Shifting microbial community structure across a marine terrace grassland chronosequence, Santa Cruz, California

Changes in the biomass and structure of soil microbial communities have the potential to impact ecosystems via interactions with plants and weathering minerals. Previous studies of forested long-term (1000s - 100,000s of years) chronosequences suggest that surface microbial communities change with soil age. However, significant gaps remain in our understanding of long-term soil microbial community dynamics, especially for non-forested ecosystems and in subsurface soil horizons. We investigated soil chemistry, aboveground plant productivity, and soil microbial communities across a grassland chronosequence (65,000-226,000 yrs old) located near Santa Cruz, CA. Aboveground net primary productivity (ANPP) initially increased to a maximum and then decreased for the older soils. We used polar lipid fatty acids (PLFA) to investigate microbial communities including both surface (<0.1 m) and subsurface (≥0.2 m) soil horizons. PLFAs characteristic of Gram-positive bacteria and actinobacteria increased as a fraction of the microbial community with depth while the fungal fraction decreased relative to the surface. Differences among microbial communities from each chronosequence soil were found primarily in the subsurface where older subsurface soils had smaller microbial community biomass, a higher proportion of fungi, and a different community structure than the younger subsurface soil. Subsurface microbial community shifts in biomass and community structure correlated with, and were likely driven by, decreasing soil P availability and Ca concentrations, respectively. Trends in soil chemistry as a function of soil age led to the separation of the biological (≤1 m depth) and geochemical (>1 m) cycles in the old, slowly eroding landscape we investigated, indicating that this separation, commonly observed in tropical and subtropical ecosystems, can also occur in temperate climates. This study is the first to investigate subsurface microbial communities in a long-term chronosequence. Our results highlight connections between soil chemistry and both the aboveground and belowground parts of an ecosystem.     

Retention of provitamin A carotenoids in high beta-carotene maize (Zea mays) during traditional African household processing

High beta-carotene maize, biofortified with beta-carotene through plant breeding, is being developed as a cost-effective, sustainable agronomic approach to alleviating the problem of vitamin A deficiency in Africa. We used high beta-carotene maize (10.49+/-0.16 microg beta-carotene/g) to prepare traditional maize porridges and compared the carotenoid contents in the following: (1) whole kernels; (2) wet milled flour; (3) wet milled flour, fermented; (4) wet milled flour, cooked; (5) wet milled flour, fermented and cooked. The cumulative losses of beta-carotene in the final, cooked products were 24.5% (95% CI 22.8-26.2%) and 24.8% (95% CI 23.1-26.5%), for the fermented and unfermented porridges, respectively. Thus, fermentation, a traditional technology with documented nutritional and other health benefits, does not adversely affect the retention of beta-carotene in porridges prepared with high beta-carotene maize. The relatively good retention of beta-carotene during traditional maize processing provides additional experimental support for the feasibility of maize biofortification as a means to alleviate vitamin A deficiency.     

Predictors of depression and anxiety in first-year veterinary students: a preliminary report

Historically, veterinary medical students' mental health has rarely been investigated, but recently there has been renewed interest in this topic. The present study evaluated depression and anxiety levels in a cross-sectional investigation of 93 first-year veterinary medical students enrolled at Kansas State University (KSU). During their first semester, students completed the Center for Epidemiological Studies Depression Scale (CES-D) and the Mental Health Inventory's Anxiety Scale (MHI-A). Results indicate that 32% of these first-year KSU veterinary students were experiencing clinical levels of depressive symptoms. Additionally, students reported elevated anxiety scores. Predictors of depression and anxiety levels include homesickness, physical health, and unclear instructor expectations. Areas of intervention with a focus on improving veterinary medical student well-being are discussed.     

Quantifying badger exposure and the risk of bovine tuberculosis for cattle herds in county Kilkenny, Ireland

The objectives of the study were to quantify the levels of badger exposure for cattle and to test the hypothesis that increased badger exposure does not increase the risk of bovine tuberculosis (BTB) in a herd. Information that became available from the targeted removal of badgers over the study period, and from a badger-removal project in county Kilkenny, during 1996-1999 was used. The specific location of cattle within each farm, and the length of time that cattle spent in each farm field during the grazing season, and in the barnyard during winter, was used to build an exposure coefficient to quantify the amount of badger exposure that cattle encountered either on pasture or in the barn. The study design was a matched case-control study in which the control herds were selected using incidence density sampling. During the 4-year study period, 543 badgers were removed and of these 96 badgers were classified as tuberculosis positive; 96 BTB herd breakdowns occurred. There was a significant association between case herds and having a higher badger sett exposure coefficient during 1996-1998. No significant association between case herds and having a higher exposure coefficient based on the number of badgers, or the number of tuberculous badgers, during September 1997-December 1999 was found.     

Carrying capacity, migration, and dispersal in Yellowstone bison

The conservation of bison in Yellowstone National Park, from near extinction in the late 19th century to a recent high of 5000, has led to long-term societal conflict regarding perceived overabundance, trans-boundary movements, and potential transmission of brucellosis from bison to livestock. We synthesized available information to address two central questions in this debate: (1) has the Yellowstone bison population surpassed numbers that can be supported by the forage base in the park; and (2) why do some bison move outside the park during winter, even when numbers are below food-limited carrying capacity? A spatially-explicit model of the system that integrated abiotic variables with biotic processes indicated bison have not reached a theoretical food-limited carrying capacity of 6200 in Yellowstone National Park. However, more bison began to migrate earlier to lower-elevation winter ranges as numbers increased and climatic factors interacted with density to limit nutritional intake and foraging efficiency. A gradual expansion of the winter range as bison numbers increased enabled relatively constant population growth and increased food-limited carrying capacity. Current management actions attempt to preserve bison migration to essential winter range areas within and adjacent to the park, while actively preventing dispersal and range expansion to outlying areas via hazing and removals (i.e., dispersal sink). A population of 2500–4500 bison should satisfy collective interests concerning the park’s forage base, bison movement ecology, retention of genetic diversity, brucellosis risk management, and prevailing social conditions.     

Successful treatment of bilateral paecilomyces pyelonephritis in a German shepherd dog

A six‐year‐old female entire German shepherd dog was investigated for polyuria, polydipsia and lethargy. Investigations revealed a mild azotaemia and abdominal ultrasound revealed marked bilateral dilation of the renal pelves with echogenic material and proximal left hydroureter. Urine cytological examination and aspirates from the right renal pelvis revealed mats of fungal hyphae consistent with fungal bezoar formation. Fungal cultures revealed a profuse growth of Paecilomyces variotii. Initial treatment with oral itraconazole was unsuccessful, leading to bilateral nephrotomies to remove the fungal material. Postoperatively the Paecilomyces infection persisted despite continued itraconazole therapy. Treatment was commenced with amphotericin B, leading to resolution of the dog's clinical signs. To the authors’ knowledge this is the first report of canine Paecilomyces pyelonephritis, without disseminated systemic disease, which documents its successful treatment.     

In vitro activity of ponazuril against Theileria equi

The equid hemoprotozoan parasite Theileria equi is endemic in most regions worldwide. Infection of horses is a cause of significant economic loss due to costs associated with disease and restriction of trade with non-endemic nations. The ability of certain drugs such as imidocarb dipropionate to eliminate persistent T. equi infection and transmission risk is controversial. The anti-protozoal agent ponazuril has been used successfully to treat equine Sarcosystis neurona and Toxoplasma gondii. The hypothesis that ponazuril inhibits replication of T. equi in vitro was tested. T. equi infected equine erythrocyte cultures were treated with ponazuril at multiple concentrations. Cessation of parasite replication was observed over a 5-day period and the degree of inhibition was variable between drug concentrations. Ponazuril inhibited T. equi in erythrocyte culture at all concentrations tested but parasite elimination required at least 500 μg/mL. The high dose of ponazuril required for in vitro inhibition likely limits its ability to control or clear T. equi infection in vivo, however additional research to evaluate related drugs is warranted.