摘要:

The accumulation and persistance in soil and other natural habitats of the insecticidal toxins fromBacillus thuringiensismay result in environmental hazards, such as toxicity to nontarget species and the selection of toxin-resistant target species. We describe the use of flow cytometry as a method for detecting and tracking the fate of these insecticidal toxins in soil that does not require their extraction and purification. The toxins fromB.thuringiensissubspp.tenebrionisandkurstakiwere bound on clay- or silt-sized particles separated from Kitchawan soil that was unamended (naturally contains predominantly kaolinite) or amended to 6% v/v with the clay minerals montmorillonite or kaolinite (as an internal control). The particle–toxin mixtures were suspended in 0.1 M phosphate buffer (pH 7) containing 3% nonfat milk powder to block nonspecific binding of antibody, resuspended in a solution of antibody to the toxin fromB.thuringiensissubsp.tenebrionis, and then resuspended in a solution of anti-rabbit antibody conjugated with fluorescein isothiocyanate (FITC–Ab). Controls consisted of the particles alone and bound complexes of the particles with the toxin fromB.thuringiensissubsp.kurstaki. All particles that bound the toxin fromB.thuringiensissubsp.tenebrionisshowed a significant shift in the peak of fluorescence to the right on thexaxis as compared with the nonspecific fluorescence from the control FITC–Ab complexes with particles in the absence of the toxin. There was also a slight shift in the peak to the right for some particles that bound the toxin fromB.thuringiensissubsp.tenebrionis, as there is some cross-reactivity between the toxins fromB.thuringiensissubspp.tenebrionisandkurstakiand the antibodies that they induce. This method is more sensitive and rapid than the dot-blot ELISA, and processing of many samples is easily accomplished.Key words: flow cytometry, soil, insecticidal toxins,Bacillus thuringiensis, clay, silt.

ISSN:0008-4166    

DOI:10.1139/m97-153

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The bacterial flora of an experimental plant that processes liquid swine manure by an aerated compartmented (multistage) lagoon system has been studied. The total flora is characterized by a larger number of oligotrophic bacteria than eutrophic ones. Each compartment displays a specific flora, different from the flora in the manure, and consisting of a complex assembly of Gram-negative and Gram-positive ubiquitous species, such asAeromonasspp. andPseudomonasspp., and specialized species, such asSphingobacteriumspp. andCorynebacteriumspp. The fecal indicator microorganisms have been shown to disappear in the course of the processing. A significant population of nitrifying bacteria has been observed at levels up to 104bacteria∙mL−1.Key words: swine manure, processing lagoon, bacterial flora, wastewate

ISSN:0008-4166    

DOI:10.1139/m97-154

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Genetic control of polygalacturonase (PG) activity fromFusarium oxysporumf.sp.radicis lycopersiciwas analyzed on pectin and glucose cultures. One exopolygalacturonase fromF.oxysporumf.sp.radicis lycopersiciwas strongly induced, in stationary culture, when the fungus was grown on apple pectin, while on glucose no extracellular PG activity could be detected. Although SDS–PAGE detected the presence of a putative PG band (66 kDa) in both conditions, specific antibodies obtained against the purified PG only detected it in PG-inducing conditions, that is to say, when apple pectin was used as the carbon source. Northern blot analysis of RNA of two isolates ofF.oxysporumf.sp.radicis lycopersici(r6and r2) confirmed that this regulation of PG synthesis was exerted at the transcriptional level. Only one single mRNA species of around 1400 nucleotides was detected on the cultures containing pectin and was absent in glucose-grown cultures. Southern blot analysis of genomic DNA indicated thatpggene seems to be present in a single copy in the genomes ofF.oxysporumf.sp.radicis lycopersicir6and r2andFusarium oxysporumf.sp.lycopersici, showing similar hybridization patterns in all species. The partial sequence of thispggene fromF.oxysporumf.sp.radicis lycopersicir6, which is also reported, showed high similarity to diverse PGs already reported. Exopolygalacturonase ofF.oxysporumf.sp.radicis lycopersicir6is heavily glycosylated; its deglycosylated form had a molecular mass of 50 kDa.Key words: polygalacturonase,Fusarium oxysporumf.sp.radicis lycopersici, regulation.

ISSN:0008-4166    

DOI:10.1139/m97-155

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Methods for encapsulating pollutant-degrading bacteria into microbeads of carrageenan type I, carrageenan type II, and guar gum are described. Cell suspensions in solutions of encapsulating agents were passed through a low-pressure nozzle into an aqueous medium. The resultant aerosols polymerized to form microbeads that ranged in diameter from 2–70 μm. Pentachlorophenol degradation experiments with an encapsulatedSphingomonassp. showed degradation rates similar to those seen using free cells. These results describe three additional matrices for the microencapsulation of bacteria that have potential for use in bioremediation processes.Key words:Sphingomonas, pentachlorophenol, immobilization, encapsulation, bioremediation.

ISSN:0008-4166    

DOI:10.1139/m97-156

出版商:NRC Research Press    

年代:1997

数据来源: NRC