The fat that matters: Soil food web analysis using fatty acids and their carbon stable isotope signature

Chemical taxonomy based upon the composition of lipids is widely applied to investigate microbial communities and fatty acids have recently been employed to connect soil microbial and faunal food webs as well as to elucidate functional groups at higher trophic levels. The additional use of compound-specific isotopic analysis of ¹³C/¹²C ratios in fatty acids allows assessing specific trophic links and belowground carbon fluxes. In this review systematic patterns and processes underlying variations in the composition of fatty acids and their ¹³C/¹²C ratio are described. The emphasis is on biomarker fatty acids, their incorporation and modification, effects of pool size, and analytical methods. Further development of the application of fatty acid profiling to soil ecology should include both advances in experimental research and growth of theory. Accordingly, areas in which future experimentation can lead to progress in soil food web analysis are identified. Overall, combining fatty acid biomarker and their isotopic ratios will allow detailed insight into belowground trophic interactions.     

The fungitoxicity of substituted 2-phenylbenzofurans

Thirty-seven 2-phenylbenzofurans, variously substituted in the homocyclic rings, were synthesised and assessed for antifungal activity in laboratory tests. High activity was shown only by compounds containing a hydroxy group, though amino compounds were also fungitoxic but at a lower level. Possible mechanisms by which these substitutions impart fungitoxicity are discussed with particular reference to the partitioning properties of the molecule.     

An inter-laboratory comparison of multi-enzyme and multiple substrate-induced respiration assays to assess method consistency in soil monitoring

The use of indicators in soil monitoring schemes to detect changes in soil quality is receiving increased attention, particularly the application of soil biological methods. However, to date, the ability to compare information from different laboratories applying soil microbiological techniques in broad-scale monitoring has rarely been taken into account. This study aimed to assess the consistency and repeatability of two techniques that are being evaluated for use as microbiological indicators of soil quality: multi-enzyme activity assay and multiple substrate-induced respiration (MSIR). Data were tested for intrinsic (within-assay plate) variation, inter-laboratory repeatability (geometric mean regression and correlation coefficient) and land-use discrimination (principal components analysis). Intrinsic variation was large for both assays suggesting that high replicate numbers are required. Inter-laboratory repeatability showed diverging patterns for the enzyme assay and MSIR. Discrimination of soils was significant for both techniques with relatively consistent patterns; however, combined laboratory discrimination analyses for each technique showed inconsistent correspondence between the laboratories. These issues could be addressed through the adoption of reliable analytical standards for biological methods along with adequate replication. However, until the former is addressed, dispersed analyses are not currently advisable for monitoring schemes.     

Potential for monoterpenes to affect ectomycorrhizal and saprotrophic fungal activity in coniferous forests is revealed by novel experimental system

The fungal community in coniferous forest soils plays a pivotal role in ecosystem processes such as decomposition and carbon and nutrient cycling. Both saprotrophic (SP) and ectomycorrhizal (ECM) fungi occur throughout the upper soil horizons in coniferous forests and could therefore be exposed to high concentrations of monoterpenes occurring in the needle litter and roots of some tree species. Previous work has noted the differential effects of monoterpenes on the mycelial growth of a range of both SP and ECM fungi when grown in artificial nutrient media. This study used a novel experimental system to assess the effect of environmentally relevant concentrations of monoterpenes on the activity of ECM and SP fungi grown on more natural substrata. Exposure of the ECM fungus Paxillus involutus (Batsch) Fr. to vapours of either α-pinene or β-pinene resulted in a significantly greater proportion of root tips being colonised by the fungus when it was grown with seedlings of Picea abies (L.) Karst. Exposure to monoterpenes resulted in a significant decrease in respiration rate of two species of litter degrading SP fungi, Mycena galopus var. candida J. E. Lange and Collybia butyracea (Bull.) P. Kumm. There was no difference in response between the two SP species, despite the fact that previous tests in liquid nutrient media, with monoterpenes at higher concentrations, indicated that one species was sensitive and one was not. The high volatility and low solubility of monoterpenes in water make them challenging to work with. The experimental system developed here, although still artificial, provides a bridge between pure culture studies in defined media and all the complexities of forest soils in the field, by allowing the exposure of fungi to environmentally relevant monoterpene concentrations in more natural substrata.     

Surgical resection of a dysgerminoma in a mare

A mare was referred for further evaluation of a mass found in the left caudal abdomen during a routine postpartum reproductive palpation. The mare was clinically normal with no history of health problems. Ultrasonographic examination of the mass confirmed its presence, but the origin of the mass could not be accurately determined. Routine haematology and serum biochemistry results were within normal limits. The mare was initially treated conservatively with antibiotics, but the mass continued to increase in size, so it was surgically excised. The mass involved the left ovary. The mare showed transient abdominal pain after surgery, but developed no other complications and was in foal 7 months later. On histology, the mass was diagnosed as a dysgerminoma, a rare ovarian tumour of germ cell origin.     

Pathogenesis studies with Australian bat lyssavirus in grey-headed flying foxes (Pteropus poliocephalus)

OBJECTIVE: To examine the susceptibility of the grey-headed flying fox (Pteropus poliocephalus) to Australian bat lyssavirus (ABL), and to provide preliminary observations on the pathogenesis of the disease in flying foxes. PROCEDURE: Ten flying foxes were inoculated intramuscularly with ABL, and four with a bat-associated rabies virus. Inoculated animals were observed daily, and clinical samples collected every 9 to 14 days. Animals with abnormal clinical signs were euthanased, and samples collected for histological, serological, virological and immunohistological examinations. At 3 months post inoculation (PI), all survivors were euthanased, and each submitted to a similar examination. RESULTS: Three ABL-inoculated flying foxes, and two rabies-inoculated animals developed abnormal clinical signs between 15 and 24 days PI. All three ABL-inoculated animals had histological lesions consistent with a lyssavirus infection, and lyssaviral antigen was identified in the central nervous system (CNS) of each. Virus was isolated from the brain of two affected animals. Of the rabies-inoculated flying foxes, both had histological lesions and viral antigen in the CNS. Virus was recovered from the brain of only one. None of the five affected flying foxes developed anti-lyssavirus antibodies, but, by 3 months PI, five of the seven ABL-inoculated survivors, and one of the two rabies virus-inoculated survivors, had seroconverted. The dynamics of the immune responses were quite variable. CONCLUSIONS: The response of flying foxes to ABL, administered by a peripheral route of inoculation, was similar to that of bats inoculated peripherally with bat-derived rabies viruses.     

Treatment response and long term follow up in nineteen dogs diagnosed with chronic enteropathy in Australia

Chronic enteropathy (CE) in dogs is common worldwide, but little data is available from Australia. The aim of this study was to describe treatment response and long‐term outcome in a cohort of dogs with CE. Dogs were prospectively enrolled at Murdoch University and the University of Melbourne. After diagnostic investigation to rule out diseases other than CE, dogs underwent sequential therapeutic trials until achieving a clinical response (diet then antibiotics, and finally immunosuppressants). Success was defined as 75% reduction of clinical severity for a minimum of five weeks. A total of 21 dogs were enrolled, and 19 completed the study. One dog was euthanised for lack of response to treatment and one excluded for lack of owner compliance. Most dogs responded to diet (n = 10), followed by antibiotics (n = 7) and immunosuppressants (n = 2). Long‐term remission (median 21.1 months, [3.0‐44.7]) was achieved in eight out of ten dietary responders without additional treatment. In contrast, only two dogs with antibiotic response remained in long‐term remission, of which one needed on‐going antibiotic treatment. Longer term remission was achieved in the two dogs treated with immunosuppressants with on‐going low dose therapy. This study concludes that most dogs referred for CE in Australia respond to dietary treatment (even after previous dietary interventions), and remission is long‐term compared to dogs treated with an antibiotic. Furthermore, the need for long‐term antibiotics in some dogs to maintain response may lead to antibiotic resistance. This study supports adequate dietary trials for CE in dogs, and a need for alternative second‐line treatments.     

Hydrogen isotopes in Eocene river gravels and paleoelevation of the Sierra Nevada

We determine paleoelevation of the Sierra Nevada, California, by tracking the effect of topography on precipitation, as recorded in hydrogen isotopes of kaolinite exposed in gold-bearing river deposits from the Eocene Yuba River. The data, compared with the modern isotopic composition of precipitation, show that about 40 to 50 million years ago the Sierra Nevada stood tall (>/=2200 meters), a result in conflict with proposed young surface uplift by tectonic and climatic forcing but consistent with the Sierra Nevada representing the edge of a pre-Eocene continental plateau.