Performance of phosphate-solubilizing bacteria in soil under high phosphorus conditions

A way to bring phosphate-saturated soils back to an environmentally safe P level is by P mining through plants. Phosphate-solubilizing bacteria (PSB) could be very useful for increasing mining efficiency over time. The goal of this research was to investigate the adaptation and performance of PSB in conditions of high total P content in soil. In the first experiment, the P-solubilizing capacity of five PSB species (three Bacillus spp. and two Pseudomonas spp.) were tested under fully controlled conditions on several growth media with different forms of insoluble phosphate (FePO₄, AlPO₄, or (Ca)₃(PO₄)₂) added at different rates. The colony growth after 14 days of inoculation demonstrated that all five bacteria were able to proliferate and solubilize P on each of the tested growth media, in contradiction with the normally used technique of halo determination. In the second experiment, the same bacterial species were inoculated in pure quartz sand amended with a nutrient solution and P was added separately in an insoluble form, as Fe–P, Al–P, or Ca–P. The extractable ammonium lactate ranged from 3.2 to 6.9 and 29.0 to 40.7 mg?kg^?1 sand for the insoluble Al–P and Fe–P treatments, respectively. Pseudomonas putida and Bacillus brevis performed best as PSB at high P concentration where the P is fixed with Al or Fe. In the third experiment, P. putida and B. brevis were inoculated in an acidic sandy, P-saturated soil for 4 weeks. The inoculation of the PSB gave promising results in solubilizing P.     

Enhancement of Stress Resistance of the Guppy Poecilia reticulata through Feeding with Vitamin C Supplement

This study investigated the use of vitamin C supplement in formulated diets and live Artemia juveniles to enhance the stress resistance of the guppy Poecilia reticulata . To evaluate the stress resistance, fish were subjected to osmotic shock in pre-aerated water containing 35 ppt sodium chloride. Ascorbyl acid-polyphosphate and ascorbyl palmitate were used as vitamin C sources for formulated diets and live Artemia juveniles, respectively. Results showed that guppies fed moist formulated diets supplemented with ascorbic acid at 1,000 mg/kg or 2,000 mg/kg diet displayed significantly higher levels of stress resistance than fish fed control formulated diet for 13 d. The stress resistance of fish fed a lower dose (200 mg/kg diet), however, did not differ significantly from that of the control. On the other hand, the stress resistance of guppies fed Artemia juveniles bio-encapsulated with 10% or 20% ascorbyl palmitate did not show significant difference from that of fish fed control Artemia after 20 d. The stress resistance of these three groups of Artemia- fed fish, however, was significantly higher than that of fish fed the control formulated diet. Biochemical analyses showed that raising the ascorbic acid level in feeds resulted in a concomitant increase in the incorporated ascorbic acid level in the whole-body tissue of the guppy. The increased stress resistance of the guppy fed a vitamin C supplemented diet has also been demonstrated in four commercial farms. The potential application of the improved stress resistance in the ornamental fish industry was discussed.     

Abundance and distribution of<Emphasis Type="Italic"> Xylosandrus germanus</Emphasis> (Blandford 1894) (Coleoptera,Scolytidae) in Belgium: new observations and an attempt to outline its range

In Belgium, the current distribution and abundance of Xylosandrus germanus (Coleoptera, Scolytidae), a relatively new species to the Belgian fauna, is poorly known. Therefore, data on the range and population levels of this ambrosia beetle, on a regional and local scale respectively, are presented. Based on those results, the beetles range is discussed. Among the analysed biotic and abiotic factors that could influence the species settlement and population levels, climatic ones, and temperature in particular, seem to exert a crucial influence.     

Bombus terrestris as pollinator‐and‐vector to suppress Botrytis cinerea in greenhouse strawberry

BACKGROUND: Bombus terrestris L. bumblebees are widely used as commercial pollinators, but they might also be of help in the battle against economically important crop diseases. This alternative control strategy is referred to as pollinator‐and‐vector technology. The present study was designed to investigate the capacity of B. terrestris to fulfil this role in greenhouse strawberry flowers, which were manually inoculated with a major plant pathogen, the grey mould Botrytis cinerea Pers.: Fr. A model microbiological control agent (MCA) product Prestop‐Mix was loaded in a newly developed two‐way bumblebee dispenser, and, in addition, the use of the diluent Maizena‐Plus (corn starch) was tested. RESULTS: Importantly, loading of the MCA caused no adverse effects on bumblebee workers, with no loss of survival or impairment of flight activity of the workers during the 4 week flowering period. Secondly, vectoring of Prestop‐Mix by bumblebees resulted in a higher crop production, as 71% of the flowers developed into healthy red strawberries at picking (preharvest yield) as compared with 54% in the controls. In addition, these strawberries were better protected, as 79% of the picked berries remained free of B. cinerea after a 2 day incubation (post‐harvest yield), while this percentage was only 43% in the control. Overall, the total yield (preharvest × post‐harvest) was 2–2.5 times higher than the total yield in the controls (24%) in plants exposed to bumblebees vectoring Prestop‐Mix. Thirdly, the addition of the diluent Maizena‐Plus to Prestop‐Mix at 1:1 (w/w) resulted in a similar yield to that of Prestop‐Mix used alone, and in no negative effects on the bumblebees, flowers and berries. CONCLUSIONS: This greenhouse study provides strong evidence that B. terrestris bumblebees can vector a MCA to reduce B. cinerea incidence in greenhouse strawberries, resulting in higher yields. Similar yields obtained in the treatments with Prestop‐Mix and Prestop‐Mix + Maizena‐Plus suggest an equally efficient dissemination of the biocontrol agent into the flowers with only half the initial concentration of Prestop‐Mix, which illustrates the importance of the diluent. Copyright © 2011 Society of Chemical Industry     

A laboratory evaluation to determine the compatibility of microbiological control agents with the pollinator Bombus terrestris

BACKGROUND: This study was undertaken to identify any potential adverse side effects of the use of seven microbiological control agents (MCAs) on the bumblebee, Bombus terrestris L., in the context of combined use in integrated pest management (IPM). AQ10^® (Ampelomyces quisqualis), Binab‐T‐vector^® (Hypocrea parapilulifera + T. atroviride; 1/1), Prestop‐Mix^® (Gliocladium catenulatum J1446), Serenade^® (Bacillus subtilis QST713), Trianum‐P^® (Trichoderma harzianum T22), Botanigard^® (Beauveria bassiana GHA) and Granupom^® (Cydia pomonella granulovirus), comprising five biofungicides and two bioinsecticides, were investigated. Bumblebee workers were exposed under laboratory conditions to each MCA at its maximum field recommended concentration (MFRC) via three different routes of exposure: dermal contact and orally via either treated sugar water or pollen. RESULTS: The tested MCAs were found to be safe for workers of B. terrestris, with the exception of Botanigard^® and Serenade^®. Exposure to Botanigard^® via contact at its MFRC caused 92% mortality after 11 weeks, while the 1/10 MFRC killed 46% of exposed workers. For Serenade^®, topical contact and oral delivery via sugar water resulted in 88 and 100% worker mortality respectively. With lower concentrations (1/2, 1/5 and 1/10 MFRC) the toxicity decreased, but the effect depended on the route of exposure. In addition to lethal effects, nests were also evaluated for sublethal effects after treatment with the seven MCAs at their respective MFRCs over 11 weeks. In these bioassays, only Botanigard^® and Serenade^® gave rise to a significant (P < 0.05) decrease in drone production. Sublethal effects on foraging behaviour were also evaluated, and only Botanigard at its MFRC delivered via treated sugar water induced negative effects. CONCLUSION: The results demonstrated that most of the MCAs tested can be considered safe for use in combination with B. terrestris, based on the International Organisation for Biological Control of Noxious Animals and Plants (IOBC) classification. However, some can be harmful, such as the biofungicide Serenade^® and the bioinsecticide Botanigard^®. Therefore, it is recommended that all should be tested before use in combination with pollinators. In this context, it is also advisable that these MCAs should be evaluated in more realistic field situations for the assessment of potentially deleterious effects on foraging behaviour. Copyright © 2009 Society of Chemical Industry     

Oral immunisation of pigs with fimbrial antigens of enterotoxigenic E. coli: an interesting model to study mucosal immune mechanisms

The intestinal mucosal immune system can discriminate actively between harmful pathogenic agents and harmless food antigens resulting in different immune responses namely IgA production and oral tolerance, respectively. Recently, a pig model has been developed for studying intestinal mucosal immune responses in which F4 fimbrial antigens of enterotoxigenic Escherichia coli (F4 ETEC) are used as oral antigens. A unique feature of this model is that soluble F4 antigens can be administered to pigs which have a receptor for this fimbriae (F4R(+)) on their small intestinal villous enterocytes and pigs which do not have this receptor (F4R(-)). Oral administration of F4 to the F4R(+) pigs results in an intestinal mucosal immune response that completely protects the pigs against a challenge infection. In F4R(-) pigs such an intestinal mucosal immune response does not occur. However, a priming of the systemic immune system can be seen similar to the priming in pigs fed with the same dose of a food antigen, suggesting that F4 in F4R(-) pigs behaves as a food antigen. The fact that different mucosal immune responses can be induced with soluble F4, makes it an interesting model to study mucosal immune mechanisms in the pig.     

Histologic and micro-computed tomographic evaluation of the osseointegration of a nonresorbable bone substitute in alveoli of ponies after tooth extraction

OBJECTIVE: To evaluate the biological behavior of a nonresorbable bone substitute (NRBS) in the alveoli of ponies, compared with tissue quality in naturally healing alveoli, after cheek tooth extraction. ANIMALS: 5 clinically normal ponies. PROCEDURES: In each pony, both maxillary fourth premolars (Triadan 108/208) were repulsed bilaterally during anesthesia. One randomly chosen alveolus was filled with NRBS and isolated from the oral cavity by use of dental impression material and a spring-wire retention device. The other alveolus was occluded in its occlusal third portion with dental impression material. One year after surgery, cylindrical lateromedial biopsy specimens were collected from the apical, middle, and occlusal level of each alveolus. Biopsy samples were evaluated for bone mineral density and bone volume via micro-computed tomography; qualitative histologic characteristics were evaluated via light microscopy. RESULTS: Bone mineral density and bone volume were greater in control alveoli, compared with NRBS-treated alveoli. Control alveoli were characterized by the presence of few mature bone trabeculae and wide spaces containing fat tissue and mesenchymal stroma. In treated alveoli, biocompatibility and osteoconductive properties of the NRBS were excellent; continuous bone formation and bone remodeling were also evident. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the NRBS was integrated well in calcified alveolar tissues in ponies 1 year after maxillary cheek tooth extraction. Further research is necessary to establish the benefits of this NRBS in the development of a dental implant surgical technique in equids.     

Transcytosis of F4 fimbriae by villous and dome epithelia in F4-receptor positive pigs supports importance of receptor-dependent endocytosis in oral immunization strategies

Very few antigens have been described that induce an intestinal immunity when given orally. Our laboratory demonstrated that oral administration of isolated F4 (K88) fimbriae of Escherichia coli to F4-receptor positive (F4R(+)) pigs induces protective mucosal immunity against challenge infection. However, presence of F4-receptors (F4R) on villous enterocytes is a prerequisite for inducing the immune response, as no F4-specific antibody-secreting cells (ASC) can be induced in F4R(-) pigs. In this study, the in vivo binding of isolated F4 fimbriae (F4) to the gut epithelium was examined in F4R(+) and F4R(-) pigs. It was further investigated whether binding of F4 to the F4R results in endocytosis in and translocation across the gut epithelium using microscopy. F4 did not adhere to the intestinal epithelium of F4R(-) pigs, whereas it strongly adhered to the villous epithelium and the follicle-associated epithelium (FAE) of the jejunum and ileum of F4R(+) pigs. Following binding to F4R, F4 was endocytosed by villous enterocytes, follicle-associated enterocytes and M cells. Transcytosis of F4 across the epithelium resulted in the appearance of F4 in the lamina propria and dome region of the jejunal and ileal PP. This is the first study showing transcytosis of fimbriae across the gut epithelium. This receptor-dependent transcytosis can explain the success of F4 fimbriae as oral immunogen for inducing protective immunity in F4R(+) pigs strengthening the importance of receptor-dependent endocytosis and translocation in oral vaccine strategies. Further identification of the receptor responsible for this transport is in progress.     

Runoff generation in a degraded Andean ecosystem: Interaction of vegetation cover and land use

Tropical mountain regions are affected by rapid land use/-cover change, which may threaten their (eco-)hydrological functions. Although there is a growing interest in evaluating the effect of land use/-cover change on mountain hydrology, quantitative assessments of the impact of land use/-cover on hydrological processes are hampered by the lack of field measurements characterizing runoff generation processes. In this paper, we present results from field experiments of rainfall runoff mechanisms in the southern Ecuadorian Andes. A rainfall simulator was used to quantify the hydrological response of distinct land use/-cover types to intense rainfall (about 40 mm/h). The rainfall runoff experiments indicate that degraded and abandoned land generate surface runoff within a few minutes after the start of the rainfall event. These lands have a very rapid and sharp hillslope hydrological response, as Hortonian overland flow is the dominant runoff generation mechanism. In contrast, surface runoff on arable and rangelands is rare, as their soils are characterized by a high infiltration capacity (i.e. > 29 mm/h). Our experiments provide evidence that runoff generation in degraded Andean ecosystems is mainly controlled by the surface vegetation cover and land management. When reducing the surface vegetation cover, the soil is increasingly affected by rapid hillslope runoff as the presence of large amounts of smectites in the outcropping soft rocks makes the material very prone to sealing and crusting, thereby enhancing runoff generation.