Variation in physiological host range in three strains of two species of the entomopathogenic fungus Beauveria

Knowledge of the host range of a biocontrol agent (BCA) is fundamental. Host range determines the BCA's economic potential, as well as the possible risk for non-target organisms. Entomopathogenic fungal strains belonging to the genus Beauveria are widely used as BCA, but our knowledge of their physiological host range is only partial. The aim of this study was to improve our understanding of the physiological host range of three Beauveria strains belonging to two species, B. hoplocheli and B. bassiana. We performed laboratory mortality bioassays to assess their pathogenicity and virulence against nine insect pests, belonging to three orders: Lepidoptera, Coleoptera and Diptera. Mortality rate, mean survival time and mycosis rate were used to estimate virulence. Pathogenicity was assessed as the capacity to cause a disease and induce mortality. Virulence was assessed as the severity of the disease based on mortality rate, mean survival time and mycosis rate. The results of this study revealed significant differences in the physiological host range of the three Beauveria strains tested. The three strains were pathogenic to all Diptera and Lepidoptera species tested. In the case of the Coleoptera, only the B. hoplocheli strain was pathogenic to the white grub Hoplochelus marginalis and only the B. bassiana strains were pathogenic to Alphitobius diaperinus. The B. hoplocheli strain was less virulent on Lepidoptera and Diptera than the two B. bassiana strains. The latter both exhibited very similar virulence patterns. The fact that B. hoplocheli and B. bassiana strains have different host ranges means that they can be used as BCA to target different pests. Impacts on non-target insects across multiple orders cannot be ruled out in the absence of ecological host range studies

Water quality monitoring: a ‘toolbox’ in response to the EU’s Water Framework Directive requirements

International audienc

Implications of bio-efficacy and persistence of insecticides when indoor residual spraying and longlasting insecticide nets are combined for malaria prevention.

Bio-efficacy and residual activity of insecticides used for indoor residual spraying (IRS) and long-lasting insecticide nets (LLINs) were assessed against laboratory-reared and wild populations of the malaria vector, Anopheles arabiensis in south eastern Tanzania. Implications of the findings are examined in the context of potential synergies and redundancies where IRS and LLINs are combined. METHODS: Bioassays were conducted monthly for six months on three LLIN types (Olyset(R) PermaNet 2.0(R),and Icon Life(R)) and three IRS treatments (2 g/m2 pirimiphos-methyl, 2 g/m2 DDT and 0.03 g/m2 lambda-cyhalothrin, sprayed on mud walls and palm ceilings of experimental huts). Tests used susceptible laboratory-reared An. arabiensis exposed in cones (nets and IRS) or wire balls (nets only). Susceptibility of wild populations was assessed using WHO diagnostic concentrations and PCR for knock-down resistance (kdr) genes. IRS treatments killed [greater than or equal to] 85% of mosquitoes exposed on palm ceilings and [greater than or equal to] 90% of those exposed on mud walls, but up to 50% of this toxicity decayed within 1-3 months, except for DDT. By 6th month, only 7.5%, 42.5% and 30.0% of mosquitoes died when exposed to ceilings sprayed with pirimiphos-methyl, DDT or lambda-cyhalothrin respectively, while 12.5%, 36.0% and 27.5% died after exposure to mud walls sprayed with the same insecticides. In wire-ball assays, mortality decreased from 98.1% in 1st month to 92.6% in 6th month in tests on PermaNet 2.0(R), from 100% to 61.1% on Icon Life(R) and from 93.2% to 33.3% on Olyset(R) nets. In cone bioassays, mortality reduced from 92.8% in 1st month to 83.3% in 6th month on PermaNet 2.0(R), from 96.9% to 43.80% on Icon Life(R) and from 85.6% to 14.6% on Olyset(R). Wild An. arabiensis were 100% susceptible to DDT, 95.8% to deltamethrin, 90.2% to lambda cyhalothrin and 95.2% susceptible to permethrin. No kdr gene mutations were detected. CONCLUSIONS: In bioassays where sufficient contact with treated surfaces is assured, LLINs and IRS kill high proportions of susceptible An. arabiensis mosquitoes, though these efficacies decay gradually for LLINs and rapidly for IRS. It is, therefore, important to always add intact nets in sprayed houses, guaranteeing protection even after the IRS decays, and to ensure accurate timing, quality control and regular re-spraying in IRS programmes. By contrast, adding IRS in houses with intact LLINs is unlikely to improve protection relative to LLINs alone, since there is no guarantee that unfed vectors would rest long enough on the sprayed surfaces, and because of the rapid IRS decay. However, there is need to clarify these effects using data from observations of free flying mosquitoes in huts. Physiological susceptibility of An. arabiensis in the area remains 100% against DDT, but is slightly reduced against pyrethroids, necessitating caution over possible spread of resistance. The loss of LLIN toxicity, particularly Olyset(R) nets suggests that protection offered by these nets against An. arabiensis may be primarily due to physical bite prevention rather than insecticidal efficacy

Nitrogen and phosphorus limitation of oceanic microbial growth during spring in the Gulf of Aqaba

Bioassay experiments were performed to identify how growth of key groups within the microbial community was simultaneously limited by nutrient (nitrogen and phosphorus) availability during spring in the Gulf of Aqaba's oceanic waters. Measurements of chlorophyll a (chl a) concentration and fast repetition rate (FRR) fluorescence generally demonstrated that growth of obligate phototrophic phytoplankton was co-limited by N and P and growth of facultative aerobic anoxygenic photoheterotropic (AAP) bacteria was limited by N. Phytoplankton exhibited an increase in chl a biomass over 24 to 48 h upon relief of nutrient limitation. This response coincided with an increase in photosystem II (PSII) photochemical efficiency (F v /F m), but was preceded (within 24 h) by a decrease in effective absorption crosssection (σPSII) and electron turnover time (τ). A similar response for τ and bacterio-chl a was observed for the AAPs. Consistent with the up-regulation of PSII activity with FRR fluorescence were observations of newly synthesized PSII reaction centers via low temperature (77K) fluorescence spectroscopy for addition of N (and N + P). Flow cytometry revealed that the chl a and thus FRR fluorescence responses were partly driven by the picophytoplankton (æ10 μm) community, and in particular Synechococcus. Productivity of obligate heterotrophic bacteria exhibited the greatest increase in response to a natural (deep water) treatment, but only a small increase in response to N and P addition, demonstrating the importance of additional substrates (most likely dissolved organic carbon) in moderating the heterotrophs. These data support previous observations that the microbial community response (autotrophy relative to heterotrophy) is critically dependent upon the nature of transient nutrient enrichment. © Inter-Research 2009

Yield Enhancement of Digital Microfluidics-Based Biochips Using Space Redundancy and Local Reconfiguration

As microfluidics-based biochips become more complex, manufacturing yield will have significant influence on production volume and product cost. We propose an interstitial redundancy approach to enhance the yield of biochips that are based on droplet-based microfluidics. In this design method, spare cells are placed in the interstitial sites within the microfluidic array, and they replace neighboring faulty cells via local reconfiguration. The proposed design method is evaluated using a set of concurrent real-life bioassays.Comment: Submitted on behalf of EDAA (http://www.edaa.com/

Susceptibility of the Endangered Karner Blue Butterfly (Lepidoptera: Lycaenidae) to \u3ci\u3eBacillus Thuringiensis\u3c/i\u3e Var. \u3ci\u3eKurstaki\u3c/i\u3e Used for Gypsy Moth Suppression in Michigan

We investigated the phenological and physiological susceptibility of the endangered Karner blue butterfly (Lycaeides melissa samuelis) to Bacillus thuringiensis var. kurstaki (Bt), a product widely used for gypsy moth (Lymantria dispar) suppression in Michigan and other infested states. We monitored phenology of the bivoltine Karner blue in two regions of Michigan from 1993 to 1995 to determine if larval stages overlapped temporally with the period of Bt application for gypsy moth suppression. Karner blue larvae of the spring generation were found during the period that Bt was applied in nearby areas in 1993 only. However, spring-generation adults or newly laid eggs were observed up to 11 days before applications in 1994 and 1995. Since Karner blue eggs develop within one week, summer-generation larvae were most likely present during or shortly after 1994 and 1995 Bt application periods. These larvae would have been at risk, assuming Bt persistence of 4 to 6 days. Physiological susceptibility of Karner blue larvae to Bt was determined in a laboratory bioassay. Larvae were reared on wild lupine (Lupinus perennis) foliage that was untreated, or sprayed with Bt formulations at rates of 30-37 or 90 BIU/ha. A similar bioassay with second instar gypsy moth larvae on similarly treated white oak (Quercus alba) foliage was conducted concurrently. Karner blue survival was 100%, 27% and 14% on control, low and high Bt treatments, respectively. Early and late Karner blue instars were equally susceptible to Bt. Survival of gypsy moth was 80%, 33% and 5% on control, low and high Bt treatments, respectively, and did not differ significantly from Karner blue survival. We conclude that Karner blue is both phenologically and physiologically susceptible to Bt used for gypsy moth suppression, although the larval generation at risk and extent of phenological overlap may vary from year to year

Nitrogen and phosphorus limitation of phytoplankton growth in New Zealand lakes: Implications for eutrophication control

We examine macronutrient limitation in New Zealand (NZ) lakes where, contrary to the phosphorus (P) only control paradigm, nitrogen (N) control is widely adopted to alleviate eutrophication. A review of published results of nutrient enrichment experiments showed that N more frequently limited lake productivity than P; however, stoichiometric analysis of a sample of 121 NZ lakes indicates that the majority (52.9%) of lakes have a mean ratio of total nitrogen (TN) to total phosphorus (TP) (by mass) indicative of potential P-limitation (>15:1), whereas only 14.0% of lakes have mean TN:TP indicative of potential N-limitation (<7:1). Comparison of TN, TP, and chlorophyll a data between 121 NZ lakes and 689 lakes in 15 European Union (EU) countries suggests that at the national scale, N has a greater role in determining lake productivity in NZ than in the EU. TN:TP is significantly lower in NZ lakes across all trophic states, a difference that is driven primarily by significantly lower in-lake TN concentrations at low trophic states and significantly higher TP concentrations at higher trophic states. The form of the TN:TP relationship differs between NZ and the EU countries, suggesting that lake nutrient sources and/or loss mechanisms differ between the two regions. Dual control of N and P should be the status quo for lacustrine eutrophication control in New Zealand and more effort is needed to reduce P inputs

Development and application of a bioassay for follicle-stimulating hormone : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physiology at Massey University

Follicle-stimulating hormone (FSH) is involved in the regulation and maintenance of vital reproductive processes, such as gametogenesis, follicular development and ovulation. Produced in the anterior pituitary, FSH is a glycoprotein hormone that exists as a family of isohormones. Follicle-stimulating hormone concentrations have traditionally been measured by radioimmunoassay (RIA). However, results generated using RIA are a determination of the immunological activity of FSH. The potential of FSH to generate a biological response cannot be measured by RIA. Therefore, the identification of physiologically significant differences in the activity of these isoforms requires the use of assay systems that can differentiate between the biological activity of the FSH isoforms. Commonly used assays for measuring the biological activity of FSH are based on the measurement of aromatase activity in cultured rat Sertoli cells following stimulation with FSH. However, these assays have an inherently high ethical cost involved due to the use of primary tissue culture. In addition, the variation in these assays associated with differences between animals is difficult to eliminate. Recently a bioassay for human FSH has been described based on FSH stimulation of cyclic AMP production by a Chinese hamster ovary (CHO) cell line stably expressing the human FSH receptor (FSH-R). The purpose of this study was to evaluate the potential usefulness of this CHO FSH-R cell line expressing the human receptor for FSH to be used as a bioassay to measure the biological activity of ovine FSH. The receptor cell line bioassay described in this study is based on the ability of FSH to stimulate cAMP production by cultured CHO FSH-R cells. Optimisation of the culture system to enable the bioactivity of ovine FSH to be measured by bioassay was undertaken. This involved optimising the density of cultured cells, the time in culture and time exposed to FSH and the most suitable dose range for FSH. The influence of matrix effects, such as those exerted by serum was also investigated. The specificity of the assay towards FSH was also determined as was the sensitivity, accuracy and precision of the assay. No stimulation of cAMP production was seen in CHO FSH-R cells following treatment with α-FSH, β-FSH, LH, TSH, GH, prolactin or vasopressin at concentrations up to 10 μg/ml. Although the methodology used differed slightly depending on the presence or absence of serum, all assayed were performed using the following methods and materials. Freshly thawed FSH-R cells were bulked up in culture, and aliquots of 1 x 105 to 5 x 105 cells/well dispensed into 48 well culture dishes and incubated overnight at 37°C. The assay culture media was then replaced with 0.25 ml fresh media (α-MEM + 0.1% BSA + 0.25 mM 3-isobutyl-1-methyl-xanthine) containing varying doses of NIH-FSH-RP2 (RP2) FSH preparations or FSH containing samples, and the cells incubated for 4 hours at 37°C. The assay culture media was then removed and stored frozen at -20°C until assayed for cyclic adenosine monophosphate (cAMP) by RIA. Once optimal assay conditions were determined, the CHO FSH-R cell bioassay was used to measure FSH concentrations in ovine serum, pituitary extracts and medium from cultures of ovine pituitary cells. It was found that the concentrations of FSH in serum from intact sheep was close to the detection limit of the assay. Thus, while FSH concentrations could be measured in serum from some sheep, other animals had concentrations that were too low to be accurately measured by the bioassay in its present form. The assay was, however, well suited to measuring FSH concentrations in serum from sheep that had elevated concentrations of FSH. In one study, FSH concentrations measured by the bioassay were compared to those measured by RIA in sheep that had been ovariectomised and then hypophysectomised. It was found that the profile of FSH concentrations following hypophysectomy was similar whether measured by RIA or by bioassay (R2=0.7513), though absolute concentrations sometimes differed. This suggested that the immunoassay and bioassay were not always measuring the same characteristics of FSH. The assay was also used to measure FSH concentrations in samples of ovine hypophyseal venous blood. However, the results obtained for these samples indicated a poor correlation between FSH concentrations obtained by bioassay and RIA. Levels of bioactive FSH in hypophyseal venous blood fluctuated markedly and were up to 10-fold higher than the associated RIA concentrations. The CHO-cell bioassay was also found to be very suitable for measuring pituitary concentrations of FSH. In one study, pituitary extracts underwent chromatography and the separated isoforms of FSH were analysed by bioassay and RIA. Again, there was excellent correlation (R2=0.9328) between the concentrations of FSH measured both assay types. However, some differences were apparent suggesting a discrepancy in the biological and immunological characteristics of different FSH isoforms. The bioassay was also used to measure FSH concentrations in media from pituitary cells in tissue culture where serially diluted samples displayed good parallelism with the RP2 FSH standard curve. Results of this study demonstrate that the CHO FSH-R cell bioassay is suitable for measuring the biological activity of ovine FSH in a variety of biological fluids. The use of a permanent cell line eliminates the high ethical cost associated with primary tissue culture that other bioassay systems have. The inherent variation associated with culture systems utilising tissue from different sources is also avoided. The sensitivity of the bioassay is suitable for measuring FSH in surgically altered sheep or hypophyseal blood concentrations where FSH levels are generally higher than those in the peripheral circulation. In addition to blood samples, the bioassay is also excellent for monitoring FSH activity in pituitary extracts and in media from tissue culture. However, the sensitivity of the bioassay currently does not always allow measurement of bioactive FSH concentrations in serum samples with low FSH levels. In summary, the CHO FSH-R cell bioassay described in this study offers a useful alternative to RIA and other bioassays for monitoring the biological activity of ovine FSH and its isoforms in various biological fluids. It is concluded that this convenient and robust bioassay may have considerable application in future investigations of ovine FSH bioactivity