Chapters authored
Menaquinone as Well as Ubiquinone as a Crucial Component in the Escherichia coli Respiratory Chain
Part of the book: Chemical Biology
Survival Strategy of Escherichia coli in Stationary Phase: Involvement of σE-Dependent Programmed Cell Death
In a natural habitat, microbes respond to alterations in the amounts of nutrients or to stresses such as osmotic stress and stresses caused by low or high pH, salt, heat, and antibiotics by changing their mode for proliferation or survival. Similarly, Escherichia coli cells in a test tube change the growth mode according to environmental conditions when they enter a stationary phase. Until a sufficient supply of nutrients, the organism survives under such stressful and nutrient-limited conditions by altering gene expression to be more protective against such conditions. The definite trigger of the onset of stationary phase is still unclear, but several lines of evidence indicate that the regulation mechanism is very complicated and involves several transcriptional factors including alternative sigma factors, σE and σS. In addition, E. coli cells behave as a community of species and give rise to programmed cell death (PCD) for ensuring survival by controlling the cell number and supplying nutrients to sibling cells in long-term stationary phase (LTSP). The main PCD is probably performed by σE in E. coli. In this chapter, physiological functions of σE and PCD are introduced and reviewed and their possible involvement in survival mechanisms in stationary phase, especially LTSP, is shown.
Part of the book: Escherichia coli
Potential of Thermotolerant Ethanologenic Yeasts Isolated from ASEAN Countries and Their Application in High- Temperature Fermentation
Thermotolerant ethanologenic yeasts receive attention as alternative bio-ethanol producers to traditionally used yeast, Saccharomyces cerevisiae. Their utilization is expected to provide several benefits for bio-ethanol production due to their characteristics and robustness. They have been isolated from a wide variety of environments in a number of ASEAN countries: Thailand, Vietnam, Laos, and Indonesia. One of these yeasts, Kluyveromyces marxianus has been investigated regarding characteristics. Some strains efficiently utilize xylose, which is a main component of the 2nd generation biomass. In addition, the genetic basis of K. marxianus has been revealed by genomic sequencing and is exploited for further improvement of the strains by thermal adaptation or gene engineering techniques. Moreover, the glucose repression of K. marxianus and its mechanisms has been investigated. Results suggest that K. marxianus is an alternative to S. cerevisiae in next-generation bio-ethanol production industry. Indeed, we have succeeded to apply K. marxianus for bio-ethanol production in a newly developed process, which combines high-temperature fermentation with simultaneous fermentation and distillation under low pressure. This chapter aims to provide valuable information on thermotolerant ethanologenic yeasts and their application, which may direct the economic bioproduction of ethanol and other useful materials in the future.
Part of the book: Fuel Ethanol Production from Sugarcane