Comparison of laboratory and field testing performance evaluations of siloxane-polyurethane fouling-release marine coatings

A series of eight novel siloxane-polyurethane fouling-release (FR) coatings were assessed for their FR performance in both the laboratory and in the field. Laboratory analysis included adhesion assessments of bacteria, microalgae, macroalgal spores, adult barnacles and pseudobarnacles using high-throughput screening techniques, while field evaluations were conducted in accordance with standardized testing methods at three different ocean testing sites over the course of six-months exposure. The data collected were subjected to statistical analysis in order to identify potential correlations. In general, there was good agreement between the laboratory screening assays and the field assessments, with both regimes clearly distinguishing the siloxane-polyurethane compositions comprising monofunctional poly(dimethyl siloxane) (PDMS) (m-PDMS) as possessing superior, broad-spectrum FR properties compared to those prepared with difunctional PDMS (d-PDMS). Of the seven laboratory screening techniques, the Cellulophaga lytica biofilm retraction and reattached barnacle (Amphibalanus amphitrite) adhesion assays were shown to be the most predictive of broad-spectrum field performance.     

Towards an interactive,process‐based approach to understanding range shifts: developmental and environmental dependencies matter

Many species are undergoing distributional shifts in response to climate change. However, wide variability in range shifting rates has been observed across taxa, and even among closely‐related species. Attempts to link climate‐mediated range shifts to traits has often produced weak or conflicting results. Here we investigate interactive effects of developmental processes and environmental stress on the expression of traits relevant to range shifts. We use an individual‐based modelling approach to assess how different developmental strategies affect range shift rates under a range of environmental conditions. We find that under stressful conditions, such as at the margins of the species’ fundamental niche, investment in prolonged development leads to the greatest rates of range shifting, especially when longer time in development leads to improved fecundity and dispersal‐related traits. However, under benign conditions, and when traits are less developmentally plastic, shorter development times are preferred for rapid range shifts, because higher generational frequency increases the number of individual dispersal events occurring over time. Our results suggest that the ability of a species to range shift depends not only on their dispersal and colonisation characteristics but also how these characteristics interact with developmental strategies. Benefits of any trait always depended on the environmental and developmental sensitivity of life history trait combinations, and the environmental conditions under which the range shift takes place. Without considering environmental and developmental sources of variation in the expression of traits relevant to range shifts, there is little hope of developing a general understanding of intrinsic drivers of range shift potential.     

The Role of Ceramide Synthases in the Pathogenicity of Cryptococcus neoformans

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Regional Endothermy in a Coral Reef Fish?

Although a few pelagic species exhibit regional endothermy, most fish are regarded as ectotherms. However, we document significant regional endothermy in a benthic reef fish. Individual steephead parrotfish, Chlorurus microrhinos (Labridae, formerly Scaridae) were tagged and their internal temperatures were monitored for a 24 h period using active acoustic telemetry. At night, on the reef, C. microrhinos were found to maintain a consistent average peritoneal cavity temperature 0.16 ± 0.005 °C (SE) warmer than ambient. Diurnal internal temperatures were highly variable for individuals monitored on the reef, while in tank-based trials, peritoneal cavity temperatures tracked environmental temperatures. The mechanisms responsible for a departure of the peritoneal cavity temperature from environmental temperature occurred in C. microrhinos are not yet understood. However, the diet and behavior of the species suggests that heat in the peritoneal cavity may result primarily from endogenous thermogenesis coupled with physiological heat retention mechanisms. The presence of limited endothermy in C. microrhinos indicates that a degree of uncertainty may exist in the manner that reef fish respond to their thermal environment. At the very least, they do not always appear to respond to environmental temperatures as neutral thermal vessels and do display limited, but significant, visceral warming.     

Native fish entrapment in irrigation systems: A step towards understanding the significance of the problem

Summary   The Australian irrigation industry diverts significant volumes of water from our rivers, and as such, may also divert and entrain riverine fish. Although it is widely acknowledged that our native fish fauna have been greatly affected by a variety of anthropogenic changes, little is known about the extent or significance of fish entrainment in irrigation systems. This paper presents results from a preliminary investigation into the diversion of fish into irrigation channels undertaken in the Goulburn-Murray Irrigation Network, Victoria, Australia. The case study and our knowledge of the life-history strategies of the Basin's fish fauna suggest that the loss of native fish into irrigation networks may be a substantial problem, which, up until recently, has been largely ignored. We strongly suggest that the impact of diversions on native fish populations requires urgent further investigation and quantification, through the cooperation of water management authorities and fish biologists.     

Automated acquisition of electron microscopic random conical tilt sets

Single particle reconstruction using the random conical tilt data collection geometry is a robust method for the initial determination of macromolecular structures by electron microscopy. Unfortunately, the broad adoption of this powerful approach has been limited by the practical challenges inherent in manual data collection of the required pairs of matching high and low tilt images (typically 60 degrees and 0 degrees). The microscopist is obliged to keep the imaging area centered during tilting as well as to maintain accurate focus in the tilted image while minimizing the overall electron dose, a challenging and time consuming process. To help solve these problems, we have developed an automated system for the rapid acquisition of accurately aligned and focused tilt pairs. The system has been designed to minimize the dose incurred during alignment and focusing, making it useful in both negative stain and cryo-electron microscopy. The system includes a feature for montaging untilted images to ensure that all of the particles in the tilted image may be used in the reconstruction.     

In Vivo Studies in Rhodospirillum rubrum Indicate That Ribulose-1,5-bisphosphate Carboxylase/Oxygenase (Rubisco) Catalyzes Two Obligatorily Required and Physiologically Significant Reactions for Distinct Carbon and Sulfur Metabolic Pathways

All organisms possess fundamental metabolic pathways to ensure that needed carbon and sulfur compounds are provided to the cell in the proper chemical form and oxidation state. For most organisms capable of using CO₂ as sole source of carbon, ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) catalyzes primary carbon dioxide assimilation. In addition, sulfur salvage pathways are necessary to ensure that key sulfur-containing compounds are both available and, where necessary, detoxified in the cell. Using knock-out mutations and metabolomics in the bacterium Rhodospirillum rubrum, we show here that Rubisco concurrently catalyzes key and essential reactions for seemingly unrelated but physiologically essential central carbon and sulfur salvage metabolic pathways of the cell. In this study, complementation and mutagenesis studies indicated that representatives of all known extant functional Rubisco forms found in nature are capable of simultaneously catalyzing reactions required for both CO₂-dependent growth as well as growth using 5-methylthioadenosine as sole sulfur source under anaerobic photosynthetic conditions. Moreover, specific inactivation of the CO₂ fixation reaction did not affect the ability of Rubisco to support anaerobic 5-methylthioadenosine metabolism, suggesting that the active site of Rubisco has evolved to ensure that this enzyme maintains both key functions. Thus, despite the coevolution of both functions, the active site of this protein may be differentially modified to affect only one of its key functions.     

Kinetic Characterization of 100 Glycoside Hydrolase Mutants Enables the Discovery of Structural Features Correlated with Kinetic Constants

The use of computational modeling algorithms to guide the design of novel enzyme catalysts is a rapidly growing field. Force-field based methods have now been used to engineer both enzyme specificity and activity. However, the proportion of designed mutants with the intended function is often less than ten percent. One potential reason for this is that current force-field based approaches are trained on indirect measures of function rather than direct correlation to experimentally-determined functional effects of mutations. We hypothesize that this is partially due to the lack of data sets for which a large panel of enzyme variants has been produced, purified, and kinetically characterized. Here we report the k_cat and K_M values of 100 purified mutants of a glycoside hydrolase enzyme. We demonstrate the utility of this data set by using machine learning to train a new algorithm that enables prediction of each kinetic parameter based on readily-modeled structural features. The generated dataset and analyses carried out in this study not only provide insight into how this enzyme functions, they also provide a clear path forward for the improvement of computational enzyme redesign algorithms.     

Influence of Nematode Parasitism,Body Size,Temperature, and Diel Period on the Flight Capacity of <Emphasis Type="Italic">Sirex noctilio</Emphasis> F. (Hymenoptera: Siricidae)

Sirex noctilio F. (Hymenoptera: Siricidae) is a woodwasp of pine trees that has recently invaded and established in North American forests. Although S. noctilio has had a limited impact in North America to date, there is some concern that it could have a significant impact on pine plantations, especially in the southeastern U.S.A. Moreover, there are few data on the flight capacity of male S. noctilio. We found no association between parasitism by D. siricidicola and whether or not S. noctilio initiated flight on the flight mill. Male wasps that were parasitized by nematodes were heavier than non-parasitized males, but there was no significant difference in mass between parasitized and non-parasitized females. We also examined the flight capacity of male and female S. noctilio in relation to nematode parasitism, body mass, temperature (for only males), and diel period. Body mass, temperature, and diel period affected flight in S. noctilio such that wasps were generally observed to fly faster, farther, and more frequently if they were heavier, flying at warmer temperatures, and flying during the photoperiod. The fact that nematode-parasitized male wasps were found to fly farther than the non-parasitized males is consistent with the hypothesis that nematode parasitism does not negatively affect the flight capacity of S. noctilio.     

Quantitative trait loci controlling light and hormone response in two accessions of Arabidopsis thaliana

We have mapped quantitative trait loci (QTL) responsible for natural variation in light and hormone response between the Cape Verde Islands (Cvi) and Landsberg erecta (Ler) accessions of Arabidopsis thaliana using recombinant inbred lines (RILs). Hypocotyl length was measured in four light environments: white, blue, red, and far-red light and in the dark. In addition, white light plus gibberellin (GA) and dark plus the brassinosteroid biosynthesis inhibitor brassinazole (BRZ) were used to detect hormone effects. Twelve QTL were identified that map to loci not previously known to affect light response, as well as loci where candidate genes have been identified from known mutations. Some QTL act in all environments while others show genotype-by-environment interaction. A global threshold was established to identify a significant epistatic interaction between two loci that have few main effects of their own. LIGHT1, a major QTL, has been confirmed in a near isogenic line (NIL) and maps to a new locus with effects in all light environments. The erecta mutation can explain the effect of the HYP2 QTL in the blue, BRZ, and dark environments, but not in far-red. LIGHT2, also confirmed in an NIL, has effects in white and red light and shows interaction with GA. The phenotype and map position of LIGHT2 suggest the photoreceptor PHYB as a candidate gene. Natural variation in light and hormone response thus defines both new genes and known genes that control light response in wild accessions.