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Spore Concentration (spore + concentration)
Selected AbstractsImmunological quantification of the nematode parasitic bacterium Pasteuria penetrans in soilFEMS MICROBIOLOGY ECOLOGY, Issue 3 2001S Fould Abstract Currently, the abundance of Pasteuria penetrans in soils, an unculturable bacterial parasite of root-knot nematodes (Meloidogyne spp.), is estimated by the percentage of nematode juveniles infected with bacteria and the number of spores attached to their cuticle. Indirect immunofluorescence led to detection of free spores directly in soil suspensions using UV light and polyclonal antibodies raised against two P. penetrans populations (ORS-21414-Sen and PP1). Three extraction methods were compared in order to improve spore recovery. A gentle shaking/sieving method recovered more than 90% of the spores inoculated in soils and was more efficient and simple than aqueous two-phase partitioning and polyethylene glycol extractions. All the spores inoculated in sandy or sandy,clay soils were detected with immunofluorescence microscopy. The quantification of the spores was improved using an ELISA technique that showed a good correlation between optical density and spore concentration in inoculated soils. Specific antibodies provide a suitable method to quantify P. penetrans and may be used to follow the evolution of the real pool of bacteria either in native suppressive soils or in inoculated ones. [source] Entomopathogenic potential of Metarhizium anisopliae isolated from engorged females and tested in eggs and larvae of Boophilus microplus (Acari: Ixodidae)JOURNAL OF BASIC MICROBIOLOGY, Issue 4 2004Éverton Kort Kamp Fernandes The purpose of this work was to evaluate the in vitro virulence of three isolates of Metarhizium anisopliae var. anisopliae to eggs and larvae of the tick Boophilus microplus. The fungus tested was isolated from engorged females of B. microplus collected in the field, and identified as Ma01, Ma02 e Ma04. These isolates were evaluated by immersion of eggs and larvae in suspension with different conidial concentrations: 105, 106, 107 e 108 conidia/ml. In each isolate there was a treatment group for each spore concentration and a control group with 10 repetitions. It was observed in the treated egg groups that there was a hatching percentage that was much less than that observed in the control groups. This was in inverse proportion to the conidia concentration/ml. Larval bioassays of all the tested isolates resulted in a high mortality of larvae in direct proportion to the spore concentration/ml, 10 days after the conidia suspensions were inoculated. To consolidate the infection, the fungus used in bioassays was re-isolated. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chitosan Protects Cooked Ground Beef and Turkey Against Clostridium perfringens Spores During ChillingJOURNAL OF FOOD SCIENCE, Issue 6 2006Vijay K. Juneja ABSTRACT:, We investigated the inhibition of Clostridium perfringens spore germination and outgrowth by the biopolymer chitosan during abusive chilling of cooked ground beef (25% fat) and turkey (7% fat) obtained from a retail store. Chitosan was mixed into the thawed beef or turkey at concentrations of 0.5%, 1.0%, 2.0%, or 3.0% (w/w) along with a heat-activated 3-strain spore cocktail to obtain a final spore concentration of 2 to 3 log10 CFU/g. Samples (5 g) of the ground beef or turkey mixtures were then vacuum-packaged and cooked to 60 °C in 1 h in a temperature-controlled water bath. Thereafter, the products were cooled from 54.4 to 7.2 °C in 12, 15, 18, or 21 h, resulting in 4.21, 4.51, 5.03, and 4.70 log10 CFU/g increases, respectively, in C. perfringens populations in the ground beef control samples without chitosan. The corresponding increases for ground turkey were 5.27, 4.52, 5.11, and 5.38 log10 CFU/g. Addition of chitosan to beef or turkey resulted in concentration- and time-dependent inhibition in the C. perfringens spore germination and outgrowth. At 3%, chitosan reduced by 4 to 5 log10 CFU/g C. perfringens spore germination and outgrowth (P, 0.05) during exponential cooling of the cooked beef or turkey in 12, 15, or 18 h. The reduction was significantly lower (P < 0.05) at a chilling time of 21 h, about 2 log10 CFU/g, that is, 7.56 log10 CFU/g (unsupplemented) compared with 5.59 log10 CFU/g (3% chitosan). The results suggest that incorporation of 3% chitosan into ground beef or turkey may reduce the potential risk of C. perfringens spore germination and outgrowth during abusive cooling from 54.4 to 7.2 °C in 12, 15, or 18 h. [source] Evaluation of the biocontrol potential of various Metarhizium isolates against green peach aphid Myzus persicae (Homoptera: Aphididae)PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 6 2010Le-Tian Shan Abstract BACKGROUND: Twenty-three isolates of Metarhizium anisopliae (Metschnikof) Sorokin and M. acridum (Driver & Milner) JF Bischoff, Rehner & Humber from non-aphid host insects around the globe were evaluated for their aphid biocontrol potential, which is not well known. RESULTS: The apterous adults of green peach aphid Myzus persicae (Sulzer) were exposed to the fungal sprays of 11.5, 99 and 1179 conidia mm,2 and blank control in three leaf-dish bioassays. All the tested isolates except one were proven to be infective to the aphid species at 21 ± 1 °C and 14:10 h light:dark photoperiod, causing corrected mortalities of 10.1,95.3% at the high spore concentration. The data from ten isolates causing > 50% mortality at the high concentration were found to fit a time,concentration,mortality model well, yielding parameters for the estimates of their LC50 and LT50 that vary with post-spray time and spore concentration respectively. Four isolates of M. anisopliae (ARSEF 759, 4132, 2080 and 576) had LC50 values of 44,80 conidia mm,2 on day 8 and LT50 values of 4.9,6.8 days at 100 conidia mm,2, with 91,98% of the killed aphids being well mycotised after death. CONCLUSION: The Metarhizium infectivity to M. persicae differs greatly among the tested isolates. The four mentioned isolates with desired virulence and sporulation potential are excellent candidates for microbial control of aphids. Copyright © 2010 Society of Chemical Industry [source] A Procedure for High-Yield Spore Production by Bacillus s ubtilisBIOTECHNOLOGY PROGRESS, Issue 4 2005Sandra M. Monteiro Bacillus subtilis spores have a number of potential applications, which include their use as probiotics and competitive exclusion agents to control zoonotic pathogens in animal production. The effect of cultivation conditions on Bacillus subtilis growth and sporulation was investigated in batch bioreactions performed at a 2-L scale. Studies of the cultivation conditions (pH, dissolved oxygen concentration, and media composition) led to an increase of the maximum concentration of vegetative cell from 2.6 × 109 to 2.2 × 1010 cells mL - 1 and the spore concentration from 4.2 × 108 to 5.6 × 109 spores mL - 1. A fed-batch bioprocess was developed with the addition of a nutrient feeding solution using an exponential feeding profile obtained from the mass balance equations. Using the developed feeding profile, starting at the middle of the exponential growth phase and finishing in the late exponential phase, an increase of the maximum vegetative cell concentration and spore concentration up to 3.6 × 1010 cells mL - 1 and 7.4 × 109 spores mL - 1, respectively, was obtained. Using the developed fed-batch bioreaction a 14-fold increase in the concentration of the vegetative cells was achieved. Moreover, the efficiency of sporulation under fed-batch bioreaction was 21%, which permitted a 19-fold increase in the final spore concentration, to a final value of 7.4 × 109 spores mL - 1. This represents a 3-fold increase relative to the highest reported value for Bacillus subtilis spore production. [source] Respiration and annual fungal production associated with decomposing leaf litter in two streamsFRESHWATER BIOLOGY, Issue 9 2004M. D. Carter Summary 1. We compared fungal biomass, production and microbial respiration associated with decomposing leaves in one softwater stream (Payne Creek) and one hardwater stream (Lindsey Spring Branch). 2. Both streams received similar annual leaf litter fall (478,492 g m,2), but Lindsey Spring Branch had higher average monthly standing crop of leaf litter (69 ± 24 g m,2; mean ± SE) than Payne Creek (39 ± 9 g m,2). 3. Leaves sampled from Lindsey Spring Branch contained a higher mean concentration of fungal biomass (71 ± 11 mg g,1) than those from Payne Creek (54 ± 8 mg g,1). Maximum spore concentrations in the water of Lindsay Spring Branch were also higher than those in Payne Creek. These results agreed with litterbag studies of red maple (Acer rubrum) leaves, which decomposed faster (decay rate of 0.014 versus 0.004 day,1), exhibited higher maximum fungal biomass and had higher rates of fungal sporulation in Lindsey Spring Branch than in Payne Creek. 4. Rates of fungal production and respiration per g leaf were similar in the two streams, although rates of fungal production and respiration per square metre were higher in Lindsey Spring Branch than in Payne Creek because of the differences in leaf litter standing crop. 5. Annual fungal production was 16 ± 6 g m,2 (mean ± 95% CI) in Payne Creek and 46 ± 25 g m,2 in Lindsey Spring Branch. Measurements were taken through the autumn of 2 years to obtain an indication of inter-year variability. Fungal production during October to January of the 2 years varied between 3 and 6 g m,2 in Payne Creek and 7,27 g m,2 in Lindsey Spring Branch. 6. Partial organic matter budgets constructed for both streams indicated that 3 ± 1% of leaf litter fall went into fungal production and 7 ± 2% was lost as respiration in Payne Creek. In Lindsey Spring Branch, fungal production accounted for 10 ± 5% of leaf litter fall and microbial respiration for 13 ± 9%. [source] The role of seeds and airborne inoculum in the initiation of leaf blotch (Rhynchosporium secalis) epidemics in winter barleyPLANT PATHOLOGY, Issue 2 2010J. M. Fountaine Both airborne spores of Rhynchosporium secalis and seed infection have been implied as major sources of primary inoculum for barley leaf blotch (scald) epidemics in fields without previous history of barley cropping. However, little is known about their relative importance in the onset of disease. Results from both quantitative real-time PCR and visual assessments indicated that seed infection was the main source of inoculum in the field trial conducted in this study. Glasshouse studies established that the pathogen can be transmitted from infected seeds into roots, shoots and leaves without causing symptoms. Plants in the field trial remained symptomless for approximately four months before symptoms were observed in the crop. Covering the crop during part of the growing season was shown to prevent pathogen growth, despite the use of infected seed, indicating that changes in the physiological condition of the plant and/or environmental conditions may trigger disease development. However, once the disease appeared in the field it quickly became uniform throughout the cropping area. Only small amounts of R. secalis DNA were measured in 24 h spore-trap tape samples using PCR. Inoculum levels equivalent to spore concentrations between 30 and 60 spores per m3 of air were only detected on three occasions during the growing season. The temporal pattern and level of detection of R. secalis DNA in spore tape samples indicated that airborne inoculum was limited and most likely represented rain-splashed conidia rather than putative ascospores. [source] Conidial dispersal by Alternaria brassicicola on Chinese cabbage (Brassica pekinensis) in the field and under simulated conditionsPLANT PATHOLOGY, Issue 5 2003L. Y. Chen This study investigated conidial dispersal in the field, and effects of simulated wind and rain on the dispersal of A. brassicicola on Chinese cabbage (Brassica pekinensis). Spores were sampled using a Burkard volumetric spore sampler and rotorod samplers in a Chinese cabbage crop. Disease incidence in the field was well fitted by a Gompertz curve with an adjusted r2 of >0·99. Conidia of A. brassicicola were trapped in the field throughout the growing season. Peaks of high spore concentrations were usually associated with dry days, shortly after rain, high temperature or high wind speed. Diurnal periodicity of spore dispersal showed a peak of conidia trapped around 10·00 h. The number of conidia trapped at a height of 25 cm above ground level was greater than that at 50, 75 and 100 cm. Conidial dispersal was also studied under simulated conditions in a wind tunnel and a rain simulator. Generalized linear models were used to model these data. The number of conidia caught increased significantly at higher wind speeds and at higher rain intensities. Under simulated wind conditions, the number of conidia dispersed from source plants with wet leaves was only 22% of that for plants with dry leaves. Linear relationships were found between the number of conidia caught and the degree of infection of trap plants. [source] | |||||||||||||