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

J. Appl. Cryst.の発刊に際して

Phosphate solubilizing bacteria and their role in plant growth promotion

Biological N2 fixation represents the major source of N input in agricultural soils including those in arid regions. The major N2-fixing systems are the symbiotic systems, which can play a significant role in improving the fertility and productivity of low-N soils. The Rhizobium-legume symbioses have received most attention and have been examined extensively. The behavior of some N2-fixing systems under severe environmental conditions such as salt stress, drought stress, acidity, alkalinity, nutrient deficiency, fertilizers, heavy metals, and pesticides is reviewed. These major stress factors suppress the growth and symbiotic characteristics of most rhizobia; however, several strains, distributed among various species of rhizobia, are tolerant to stress effects. Some strains of rhizobia form effective (N2-fixing) symbioses with their host legumes under salt, heat, and acid stresses, and can sometimes do so under the effect of heavy metals. Reclamation and improvement of the fertility of arid lands by application of organic (manure and sewage sludge) and inorganic (synthetic) fertilizers are expensive and can be a source of pollution. The Rhizobium-legume (herb or tree) symbiosis is suggested to be the ideal solution to the improvement of soil fertility and the rehabilitation of arid lands and is an important direction for future research.

Rhizobium-Legume Symbiosis and Nitrogen Fixation under Severe Conditions and in an Arid Climate

Soil bacteria are very important in biogeochemical cycles and have been used for crop production for decades. Plant–bacterial interactions in the rhizosphere are the determinants of plant health and soil fertility. Free-living soil bacteria beneficial to plant growth, usually referred to as plant growth promoting rhizobacteria (PGPR), are capable of promoting plant growth by colonizing the plant root. PGPR are also termed plant health promoting rhizobacteria (PHPR) or nodule promoting rhizobacteria (NPR). These are associated with the rhizosphere, which is an important soil ecological environment for plant–microbe interactions. Symbiotic nitrogen-fixing bacteria include the cyanobacteria of the genera Rhizobium, Bradyrhizobium, Azorhizobium, Allorhizobium, Sinorhizobium and Mesorhizobium. Free-living nitrogen-fixing bacteria or associative nitrogen fixers, for example bacteria belonging to the species Azospirillum, Enterobacter, Klebsiella and Pseudomonas, have been shown to attach to the root and efficiently colonize root surfaces. PGPR have the potential to contribute to sustainable plant growth promotion. Generally, PGPR function in three different ways: synthesizing particular compounds for the plants, facilitating the uptake of certain nutrients from the soil, and lessening or preventing the plants from diseases. Plant growth promotion and development can be facilitated both directly and indirectly. Indirect plant growth promotion includes the prevention of the deleterious effects of phytopathogenic organisms. This can be achieved by the production of siderophores, i.e. small metal-binding molecules. Biological control of soil-borne plant pathogens and the synthesis of antibiotics have also been reported in several bacterial species. Another mechanism by which PGPR can inhibit phytopathogens is the production of hydrogen cyanide (HCN) and/or fungal cell wall degrading enzymes, e.g., chitinase and s-1,3-glucanase. Direct plant growth promotion includes symbiotic and non-symbiotic PGPR which function through production of plant hormones such as auxins, cytokinins, gibberellins, ethylene and abscisic acid. Production of indole-3-ethanol or indole-3-acetic acid (IAA), the compounds belonging to auxins, have been reported for several bacterial genera. Some PGPR function as a sink for 1-aminocyclopropane-1-carboxylate (ACC), the immediate precursor of ethylene in higher plants, by hydrolyzing it into α-ketobutyrate and ammonia, and in this way promote root growth by lowering indigenous ethylene levels in the micro-rhizo environment. PGPR also help in solubilization of mineral phosphates and other nutrients, enhance resistance to stress, stabilize soil aggregates, and improve soil structure and organic matter content. PGPR retain more soil organic N, and other nutrients in the plant–soil system, thus reducing the need for fertilizer N and P and enhancing release of the nutrients.

Soil beneficial bacteria and their role in plant growth promotion: a review

α-Hydroxyphosphonates (±)- 3 were prepared and transformed into esters (±)- 5 . Eight lipases as well as pig liver esterase were tested as catalysts for enantioselective hydrolyses of α-(acyloxy)phosphonates in a biphasic system. Two of them proved to be useful. The highest enantioselectivity was obtained with lipase F-AP 15 and α-(acetyloxy)phenylmethylphosphonates(±)- 5a and (±)- 5b as substrates. The (S)-enantiomers were exclusively hydrolyzed to give optically pure alcohols (S)-(−)- 3a and (S)-(−)- 3b . Lipases AP 6 and F-AP 15 were used to prepare phosphonates (S)-(−)- 3b , (S)-(+)- 3d and (S)-(−)- 3e on a preparative scale with an enantiomeric excess of 81%, 87%, and 89%, respectively. The absolute configurations ofthe α-hydroxyphosphonates were assigned by Horeau's method and 1 H-NMR spectroscopy of Mosher's derivatives.

Enzymes in organic chemistry, part 1: Enantioselective hydrolysis of α-(acyloxy)phosphonates by esterolytic enzymes

N-Benzyl phosphoramidate was protected at nitrogen with a TMS, p-toluenesulfonyl, Boc, lithium carboxylate, or diethoxyphosphinyl group and metalated with s-BuLi or LDA at -78 degrees C at the benzylic carbon. For the latter three protecting groups, the intermediate alpha-amino(phenylmethyl)lithiums isomerized to N-protected alpha-aminophosphonates (phosphoramidate-aminophosphonate rearrangement). (R)-N-[1-(2)H(1)]Phenylmethyl phosphoramidate in combination with Boc or (EtO)(2)P(O) was used to demonstrate that metalation occurs with a high primary kinetic isotope effect (k(H)/k(D) 13-50) and migration of the diethoxyphosphinyl group with retention of configuration at carbon. Furthermore, the short-lived carbanion lithium pairs are partly configurationally stable as the aminophosphonates formed with the two protecting groups have enantiomeric excesses of 79 and 24%, respectively. When homochiral lithium amides derived from (R)-N-isopropyl-1-phenylethylamine and (R,R)-N,N-di(1-phenylethyl)amine were used to induce a phosphoramidate-aminophosphonate rearrangement, chiral nonracemic alpha-aminophosphonates were formed (ee 26-35%). Three racemic aminophosphonates were deprotected with hot 6 M HCl and purified by ion-exchange chromatography on Dowex 50W,H(+) to exemplify the transformation of phenyl-, p-tolyl-, and (1'-naphthyl)methylamine into aminophosphonic acids via lithiated phosphoramidates.

Transformation of arylmethylamines into alpha-aminophosphonic acids via metalated phosphoramidates: rearrangement of partly configurationally stable N-phosphorylated alpha-aminocarbanions

The biodegradation by Rhizobium huakuii PMY1 of up to 10 mM phosphonomycin as a carbon, energy, and phosphorus source with accompanying Pi release is described. This biodegradation represents a further mechanism of resistance to this antibiotic and a novel, phosphate-deregulated route for organophosphonate metabolism byRhizobium spp.

Biodegradation of Phosphonomycin by Rhizobium huakuii PMY1

Enzymes in organic chemistry, part 2: Lipase-catalysed hydrolysis of 1-acyloxy-2-arylethylphosphonates and synthesis of phosphonic acid analogues of L-phenylalanine and L-tyrosine

Friedrich Hammerschmidt

Papers

Enzymes in organic chemistry, part 1: Enantioselective hydrolysis of α-(acyloxy)phosphonates by esterolytic enzymes

Transformation of arylmethylamines into alpha-aminophosphonic acids via metalated phosphoramidates: rearrangement of partly configurationally stable N-phosphorylated alpha-aminocarbanions

Biodegradation of Phosphonomycin by Rhizobium huakuii PMY1

Enzymes in organic chemistry, part 2: Lipase-catalysed hydrolysis of 1-acyloxy-2-arylethylphosphonates and synthesis of phosphonic acid analogues of L-phenylalanine and L-tyrosine

Determination of absolute configuration of α-hydroxyphosphonates by 31P NMR spectroscopy of corresponding mosher esters