when Borrelia burgdorferi, the causative agent of Lyme disease, gains access to the CNS. In the present study, we demonstrate that substance P augments B. burgdorferi-induced expression of mRNA encoding COX-2 and subsequent secretion of PGE(2) by cultured, murine microglia. Furthermore, this effect is associated with the ability of substance P to enhance B. burgdorferi-induced NF-kappa B activation, as demonstrated by increased nuclear localization of the p65 (RelA) subunit of NF-kappa B in these cells. Interestingly, we demonstrate that substance P augments B. burgdorferi-induced expression of mRNA encoding two PGE(2) receptors, E-prostanoid receptor subtypes 2 and 4, as well as each receptor protein. In addition, these effects are mediated via interactions between substance P and its high affinity receptor, as evidenced by the absence of augmented PGE(2) synthesis in the presence of a specific neurokinin-1 receptor antagonist or in cells genetically deficient in the expression of these receptors. Taken together, the present demonstration that substance P can exacerbate B. burgdorferi-induced inflammatory responses in microglia in vitro may indicate a role for this neuropeptide in the development of CNS inflammation observed during human neuroborreliosis. 相似文献
30.