抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Chemical Routes for the Transformation of Biomass into Chemicals

Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.

/pdf/microbial-cellulose-utilization-fundamentals-and-4yec12qx1c.pdf

Microbial cellulose utilization: fundamentals and biotechnology.

KEGG(Kyoto Encyclopedia of Genes and Genomes)〔和文〕 (特集 ゲノム医学の現在と未来--基礎と臨床) -- (データベース)

Although it is generally accepted that plant community composition is key for predicting rates of ecosystem processes in the face of global change, microbial community composition is often ignored in ecosystem modeling. To address this issue, we review recent experiments and assess whether microbial community composition is resistant, resilient, or functionally redundant in response to four different disturbances. We find that the composition of most microbial groups is sensitive and not immediately resilient to disturbance, regardless of taxonomic breadth of the group or the type of disturbance. Other studies demonstrate that changes in composition are often associated with changes in ecosystem process rates. Thus, changes in microbial communities due to disturbance may directly affect ecosystem processes. Based on these relationships, we propose a simple framework to incorporate microbial community composition into ecosystem process models. We conclude that this effort would benefit from more empirical data on the links among microbial phylogeny, physiological traits, and disturbance responses. These relationships will determine how readily microbial community composition can be used to predict the responses of ecosystem processes to global change.

https://www.pnas.org/content/pnas/105/Supplement_1/11512.full.pdf

Resistance, resilience, and redundancy in microbial communities

Integrating engineering design improvements with exoelectrogen enrichment process to increase power output from microbial fuel cells

The genus Geobacillus comprises a group of Gram-positive thermophilic bacteria, including obligate aerobes, denitrifiers, and facultative anaerobes that can grow over a range of 45-75°C. Originally classified as group five Bacillus spp., strains of Bacillus stearothermophilus came to prominence as contaminants of canned food and soon became the organism of choice for comparative studies of metabolism and enzymology between mesophiles and thermophiles. More recently, their catabolic versatility, particularly in the degradation of hemicellulose and starch, and rapid growth rates have raised their profile as organisms with potential for second-generation (lignocellulosic) biorefineries for biofuel or chemical production. The continued development of genetic tools to facilitate both fundamental investigation and metabolic engineering is now helping to realize this potential, for both metabolite production and optimized catabolism. In addition, this catabolic versatility provides a range of useful thermostable enzymes for industrial application. A number of genome-sequencing projects have been completed or are underway allowing comparative studies. These reveal a significant amount of genome rearrangement within the genus, the presence of large genomic islands encompassing all the hemicellulose utilization genes and a genomic island incorporating a set of long chain alkane monooxygenase genes. With G+C contents of 45-55%, thermostability appears to derive in part from the ability to synthesize protamine and spermine, which can condense DNA and raise its Tm.

/pdf/the-genus-geobacillus-and-their-biotechnological-potential-2i3rmlqdc4.pdf

The genus Geobacillus and their biotechnological potential.

Development of a versatile shuttle vector for gene expression in Geobacillus spp.

Three types of oxygenase biocatalysts are treated in detail in this review: the non-haem iron alkene mono-oxygenases, the haem and vanadium haloperoxidases, and flavin-based Baeyer–Villiger mono-oxygenases. Other oxygenases are briefly included for comparison. Characteristics of the biocatalysts are presented, and the scope and limitations concerning their applicability for the selective introduction of oxygen are discussed. Key issues include catalytic activity, productivity, cloning and expression, as well as process engineering aspects. Various bottlenecks are identified for the different biocatalysts and measures to increase the number of oxygenase reactions in practical use are discussed.

Biocatalysts for selective introduction of oxygen

Xanthobacter strain Py2 is a gram-negative bacterial strain which was isolated on propene as a sole carbon and energy source (34). The metabolism of propene involves an alkene-specific monooxygenase which converts propene to epoxypropane. Further metabolism involves isomerization and carboxylation of the epoxide, ultimately yielding acetoacetate (Fig. ​(Fig.1),1), which feeds into the central metabolism (1, 6, 36). 



FIG. 1

Initial steps in the metabolism of propene in Xanthobacter strain Py2.



The Xanthobacter strain Py2 alkene monooxygenase (Xamo) will catalyze the epoxidation of a range of alkenes, some with a high degree of stereospecificity, but will not hydroxylate the homologous alkanes (35). This contrasts with alkane monooxygenases such as those based on cytochrome P-450 (28) or nonheme iron (e.g., ω-hydroxylase [27] and methane monooxygenase [MMO] [11]), which appear to generate a highly reactive iron-oxygen intermediate which can attack both unactivated C-H bonds and carbon-carbon double bonds. This reaction specificity and stereospecificity make Xamo an enzyme of considerable interest as a biocatalyst for the production of chiral 1,2-epoxides. Additionally, Xamo has been shown to be responsible for catalyzing the initial step in the cometabolic degradation of a number of chlorinated alkenes of environmental concern, including vinyl chloride, trichloroethene, and 1,3-dichloropropene (9), and it can even be induced by the presence of these chlorinated alkenes, although there is no evidence for growth on these substrates (10). Xamo has been resolved into four components: an NADH-dependent reductase, a Rieske-type ferredoxin, an oxygenase, and a small protein which may be a coupling or effector protein (29). The oxygenase is an α2β2γ2 hexamer which was reported to contain approximately four atoms of nonheme iron per hexamer on the basis of colorimetric iron analysis and the lack of a significant UV- or visible-light chromophore. Sequence (25) and electron paramagnetic resonance evidence (12) has demonstrated that an alkene-specific monooxygenase derived from the gram-positive bacterium Rhodococcus rhodochrous (formerly Nocardia corallina) B276 has a binuclear nonheme iron center of the type found in soluble MMO. However, the Xanthobacter enzyme is more complex than that from Rhodococcus, having a two-component (reductase and ferredoxin) redox system typical of aromatic dioxygenases (3) and a more complex oxygenase structure.

We have recently reported the sequencing of the first open reading frame (ORF) in the Xamo gene cluster (42). The predicted polypeptide sequence showed strong homology to the nonheme iron binding subunit in aromatic monooxygenases and MMO, particularly around the iron binding domain. Modelling of the predicted Xanthobacter polypeptide on the coordinates of the α-subunit in the MMO crystal structure (24) allowed us to conclude that Xamo is also a nonheme iron monooxygenase. In this paper, we report the entire sequence of the six ORFs which encode Xamo. The predicted amino acid sequences of all six polypeptides encoded by these ORFs show strong homology with those of aromatic monooxygenases, including benzene monooxygenase and toluene 4-monooxygenase. This led us to investigate whether Xamo could catalyze the monohydroxylation of aromatic hydrocarbons or grow on them as sole sources of carbon and energy.

The Alkene Monooxygenase from Xanthobacter Strain Py2 Is Closely Related to Aromatic Monooxygenases and Catalyzes Aromatic Monohydroxylation of Benzene, Toluene, and Phenol

David J. Leak

Papers

Integrating engineering design improvements with exoelectrogen enrichment process to increase power output from microbial fuel cells

The genus Geobacillus and their biotechnological potential.

Development of a versatile shuttle vector for gene expression in Geobacillus spp.

Biocatalysts for selective introduction of oxygen

The Alkene Monooxygenase from Xanthobacter Strain Py2 Is Closely Related to Aromatic Monooxygenases and Catalyzes Aromatic Monohydroxylation of Benzene, Toluene, and Phenol