Metabolism and foraging strategies of mid‐latitude mesozooplankton during cyanobacterial blooms as revealed by fatty acids,amino acids,and their stable carbon isotopes

Increasing sea surface temperatures (SST) and blooms of lipid‐poor, filamentous cyanobacteria can change mesozooplankton metabolism and foraging strategies in marine systems. Lipid shortage and imbalanced diet may challenge the build‐up of energy pools of lipids and proteins, and access to essential fatty acids (FAs) and amino acids (AAs) by copepods. The impact of cyanobacterial blooms on individual energy pools was assessed for key species temperate Temora longicornis and boreal Pseudo‐/Paracalanus spp. that dominated field mesozooplankton communities isolated by seasonal stratification in the central Baltic Sea during the hot and the cold summer. We looked at (a) total lipid and protein levels, (b) FA trophic markers and AA composition, and (c) compound‐specific stable carbon isotopes (δ¹³C) in bulk mesozooplankton and in a subset of parameters in particulate organic matter. Despite lipid‐poor cyanobacterial blooms, the key species were largely able to cover both energy pools, yet a tendency of lipid reduction was observed in surface animals. Omni‐ and carnivory feeding modes, FA trophic makers, and δ¹³C patterns in essential compounds emphasized that cyanobacterial FAs and AAs have been incorporated into mesozooplankton mainly via feeding on mixo‐ and heterotrophic (dino‐) flagellates and detrital complexes during summer. Foraging for essential highly unsaturated FAs from (dino‐) flagellates may have caused night migration of Pseudo‐/Paracalanus spp. from the deep subhalocline waters into the upper waters. Only in the hot summer (SST>19.0°C) was T. longicornis submerged in the colder subthermocline water (~4°C). Thus, the continuous warming trend and simultaneous feeding can eventually lead to competition on the preferred diet by key copepod species below the thermocline in stratified systems. A comparison of δ¹³C patterns of essential AAs in surface mesozooplankton across sub‐basins of low and high cyanobacterial biomasses revealed the potential of δ¹³C‐AA isoscapes for studies of commercial fish feeding trails across the Baltic Sea food webs.     

The acetyl xylan esterase II gene from Penicillium purpurogenum is differentially expressed in several carbon sources, and tightly regulated by pH

The expression of the acetyl xylan esterase II (axeII) gene from Penicillium purpurogenum is repressed by glucose and induced by xylan, as well as to a small degree by xylose and xylitol. This gene is expressed at neutral pH, but not under alkaline or acidic conditions, in agreement with previous findings for other xylanolytic genes of this organism. This is the first report showing pH regulation of an axe gene.     

Classifying genotypic data from plant breeding trials: a preliminary investigation using repeated checks

Summary Several subjective choices must be made when classifying genotypes based on data from plant breeding trials. One choice involves the method used to weight the contribution each environment makes to the classification. A second involves the use of either genotype-means for each environment or genotypevalues for each block, i.e., considering each block to be a different environment. Another involves whether environments (or blocks) in which genotypes are nonsignificantly different should be included or excluded from such classifications. An alternative to the use of raw or standardized data, is proposed in which each environment is weighted by a discrimination index (DI) that is based on the concept of repeatability. In this study the effect of three weighting methods (raw, standardized and DI), the choice of using environments or blocks, and the choice of including or excluding environments or blocks in which genotypic effects were not significant, were considered in factorial combination to give 12 options. A data set comprised of five check cultivars each repeated six times in each of three blocks at six environments was used. The effect of these options on the ability of a hierarchical clustering technique to correctly classify the repeats into five groups, each consisting of all the six repeats of a particular check cultivar, was investigated. It was found that the DI weighting method generally led to better recovery of the known structure. Using block data rather than environmental data also improved structure recovery for each of the three weighting methods. The exclusive use of environments in which genotypic effects were significant decreased structure recovery while the contrary generally occurred for blocks. The best structure recovery was obtained from the DI weighting applied to blocks (whether genotypes were significant or not).     

Enhanced vigilance in monogamous pairs of the lizard, Tiliqua rugosa

The Australian sleepy lizard, Tiliqua rugosa, forms monogamouspairs for up to 8 weeks each spring before mating. We observedthat males had food in their mouths significantly less oftenwhen they were in pain than when they were alone. Females hadfood in the mouth independent of the presence or absence ofmales. Among females that had been feeding, indicated by foodin the mouth, we observed them feeding, as we approached, lessoften when they were in pairs than when they were alone. Amongfemales in pairs with food in their mouths, we observed themfeeding less often when their male partners were not feedingthan when their partners were feeding. This suggests that femalesare alerted to approaching danger earlier when they are in apair, and alerted earlier in a pair when their male partneris not feeding. Enhanced vigilance may be one function of pairingbehavior.     

The evolution of cooperation

Darwin recognized that natural selection could not favor a trait in one species solely for the benefit of another species. The modern, selfish-gene view of the world suggests that cooperation between individuals, whether of the same species or different species, should be especially vulnerable to the evolution of noncooperators. Yet, cooperation is prevalent in nature both within and between species. What special circumstances or mechanisms thus favor cooperation? Currently, evolutionary biology offers a set of disparate explanations, and a general framework for this breadth of models has not emerged. Here, we offer a tripartite structure that links previously disconnected views of cooperation. We distinguish three general models by which cooperation can evolve and be maintained: (i) directed reciprocation--cooperation with individuals who give in return; (ii) shared genes--cooperation with relatives (e.g., kin selection); and (iii) byproduct benefits--cooperation as an incidental consequence of selfish action. Each general model is further subdivided. Several renowned examples of cooperation that have lacked explanation until recently--plant-rhizobium symbioses and bacteria-squid light organs--fit squarely within this framework. Natural systems of cooperation often involve more than one model, and a fruitful direction for future research is to understand how these models interact to maintain cooperation in the long term.     

Direct numerical simulations of micro-bubble expansion in gas embolotherapy

We are currently developing a novel gas embolotherapy technique that involves the selective, acoustic vaporization of liquid perfluorocarbon droplets in or near a tumor as a possible treatment for cancer The resulting bubbles can then stick within the tumor vasculature to occlude blood flow and "starve" the tumor The potential development of high stresses during droplet vaporization is a major concern for safe implementation of this technique. No prior study, either experimentally or theoretically, addresses this important issue. In this work, the acoustic vaporization procedure of the therapy is investigated by direct numerical simulations. The nonlinear, multiphase, computational model is comprised of an ideal gas bubble surrounded by liquid inside a long tube. Convective and unsteady inertia, viscosity, and surface tension affect the bubble dynamics and are included in this model, which is solved by a novel fixed-grid, sharp-interface, moving boundary method. We assess the potential for flow-induced wall stresses to rupture the vessel or damage the endothelium during vaporization under a range of operating conditions by varying dimensionless parameters--Reynolds, Weber, and Strouhal numbers, inertial energy and initial droplet size. It is found that the wall pressure is typically highest at the start of the bubble expansion, but the maximum wall shear stress occurs at a later time. Smaller initial bubble diameters, relative to the vessel diameter, result in lower wall stresses.     

Hereditary forms of intrahepatic cholestasis

Several genes that are mutated in hereditary forms of intrahepatic cholestasis have been identified or mapped, providing new insights into the process of enterohepatic bile acid circulation in health and disease and new tools with which to study this process. Murine models of several of these disorders have been generated. Unanticipated genetic heterogeneity has been identified.     

Evolution of phage with chemically ambiguous proteomes

Background  

The widespread introduction of amino acid substitutions into organismal proteomes has occurred during natural evolution, but has been difficult to achieve by directed evolution. The adaptation of the translation apparatus represents one barrier, but the multiple mutations that may be required throughout a proteome in order to accommodate an alternative amino acid or analogue is an even more daunting problem. The evolution of a small bacteriophage proteome to accommodate an unnatural amino acid analogue can provide insights into the number and type of substitutions that individual proteins will require to retain functionality.     

Clean technology: industry and environment, a viable partnership?

The industrial sector is becoming increasingly interested in eliminating potential pollution at source and reducing energy use. Biotechnology provides cheaper, cleaner alternatives to a wide range of traditional processes--but its adoption has been slower than expected. If industry is to become truly compatible with the environment, companies and the public will have to be convinced of the ecological and economic value of clean technology.