Microbial respiration and substrate weight loss—II: A model of the influences of chemical composition

Three models of the influences of chemical composition on microbial respiration and substrate weight loss are presented. The three approaches represent different means of incorporating influences of temperature and moisture upon chemical-specific respiration rates. Although influences of temperature and moisture dominate microbial respiration patterns, chemical-specific respiration rates do exist with ethanol soluble substrate components respiring about 5–10 × as rapidly as nonethanol soluble components (depending upon temperature). Simulation models are utilized to project and relate the laboratory measures of microbial respiration to field measures of substrate weight loss. Utilizing chemical-specific respiration rates, simulated rates of weight loss from ethanol soluble and non-ethanol soluble substrate components are 48% and 12% per yr. Measured rates are 49% and 11%. After the initial period of relatively high leaching, changes in substrate weight and chemical composition result largely from changing microbial respiration rates which are chemical-specific and independently influenced by temperature and moisture.     

Mechanisms of quorum sensing and strategies for quorum sensing disruption in aquaculture pathogens

In many countries, infectious diseases are a considerable threat to aquaculture. The pathogenicity of micro‐organisms that infect aquaculture systems is closely related to the release of virulence factors and the formation of biofilms, both of which are regulated by quorum sensing (QS). Thus, QS disruption is a potential strategy for preventing disease in aquaculture systems. QS inhibitors (QSIs) not only inhibit the expression of virulence‐associated genes but also attenuate the virulence of aquaculture pathogens. In this review, we discuss QS systems in important aquaculture pathogens and focus on the relationship between QS mechanisms and bacterial virulence in aquaculture. We further elucidate QS disruption strategies for targeting aquaculture pathogens. Four main types of QSIs that target aquaculture pathogens are discussed based on their mechanisms of action.     

Analysis of antioxidant activities of common vegetables employing oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) assays: a comparative study

A total of 927 freeze-dried vegetable samples, including 111 white cabbages, 59 carrots, 51 snap beans, 57 cauliflower, 33 white onions, 48 purple onions, 130 broccoli, 169 tomatoes, 25 beets, 88 peas, 88 spinach, 18 red peppers, and 50 green peppers, were analyzed using the oxygen radical absorption capacity (ORAC) and ferric reducing antioxidant capacity (FRAP) methods. The data show that the ORAC and FRAP values of vegetable are not only dependent on species, but also highly dependent on geographical origin and harvest time. The two antioxidant assay methods, ORAC and FRAP, also give different antioxidant activity trends. The discrepancy is extensively discussed based on the chemistry principles upon which these methods are built, and it is concluded that the ORAC method is chemically more relevant to chain-breaking antioxidants activity, while the FRAP has some drawbacks such as interference, reaction kinetics, and quantitation methods. On the basis of the ORAC results, green pepper, spinach, purple onion, broccoli, beet, and cauliflower are the leading sources of antioxidant activities against the peroxyl radicals.     

Environmental control of net ecosystem CO2 exchange in a treed, moderately rich fen in northern Alberta

Peatlands cover about 21% of the landscape and contain about 80% of the soil carbon stock in western Canada. However, the current rates of carbon accumulation and the environmental controls on ecosystem photosynthesis and respiration in peatland ecosystems are poorly understood. As part of Fluxnet-Canada, we continuously measured net ecosystem carbon dioxide exchange (NEE) using the eddy covariance technique in a treed fen dominated by stunted Picea mariana and Larix laricina trees during August 2003–December 2004. The total carbon stock in the ecosystem was approximately 51,000 g C m⁻², with only 540 g C m⁻² contributed by live above ground vegetation. The NEE measurements were used to parameterize simple physiological models to assess temporal variation in maximum ecosystem photosynthesis (A_max) and ecosystem respiration rate at 10 °C (R₁₀). During mid-summer the ecosystem had a relatively high A_max (approx. 30 μmol m⁻² s⁻¹) with relatively low R₁₀ (approx. 4 μmol m⁻² s⁻¹). The peak mid-day NEE uptake rate during July and August was 10 μmol m⁻² s⁻¹. The ecosystem showed large seasonal variation in photosynthetic and respiratory activity that was correlated with shifts in temperature, with both spring increases and fall decreases in A_max well predicted by the mean daily air temperature averaged over the preceding 21 days. Leaf-level gas exchange and spectral reflectance measurements also suggested that seasonal changes in photosynthetic activity were primarily controlled by shifts in temperature. Ecosystem respiration was strongly correlated with changes in ecosystem photosynthesis during the growing season, suggesting important links between plant activity and mycorrhizae and microbial activity in the shallow layers of the peat. Only very low rates of respiration were observed during the winter months. During 2004, the peatland recorded a net annual gain of 144 g C m⁻² year⁻¹, the result of a difference between gross photosynthesis of 713 and total ecosystem respiration of 569 g C m⁻² year⁻¹.     

A quantitative stable-isotope LC-MS method for the determination of folic acid in fortified foods

A stable-isotope liquid chromatography-mass spectrometry (LC-MS) assay was developed for the quantitative determination of folic acid in fortified foods. Folic acid was extracted from food samples into a phosphate buffer, purified on a C-18 Sep-Pak cartridge, and analyzed by LC-MS in the negative ion mode using electrospray ionization. The analyte was quantified using (13)C(5)-folic acid as an internal standard. The coefficient of variation for the precision of the method was 5.6% based on the analysis of four sample replicates. The accuracy of the method was assessed using a standard method of addition of folic acid to a shredded whole-wheat cereal. The quantitative determination of folic acid in this matrix was linear over 1 order of magnitude having a concentration range of 2.4 to 24 microg/g of food (or 0.05 to 0.5 microg of analyte injected into the LC-MS). The overall quantitative efficiency of the method was evaluated using a standard reference material (infant formula SRM 1846). The method was applied to the determination of folic acid in several test samples (fortified breakfast cereals), and the values were in accord with the manufacturer's claim. This method advances a LC-MS technique for the determination of folic acid in fortified foods based on stable-isotope dilution methodology. The specificity of the technique and quantitative accuracy of the method in various food substrates suggests that the method may be adapted for routine analysis in other fortified foods.     

Early maritime economy and El Nino events at quebrada tacahuay, peru

The archaeological site of Quebrada Tacahuay, Peru, dates to 12,700 to 12,500 calibrated years before the present (10,770 to 10,530 carbon-14 years before the present). It contains some of the oldest evidence of maritime-based economic activity in the New World. Recovered materials include a hearth, lithic cutting tools and flakes, and abundant processed marine fauna, primarily seabirds and fish. Sediments below and above the occupation layer were probably generated by El Nino events, indicating that El Nino was active during the Pleistocene as well as during the early and middle Holocene.     

Predatory dinosaur remains from madagascar: implications for the cretaceous biogeography of gondwana

Recent discoveries of fossil vertebrates from the Late Cretaceous of Madagascar include several specimens of a large theropod dinosaur. One specimen includes a nearly complete and exquisitely preserved skull with thickened pneumatic nasals, a median frontal horn, and a dorsal projection on the parietals. The new materials are assigned to the enigmatic theropod group Abelisauridae on the basis of a number of unique features. Fossil remains attributable to abelisaurids are restricted to three Gondwanan landmasses: South America, Madagascar, and the Indian subcontinent. This distribution is consistent with a revised paleogeographic reconstruction that posits prolonged links between these landmasses (via Antarctica), perhaps until late in the Late Cretaceous.