Biosynthesis of Cephalosporins

Abstract

Certain aerobic, Gram-negative bacteria, including the epiphytic plant pathogen, Pseudomonas syringae, possess a membrane protein that enables them to nucleate crystallization in supercooled water. Currently, these ice-nucleating (IN) bacteria are being used in snow making and have potential applications in the production and texturing of frozen foods, and as a replacement of silver iodide in cloud seeding. A negative aspect of these IN bacteria is frost damage to plant surfaces. Thus, of the various types of biological ice nucleators, bacteria have been the subject of most research and also appear relevant to the anticipated practical uses. The intent of this review is to explain the identification and ecology of the ice-nucleating bacteria, as well as to discuss aspects of molecular biology related to ice nucleation and consider existing and potential applications of this unique phenomenon.     

Rab and ARF GTPase regulation of exocytosis (Review)

Our understanding of the mechanisms governing of Rab and Arf protein function has exploded in recent years with a convergence of information from model genetic organisms, biochemical studies, cell biological observations and protein structural information. However, the list of known Rab and Arf interacting factors still remains small relative to the number of these small GTPases that have been identified through complete genomic sequencing. It can be anticipated that the factors listed and discussed in this review probably represent a small fraction of the Rab and Arf accessory molecules that remain to be discovered. The identification of regulators and accessory molecules for the Rab and Arf families has allowed investigators to elaborate themes and develop a framework for a mechanistic understanding of these proteins. The themes are highlighted in this review, which aims to concentrate on Rab and Arf function in exocytosis.     

Recent advances in plasmid-based tools for establishing novel microbial chassis

A key challenge for domesticating alternative cultivable microorganisms with biotechnological potential lies in the development of innovative technologies. Within this framework, a myriad of genetic tools has flourished, allowing the design and manipulation of complex synthetic circuits and genomes to become the general rule in many laboratories rather than the exception. More recently, with the development of novel technologies such as DNA automated synthesis/sequencing and powerful computational tools, molecular biology has entered the synthetic biology era. In the beginning, most of these technologies were established in traditional microbial models (known as chassis in the synthetic biology framework) such as Escherichia coli and Saccharomyces cerevisiae, enabling fast advances in the field and the validation of fundamental proofs of concept. However, it soon became clear that these organisms, although extremely useful for prototyping many genetic tools, were not ideal for a wide range of biotechnological tasks due to intrinsic limitations in their molecular/physiological properties. Over the last decade, researchers have been facing the great challenge of shifting from these model systems to non-conventional chassis with endogenous capacities for dealing with specific tasks. The key to address these issues includes the generation of narrow and broad host plasmid-based molecular tools and the development of novel methods for engineering genomes through homologous recombination systems, CRISPR/Cas9 and other alternative methods. Here, we address the most recent advances in plasmid-based tools for the construction of novel cell factories, including a guide for helping with “build-your-own” microbial host.     

Trans fat diet causes decreased brood size and shortened lifespan in Caenorhabditis elegans delta-6-desaturase mutant fat-3

Trans-fatty acids (TFAs) enter the diet through industrial processes and can cause adverse human health effects. The present study was aimed to examine the effects of dietary cis- and trans-fatty acids on the model organism Caenorhabditis elegans. Cis- or trans-18:1n9 triglycerides (25 μM) caused no apparent changes in the numbers of viable progeny of wild-type N2 animals. However, in fat-3 mutants lacking delta-6-desaturase, the trans-isomer caused modest decreases in lifespan and progeny after three generations. Long-chain polyunsaturated fatty acids (PUFA) profiles were significantly altered in fat-3 mutants compared to wild type but were not altered after exposure to dietary cis- or trans-18:1n9. Genome-wide expression analysis of fat-3 mutants revealed hundreds of changes. Several genes involved in fat metabolism (acs-2, fat-7, mdt-15) were significantly increased by cis- or trans-18:1n9 without discrimination between isomers. These results provide support for the hypothesis that dietary trans fats are detrimental to development and aging.     

Losing Sight of Regressive Evolution

When we teach evolution to our students, we tend to focus on “constructive” evolution, the processes which lead to the development of novel or modified structures. Most biology students are familiar with the subjects of finches’ beaks, giraffes’ necks, and hair in mammals. Of course, there is nothing inherently wrong with a constructivist approach to teaching evolution, but if it is our only focus, we may overlook the flip side of the coin. By the flip side of the coin, of course, we are referring to regressive evolution: the loss or degeneration of a trait. Regressive evolution does not often make its way into biology textbooks, but it is of great relevance nonetheless. In all likelihood, when a new trait evolves or an existing one is modified, something is sacrificed in return. In order to develop a flipper, a marine mammal must sacrifice individual digits. You may be familiar with one or more of the following familiar characters lost through regressive evolution: teeth in birds, scales in mammals, and tails in higher primates. For aficionados of cave biology like us, one of the most interesting examples of regressive evolution concerns cave fish: Why do cave fish lose their eyes?     

Susceptibility of the Hymenopteran Parasitoids Apoanagyrus ( = Epidinocarsis ) lopezi (Encyrtidae) and Phanerotoma sp. (Braconidae) to the Entomopathogenic Fungus Metarhizium anisopliae var. acridum (Deuteromycotina: Hyphomycetes)

Laboratory and so-called extended laboratory bioassays were conducted in Benin, West Africa, to investigate the pathogenicity and virulence of the entomopathogenic fungus Metarhizium anisopliae var. acridum , a biocontrol agent against locusts and grasshoppers, to two hymenopteran parasitoids, Apoanagyrus ( = Epidinocarsis ) lopezi and Phanerotoma sp. Treatments were carried out under simulated field conditions at standard field dose rates of 2.5 and 5.0 ×10 12 conidia ha -1 . Test organisms were continuously (3 weeks) exposed to spray residues in artificial or simulated natural environments. The standard strain IMI 330 189 of the mycopesticide Green Muscle caused a significant reduction of 24% in the longevity ( = average survival time, AST) of A. lopezi , relative to the untreated control. Mycosis was confirmed in 16% of all cadavers. AST was shorter under low relative humidity (RH) conditions, and these conditions seemed to enhance susceptibility to fungal infection. However, this effect was only marginally significant. In contrast, average longevity of untreated A. lopezi was slightly yet significantly shorter at low RH (50-60%) than at high RH (80-90%). In the extended laboratory assay, the same isolate had no significant effect on mortality, parasitoid emergence ( = beneficial capacity) and sex ratio. In a further screening test with isolates IIBC I91 609, IIBC I93 833 and IMI 330 189 (reference), no infection of A. lopezi was confirmed. Similarly, Phanerotoma sp. was not susceptible to IMI 330 189. It is concluded that mycopesticides based on the three strains tested pose a low risk to parasitic hymenopterans under field conditions.     

Gaia again

The ideas of the Gaia hypothesis from the 1960s are today largely included in global ecology and Earth system sciences. The interdependence between biosphere, oceans, atmosphere and geosphere is well-established by data from global monitoring. Nevertheless the theory underlying the holistic view of the homeostatic Earth has remained obscure. Here the foundations of Gaia theory are examined from the recent formulation of the 2nd law of thermodynamics as an equation of motion. According to the principle of increasing entropy, all natural processes, inanimate just as animate, consume free energy, the thermodynamic driving force. All species, abiotic just as biotic are viewed as mechanisms of energy transduction for the global system to evolve toward a stationary state in its surroundings. The maximum entropy state displays homeostasis by being stable against internal fluctuations. When surrounding conditions change or when new mechanisms emerge, the global system readjusts its flows of energy to level newly appeared gradients. Thus, the propositions of Gaia theory and holistic understanding of the global system are recognized as consequences of thermodynamic imperatives.     

冰核细菌表达冰核蛋白特性的研究

选用１００２５Ａ和ＱＦ－９５－Ｆ１９两株分离自杨树的冰核活性细菌,探讨了两株菌不同生长阶段与它们冰核活性表达的特性。实验结果显示,冰核活性细菌在ＭＰＤＡ培养液中表达冰核蛋白的特性及活性与细菌浓度、菌龄以及培养的环境条件相关,两株菌在表达冰核活性时对培养基的营养组分没有表现出特殊的要求。同时还进一步阐明了不同生长温度冰核活性细菌对冰核蛋白表达的影响。