Culture medium influence on growth,fatty acid,and pigment composition of <Emphasis Type="Italic">Choricystis minor</Emphasis> var. <Emphasis Type="Italic">minor</Emphasis>: a suitable microalga for biodiesel production

The purposes of this study were to assess the influence of culture medium on biomass production, fatty acid, and pigment composition of Choricystis minor var. minor and to evaluate the use of this microalga as a source of fatty raw material for biodiesel production. Cultures of C. minor var. minor were grown using WC (Wright’s cryptophyte) and BBM (Bold’s Basal medium) media. BBM medium produced more biomass (984.3 mg L^?1) compared to the WC medium (525.7 mg L^?1). Despite this result, WC medium produced a higher methyl ester yield for biodiesel production than the BBM medium (170.0 and 90.2 mg g^?1 of biomass, respectively). The average percentage of fatty acids obtained using the WC medium (17.0 %) was similar to soybean (18.0 %) and with similar biomass fatty acid profile. However, for pigment production, carotenoids and chlorophyll concentrations were twice as high when using the BBM medium.     

Does Grazing Matter for Soil Organic Carbon Sequestration in the Western North American Great Plains?

Ecosystems - Considerable uncertainty remains regarding grazing-induced influences on soil organic carbon (SOC) sequestration in semiarid grassland ecosystems due to three important complications...     

Characterization and experimental infection of Flexibacter maritimus (Wakabayashi et al. 1986) in hatcheries of post-larvae of Litopenaeus vannamei Boone, 1931.

A preliminary study to characterize filamentous bacteria, whose presence is related to high mortality of Litopenaeus vannamei larvae cultured in Santa Catarina State, Brazil, is reported. The extract of infected larvae was diluted in different concentrations, cultured in marine agar (Difco, Marine Agar 2216) and incubated at 30 degrees C for 48 hours. The biochemical characterization included hydrolytic reactions of starch, gelatin and tyrosine, growth in TCBS agar, growth in 0 and 37 per thousand salinity, pigment production in tyrosine agar, production of H2S, nitrate reduction, congo red reaction, oxidase and catalase. The isolated bacteria belong to the species Flexibacter maritimus, Gram-negative bacilli of 0.4-0.5 microm width and 15 microm length. Experiments were carried out on pathogenicity of F. maritimus in post-larvae of L. vannamei. Survival and symptoms in L. vannamei post-larvae 24 hours after inoculation with F. maritimus and its growth in marine agar were evaluated. Mortality was detected around 92,5% as well as symptoms like melanized lesions in several parts of body, discolouration of gills, bad formation of appendages and of the last abdominal segment, low motility and feeding reduction. The experimental infection results suggested that isolated bacteria of the genus Flexibacter are pathogenic to the shrimp Litopenaeus vannamei post-larvae.     

Linaria dalmatica invades south-facing slopes and less grazed areas in grazing-tolerant mixed-grass prairie

Identifying environments where invasive plants are most invasive is key to understanding causes of invasion and developing effective management strategies. In mixed-grass prairie, invasive plants are often successful in relatively wet, nitrogen-rich areas, and areas protected from grazing. Dalmatian toadflax, a common invader of mixed-grass prairie, can also be favored by high water and nitrogen availability, but is thought to be relatively unpalatable to cattle, and therefore favored by grazing. We used spatially-adjusted model selection techniques to quantify relationships between toadflax cover (measured using very high-resolution aerial imagery), and relative snow deposition (estimated with a blowing snow model), slope, aspect, soil texture, and grazing intensity (estimated by proximity to water tanks). Toadflax was common throughout the 400 ha study site, occurring in 742 of 1,861 images. Toadflax cover was high on steeper slopes, particularly those with southern aspects. These two topographic variables were more effective in explaining toadflax distribution than modeled snow deposition, suggesting that factors other than snow deposition cause toadflax invasion on south-facing slopes. Toadflax cover was also high in areas further from water tanks, indicating that grazing may inhibit toadflax invasion. More broadly, this result suggests that grazing can reduce invasion of even relatively unpalatable species in ecosystems with long evolutionary histories of grazing.     

Regional grassland productivity responses to precipitation during multiyear above‐ and below‐average rainfall periods

There is considerable uncertainty in the magnitude and direction of changes in precipitation associated with climate change, and ecosystem responses are also uncertain. Multiyear periods of above‐ and below‐average rainfall may foretell consequences of changes in rainfall regime. We compiled long‐term aboveground net primary productivity (ANPP) and precipitation (PPT) data for eight North American grasslands, and quantified relationships between ANPP and PPT at each site, and in 1–3 year periods of above‐ and below‐average rainfall for mesic, semiarid cool, and semiarid warm grassland types. Our objective was to improve understanding of ANPP dynamics associated with changing climatic conditions by contrasting PPT–ANPP relationships in above‐ and below‐average PPT years to those that occurred during sequences of multiple above‐ and below‐average years. We found differences in PPT–ANPP relationships in above‐ and below‐average years compared to long‐term site averages, and variation in ANPP not explained by PPT totals that likely are attributed to legacy effects. The correlation between ANPP and current‐ and prior‐year conditions changed from year to year throughout multiyear periods, with some legacy effects declining, and new responses emerging. Thus, ANPP in a given year was influenced by sequences of conditions that varied across grassland types and climates. Most importantly, the influence of prior‐year ANPP often increased with the length of multiyear periods, whereas the influence of the amount of current‐year PPT declined. Although the mechanisms by which a directional change in the frequency of above‐ and below‐average years imposes a persistent change in grassland ANPP require further investigation, our results emphasize the importance of legacy effects on productivity for sequences of above‐ vs. below‐average years, and illustrate the utility of long‐term data to examine these patterns.     

Infection of Melanoplus sanguinipes Grasshoppers following Ingestion of Rangeland Plant Species Harboring Vesicular Stomatitis Virus

Knowledge of the many mechanisms of vesicular stomatitis virus (VSV) transmission is critical for understanding of the epidemiology of sporadic disease outbreaks in the western United States. Migratory grasshoppers [Melanoplus sanguinipes (Fabricius)] have been implicated as reservoirs and mechanical vectors of VSV. The grasshopper-cattle-grasshopper transmission cycle is based on the assumptions that (i) virus shed from clinically infected animals would contaminate pasture plants and remain infectious on plant surfaces and (ii) grasshoppers would become infected by eating the virus-contaminated plants. Our objectives were to determine the stability of VSV on common plant species of U.S. Northern Plains rangelands and to assess the potential of these plant species as a source of virus for grasshoppers. Fourteen plant species were exposed to VSV and assayed for infectious virus over time (0 to 24 h). The frequency of viable virus recovery at 24 h postexposure was as high as 73%. The two most common plant species in Northern Plains rangelands (western wheatgrass [Pascopyrum smithii] and needle and thread [Hesperostipa comata]) were fed to groups of grasshoppers. At 3 weeks postfeeding, the grasshopper infection rate was 44 to 50%. Exposure of VSV to a commonly used grasshopper pesticide resulted in complete viral inactivation. This is the first report demonstrating the stability of VSV on rangeland plant surfaces, and it suggests that a significant window of opportunity exists for grasshoppers to ingest VSV from contaminated plants. The use of grasshopper pesticides on pastures would decrease the incidence of a virus-amplifying mechanical vector and might also decontaminate pastures, thereby decreasing the inter- and intraherd spread of VSV.Vesicular stomatitis virus (VSV) is a highly transmissible rhabdovirus that causes economically important, Office of International Epizootics (OIE)-reportable disease outbreaks, primarily in horses and cattle of western U.S. rangelands. Vesicular stomatitis (VS) is endemic in portions of the southeastern United States, Mexico, and South America. Outbreaks in the western United States are sporadic, occurring every 2 to 9 years over the past 23 years, with the most recent outbreak in 2006. During outbreaks, clinically infected animals salivate excessively and shed copious amounts of virus (4 to 6 log units of virus per ml) (8). Virus-laden saliva contaminates facilities (e.g., water and feed troughs, stables, and corrals) as well as the environment (e.g., plants and soil), allowing extensive animal-to-animal transmission once the virus is in the herd (16). Insects are believed to play important roles in the initial introduction of the virus into a herd from undetermined natural reservoirs, as well as transmitting it across large distances between herds of similar or different species during animal movement quarantines (8).The protocol of veterinary practitioners regarding VS is to control the spread of virus during outbreaks by keeping all animals on the premises; cleaning and disinfecting all personnel materials, instruments, equipment, vehicles, feed bunks, and water sources; and instructing personnel to shower and change clothing and boots when moving between herds. According to the OIE, soil and plants are suspected sources of virus, although no report to date confirms this. Therefore, decontamination of corrals and pastures is not a current recommendation. Sand flies, black flies, and biting midges (Culicoides sonorensis) have all been shown to be competent vectors, capable of transmitting the virus during blood feeding (2, 3, 12, 17). Thus, the control of biting insects in barns and other housing areas with screens and repellents is advised.Although research has traditionally focused on these hematophagous insects as important VSV vectors, the migratory grasshopper Melanoplus sanguinipes (Fabricius) was recently shown to be an efficient amplifying reservoir and a possible mechanical vector for VSV (10). M. sanguinipes is distributed in North America from Alaska to Mexico and from coast to coast. It is a serious pest of both crops and grasslands, causing more crop damage than any other species of grasshopper in the United States (14). Grasshoppers are typically ingested by grazing animals when they are immobile during one of five molting stages. It is estimated that grazing cattle consume approximately 50 of these molting grasshoppers per day (10). In a previous study, grasshoppers were shown to amplify ingested VSV as much as 1,400-fold and to maintain high virus titers for at least 28 days (10). The route of VSV entry into cattle eating the infected grasshoppers was via scarifications on the tongue and gums, typically seen in cattle on rangeland pastures. Of significance to this study, the grasshopper-cattle-grasshopper transmission cycle is based on the assumptions that (i) virus shed from clinically infected animals would contaminate pasture plants and remain infectious on plant surfaces and (ii) grasshoppers would become infected by eating the virus-contaminated plants. To determine the stability of VSV on plants and the window of opportunity for grasshoppers to ingest viable VSV from those contaminated plants, we exposed rangeland plant species typically consumed by grasshoppers to VSV and determined the titer of virus over time. Several plant species harbored viable virus as long as 24 h. Grasshoppers were fed virus-contaminated plants, held for 21 days, and tested for virus. Current decontamination practices during VSV outbreaks do not address the viral contamination of pastures or the control of nonhematophagous virus-amplifying insect species such as grasshoppers. To that end, a commonly used no-withdrawal grasshopper pesticide was evaluated for its ability to inactivate VSV. A decontamination/deinfestation approach, as an additional VS control strategy for livestock in pastures, is discussed.     

Contributions of Hydrology to Vesicular Stomatitis Virus Emergence in the Western USA

Ecosystems - Relationships between environmental variables associated with the spread of vector-borne pathogens, such as RNA viruses transmitted to humans and animals, remain poorly understood....