Characterization of isolated yeast growth response to methionine analogs

Methionine is one of the first limiting amino acids in poultry nutrition. The use of methionine-rich natural feed ingredients, such as soybean meal or rapeseed meal may lead to negative environmental consequences. Amino acid supplementation leads to reduced use of protein-rich ingredients. The objectives of this study were isolation of potentially high content methionine-containing yeasts, quantification of methionine content in yeasts and their respective growth response to methionine analogs. Minimal medium was used as the selection medium and the isolation medium of methionine-producing yeasts from yeast collection and environmental samples, respectively. Two yeasts previously collected along with six additional strains isolated from Caucasian kefir grains, air-trapped, cantaloupe, and three soil samples could grow on minimal medium. Only two of the newly isolated strains, K1 and C1, grew in minimal medium supplied with either methionine analogs ethionine or norleucine at 0.5% (w/v). Based on large subunit rRNA sequences, these isolated strains were identified as Pichia udriavzevii/Issatchenkia orientalis. P. kudriavzevii/I. orentalis is a generally recognized as a safe organism. In addition, methionine produced by K1 and C1 yeast hydrolysate yielded 1.3 ± 0.01 and 1.1 ± 0.01 mg g^?1 dry cell. Yeast strain K1 may be suitable as a potential source of methionine for dietary supplements in organic poultry feed but may require growth conditions to further increase their methionine content.     

Incorporating Recreational Users into Marine Protected Area Planning: A Study of Recreational Boating in British Columbia, Canada

Marine protected areas (MPAs) and zoning plans require an understanding of stakeholders if they are to be successful at achieving social and biological objectives. This study examines recreational boaters in a proposed MPA in British Columbia, Canada, using the recreation opportunity spectrum (ROS) and models of recreation conflict as a basis for investigation. Boaters (n = 543) visiting the region during the summer completed face-to-face surveys. Results show variability in boater setting preferences, supporting an ROS-based approach to MPA planning and zoning. While boaters as a whole placed the greatest importance on natural settings, sailboat operators expressed stronger preferences for natural and quiet settings relative to motorboats, and motorboat operators expressed stronger preferences for settings characterized by built facilities and extractive activities relative to sailboats. Several marine activities emerged as sources of perceived conflict for boaters, including personal watercraft, commercial whale watching vessels, and shellfish aquaculture. Our analysis indicates that while some of these may be addressed through zoning, others are better addressed through education and communication. Recommendations for both MPA management and future research are made.     

A mechanistic model of GPS collar location data: Implications for analysis and bias mitigation

Global positioning system (GPS) collars have revolutionized the collection of animal location data; however, it is well-recognized that considerable bias can be present in these data due to habitat or behavior-induced obstruction of satellite signals resulting in inaccurate or missing locations. To date, no explicit theoretical framework of GPS fix acquisition specific to animal telemetry has been presented, and studies make differing assumptions regarding factors influencing GPS fix acquisition and how these data should be analyzed. Inappropriate statistical models have been used, interaction effects have been misunderstood, and the implementation of bias mitigation techniques has been problematic. Herein we outline current conceptual and analytical problems in the GPS animal telemetry literature, and subsequently present a theoretical model-based framework for GPS fix acquisition that clarifies the single and interactive effects of habitat and behavioral obstruction, fix interval, and collar model on GPS collar performance. By recognizing that GPS fix acquisition is a Bernoulli process, it becomes apparent that all forms of obstruction inherently interact with each other, making generalizations across study areas, study species, and collar models problematic. Stationary collar tests to determine the probability of fix acquisition (PFA), location accuracy, and the response to sources of obstruction are thus of limited applicability to animal-deployed collars. Bias mitigation techniques that extrapolate PFA models across samples, especially those using stationary collar tests to correct animal-deployed collars, are theoretically unsound. It is also demonstrated that nonlinearities in the relationships between sources of obstruction and PFA complicate PFA modeling with limited data and that even slight model misspecification can lead to considerable errors in correction factors, especially when using inverse weighting to mitigate bias. By emphasizing the importance of GPS collar sensitivity and ephemeris retention, the theoretical framework predicts that newer, more sensitive GPS collars will be less severely biased by sources of obstruction than reported for the older, less sensitive collars that have been used in the majority of GPS performance studies to date and we expect this trend to continue. This heuristic modeling exercise should be of value to researchers planning and analyzing studies using GPS collars and it also establishes a starting point for future theoretical investigations into GPS collar performance and bias mitigation.     

The Identification and Determination of Airborne Particulates By Means of the Ring Oven Technique

The ring oven technique was first introduced as a means for conducting separations and concentrations on filter paper for final spot test analysis. By means of the technique, a complete qualitative scheme of separation and analysis can be made on a single drop of unknown. Recently, the effectiveness of the ring oven as a tool for quantitative analysis has been recognized. The method is particularly attractive for studies of airborne particulates. Samples of airborne particulates can be collected by high volume samplers, tape samplers, electrostatic precipitators, or by other appropriate means. The samples may be put into solution and an aliquot added to filter paper on a ring oven and washed to the ring zone for final identification and estimation. Any necessary separations can normally be carried out during the ring oven operations. A convenient approach for most studies is to collect the samples on tapes and carry out the necessary dissolution, separation, identification, and estimation steps directly on the tape itself. The ring oven methods are usually selective or even specific. The method applies to the microgram to nanogram range and the accuracies are comparable with those obtained by emission spectroscopy, polarography, fluorimetry, and spectrophotometry.     

Discussion of “Sensitivity of a molecular marker based positive matrix factorization model to the number of receptor observations” by YuanXun Zhang,Rebecca J. Sheesley,Min-Suk Bae and James J. Schauer

There is no specific number of samples that ensure a satisfactory PMF analysis. The statement made in this paper with respect to a specific number of samples is only applicable to this data set and should not be applied to any other data set.     

Contemporary threats and air pollution

It is now well understood that air pollution produces significant adverse health effects in the general public and over the past 60 years, there have been on-going efforts to reduce the emitted pollutants and their resulting health effects. There are now shifting patterns of industrialization with many heavily polluting industries moving from developed countries with increasingly stringent air quality standards to the developing world. However, even in decreasing concentrations of pollutants, health effects remain important possibly as a result of changes in the nature of the pollutants as new chemicals are produced and as other causes of mortality and morbidity are reduced. In addition, there is now the potential for deliberate introduction of toxic air pollutants by local armed conflicts and terrorists. Thus, there are new challenges to understand the role of the atmospheric environment on public health in this time of changing economic and demographic conditions overlaid with the willingness to indirectly attack governments and other established entities through direct attacks on the general public.     

Reduced Feather Growth Rates of Two Common Birds Inhabiting Central Amazonian Forest Fragments

Abstract: Forest fragmentation may negatively affect populations typically found within continuous forest tracts. Some effects, such as absence from small fragments, are obvious, but other effects may be subtle and easily overlooked. We evaluated the hypothesis that forest birds dwelling in fragments, where microclimatic conditions have been shown to be hotter and drier than in continuous forest, may be in poorer physiological condition than those in the forest interior. We studied two bird species, the Wedge-billed Woodcreeper (  Glyphorynchus spirurus ) and the White-crowned Manakin (    Pipra pipra ), common to the fragmented landscape north of Manaus, Brazil. We analyzed feather growth rates in Pipra and Glyphorynchus captured in 1-, 10-, and 100-ha forest fragments and continuous forest. Mean daily feather growth rates of the outer right rectrix of birds captured in fragments were significantly slower than feather growth rates of birds captured in continuous forest. Based on recapture data, Wedge-billed Woodcreepers probably grew their feathers in sites where they were first captured. White-crowned Manakins, however, were highly mobile and were recaptured rarely. Although we cannot conclusively show that fragmentation caused birds to be in poorer physiological condition, the data indicate that birds in poorer physiological condition were more likely to be captured in fragments than in continuous forest. Thus, our data suggest that forest fragmentation may have subtle but important effects on species that are relatively common after landscape alteration.     

Mechanism of Peroxyacetyl Nitrate Formation

It is proposed that peroxyacetyl nitrate and its homologues are formed in polluted air by a reaction between acylate (or aroylate) radicals and nitrogen trioxide. The proposed reaction accounts for the delayed formation of peroxyacetyl nitrate upon the irradiation of low concentrations of hydrocarbons and nitrogen oxides in air. It also explains why peroxyacetyl nitrate is not formed in photooxidations at high reactant concentrations. It accounts for the formation of peroxyacetyl nitrate in the dark reaction of acetaldehyde, oxygen, and N₂O₅; and, finally, it explains the inhibiting effect that excess NO₂ has on that dark reaction. The proposed reaction could yield either the accepted peroxyacetyl nitrate molecular structure or a molecular structure called acetyl pernitrate that does not include an oxygen-oxygen bond. The chemical properties of the molecule can be reconciled with either formulation.