The cyclodextrins and their applications in biotechnology

Cyclodextrins and their derivatives enhance the solubility of complexed substrates in aqueous media, but do not damage the microbial cells or the enzymes. Therefore the enzymatic conversion of lipophilic substrates can be intensified (accelerated, or performed at higher substrate concentrations). Examples are the hydrolysis of triglycerides and lanatoside glycosides or the conversion of hydrocortisone to prednisolon and of cholesterol to androstenedione. In the presence of an appropriate cyclodextrin-derivative (e.g. 2,6-dimethyl-β-cyclodextrin). The lipid-like inhibitor substances are complexed, therefore the propagation of Bordatella pertussis and the production of pertussis toxin increases up to 100-fold. Cyclodextrins or their fatty acid complexes can substitute mammalian serum in tissue cultures. A highly soluble γ-cyclodextrin-nystatin complex can protect tissue cultures from fungal infections. The tolerance level to toxic compounds during biological detoxication of organic chemical industries sewage can be elevated by admixing small amounts of β-cyclodextrin to the system, because the complexed toxic substances do not kill the detoxicating microbes.     

Syntenic relationships between Medicago truncatula and Arabidopsis reveal extensive divergence of genome organization

Arabidopsis and Medicago truncatula represent sister clades within the dicot subclass Rosidae. We used genetic map-based and bacterial artificial chromosome sequence-based approaches to estimate the level of synteny between the genomes of these model plant species. Mapping of 82 tentative orthologous gene pairs reveals a lack of extended macrosynteny between the two genomes, although marker collinearity is frequently observed over small genetic intervals. Divergence estimates based on non-synonymous nucleotide substitutions suggest that a majority of the genes under analysis have experienced duplication in Arabidopsis subsequent to divergence of the two genomes, potentially confounding synteny analysis. Moreover, in cases of localized synteny, genetically linked loci in M. truncatula often share multiple points of synteny with Arabidopsis; this latter observation is consistent with the large number of segmental duplications that compose the Arabidopsis genome. More detailed analysis, based on complete sequencing and annotation of three M. truncatula bacterial artificial chromosome contigs suggests that the two genomes are related by networks of microsynteny that are often highly degenerate. In some cases, the erosion of microsynteny could be ascribed to the selective gene loss from duplicated loci, whereas in other cases, it is due to the absence of close homologs of M. truncatula genes in Arabidopsis.     

Bioengineering of bacterial magnetic particles and their applications in biotechnology

Magnetic particles have attracted much attention for their versatile uses in biotechnology, especially in medical applications. The major advantage of magnetic particles is that they can be easily manipulated by magnetic forces. Magnetotactic bacteria synthesize nano-sized biomagnetites, otherwise known as bacterial magnetic particles (BacMPs) that are individually enveloped by a lipid bilayer membrane. The mechanisms of BacMP synthesis have been analyzed by genomic, proteomic, and bioinformatic approaches. Based on those studies in Magnetospirillum magneticum AMB-1, functional nanomaterials have been designed and produced. Through genetic engineering, functional proteins such as enzymes, antibodies, and receptors have been successfully displayed on BacMPs. These functional BacMPs have been utilized in various biosensors and bio-separation processes. Here, recent papers and patents for bioengineering of BacMPs and their applications in biotechnology are reviewed. The elucidation of the mechanism of magnetic particle synthesis has provided a roadmap for the design of novel biomaterials that can play useful roles in multiple disciplinary fields.     

Genetic dissection of resistance to anthracnose and powdery mildew in Medicago truncatula

Medicago truncatula was used to characterize resistance to anthracnose and powdery mildew caused by Colletotrichum trifolii and Erysiphe pisi, respectively. Two isolates of E. pisi (Ep-p from pea and Ep-a from alfalfa) and two races of C. trifolii (races 1 and 2) were used in this study. The A17 genotype was resistant and displayed a hypersensitive response after inoculation with either pathogen, while lines F83005.5 and DZA315.16 were susceptible to anthracnose and powdery mildew, respectively. To identify the genetic determinants underlying resistance in A17, two F7 recombinant inbred line (RIL) populations, LR4 (A17 x DZA315.16) and LR5 (A17 x F83005.5), were phenotyped with E. pisi isolates and C. trifolii races, respectively. Genetic analyses showed that i) resistance to anthracnose is governed mainly by a single major locus to both races, named Ct1 and located on the upper part of chromosome 4; and ii) resistance to powdery mildew involves three distinct loci, Epp1 on chromosome 4 and Epa1 and Epa2 on chromosome 5. The use of a consensus genetic map for the two RIL populations revealed that Ct1 and Epp1, although located in the same genome region, were clearly distinct. In silico analysis in this region identified the presence of several clusters of nucleotide binding site leucine-rich repeat genes. Many of these genes have atypical resistance gene analog structures and display differential expression patterns in distinct stress-related cDNA libraries.     

Nantotechniques and approaches in biotechnology

Nanotechnology has enabled the development of an amazing variety of methods for fabricating nanotopography and nanopatterned chemistry in recent years. Some of these techniques are directed towards producing single component particles, as well as multi-component assembly or self-assembly. Other methods are aimed at nanofeaturing and patterning surfaces that have a specific chemistry or topography. This article concentrates mainly on surface-directed nanobiotechnologies because they are nearer to commercial realisation, such as use in tissue engineering, control of biofouling and cell culture, than those directed at producing nanoparticles.     

甲基营养微生物的甲醛代谢途径及其在环境生物技术中的应用

甲醛是一种毒性很高的一碳化合物,甲基营养菌是一类能在有高浓度甲醛的环境中生存的微生物,它们体内有多种降解甲醛的氧化途径和将甲醛转化为细胞组分的同化途径。丝氨酸途径和酮糖单磷酸途径是同时存在于甲基营养型细菌中的两种甲醛同化途径,木酮糖单磷酸途径是甲基营养型酵母菌中独有的甲醛同化途径。为了充分挖掘甲基营养型微生物在环境生物技术中的潜在应用价值,最近有很多研究尝试利用甲基营养微生物的细胞及其甲醛代谢途径关键酶开发甲醛污染检测方法和生物治理技术,对这方面的研究进展进行综述。     

A Medicago truncatula mutant hyper-responsive to mycorrhiza and defective for nodulation

One key strategy for the identification of plant genes required for mycorrhizal development is the use of plant mutants affected in mycorrhizal colonisation. In this paper, we report a new Medicago truncatula mutant defective for nodulation but hypermycorrhizal for symbiosis development and response. This mutant, called B9, presents a poor shoot and, especially, root development with short laterals. Inoculation with Glomus intraradices results in significantly higher root colonisation of the mutant than the wild-type genotype A17 (+20% for total root length, +16% for arbuscule frequency in the colonised part of the root, +39% for arbuscule frequency in the total root system). Mycorrhizal effects on shoot and root biomass of B9 plants are about twofold greater than in the wild-type genotype. The B9 mutant of M. truncatula is characterised by considerably higher root concentrations of the phytoestrogen coumestrol and by the novel synthesis of the coumestrol conjugate malonyl glycoside, absent from roots of wild-type plants. In conclusion, this is the first time that a hypermycorrhizal plant mutant affected negatively for nodulation (Myc⁺⁺, Nod ^−/+ phenotype) is reported. This mutant represents a new tool for the study of plant genes differentially regulating mycorrhiza and nodulation symbioses, in particular, those related to autoregulation mechanisms.     

Spectroscopic and biophysical approaches for studying the structure and function of the P-glycoprotein multidrug transporter.

Multidrug resistance is a serious obstacle to the successful chemotherapeutic treatment of many human cancers. A major cause of multidrug resistance is the overexpression of a 170-kDa plasma membrane protein, known as P-glycoprotein, which appears to function as an ATP-driven efflux pump with a very broad specificity for hydrophobic drugs, peptides, and natural products. P-Glycoprotein is a member of the ABC superfamily and is proposed to consist of two homologous halves, each comprising six membrane-spanning segments and a cytosolic nucleotide binding domain. In recent years, P-glycoprotein has been purified and functionally reconstituted into lipid bilayers, where it retains both ATPase and drug transport activity. The availability of purified active protein has led to substantial advances in our understanding of the molecular structure and mechanism of action of this unique transporter. This review will focus on the recent application of fluorescence spectroscopy, infra-red spectroscopy, circular dichroism spectroscopy, electron microscopy, and other biophysical techniques to the study of P-glycoprotein structure and function.     

Localisation of glutathione and homoglutathione in Medicago truncatula is correlated to a differential expression of genes involved in their synthesis

Glutathione (GSH) and homoglutathione (hGSH) were quantified in Medicago truncatula during plant development. hGSH was detectable only 48 h after seed germination whereas GSH was present in the dry seeds, indicating that only GSH is used for sulphur storage in seeds. The hGSH was detectable only in the underground part of mature plants whereas GSH was present in all the organs. γ-EC synthetase (γ-ECS) and GSH synthetase (GSHS) activities were found in roots and leaves whereas hGSH synthetase (hGSHS) was found only in roots. Full-length cDNA encoding γ-ECS and two partial cDNAs ( gshs1 and gshs2 ) showing high identity with GSHS were isolated in M. truncatula . High γ-ECS activity was detected in protein extracts of a γ-ECS-deficient E. coli strain expressing the M. truncatula γ-ECS. Northern blot analysis showed that the γ-ECS gene was similarly expressed in all the mature plant organs tested, whereas gshs1 had a higher expression in leaves and flowers and gshs2 was preferentially expressed in roots and nodules. We hypothesise that gshs1 and gshs2 encode a GSHS and an hGSHS, respectively.     

Microsatellite diversity and broad scale geographic structure in a model legume: building a set of nested core collection for studying naturally occurring variation in Medicago truncatula

Background  

Exploiting genetic diversity requires previous knowledge of the extent and structure of the variation occurring in a species. Such knowledge can in turn be used to build a core-collection, i.e. a subset of accessions that aim at representing the genetic diversity of this species with a minimum of repetitiveness. We investigate the patterns of genetic diversity and population structure in a collection of 346 inbred lines representing the breadth of naturally occurring diversity in the Legume plant model Medicago truncatula using 13 microsatellite loci distributed throughout the genome.