Summertime and early autumn activity of some enzymes in the carbohydrate and fatty acid metabolism of the crucian carp

In June, July, and September the activities of five enzymes involved in the carbohydrate and fatty acid metabolism, namely phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS), cytochrome oxidase (cyt ox) and 3-hydroxy-acyl-CoA dehydrogenase (HAD), were measured in the heart, liver, red muscle, white muscle, and gill lamellae of crucian carp (Carassius carassius). LDH activity was measured in both reducing (LDHr) and oxidizing (LDHo) directions.The PFK activity in red and white muscle increased significantly between July and September indicating a preparation to winter anoxia by an increased glycylytic capacity in these organs. The HAD activity of the liver had increased significantly (by more than 50%) by September, also a preparation to winter anoxia as HAD is used in the reversed -oxidation (chain elongation of fatty acids). The LDHr and cyt ox activities in the heart and white muscle were highest in July. This shows that both the anaerobic and aerobic capacities are elevated in mid-summer when water temperature is high and oxygen concentration of the water could fluctuate greatly. The LDHo and CS activities in gill lamellae were lowest in July. The results show that the metabolism of crucian carp is under seasonal influence and that a preparation to winter hypoxia/anoxia could be detected in September.     

Factors influencing the abundance of three common nearshore fishes in south‐west Lake Michigan

Variation in the distribution and abundance of nearshore fishes is critical to understand food web processes and fishery management issues in Lake Michigan. This study characterised patterns in abundance of three common nearshore species, yellow perch Perca flavescens (Mitchell), round goby Neogobius melanostomus (Pallas) and alewife Alosa pseudoharengus (Wilson), in relation to spatio‐temporal, abiotic and biotic factors using gillnet sampling conducted across 5 years at multiple locations representing different substrates. Significant variations were observed in alewife and round goby catches between locations. A negative relationship between round goby and age‐0 yellow perch catch was observed, indicating potential competition between the two species. This study demonstrates that variability in nearshore fish communities can be driven by factors including substrate and interspecific interactions. Given the prominent role these species play in Lake Michigan's food web and thus their importance to fishery production, a thorough understanding of these factors is warranted.     

Conserving indigenous crayfish: stock assessment and habitat requirements in the threatened Austropotamobius italicus

• 1. As part of the Austropotamobius pallipes species complex, the crayfish Austropotamobius italicus is a species of community interest whose preservation requires the designation of Special Areas of Conservation (SACs) (Annex II, EU Habitats Directive). This study aimed at (1) assessing the conservation status of this threatened indigenous species by stock assessment in central Italy and (2) identifying some aspects of its elective habitat.
• 2. Surveys were conducted in nine streams harbouring A. italicus (streams WI) and in 10 streams where crayfish populations became extinct at least 5 years before the study (streams WO).
• 3. The results confirmed that A. italicus is a K‐selected species, with a relatively slow growth rate (males: 0.34; females: 0.37) and a long life expectancy (males: 8.2 years; females: 7.8 years). The extant populations are healthy, showing balanced sex‐ratios and well structured age‐class compositions. Mortality is mainly due to fishing, which is illegal in Tuscany.
• 4. Principal Components Analyses showed that the streams WI and WO differ in the abundance of allochthonous plant detritus but not in the taxonomic composition of their macroinvertebrate communities. Age classes were found to be spatially segregated, juveniles mainly using cobbles as substrates and adults seemingly avoiding them.
• 5. The loss of the pristine riverine landscape seems to have been responsible, together with illegal fishing, for the local extinction of the species. As a consequence, retaining, enhancing, and restoring the habitat and its complexity are required for the preservation of A. italicus.
• 6. The designation of SACs might help in this endeavour if accompanied by programmes aimed at publicizing the need for conservation of this species. Unfortunately, crayfish‐focused projects supported by LIFE in Italy since 1992 (4%) and the SACs involved (1.4%) have been relatively few, despite the poor conservation status of this species and its well recognized ecological role.

Copyright © 2008 John Wiley & Sons, Ltd.     

Cloning,Expression, and Purification of a GDSL-like Lipase/Acylhydrolase from a Native Lipase-Producing Bacterium,Lactobacillus fermentum

Background: Lipase enzymes are of great importance in various industries. Currently, extensive efforts have been focused on exploring new lipase producer microorganism as well as genetic and protein engineering of available lipases to improve their functional features. Methods: For screening lipase-producing lactobacilli, isolated strains were inoculated onto tributyrin agar plates. Molecular identification of lipase-producing Lactobacilli was performed by sequencing the 16Sr DNA gene, and a phylogenetic tree was constructed. The LAF_RS05195 gene, encoding lipase protein in L. fermentum isolates, was identified using specific primers, amplified by PCR (918 bp) and cloned into the pET28a (+) vector. The recombinant proteins were expressed 2, 4, 6, and 12 hours after induction with IPTG and assessed using the SDS-PAGE. Enzymatic activity of the purified recombinant protein was measured at 410 nm in the presence of ρ-NPA and ρ-NPP. Results:Among five identified native lipase-producing isolates, one isolate showed 98% similarity with Enterococcus species. The other four isolates indicated 98% similarity to L. fermentum. After purification steps with Ni-NTA column, a single protein band of about 34 kDa was detected on SDS- PAGE gel. The enzymatic activity of purified recombinant protein alongside ρ-NPA and ρ-NPP was measured to be 0.6 U/ml and 0.2 U/ml, respectively. Conclusion:In the present research, a novel lipase/esterase from L. fermentum was cloned and expressed. The novel lipase/esterase has the merit to be further studied due to its substrate specificity. Key Words: Escherichia coli, Gene expression, Lactobacillus, Lipase, Phylogeny     

Effects of pulsation rate and viscosity on pulsation-induced taste enhancement: new insights into texture-taste interactions

Oral stimulation with high-tastant concentrations that are alternared with low-tastant concentrations or water rinses (pulsatile stimulation) results in taste intensity ratings that are higher than continuous stimulation with the same average tastant concentration. This study tested the combined effects of taste pulsation rate and viscosity on pulsation-induced taste enhancement in apple juice. According to a tastant-kinetics hypothesis, less pulsation-induced taste enhancement is expected at enhanced pulsation rates in the high-viscous proximal stimulus compared to lower viscous stimuli. High-concentration sucrose apple juice pulses and low-concentration sucrose apple juice intervals were alternated at different pulsation periods (pulse + interval in seconds) every 2.5 s (period length = 5 s) or every 1.25 s (period length = 2.5 s). Pulsed stimuli were presented at two viscosity levels by the addition of pectin (0 and 10 g/L). Sweetness intensities of pulsed stimuli were compared to a continuous reference of the same net but nonalternating sucrose concentration. Sweetness ratings were higher for pulsatile stimuli than for continuous stimuli. In low-viscous stimuli, enhancement depended on the pulsation period and peaked at 5 s periods. In high-viscous stimuli, the same enhancement was observed for both pulsation periods. These results contradict a tastant-kinetics hypothesis of viscosity-induced taste suppression because impaired tastant kinetics by viscosity would predict the opposite: lower pulsation-induced taste enhancement for viscous stimuli, especially at higher pulsation rates. Instead, these observations favor an explanation based on perceptual texture-taste interactions, which predict the observed independence between viscosity and pulsation rate.     

Soil texture affects soil microbial and structural recovery during grassland restoration

Many biotic and abiotic factors influence recovery of soil communities following prolonged disturbance. We investigated the role of soil texture in the recovery of soil microbial community structure and changes in microbial stress, as indexed by phospholipid fatty acid (PLFA) profiles, using two chronosequences of grasslands restored from 0 to 19 years on silty clay loam and loamy fine sand soils in Nebraska, USA. All restorations were formerly cultivated fields seeded to native warm-season grasses through the USDA’s Conservation Reserve Program. Increases in many PLFA concentrations occurred across the silty clay loam chronosequence including total PLFA biomass, richness, fungi, arbuscular mycorrhizal fungi, Gram-positive bacteria, Gram-negative bacteria, and actinomycetes. Ratios of saturated:monounsaturated and iso:anteiso PLFAs decreased across the silty clay loam chronosequence indicating reduction in nutrient stress of the microbial community as grassland established. Multivariate analysis of entire PLFA profiles across the silty clay loam chronosequence showed recovery of microbial community structure on the trajectory toward native prairie. Conversely, no microbial groups exhibited a directional change across the loamy fine sand chronosequence. Changes in soil structure were also only observed across the silty clay loam chronosequence. Aggregate mean weighted diameter (MWD) exhibited an exponential rise to maximum resulting from an exponential rise to maximum in the proportion of large macroaggregates (>2000 μm) and exponential decay in microaggregates (<250 μm and >53 μm) and the silt and clay fraction (<53 μm). Across both chronosequences, MWD was highly correlated with total PLFA biomass and the biomass of many microbial groups. Strong correlations between many PLFA groups and the MWD of aggregates underscore the interdependence between the recovery of soil microbial communities and soil structure that may explain more variation than time for some soils (i.e., loamy fine sand). This study demonstrates that soil microbial responses to grassland restoration are modulated by soil texture with implications for estimating the true capacity of restoration efforts to rehabilitate ecosystem functions.     

Antioxidant Capacity of Beetroot: Traditional vs Novel Approaches

Red beetroot has been ranked among the 10 most potent antioxidant vegetables, although only extraction-based methods have been used to evaluate its total antioxidant capacity. Therefore, the present study aims at comparing the traditional extraction-based method with two more recent approaches (QUENCHER -QUick, Easy, New, CHEap and Reproducible- and GAR -global antioxidant response method), in order to establish their suitability in the case of beetroot. Our results indicate that the total antioxidant capacity of beetroot would be underestimated when using extraction-based procedures, since both QUENCHER and GAR methods resulted in a higher total antioxidant capacity. The effect of a thermal treatment on the total antioxidant capacity of beetroot varies among the methods evaluated and our findings suggest different compounds responsible for the total antioxidant capacity detected in each pre-processing method. Remarkably, the present study demonstrates that the traditional extraction-based method seems useful to screen for (changes in) the “bioavailable” antioxidant potential of the root.