Dewatering of Extracellular Polymer and Activated Sludges by Thermochemical Treatment

Of the dewatering characteristics of activated sludges in our previous paper, the dewatering rate of sludge decreased in proportion to increasing amounts of extracellular polymer. As extracellular polymer in activated sludge was one of the important factors in the dewatering process, the change of the dewatering characteristics of thermochemically treated sludge (containing extracellular polymer) were compared with that of extracellular polymer extracted from sludge. The ultrafiltration rate of extracellular polymer flocculated by thermochemical treatment was much faster than that without treatment, indicating improved dewatering characteristics. Under the same treatment conditions, the dewatering characteristics of sludge were also much improved. The addition of the extracellular polymer treated thermochemically below pH 3 had no effect on the dewatering characteristics of the sludge. The addition of a flocculant to the thermochemically treated sludge was found to further improve the dewatering characteristics. The thermochemical treatment under low pH condition facilitated the flaking of the cake from the filter.     

苏云金芽孢杆菌的一个新亚种(Btsubsp.sinensis)

198 9年自云南昆明市石林的红棕壤中分离到数株苏云金芽孢杆菌 (Ｂａｃｉｌｌｕｓｔｈｕｒｉｎｇｉｅｎ ｓｉｓ,Ｂｔ)菌株[1] ,对其中的一株ＹＫ30 0 4进行了生物学特性、杀虫特性研究及分类鉴定。1　材料与方法1.1　供鉴定的Ｂｔ菌株由云南昆明市石林的红棕壤中分离的苏云金芽孢杆菌ＹＫ30 0 4菌株。1.2　标准Ｂｔ菌株血清型Ｈ1 Ｈ4 1、Ｈ4 4 Ｈ55及Ｈ57 Ｈ69标准Ｂｔ菌株由法国巴斯德研究院ＤｒＬｅｃａｄｅｔ提供 ,其余为本实验室保存。1.3　生物测定用昆虫小菜蛾 (Ｐｌｕｔｅｌｌａｘｙｌｏｓｔｅｌｌａ) 3龄幼虫 ;斜纹夜盗蛾 (Ｐｒ…     

Common occurrence of enterotoxin genes and enterotoxicity in Bacillus thuringiensis

Seventy-four strains of Bacillus thuringiensis thuringiensis representing 24 serovars were examined for the presence of three enterotoxin genes/operons; the non-haemolytic enterotoxin Nhe, the haemolytic enterotoxin hbl and the Bacillus cereus toxin bceT using polymerase chain reaction. The nheBC genes were found in all strains examined, the hblCD genes in 65 of the 74 strains and bceT in 63 strains. There was little consistency of the distribution of enterotoxin loci among strains of the same serovar in serovars that were well represented in our collection. Culture supernatants from all but one strain inhibited protein synthesis in Vero cells, generally with a toxicity equivalent to that seen in strains of B. cereus isolated from incidents of food poisoning. Microbiological Societies.     

Bacillus thuringiensis: a biotechnology model

This paper is on the different biotechnological approaches that have been used to improve Bacillus thuringiensis (Bt) for the control of agricultural insect pests and have contributed to the successful use of this biological control agent; it describes how a better knowledge of the high diversity of Bt strains and toxins genes together with the development of efficient host-vector systems has made it possible to overcome a number of the problems associated with Bt based insect control measures. First we present an overview of the biology of Bt and of the mode of action of its insecticidal toxins. We then describe some of the progress that has been made in furthering our knowledge of the genetics of Bt and of its insecticidal toxin genes and in the understanding of their regulation. The paper then deals with the use of recombinant DNA technology to develop new Bt strains for more effective pest control or to introduce the genes encoding partial-endotoxins directly into plants to produce insect-resistant trangenic plants. Several examples describing how biotechnology has been used to increase the production of insecticidal proteins in Bt or their persistence in the field by protecting them against UV degradation are presented and discussed. Finally, based on our knowledge of the mechanism of transposition of the Bt transposon Tn4430, we describe the construction of a new generation of recombinant strains of Bt, from which antibiotic resistance genes and other non-Bt DNA sequences were selectively eliminated, using a new generation of site-specific recombination vectors. In the future, continuing improvement of first generation products and research into new sources of resistance is essential to ensure the long-term control of insect pests. Chimeric toxins could also be produced so as to increase toxin activity or direct resistance towards a particular type of insect. The search for new insecticidal toxins, in Bt or other microorganisms, may also provide new weapons for the fight against insect damage.     

苏云金芽胞杆菌治理镍污染的方法的建立

利用微生物治理重金属污染已经成为一个研究的热点,并被视为将最终替代传统的物理、化学等处理方式的一种方法.但由于一些微生物存在安全性、繁殖速度慢等问题而造成了处理效果不佳.因此,以安全性高、繁殖速度快的苏云金芽胞杆菌(Bacillus thuringiensis,简称Bt)为研究载体,寻找最适Bt的镍污染处理方法对于提高...     

A Strain of Bacillus thuringiensis for the Control of Plant‐parasitic Nematodes

An isolate of Bacillus thuringiensis, designated CR‐371, was evaluated for efficacy in controlling plant‐parasitic nematodes. This isolate was first shown to be nematicidal to Caenorhabditis elegans in an in vitro laboratory assay. Treatment resulted in a significant reduction in galls due to root‐knot nematode on tomato in a greenhouse trial. In two field trials in Puerto Rico, CR‐371‐treated tomatoes and pepper had significantly fewer root galls due to Meloidogyne incognita than untreated controls, and populations of Rotylenchulus reniformis were smaller. In one experiment, CR‐371 treatment was associated with significant increases in pepper yields, while in the second trial small yield increases of pepper and tomato occurred. In a greenhouse trial, incorporation of CR‐371 into a methyl cellulose seed coat gave similar control of root‐knot nematode on tomato as compared to CR‐371 applied as a drench. CR‐371‐treated strawberry plants also had smaller populations of Pratylenchus penetrans in roots in a greenhouse trial in Massachusetts.     

海口市污水处理厂活性污泥中细菌的分离鉴定及耐药性分析

为了解海口市白沙门污水处理厂活性污泥中细菌抗生素耐性情况,采用平板分离技术分离、纯化细菌,并通过BIOLOG微生物鉴定系统对筛选到的细菌进行鉴定,同时采用Kirby-Bauer纸片琼脂扩散法进行药敏试验并进行抗生素耐性分析。本研究共分离到18株细菌,分属8个属,14个种,其中G+和G-均为9株。抗生素药敏性试验结果表明,所有菌株均耐药,菌株单重耐药率、双重耐药性及多重耐药性分别为50%、38.9%、和11.1%。菌株对9种常用抗生素:头孢他啶、环丙沙星、庆大霉素、链霉素、氨苄西林、红霉素、氯霉素、四环素、卡那霉素的耐药率分别为61.1%、0%、5.6%、16.7%、50%、16.7%、11.1%、0%、5.6%。综上所述,白沙门污水处理厂活性污泥中的细菌耐药性比较严重,存在潜在的环境生态和人畜健康风险。本研究揭示了当前白沙门污水处理厂活性污泥中细菌对常见抗生素耐药的严重现状,为建议污水处理厂加强出水及污泥中抗生素耐药性及耐药基因的检测并评估其生态影响提供基础,避免出水及污泥中的抗性菌和耐药基因可能带来的风险问题。     

A Bacillus thuringiensis isolate possessing a spore-associated filament

We report on a novel bacterium, isolated during a screen for environmental isolates of Bacillus thuringiensis, that possesses a novel filamentous structure. Nucleotide sequence from the isolate's 16S rRNA gene places the bacterium unambiguously within the Bacillus thuringiensis/Bacillus cereus group. Phase-contrast and electron microscopy indicate the presence of both a parasporal body and a long filament which are retained after sporulation. The filament is shown to consistently arise from the end of the exosporium and next to the parasporal body. Upon spore germination, the parasporal body/filament complex is retained on the cell wall of the resulting bacterium.     

Degradation of Benzophenone, a Potential Xenoestrogen, by a Yeast Isolated from the Activated Sludge of a Sewage Treatment Plant in Hokkaido

Summary Benzophenone (BPH) is an important intermediate in the production of medicines and cosmetics, but is also known as a xenoestrogen in its effect on mammals. We screened BPH-degrading microbes for potential bioremediation, and found degradation activity in the activated sludge of a sewage treatment plant in Hokkaido. A microbial strain with notable BPH-degrading activity (strain MU-1) was isolated from the sample. MU-1 degraded more than 95% of BPH (100–1000 ppm) as a sole carbon source within several days. However, it took a relatively long time for MU-1 to degrade a high concentration of BPH (5000–10,000 ppm), probably due to a toxic effect of BPH. The GC/MS analysis of the metabolites of BPH degradation suggested that BPH was degraded into hydrophilic compounds with very low molecular mass via conversion to phenol. The phylogenetic study based on rDNA sequences suggested that MU-1 was the black yeast Rhinocladiella aquaspersa. To our knowledge, this is the first report describing a BPH-degrading microbe.     

Common features of Bacillus thuringiensis toxins specific for Diptera and Lepidoptera

The complete nucleotide sequence of a cloned gene encoding a 130-kDa crystal protein of Bacillus thuringiensis (B.t.) subspecies israelensis has been determined. The recombinant protein (Bt8) was purified and shown to be a mosquito-specific toxin with a LC50 value of 43 ng/ml to third-instar larvae of Aedes aegypti. Bt8 is processed by proteases or midgut extracts of mosquito larvae into toxic fragments of 68-78 kDa. Deletion mapping indicated that the active fragment of Bt8 is localized in the N-terminal half of the protoxin molecule. The deduced amino acid sequence of Bt8 has been compared with that of Bt2, a Lepidoptera-specific toxin, previously cloned from Bacillus thuringiensis berliner. Highly homologous amino acid stretches are present in the C-terminal half of the proteins. The N-terminal parts show much less sequence homology but they display a strikingly similar distribution of hydrophilic and hydrophobic amino acids. In addition, Bt8 and Bt2 show a significant immunological cross-reaction. The data indicate that although these B.t. delta endotoxins exhibit a different insect-host specificity, they are structurally related and might use a similar mechanism to interact with insect cell membranes.     

A Replication Origin of Bacillus thuringiensis

A replication origin of Bacillus thuringiensis (Bt) was found in a Bacillus thuringiensis–Escherichia coli shuttle vector of pHT3101. Deletion analysis showed that the replication origin was segregationally stable at suitable temperature for Bt growth. The fragment containing the replication origin was cloned in pUC18 and sequenced. It was 261 base pairs in length, located in the open reading frame 2 (ORF2) of BTSPB sequence. The 261-bp fragment was cloned in pBR322, creating an improved Bt-E. coli shuttle vector pBR261, which contained two resistance genes responsible for ampicillin and tetracycline. Our study showed that the replication origin structure could be recognized by replication protein of host cells. Received: 26 July 1999 / Accepted: 30 August 1999     

A pangenomic study of Bacillus thuringiensis

Bacillus thuringiensis (B.thuringiensis) is a soil-dwelling Gram-positive bacterium and its plasmid-encoded toxins (Cry) are commonly used as biological alternatives to pesticides.In a pangenomic study,we sequenced seven B.thuringiensis isolates in both high coverage and base quality using the next-generation sequencing platform.The B.thuringiensis pangenome was extrapolated to have 4196 core genes and an asymptotic value of 558 unique genes when a new genome is added.Compared to the pangenomes of its closely related species of the same genus,B.thuringiensis pangenome shows an open characteristic,similar to B.cereus but not to B.anthracis; the latter has a closed pangenome.We also found extensive divergence among the seven B.thuringiensis genome assemblies,which harbor ample repeats and single nucleotide polymorphisms (SNPs).The identities among orthologous genes are greater than 84.5％ and the hotspots for the genome variations were discovered in genomic regions of 2.3-2.8 Mb and 5.0-5.6 Mb.We concluded that high-coverage sequence assemblies from multiple strains,before all the gaps are closed,are very useful for pangenomic studies.     

用微型动物预测保定鲁岗污水处理厂活性污泥系统理化参数

用微型动物预测了保定鲁岗污水处理厂活性污泥系统的理化参数。建立的4个多元线性回归方程对出水BOD5、出水TN、SVI和出水SS做预测,分别需5、5、8和5种微型动物,预测成功率分别为78·7%、79·3%、89·5%和62·3%。     

Bacillus thuringiensis: a genomics and proteomics perspective

Bacillus thuringiensis (Bt) is a unique bacterium in that it shares a common place with a number of chemical compounds which are used commercially to control insects important to agriculture and public health. Although other bacteria, including B. popilliae and B. sphaericus, are used as microbial insecticides, their spectrum of insecticidal activity is quite limited compared to Bt. Importantly, Bt is safe for humans and is the most widely used environmentally compatible biopesticide worldwide. Furthermore, insecticidal Bt genes have been incorporated into several major crops, rendering them insect resistant, and thus providing a model for genetic engineering in agriculture.This review highlights what the authors consider the most relevant issues and topics pertaining to the genomics and proteomics of Bt. At least one of the authors (L.A.B.) has spent most of his professional life studying different aspects of this bacterium with the goal in mind of determining the mechanism(s) by which it kills insects. The other authors have a much shorter experience with Bt but their intellect and personal insight have greatly enriched our understanding of what makes Bt distinctive in the microbial world. Obviously, there is personal interest and bias reflected in this article notwithstanding oversight of a number of published studies. This review contains some material not published elsewhere although several ideas and concepts were developed from a broad base of scientific literature up to 2010.