共查询到20条相似文献,搜索用时 15 毫秒
1.
The supernatant arising after biomass separation of Bacillus thuringiensis var. israelensis by flocculation/sedimentation was re-used after being supplemented with 25, 50 and 75% (w/v) of the original culture medium, based on corn steep liquor, glucose and mineral salts. Supplementation at 75% gave a spore concentration (1 x 10(10) c.f.u. ml(-1)) five times greater than that obtained with the other supplements. 相似文献
2.
Larry R. Beuchat Charles A. Pettigrew Mario E. Tremblay Brian J. Roselle Alan J. Scouten 《Journal of industrial microbiology & biotechnology》2005,32(7):301-308
Chlorine, chlorine dioxide (ClO2), and a commercial raw fruit and vegetable sanitizer (Fit powder) were evaluated for their effectiveness in killing vegetative cells and spores of Bacillus cereus and spores of Bacillus thuringiensis. The ultimate goal was to use one or both species as a potential surrogate(s) for Bacillus anthracis in studies that focus on determining the efficacy of sanitizers in killing the pathogen on food contact surfaces and foods. Treatment with alkaline (pH 10.5–11.0) ClO2 (200 mg/mL) produced by electrochemical technologies reduced populations of a five-strain mixture of vegetative cells and a five-strain mixture of spores of B. cereus by more than 5.4 and more than 6.4 log cfu/mL, respectively, within 5 min. This finding compares with respective reductions of 4.5 and 1.8 log cfu/mL resulting from treatment with 200 mg/mL chlorine. Treatment with a 1.5% acidified (pH 3.0) solution of Fit powder product was less effective, causing 2.5-log and 0.4-log cfu/mL reductions in the number of B. cereus cells and spores, respectively. Treatment with alkaline ClO2 (85 mg/mL), acidified (pH 3.4) ClO2 (85 mg/mL), and a mixture of ClO2 (85 mg/mL) and Fit powder product (0.5%) (pH 3.5) caused reductions in vegetative cell/spore populations of more than 5.3/5.6, 5.3/5.7, and 5.3/6.0 log cfu/mL, respectively. Treatment of B. cereus and B. thuringiensis spores in a medium (3.4 mg/mL organic and inorganic solids) in which cells had grown and produced spores with an equal volume of alkaline (pH 12.1) ClO2 (400 mg/mL) for 30 min reduced populations by 4.6 and 5.2 log cfu/mL, respectively, indicating high lethality in the presence of materials other than spores that would potentially react with and neutralize the sporicidal activity of ClO2.Published by permission of the International Association for Food Protection: Journal of Food Protection (2004) 60:1702–1708This revised version was published online in April 2005 with corrections to the text and the section heading.In section Preparation of treatment solutions the phrase 22-28°C was replaced by 22±2°C. 相似文献
3.
Soil respiration of Alaskan tundra at elevated atmospheric carbon dioxide concentrations 总被引:3,自引:0,他引:3
Summary CO2 efflux from tussock tundra in Alaska that had been exposed to elevated CO2 for 2.5 growing seasons was measured to assess the effect of long- and short-term CO2 enrichment on soil respiration. Long-term treatments were: 348, 514, and 683 μll−1 CO2 and 680 μll−1 CO2+4°C above ambient. Measurements were made at 5 CO2 concentrations between 87 and 680 μll−1 CO2. Neither long- or short-term CO2 enrichment significantly affected soil CO2 efflux. Tundra developed at elevated temperature and 680 μll−1 CO2 had slightly higher, but not statistically different, mean respiration rates compared to untreated tundra and to tundra under
CO2 control alone. 相似文献
4.
Bacillus thuringiensis strains were found to be naturally present in the soils of southern Sweden, being isolated from nine out of 12 sites examined. Forest soil samples were more rich in B. thuringiensis strains than soil samples collected from cultivated areas. A wide diversity of B. thuringiensis strains, representing different biochemical groups, was isolated; samples from Aspö and Fogdö regions showed the highest degree of diversity.R. Landén and M. Bryne are with the Department of Microbiology, Stockholm University, S-10691 Stockholm, Sweden. A. Abdel-Hameed is with the Department of Microbiology, Faculty of Pharmacy, Cairo University, Kasr-El-Aini Street, Cairo, Egypt. A. Abdel-Hameed's present address is the Department of Applied Chemistry and Microbiology, PO Box 27, Viikki, Building B, SF-00014 University of Helsinki, Helsinki, Finland 相似文献
5.
Responses of soil biota to elevated atmospheric carbon dioxide 总被引:16,自引:2,他引:14
Elizabeth G. O'Neill 《Plant and Soil》1994,165(1):55-65
Increasing concentrations of atmospheric CO2 could have dramatic effects upon terrestrial ecosystems including changes in ecosystem structure, nutrient cycling rates,
net primary production, C source-sink relationships and successional patterns. All of these potential changes will be constrained
to some degree by below ground processes and mediated by responses of soil biota to indirect effects of CO2 enrichment. A review of our current state of knowledge regarding responses of soil biota is presented, covering responses
of mycorrhizae, N-fixing bacteria and actinomycetes, soil microbiota, plant pathogens, and soil fauna. Emphasis will be placed
on consequences to biota of increasing C input through the rhizosphere and resulting feedbacks to above ground systems. Rising
CO2 may also result in altered nutrient concentrations of plant litter, potentially changing decomposition rates through indirect
effects upon decomposer communities. Thus, this review will also cover current information on decomposition of litter produced
at elevated CO2.
Summary Predictably, the responses of soil biota to CO2 enrichment and the degree of experimental emphasis on them increase with proximity to, and intimacy with, roots. Symbiotic
associations are all stimulated to some degree. Total plant mycorrhization increases with elevated CO2. VAM fungi increase proportionately with fine root length/mass increase. ECM fungi, however, exhibit greater colonization
per unit root length/mass at elevated CO2 than at current atmospheric levels. Total N-fixation per plant increases in all species examined, although the mechanisms
of increase, as well as the eventual benefit to the host relative to N uptake may vary. Microbial responses are unclear. The
assumption that changes in root exudation will drive increased mineralization and facilitate nutrient uptake should be examined
experimentally, in light of recent models. Microbial results to date suggest that metabolic activity (measured as changes
in process rates) is stimulated by root C input, rather than population size (measured by cell or colony counts). Insufficient
evidence exists to predict responses of either soil-borne plant pathogens or soil fauna (i.e., food web responses). These
are areas requiring attention, the first for its potential to limit ecosystem production through disease and the second because
of its importance to nutrient cycling processes. Preliminary data on foliar litter decomposition suggests that neither nutrient
ratios nor decomposition rates will be affected by rising CO2. This is another important area that may be better understood as the number of longer term studies with more realistic CO2 exposures increase. Evidence continues to mount that C fixation increases with CO2 enrichment and that the bulk of this C enters the belowground component of ecosystems. The global fate and effects of this
additional C may affect all hierarchical levels, from organisms to ecosystems, and will be largely determined by responses
of soil biota. 相似文献
6.
Cloning and characterization of an insecticidal crystal protein gene from Bacillus thuringiensis subspecies kenyae 总被引:1,自引:0,他引:1
Misra HS Khairnar NP Mathur M Vijayalakshmi N Hire RS Dongre TK Mahajan SK 《Journal of genetics》2002,81(1):5-11
A sporulating culture ofBacillus thuringiensis subsp.kenyae strain HD549 is toxic to larvae of lepidopteran insect species such asSpodoptera litura, Helicoverpa armigera andPhthorimaea operculella, and a dipteran insect,Culex fatigans. A 1.9-kb DNA fragment, PCR-amplified from HD549 using cryII-gene-specific primers, was cloned and expressed inE. coli. The recombinant protein produced 92% mortality in first-instar larvae ofSpodoptera litura and 86% inhibition of adult emergence inPhthorimaea operculella, but showed very low toxicity againstHelicoverpa armigera, and lower mortality against third-instar larvae of dipteran insectsCulex fatigans, Anopheles stephensi andAedes aegypti. The sequence of the cloned crystal protein gene showed almost complete homology with a mosquitocidal toxin gene fromBacillus thuringiensis var.kurstaki, with only five mutations scattered in different regions. Amino acid alignment with different insecticidal crystal proteins
using the MUTALIN program suggested presence of the conserved block 3 region in the sequence of this protein. A mutation in
codon 409 of this gene that changes a highly conserved phenylalanine residue to serine lies in this block. 相似文献
7.
Photosynthetic inhibition after long-term exposure to elevated levels of atmospheric carbon dioxide 总被引:38,自引:0,他引:38
The effect of long-term exposure to elevated levels of CO2 on biomass partitioning, net photosynthesis and starch metabolism was examined in cotton. Plants were grown under controlled conditions at 350, 675 and 1000 l l-1 CO2. Plants grown at 675 and 1000 l l-1 had 72% and 115% more dry weight respectively than plants grown at 350 l l-1. Increases in weight were partially due to corresponding increases in leaf starch. CO2 enrichment also caused a decrease in chlorophyll concentration and a change in the chlorophyll a/b ratio. High CO2 grown plants had lower photosynthetic capacity than 350 l l-1 grown plants when measured at each CO2 concentration. Reduced photosynthetic rates were correlated with high internal (non-stomatal) resistances and higher starch levels. It is suggested that carbohydrate accumulation causes a decline in photosynthesis by feedback inhibition and/or physical damage at the chloroplast level.Abbreviations Ci
internal CO2 concentration
- Chl
chlorophyll
- DMSO
dimethylsulfoxide
- HSD
honestly significant difference (procedure)
- MCW
methanolchloroform-water
- Pi
inorganic phosphate
- S.E.M.
standard error of mean 相似文献
8.
J.E. Barboza-Corona J.C. Contreras R. Velázquez-Robledo M. Bautista-Justo M. Gómez-Ramírez R. Cruz-Camarillo J.E. Ibarra 《Biotechnology letters》1999,21(12):1125-1129
Three selected strains of Bacillus thuringiensis native to Mexico produced endochitinases, chitobiosidases, and N-acetyl--glucosaminidases in a medium containing colloidal chitin as a main carbon source. Two types of chitinases were clearly identified: endochitinases and chitobiosidases. Chromosomal location of a chitinase gene in B. thuringiensis LBIT-82 was resolved. 相似文献
9.
Zhanna I. Budarina Michael A. Sinev Sergey G. Mayorov Andrei Yu. Tomashevski Igor V. Shmelev Nikolai P. Kuzmin 《Archives of microbiology》1994,161(3):252-257
To investigate the distribution of the hemolysin II determinant among strains of Bacillus cereus and Bacillus thuringiensis, thirteen strains of B. cereus and fourteen strains of B. thuringiensis strains were tested for hybridization of their chromosomal DNAs with a DNA probe containing the B. cereus hemolysin II gene. In addition, the production of hemolysin II, whose activity is not inhibited by cholesterol, was tested. The presence (absence) of the hybridization response in the microorganism's genome correlated with the presence (absence) of cholesterol-unaffected hemolysin production. Only four out of thirteen B. cereus strains were found to give a positive response in hybridization experiments, whereas thirteen out of fourteen B. thuringiensis strains responded positively. DNAs from ten B. thuringiensis strains contained a 3.5 kb EcoRV fragment, which hybridized with the B. cereus hemolysin II gene probe. The 3.5 kb EcoRV DNA fragment from one of these strains (B. thuringiensis VKM-B1555) was cloned and expressed in Escherichia coli cells. The hemolysin encoded by the cloned DNA fragment was not inhibited by cholesterol and possessed all other properties of B. cereus hemolysin II. The obtained data clearly show limited distribution of hemolysin II among B. cereus strains and demonstrate that hemolysin II is more characteristic of B. thuringiensis than B. cereus. 相似文献
10.
Andrew D.B. Leakey 《Proceedings. Biological sciences / The Royal Society》2009,276(1666):2333-2343
Crops with the C4 photosynthetic pathway are vital to global food supply, particularly in the tropical regions where human well-being and agricultural productivity are most closely linked. While rising atmospheric [CO2] is the driving force behind the greater temperatures and water stress, which threaten to reduce future crop yields, it also has the potential to directly benefit crop physiology. The nature of C4 plant responses to elevated [CO2] has been controversial. Recent evidence from free-air CO2 enrichment (FACE) experiments suggests that elevated [CO2] does not directly stimulate C4 photosynthesis. Nonetheless, drought stress can be ameliorated at elevated [CO2] as a result of lower stomatal conductance and greater intercellular [CO2]. Therefore, unlike C3 crops for which there is a direct enhancement of photosynthesis by elevated [CO2], C4 crops will only benefit from elevated [CO2] in times and places of drought stress. Current projections of future crop yields have assumed that rising [CO2] will directly enhance photosynthesis in all situations and, therefore, are likely to be overly optimistic. Additional experiments are needed to evaluate the extent to which amelioration of drought stress by elevated [CO2] will improve C4 crop yields for food and fuel over the range of C4 crop growing conditions and genotypes. 相似文献
11.
One hundred and twenty-six strains of Bacillus thuringiensis representing 57 serovars were allocated to 58 genomic types using random amplified polymorphic DNA (RAPD)-PCR patterns. Serovars darmstadiensis, israelensis, kenyae, kumamotoensis, kurstaki, morrisoni, pakistani, sotto, thuringiensis and tolworthi each encompassed identical or closely related strains. Despite this genomic homogeneity, most of these serovars also included at least one variant strain. Serovars aizawai, canadensis, entomocidus and sotto biotype dendrolimus, on the other hand, were genomically heterogeneous. Of the 57 serovars examined, 31 contained at least one strain with a closely related or identical RAPD pattern to a strain from a different serovar. We conclude that while the species is genomically diverse, the homogeneous serovars represent clonal lineages of successful insect pathogens. 相似文献
12.
Effect of light and atmospheric carbon dioxide concentration on nitrogen fixation by herbage legumes
P. M. Murphy 《Plant and Soil》1986,95(3):399-409
Summary Lucerne, red clover and white clover were grown at two atmospheric concentrations of CO2 (300 and 1000 μl l−1) and the effects on N2 fixation, nodule mass/number and root/shoot dry matter production determined. Pea plants were similarly evaluated as a comparison
with grain legumes. CO2 enrichment increased N2 fixation activity in all cases but activity/unit nodule mass was significantly increased only in the pea. The enhancement
of N2 fixation in herbage legumes by CO2 enrichment reflected an increase in nodule mass which in turn was attributed to increased nodule number, and results show
that under the experimental conditions obtaining here photosynthate supply did not limit nodule N2 fixation in these plants though it was limiting in the case of peas.
White clover growing in a 6 and 14 hour photoperiod was studied for response of the N2 fixing system to light. Long photoperiod (14 hour) plants assayed at constant temperature (20°C) did not show a significant
response to light at the end of the dark period either in terms of fixation per plant or per unit nodule mass, in contrast
with short photoperiod (6 hour) plants which showed significant responses. Short photoperiod plants compensated for reduced
photosynthates by maintaining only half the root nodule mass and fixation activity of 14 hour photoperiod plants though plants
in both systems supported similar rates of N2 fixation per unit mass of nodule during the photoperiod. Comparison of N2 fixation activities in whole and decapitated plant systems indicates the importance of shoot reserves for sustaining nitrogenase
activity in white clover during short-term interruption of photosynthesis. These results support the conclusion of the CO2 enrichment studies, that herbage legumes have the potential for supplying their nodule photosynthate requirements for sustaining
optimum rates of N2 fixation and excess carbon supply is used solely to promote further nodulation.
Nodules of short photoperiod white clover plants were less efficient in N2 fixation in that they evolved more H2 relative to N2 (C2H2) reduced than did long photoperiod plants. 相似文献
13.
The process of dissociation into variants that differ in colony morphology occurring in batch cloned cultures of two Bacillus thuringiensis strains belonging to different subspecies was studied at optimal and elevated temperatures. An increase in the cultivation temperature to 40°C resulted in an increase in the fraction of R variants to 100% after 72 h of cultivation of either of the strains. This increase was not due to the selection of forms with greater resistance to elevated temperature. The level of resistance to elevated temperature was determined by the strain genotype and did not correlate with morphological characteristics of the colonies. 相似文献
14.
The colonizing ability of a transcipient strain of Bacillus megaterium carrying a lepidopteran-specific cryIA (a) gene of Bacillus thuringiensis in the phyllospheres of various economically important plants was studied. Similar experiments were also carried out using the parental B. thuringiensis var. kurstaki strain HD1 for a comparison. While the transcipient remained on the leaves of cotton and okra for more than 28 days, its survival in phyllospheres of mulberry, peanut, chickpea, tomato and rice was rather limited to about 3 – 5 days. The persistence of B. thuringiensis, on the other hand, was extremely short (i.e. less than 4 days) on all the crop plants tested. 相似文献
15.
Franco-Rivera A Benintende G Cozzi J Baizabal-Aguirre VM Valdez-Alarcón JJ López-Meza JE 《Antonie van Leeuwenhoek》2004,86(1):87-92
Bacillus thuringiensis INTA 7-3, INTA 51-3, INTA Mo9-5 and INTA Mo14-4 strains were obtained from Argentina and characterized by determination of serotype, toxicity, plasmid composition, insecticidal gene content ( cry and vip ) and the cloning of the single- vip3A gene of the INTA Mo9-5 strain. The serotype analysis identified the serovars tohokuensis and darmstadiensis for the INTA 51-3 and INTA Mo14-4 strains, respectively, whereas the INTA Mo9-5 strain was classified as "autoagglutinated". In contrast to the plasmid patterns of INTA 7-3, INTA 51-3 and INTA Mo9-5 (which were similar to B. thuringiensis HD-1 strain), strain INTA Mo14-4 showed a unique plasmid array. PCR analysis of the four strains revealed the presence of cry genes and vip3A genes. Interestingly, it was found that B. thuringiensis 4Q7 strain, which is a plasmid cured strain, contained vip3A genes indicating the presence of these insecticidal genes in the chromosome. Bioassays towards various lepidopteran species revealed that B. thuringiensis INTA Mo9-5 and INTA 7-3 strains were highly active. In particular, the mean LC(50) obtained against A. gemmatalis larvae with the INTA Mo9-5 and INTA 7-3 strains were 7 (5.7-8.6) and 6.7 (5.6-8.0) ppm, respectively. The INTA Mo14-4 strain was non-toxic and strain INTA 51-3 showed only a weak larvicidal activity. 相似文献
16.
Bacteriocin-like inhibitor substances produced by Mexican strains of Bacillus thuringiensis 总被引:1,自引:0,他引:1
Barboza-Corona JE Vázquez-Acosta H Bideshi DK Salcedo-Hernández R 《Archives of microbiology》2007,187(2):117-126
Bacteriocins are antimicrobial peptides synthesized and secreted by bacteria and could potentially be used as natural food
preservatives. Here, we report the production of bacteriocin-like inhibitor substances (Bt-BLIS) by five Mexican strains of
Bacillus thuringiensis. Bacillus thuringiensis subsp. morrisoni (LBIT 269), B. thuringiensis subsp. kurstaki (LBIT 287), B. thuringiensis subsp kenyae (LBIT 404), B. thuringiensis subsp. entomocidus (LBIT 420) and B. thuringiensis subsp. tolworthi (LBIT 524) produced proteinaceous Bt-BLIS with high levels of activity against Bacillus cereus and other gram-positive bacteria. Although none was active against the gram-negative bacteria, Escherichia coli, Shigella species and Pseudomonas aeruginosa, the five Bt-BLIS demonstrated antimicrobial activity against Vibrio cholerae, the etiologic agent of cholera. Biochemical and biophysical studies demonstrated that the five Bt-BLIS could be categorized
into two groups, those produced by LBIT 269 and 287 (Group A) and LBIT 404, 420, 524 (Group B), based on relative time of
peptide synthesis, distinctive bacterial target specificity and stability in a wide range of temperatures and pH. Because
of their stability and bactericidal activities against B. cereus and V. cholerae agents of emetic, diarrheal and lethal syndromes in humans, these Bt-BLIS could potentially be used as biodegradable preservatives
in the food industry. 相似文献
17.
Effect of CryIC toxin from Bacillus thuringiensis on larval feeding behavior of Spodoptera exigua 总被引:1,自引:0,他引:1
Mariano Berdegué John T. Trumble William J. Moar 《Entomologia Experimentalis et Applicata》1996,80(2):389-401
The lack of data on the effect of Bacillus thuringiensis (B.t.) toxins on larval feeding behavior of the pest Spodoptera exigua (Hübner) (Noctuidae: Amphypyrini) prompted us to investigate the effect of three delivery systems of CryIC, a commercial formulation, inclusion bodies, and the activated CryIC toxin. The commercial formulation was the least and CryIC toxin the most lethal form to neonates of susceptible colonies. All but two of the treatments in choice tests with neonates and third instars showed significant avoidance of B.t. treated diet, with greater proportion of larvae from susceptible (UCR-S and AUBURN-S) and resistant (AUBURN-R) colonies on untreated diet than on diet treated with any of the CryIC forms and concentrations tested. Furthermore, third instars consumed significantly more control than treated diet for all CryIC forms, colonies and concentrations. The avoidance of CryIC toxin by neonates and third instars strongly suggests that CryIC, which also is present in the commercial formulation and in the inclusion bodies, is responsible for eliciting avoidance behavior by S. exigua larvae. Behavioral observations of third instars in a no-choice test on either treated or control diet indicated that questing behavior in susceptible larvae appears to be positively related with presence of CryIC toxin in the diet. Furthermore, resistant third instars were on the whole more active than susceptible thirds on both treated and control diet. Resistant thirds raised on CryIC treated diet (AUBURN-RC) spent more time eating treated diet than resistant larvae raised on control diet (AUBURN-R), suggesting that diet conditioning plays an important role on feeding behavior of S. exigua. The implications of these results are discussed. 相似文献
18.
The impact of elevated carbon dioxide on the phosphorus nutrition of plants: a review 总被引:1,自引:0,他引:1
Background Increasing attention is being focused on the influence of rapid increases in atmospheric CO2 concentration on nutrient cycling in ecosystems. An understanding of how elevated CO2 affects plant utilization and acquisition of phosphorus (P) will be critical for P management to maintain ecosystem sustainability in P-deficient regions.Scope This review focuses on the impact of elevated CO2 on plant P demand, utilization in plants and P acquisition from soil. Several knowledge gaps on elevated CO2-P associations are highlighted.Conclusions Significant increases in P demand by plants are likely to happen under elevated CO2 due to the stimulation of photosynthesis, and subsequent growth responses. Elevated CO2 alters P acquisition through changes in root morphology and increases in rooting depth. Moreover, the quantity and composition of root exudates are likely to change under elevated CO2, due to the changes in carbon fluxes along the glycolytic pathway and the tricarboxylic acid cycle. As a consequence, these root exudates may lead to P mobilization by the chelation of P from sparingly soluble P complexes, by the alteration of the biochemical environment and by changes to microbial activity in the rhizosphere. Future research on chemical, molecular, microbiological and physiological aspects is needed to improve understanding of how elevated CO2 might affect the use and acquisition of P by plants. 相似文献
19.
The intensity of motility of Bacillus thuringiensis was used to determine the optimal culture time of the inoculum being used for thuringiensin production. Thuringiensin production with an inoculum taken at its maximum motility was about 3 times higher than that with an inoculum taken in the late exponential phase. 相似文献
20.
Christin T. Choma Witold K. Surewicz Paul R. Carey Marianne Pozsgay Harvey Kaplan 《Journal of Protein Chemistry》1990,9(1):87-94
The secondary structure of the toxin fromBacillus thuringiensis subsp.kurstaki (Btk) HD-73 was estimated by Raman, infrared, and circular dichroism spectroscopy, and by predictive methods. Circular dichroism and infrared spectroscopy gave an estimate of 33–40% -helix, whereas Raman and predictive methods gave approximately 20%. Raman and circular dichroism spectra, as well as predictive methods, indicated that the toxin contains 32–40% -sheet structure, whereas infrared spectroscopy gave a slightly lower estimate. Thus, all of these approaches are in agreement that the native conformation of Btk HD-73 toxin is highly folded and contains considerable amounts of both -helical and -sheet structures. No significant differences were detected in the secondary structure of the toxin either in solution or as a hydrated pellet. 相似文献