Erratum to Bacterial diversity in toxic<Emphasis Type="Italic"> Alexandrium tamarense</Emphasis> blooms off the Orkney Isles and the Firth of Forth

The genetic diversity of the bacterial community associated with Alexandrium tamarense blooms was studied in blooms of the toxic dinoflagellates in the waters around the Orkney Isles and the Firth of Forth (Scotland). For toxin and molecular analysis of the bacterial communities associated with the toxic bloom, water samples were taken in 1998 and 1999 from A. tamarense blooms. The bacterial community structure, as determined by DGGE (denaturing gradient gel electrophoresis) showed clear differences between all three investigated size fractions (dinoflagellate-associated bacteria, attached bacteria and free-living bacteria), with high diversity within each sample. DNA sequence analysis of the dominant and most frequent DGGE bands revealed the dominance of α Proteobacteria, mainly of the Roseobacter clade, with similarities of 91–99%. Moreover, DGGE bands occurring at the same position in the gel throughout in most samples corroborate the presence of several specific α Proteobacteria of the Roseobacter clade. Overall, 500 bacteria were isolated from the bloom and partly phylogenetically analysed. They were members of two prokaryotic phyla, the Proteobacteria and the Bacteroidetes, related to Proteobacteria of the α and γ subdivisions (Alteromonas, Pseudoalteromonas and Colwellia). All bacteria were tested for the production of sodium channel blocking (SCB) toxins using mouse neuroblastoma assay. No production of SCB toxins was found and high performance liquid chromatography (HPLC) analysis confirmed these results. The content of total paralytic shellfish poisoning (PSP) toxin in the water samples, as measured within the toxic dinoflagellate blooms using HPLC, ranged from 53 to 2191 ng PSP l^?1 in 1998 and from 0 to 478 ng PSP l^?1 in 1999. Changes in PSP toxin content were not accompanied by changes of DGGE band patterns. We therefore presume that the bacterial groups identified in this study were not exclusively associated with toxic A. tamarense, but were generally associated with the phytoplankton.     

Toxins from anaerobic bacteria: specificity and molecular mechanisms of action

Major advances have been made in the past five years in the identification of cellular targets of toxins produced by anaerobic bacteria. These targets include the vesicular membrane docking and fusion apparatus, the actin cytoskeleton, the signal transduction machinery and the cell membrane. The recent discovery that large clostridial toxins (Clostridium difficile A and B toxins, C. sordellii lethal and hemorrhagic toxins, and alpha C. novyi toxin) are monoglucosyltransferases, together with the establishment of the perfringolysin crystal structure, has led to new insights in the field of toxins from anaerobic bacteria.     

新组合菌系SCB329-SCB933利用L-山梨糖发酵产生维生素C前体——2-酮基-L-古龙酸的研究 Ⅰ.新组合菌系SCB329-SCB933的生物学特性

采用紫外照射、化学诱变和原生质融合等方法选育到一株性状更优良的突变株SCB329,并与新筛选的一株芽孢杆菌SCB933搭配组成新的组合菌系。产酸小菌SCB329与其亲本菌株氧化葡萄糖酸杆菌性状相似。伴生大菌SCB933属苏芸金芽孢杆菌（B.thuringiensis）。新组合菌系利用L-山梨糖的发酵液提取后经纸层析,元素分析和红外吸收光谱等项鉴定,其发酵产物确系2-酮基-L-古龙酸,对新组合菌系的生物学特性也进行了研究。     

The interaction between RTX toxins and target cells.

RTX toxins are important virulence factors produced by a wide range of Gram-negative bacteria. They fall into two categories: the hemolysins, which affect a variety of cell types, and the leukotoxins, which are cell-type- and species-specific. These toxins offer interesting models for targeting, insertion and translocation of aqueous proteins into lipid membranes.     

Purification and characterization of two sugarcane bagasse-absorbable thermophilic xylanases from the mesophilic <Emphasis Type="Italic">Cellulomonas flavigena</Emphasis>

We report the purification and characterization of two thermophilic xylanases from the mesophilic bacteria Cellulomonas flavigena grown on sugarcane bagasse (SCB) as the only carbon source. Extracellular xylanase activity produced by C. flavigena was found both free in the culture supernatant and associated with residual SCB. To identify some of the molecules responsible for the xylanase activity in the substrate-bound fraction, residual SCB was treated with 3 M guanidine hydrochloride and then with 6 M urea. Further analysis of the eluted material led to the identification of two xylanases Xyl36 (36 kDa) and Xyl53 (53 kDa). The pI for Xyl36 was 5.0, while the pI for Xyl53 was 4.5. Xyl36 had a K _m value of 1.95 mg/ml, while Xyl53 had a K _m value of 0.78 mg/ml. In addition to SCB, Xyl36 and Xyl53 were also able to bind to insoluble oat spelt xylan and Avicel, as shown by substrate-binding assays. Xyl36 and Xyl53 showed optimal activity at pH 6.5, and at optimal temperature 65 and 55°C, respectively. Xyl36 and Xyl53 retained 24 and 35%, respectively, of their original activity after 8 h of incubation at their optimal temperature. As far as we know, this is the first study on the thermostability properties of purified xylanases from microorganisms belonging to the genus Cellulomonas.     

细菌成孔毒素研究进展

成孔毒素是多种致病性细菌分泌的一种重要毒力因子,通过在真核细胞膜上形成孔道结构,引起细胞裂解。基于毒素产生孔径的大小和与细胞作用方式的不同,可将其分为大成孔毒素、小成孔毒素和RTX毒素。成孔毒素主要通过改变细胞膜的通透性发挥毒性效应,导致细胞死亡,然而失去细胞通透性屏障的早期后果通常是细胞因子的释放,细胞内蛋白激酶的激活,有时会诱导细胞凋亡。     

维生素C混合发酵中产酸菌基因文库的构建

在对氧化葡萄糖酸杆菌ＳＣＢ３２９的纯培养方法进行了探索并获得了一定量的纯培养的ＳＣＢ３２９菌体的前提下,用常规方法抽提得到Ｇｌｕｃｏｎｏｂａｃｔｅｒ　ｏｘｙｄａｎｓ　ＳＣＢ３２９染色体ＤＮＡ。选用质粒ｐＫＳ作为载体,该载体具有氨苄抗性以及ｌａｃＺ基因．用限制酶对染色体进行部分消化,将一定范围内的消化片段回收后与载体连接,连接产物转化Ｅ.ｃｏｌｉＤＨ５ａ感受态细胞,利用蓝白斑特性选出重组子构建ＳＣＢ３２９基因组文库。用低熔点琼脂糖将ＳＣＢ３２９菌体包埋起来,对包埋在凝胶块中的细菌     

Control of Culex quinquefasciatus (Diptera: Culicidae) by Bacillus sphaericus and B. thuringiensis subsp. israelensis, Produced on a New Potato Extract Culture Medium

The efficacy of Bacillus sphaericus and B. thuringiensis israelensis produced on a new potato-based culture medium as well as the conventional culture medium of Luria Bertani was compared against Culex quinquefasciatus in the field. After sporulation, the spores/crystals were harvested and used. The bacterial samples controlled the larvae and pupae for three weeks. Mortality due to the bacterial toxins produced from the new culture medium was very high and comparable to that produced using conventional medium. But the cost for cultivating these bacteria using potato extract was much lower as compared with that of the conventional medium.     

Erratum to: Bacterial diversity in toxic<Emphasis Type="Italic"> Alexandrium tamarense</Emphasis> blooms off the Orkney Isles and the Firth of Forth

The genetic diversity of the bacterial community associated with Alexandrium tamarense blooms was studied in blooms of the toxic dinoflagellates in the waters around the Orkney Isles and the Firth of Forth (Scotland). For toxin and molecular analysis of the bacterial communities associated with the toxic bloom, water samples were taken in 1998 and 1999 from A. tamarense blooms. The bacterial community structure, as determined by DGGE (denaturing gradient gel electrophoresis) showed clear differences between all three investigated size fractions (dinoflagellate-associated bacteria, attached bacteria and free-living bacteria), with high diversity within each sample. DNA sequence analysis of the dominant and most frequent DGGE bands revealed the dominance of Proteobacteria, mainly of the Roseobacter clade, with similarities of 91–99%. Moreover, DGGE bands occurring at the same position in the gel throughout in most samples corroborate the presence of several specific Proteobacteria of the Roseobacter clade. Overall, 500 bacteria were isolated from the bloom and partly phylogenetically analysed. They were members of two prokaryotic phyla, the Proteobacteria and the Bacteroidetes, related to Proteobacteria of the and subdivisions (Alteromonas, Pseudoalteromonas and Colwellia). All bacteria were tested for the production of sodium channel blocking (SCB) toxins using mouse neuroblastoma assay. No production of SCB toxins was found and high performance liquid chromatography (HPLC) analysis confirmed these results. The content of total paralytic shellfish poisoning (PSP) toxin in the water samples, as measured within the toxic dinoflagellate blooms using HPLC, ranged from 53 to 2191 ng PSP l^–1 in 1998 and from 0 to 478 ng PSP l^–1 in 1999. Changes in PSP toxin content were not accompanied by changes of DGGE band patterns. We therefore presume that the bacterial groups identified in this study were not exclusively associated with toxic A. tamarense, but were generally associated with the phytoplankton.An erratum to this article can be found at Communicated by H.-D. Franke     

An evolutionary conserved mechanism of T cell activation by microbial toxins. Evidence for different affinities of T cell receptor-toxin interaction.

The enterotoxins produced by Staphylococcus aureus are the most potent mitogens known. They belong to a group of distantly related mitogenic toxins that differ in other biologic activities. In this study we have compared the molecular mechanisms by which these mitogens activate human T lymphocytes. We used the staphylococcal enterotoxins A to E, the staphylococcal toxic shock syndrome toxin, the streptococcal erythrogenic toxins A and C (scarlet fever toxins, erythrogenic toxins (ET)A, ETC), and the soluble mitogen produced by Mycoplasma arthritidis. We found that all these toxins can activate both CD4+ and CD8+ T cells and require MHC class II expression on accessory and target cells. However, T cells could be activated in the absence of class II molecules if the toxins ETA or SEB were co-cross-linked on beads together with anti-CD8 or anti-CD2 antibodies. Enterotoxins, toxic shock syndrome toxin and scarlet toxins stimulate a major fraction of human T cells, and show preferential, but not exclusive, stimulation of T cells carrying certain TCR V beta. In contrast, the mitogen of M. arthritidis, a pathogen for rodents stimulates only a minority of human T cells but activates a major fraction of murine T cells. Analysis of human T cell clones expressing V beta 5 or V beta 8 TCR showed that these clones responded also to those toxins that did not stimulate V beta 5+ and V beta 8+ T cells in bulk cultures. These results indicate that different TCR bind to these toxins with different affinities and that the specificity of the TCR-V beta-toxin interaction is quantitative rather than qualitative in nature. Taken together our findings suggest that these toxins use a common mechanism of T cell activation. They are functionally bivalent proteins crosslinking MHC class II molecules with variable parts of the TCR. Besides V beta, other parts of the TCR must be involved in this binding. The finding that murine T cells responded more weakly to the toxins produced by the human-pathogenic bacteria than to the Mycoplasma mitogen could indicate that the toxins have been adapted to the host's immune system in evolution.     

Cyt toxins produced by Bacillus thuringiensis: A protein fold conserved in several pathogenic microorganisms

Bacillus thuringiensis bacteria produce different insecticidal proteins known as Cry and Cyt toxins. Among them the Cyt toxins represent a special and interesting group of proteins. Cyt toxins are able to affect insect midgut cells but also are able to increase the insecticidal damage of certain Cry toxins. Furthermore, the Cyt toxins are able to overcome resistance to Cry toxins in mosquitoes. There is an increasing potential for the use of Cyt toxins in insect control. However, we still need to learn more about its mechanism of action in order to define it at the molecular level. In this review we summarize important aspects of Cyt toxins produced by Bacillus thuringiensis, including current knowledge of their mechanism of action against mosquitoes and also we will present a primary sequence and structural comparison with related proteins found in other pathogenic bacteria and fungus that may indicate that Cyt toxins have been selected by several pathogenic organisms to exert their virulence phenotypes.     

Amplification of genome regions in the somatic cells of mammals resistant to colchicine. III. Localization of the amplified genes in minute chromatin bodies

Small chromatin bodies (SCB) were revealed in Djungarian hamster cells resistant to colchicine. They looked like single bodies or like clusters of small particles. SCB were localized both in nucleus and cytoplasm. Similar formations were earlier observed in oocytes of insects with amplified extrachromosomal rDNA genes. DNA in the SCB was able to replicate not only during the S phase but also during other phases of the cell cycle. The restriction analysis showed that in cells with SCB DNA amplified sequences were replicated autonomously too. These data indicate that SCB in colchicine-resistant cells contain amplified genes. Besides, SCB double-minute chromosomes (DMs) were observed in some resistant sublines. In one of them, DMs were the only karyotypic alteration. The relationship between SCB, chromosomal homogeneously staining regions (HSRs) and DMs was studied. Single SCB and DMs appeared at the early stage of the development of colchicine-resistance (the level of drug resistance is 16-22). Selection of variants 170-220-fold resistant to colchicine was usually accompanied by the decrease in the cell number with SCB and DMs and by the increase in the amount of cells containing the chromosomes with HSRs. During the further enhancement of drug resistance (700-750), some decrease in the number of cells with HSRs and the appearance of the great number of cells containing large groups of SCB were found. The loss of colchicine-resistance observed during cultivation in colchicine free medium was accompanied by the disappearance of HSRs, emergence of SCB and DMs and further elimination of SCB and DMs from cells. The quantity of autonomously replicating amplified DNA fragments after digestive by HindIII was increased with the enhancement of SCB number in cultures.     

Biological effects of RTX toxins: the possible role of lipopolysaccharide

RTX toxins are a family of related exotoxins with hemolytic, leukotoxic and leukocyte-stimulating activities that are produced by a diverse array of Gram-negative bacteria.

Lipopolysaccharide might be required for the maximal production of some RTX toxins and might be a cofactor in some of the biological effects of RTX toxins.     

Inositol Hexakisphosphate-Induced Autoprocessing of Large Bacterial Protein Toxins

Large bacterial protein toxins autotranslocate functional effector domains to the eukaryotic cell cytosol, resulting in alterations to cellular functions that ultimately benefit the infecting pathogen. Among these toxins, the clostridial glucosylating toxins (CGTs) produced by Gram-positive bacteria and the multifunctional-autoprocessing RTX (MARTX) toxins of Gram-negative bacteria have distinct mechanisms for effector translocation, but a shared mechanism of post-translocation autoprocessing that releases these functional domains from the large holotoxins. These toxins carry an embedded cysteine protease domain (CPD) that is activated for autoprocessing by binding inositol hexakisphosphate (InsP₆), a molecule found exclusively in eukaryotic cells. Thus, InsP₆-induced autoprocessing represents a unique mechanism for toxin effector delivery specifically within the target cell. This review summarizes recent studies of the structural and molecular events for activation of autoprocessing for both CGT and MARTX toxins, demonstrating both similar and potentially distinct aspects of autoprocessing among the toxins that utilize this method of activation and effector delivery.     

杀蚊苏云金芽孢杆菌及其晶体蛋白研究进展

自从发现苏云金芽孢杆菌Bacillusthuringiensis(Bt)具有杀蚊活性以来,目前已发现多种Bt亚种或血清型对蚊虫具有杀虫活性,同时也发现了一些新的杀蚊晶体蛋白。在对杀蚊晶体蛋白的分子结构进行研究的基础上,对其的作用机理有了一定的了解。近年来利用DNA重组技术显著提高杀蚊晶体蛋白的合成和将不同菌种的杀蚊晶体蛋白进行联合表达,为有效控制蚊虫危害展示广阔前景。     

Modulation of gut physiology through enteric toxins

Diarrheal diseases caused by microorganisms and their toxins are a major cause of mortality and morbidity throughout the world. Acute diarrhea is mainly caused due to increased intestinal secretion, commonly as a result of infection with enterotoxin producing organisms (enterotoxigenic Escherichia coli, Vibrio cholera) or due to decreased intestinal absorption from infection with organisms that damage the intestinal epithelium (enteropathogenic E. coli sp., Shigella sp., Salmonella sp.) The studies of the impact of enteric pathogens and their virulence factors exert their effect by producing toxins, called bacterial toxins. The protein toxins are produced by diverse group of bacteria. Most of the bacterial toxins exert their effect through involvement of ADP-ribosylation proteins; otherwise essential for several cellular functions while other toxins involve guanylate cyclase systems or calcium and protein kinases for their ultimate action.     

Detection of Streptococcus suis in Bioaerosols of Swine Confinement Buildings

Streptococcus suis is an important swine pathogen that can cause septicemia, meningitis, and pneumonia. Also recognized as an emerging zoonotic agent, it is responsible for outbreaks of human infections in Asian countries. Serotype 2 is the predominant isolate from diseased animals and humans. The aerosolization of S. suis in the air of swine confinement buildings (SCB) was studied. The presence of S. suis in bioaerosols was monitored in SCB where cases of infection had been reported and in healthy SCB without reported infections. Using a quantitative-PCR (qPCR) method, we determined the total number of bacteria (1 × 10⁸ to 2 × 10⁸ airborne/m³), total number of S. suis bacteria (4 × 10⁵ to 10 × 10⁵ airborne/m³), and number of S. suis serotype 2 and 1/2 bacteria (1 × 10³ to 30 × 10³ airborne/m³) present in the air. S. suis serotypes 2 and 1/2 were detected in the air of all growing/finishing SCB that had documented cases of S. suis infection and in 50% of healthy SCB. The total number of bacteria and total numbers of S. suis and S. suis serotype 2 and 1/2 bacteria were monitored in one positive SCB during a 5-week period, and it was shown that the aerosolized S. suis serotypes 2 and 1/2 remain airborne for a prolonged period. When the effect of aerosolization on S. suis was observed, the percentage of intact S. suis bacteria (showing cell membrane integrity) in the air might have been up to 13%. Finally S. suis was found in nasal swabs from 14 out of 21 healthy finishing-SCB workers, suggesting significant exposure to the pathogen. This report provides a better understanding of the aerosolization, prevalence, and persistence of S. suis in SCB.     

Killer toxins of clinically important yeasts

The review deals with some theoretical and applied aspects of the capacity of yeasts for synthesizing toxins. Similarly to antibiotic formation in micellar fungi and actinomycetes and the synthesis of bactericins in prokaryotes, yeast cells also have their mechanism of protection from other microorganisms. The substances, essentially of the same nature, synthesized by yeast are known for more than 30 years as mycocins or killer toxins. They are proteins or glycoproteins, active mainly against yeast microorganisms. Mycocins are not active against bacteria and protozoa exhibiting only fungicidal or fungistatic action. The formation of mycocins may be determined by nucleus or plasmid DNA. In this review information on killer toxins produced by clinically important yeasts of the genera Candida, Cryptococcus and Rhodotorula is systematized.     

Toxin-producing ability among Bacillus spp. outside the Bacillus cereus group

A total of 333 Bacillus spp. isolated from foods, water, and food plants were examined for the production of possible enterotoxins and emetic toxins using a cytotoxicity assay on Vero cells, the boar spermatozoa motility assay, and a liquid chromatography-mass spectrometry method. Eight strains produced detectable toxins; six strains were cytotoxic, three strains produced putative emetic toxins (different in size from cereulide), and one strain produced both cytotoxin(s) and putative emetic toxin(s). The toxin-producing strains could be assigned to four different species, B. subtilis, B. mojavensis, B. pumilus, or B. fusiformis, by using a polyphasic approach including biochemical, chemotaxonomic, and DNA-based analyses. Four of the strains produced cytotoxins that were concentrated by ammonium sulfate followed by dialysis, and two strains produced cytotoxins that were not concentrated by such a treatment. Two cultures maintained full cytotoxic activity, two cultures reduced their activity, and two cultures lost their activity after boiling. The two most cytotoxic strains (both B. mojavensis) were tested for toxin production at different temperatures. One of these strains produced cytotoxin at growth temperatures ranging from 25 to 42 degrees C, and no reduction in activity was observed even after 24 h of growth at 42 degrees C. The strains that produced putative emetic toxins were tested for the influence of time and temperature on the toxin production. It was shown that they produced putative emetic toxin faster or just as fast at 30 as at 22 degrees C. None of the cytotoxic strains produced B. cereus-like enterotoxins as tested by PCR or by immunological methods.     

Culture-independent approach of the bacterial bioaerosol diversity in the standard swine confinement buildings, and assessment of the seasonal effect

The bacterial bioaerosol community of eight swine confinement buildings (SCB) was monitored during two visits in the winter, and one during the summer. To our knowledge, culture-independent approaches and molecular biology tools such as biomass quantification and biodiversity analyses have never been applied to swine building bioaerosol analyses. Total DNA of each sample was extracted and analysed by quantitative real-time polymerase chain reaction, denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis using primers targeting the bacterial 16S rRNA gene. Even though the total bacterial concentration was higher in winter than in summer, the total bacterial concentration for both seasons was 100 to1000 times higher than the total cultural bacteria. The concentration of bioaerosol was influenced by the temperature indoors, which was regulated with an electronic fan system driving warm air and particles outside of the SCB. Comparison of the DGGE profiles showed the same biodiversity in each SCB during both seasons. The phylogenetic analysis revealed a large number of sequences (93.8%) related to Gram-positive anaerobic bacteria, such as Clostridia , and dominated by the Clostridia cluster I ( C. disporicum ) and the Clostridia cluster XI ( C. glycolycum ). The bioaerosol diversity also contained also a low proportion of Bacteroidetes and Lactobacillales – Streptococcales sequences. Analyses of the global community and phylotype diversity showed that the main source of bioaerosols could come from the pig manure slurry.