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Durant JA Lowry VK Nisbet DJ Stanker LH Corrier DE Ricke SC 《Journal of environmental science and health. Part. B》1999,34(6):1083-1099
This study demonstrates that the growth of S. typhimurium in Luria Bertani broth supplemented with acetate, propionate, butyrate, or a mixture of the three SCFA, affected cell-association and the ability to invade cultured HEp-2 cells. Cell-association and invasion was determined after growth for 4 h of growth in the presence of the SCFA at pH 6 and 7. The results suggest that the growth rate of the culture may have affected cell-association and invasion since accompanying the significant decrease in growth rate in the presence of SCFA at pH 6 was a decrease in cell-association and invasion. However, the results also suggest that the individual SCFA may play a role in modulating cell-association and the invasion phenotype and the regulation of cell-association and invasion by the SCFA was dependent on the concentration and the pH of the medium. Although the growth rates were similar for S. typhimurium in the SCFA mixture, butyrate (100 mM) and propionate (50 mM) at pH 6, differences in cell-association and invasion were observed among these cultures. Also, at pH 7, differences were observed among the SCFA treatments even though the growth rates were similar. 相似文献
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Kate M. Munson Richard M. Vogel John L. Durant 《Journal of the American Water Resources Association》2018,54(2):527-542
We investigate the sensitivity of phosphorus loading (mass/time) in an urban stream to variations in climate using nondimensional sensitivity, known as elasticity, methods commonly used by economists and hydrologists. Previous analyses have used bivariate elasticity methods to represent the general relationship between nutrient loading and a variable of interest, but such bivariate relations cannot reflect the complex multivariate nonlinear relationships inherent among nutrients, precipitation, temperature, and streamflow. Using fixed‐effect multivariate regression methods, we obtain two phosphorus models (nonparametric and parametric) for an urban stream with high explanatory power that can both estimate phosphorus loads and the elasticity of phosphorus loading to changes in precipitation, temperature, and streamflow. A case study demonstrates total phosphorus loading depends significantly on season, rainfall, combined sewer overflow events, and flow rate, yet the elasticity of total phosphorus to all these factors remains relatively constant throughout the year. The elasticity estimates reported here can be used to examine how nutrient loads may change under future climate conditions. 相似文献
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To flee or not to flee: predator avoidance by cheetahs at kills 总被引:2,自引:0,他引:2
Mammalian carnivores are unusual because their primary competitors for food are often their primary predators. This relationship
is most evident at persistent kills where dominant competitors are attracted to both the carcass (as a free meal) and to the
killers (as potential prey). Cheetahs (Acinonyx jubatus) are frequent victims of kleptoparasitism, and cubs, and sometimes adults, are killed by lions (Panthera leo) or spotted hyenas (Crocuta crocuta). Between 1980 and 2002, we observed 639 kills made by cheetahs in Serengeti National Park, Tanzania. These kills were often
visited by scavengers, including relatively innocuous species such as vultures and jackals and potentially dangerous species,
like spotted hyenas and lions. We used cheetah behavior at kills to test a number of predictions about how cheetahs should
minimize risk at kill sites given they face an increased risk of predation of themselves or their cubs. In particular, we
examined the propensity of cheetahs of different age/sex classes to hide carcasses after making a kill, vigilance at kills,
and the delay in leaving after finishing feeding with respect to ecological factors and scavenger presence. The behavior of
single females at kills did not suggest that they were trying to avoid being killed, but the behavior of males, often found
in groups, was in line with this hypothesis. In contrast, the behavior of mother cheetahs at kills appeared to be influenced
greatly by the risk of cubs being killed. Our results suggest that cheetahs use several behavioral counterstrategies to avoid
interspecific predation of self or cubs. 相似文献
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Daphné Durant Eric Kernéïs Jean-Marc Meynard Jean-Philippe Choisis Claude Chataigner Jean-Michel Hillaireau Christophe Rossignol 《Journal of Coastal Conservation》2018,22(6):1177-1190
Storm Xynthia crossed France’s western coast between 28th February and 1st March 2010. It hit the Vendée and Charente-Maritime departments hardest, as storm surge flooded up to 23,000 ha of coastal agricultural areas (i.e. polders), causing severe damage to farming operations. However, farm-level damage in the aftermath of seawater flooding is an issue that has rarely been explored in the literature. Here we investigated the effects of storm Xynthia on agriculture at the farm scale. We focused on the case study of Saint Laurent de la Prée research farm, a mixed crop–livestock system that was severely hit. All damages were described and economic losses were quantified for the years 2010 and 2011. The results show numerous consequences of the storm in terms of crop and fodder production losses, but also farm infrastructure repairs, crop restoration and animal health problems. Economic damage costs were high, reaching €71,720 in 2010 (€500/ha flooded) and €56,195 (€390/ha) in 2011 for the case study farm. The discussion highlights the farm-level impacts of seawater flooding and the crucial factors that can explain the damage caused to agriculture by storm events in coastal areas. The results are also discussed in the wider context of global warming which is expected to cause sea level rise and more frequent storm events in the future. The vulnerability of coastal agricultural areas to storms thus exposes broader issues of coastal flooding risk management and specifically the allied protection–remediation–adaptation measures. The conclusions underline the need for future research to address prospective scenarios and subsequent adaptive strategies. 相似文献
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J. A. Durant D. J. Nisbet S. C. Ricke 《Journal of environmental science and health. Part. B》2013,48(4):503-516
Abstract The objective of this study was to determine whether fermentation by a cecal probiotic co‐culture of an Enterococcus sp. and Veillonella sp. would inhibit the in vitro growth of a S typhimurium poultry isolate. The growth rates of S. typhimurium and Enterococcus were significantly reduced at pH 5. At the two pH levels, there was a significant (p < 0.001) increase at 24 h in colony forming units for each of the bacteria enumerated from the mixed culture compared to the respective pure culture enumerations. S. typhimurium was not inhibited in mixed cultures. The mixed cultures produced more acetate than any of the pure cultures and lactate produced by Enterococcus appeared to be utilized by Veillonella. 相似文献
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Durant JA Nisbet DJ Ricke SC 《Journal of environmental science and health. Part. B》2000,35(4):503-516
The objective of this study was to determine whether fermentation by a cecal probiotic co-culture of an Enterococcus sp. and Veillonella sp. would inhibit the in vitro growth of a S. typhimurium poultry isolate. The growth rates of S. typhimurium and Enterococcus were significantly reduced at pH 5. At the two pH levels, there was a significant (p < 0.001) increase at 24 h in colony forming units for each of the bacteria enumerated from the mixed culture compared to the respective pure culture enumerations. S. typhimurium was not inhibited in mixed cultures. The mixed cultures produced more acetate than any of the pure cultures and lactate produced by Enterococcus appeared to be utilized by Veillonella. 相似文献
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Northeast Arctic cod population persistence in the Lofoten-Barents Sea system under fishing. 总被引:1,自引:0,他引:1
Jo?l M Durant Dag O Hjermann Philippe S Sabarros Nils Chr Stenseth 《Ecological applications》2008,18(3):662-669
Population growth, and hence the population's persistence, is affected by several factors such as climate, species interaction, and harvesting pressure. Proper resource management requires an understanding of these factors. We apply techniques based upon age-structured population matrices to analyze estimated stock sizes derived from annual bottom trawl sampling in the winter feeding area of northeast Arctic cod (Gadus morhua L.) from 1981 to 2003. We run generalized additive models to explain population growth rate by different explanatory variables. Cod population growth was found to be positively related to the abundance of capelin (Mallotus villosus Miller), negatively related to the number of cannibalistic cod with a two-year lag, and marginally positively related to the winter North Atlantic Oscillation index (NAO). This model remains true independently from the population status (i.e., fished or non-fished). Capelin abundance is the main variable that to some degree can be adjusted in order to maintain the population size at a given level of cod harvesting. Our results point to the importance of managing conjointly cod and capelin stocks. 相似文献