Stress responses and sugar metabolism in Bacillus subtilis: a transcriptomic portrait

The work presented in Andrzej Lulko’s thesis focuses on the regulation of gene expression of Bacillus subtilis in response to stress conditions by using the DNA microarrays. There were two major goals of the project described in his thesis: the development of the DNA microarrays technology and the implementation of this technology to investigate the effects of various stress conditions encountered for example under industrial food fermentation processes. In natural environments as well as during industrial processes, microorganisms are often challenged with a variety of unfavourable conditions. To increase their chance of survival, bacteria evolved various mechanisms to confront and adapt to encountered stresses. In general, they achieve that by a concerted reprogramming of gene expression coordinated by transcription factors and leading to a rapid and optimal adjustment to a particular stress. Such a reprogramming of gene expression can be monitored and quantified by DNA microarrays, the technology which allows measuring changes in expression levels of thousands of genes in a single experiment. The effects of three different types of stress conditions were investigated by Lulko: (i) overproduction and secretion of a heterologous protein, (ii) exposure to lactic acid and (iii) disturbance of carbon-metabolism caused by the point mutations or absence of the CcpA protein, the most important transcription factor in catabolite control regulation.

Temporal separation of distinct differentiation pathways by a dual specificity Rap-Phr system in Bacillus subtilis

In bacterial differentiation, mechanisms have evolved to limit cells to a single developmental pathway. The establishment of genetic competence in Bacillus subtilis is controlled by a complex regulatory circuit that is highly interconnected with the developmental pathway for spore formation, and the two pathways appear to be mutually exclusive. Here we show by in vitro and in vivo analyses that a member of the Rap family of proteins, RapH, is activated directly by the late competence transcription factor ComK, and is capable of inhibiting both competence and sporulation. Importantly, RapH is the first member of the Rap family that demonstrates dual specificity, by dephosphorylating the SpoOF-P response regulator and inhibiting the DNA-binding activity of ComA. The protein thus acts at the stage where competence is well initiated, and prevents initiation of sporulation in competent cells as well as contributing to the escape from the competent state. A deletion of rapH induces both differentiation pathways and interferes with their temporal separation. Together, these results indicate that RapH is an integral part of a multifactorial regulatory circuit affecting the cell's decision between distinct developmental pathways

Time-Resolved Transcriptome Analysis of Bacillus subtilis Responding to Valine, Glutamate, and Glutamine

Microorganisms can restructure their transcriptional output to adapt to environmental conditions by sensing endogenous metabolite pools. In this paper, an Agilent customized microarray representing 4,106 genes was used to study temporal transcript profiles of Bacillus subtilis in response to valine, glutamate and glutamine pulses over 24 h. A total of 673, 835, and 1135 amino-acid-regulated genes were identified having significantly changed expression at one or more time points in response to valine, glutamate, and glutamine, respectively, including genes involved in cell wall, cellular import, metabolism of amino-acids and nucleotides, transcriptional regulation, flagellar motility, chemotaxis, phage proteins, sporulation, and many genes of unknown function. Different amino acid treatments were compared in terms of both the global temporal profiles and the 5-minute quick regulations, and between-experiment differential genes were identified. The highlighted genes were analyzed based on diverse sources of gene functions using a variety of computational tools, including T-profiler analysis, and hierarchical clustering. The results revealed the common and distinct modes of action of these three amino acids, and should help to elucidate the specific signaling mechanism of each amino acid as an effector

PHYSICO-CHEMICAL PRINCIPLES AND PROCESS OF PRODUCING COMPOSITE POWDERS BY THERMAL SYNTHESIS IN VIBRATING LAYER

The purpose is the development of physico-chemical principles and creation of the process of producing and forming the properties of pure and composite powders type matrix - additive at their synthesis during their short-time (5 to 30 minutes) thermal treatment in a vibrating layer. The methodological and scientific principles of the new method of treatment of the powders, a generalized mathematical model of the process, particular analytical relationships of the parameters providing the production of the powders, an algorithm of constructing the complex process of producing items have been prepared. A powder metallurgy bay has been created, the process of producing new kinds of powders for sintered items, spraying and facing has been brought to a commercial level.Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio