Metabolic Reprogramming Under Microaerobic and Anaerobic Conditions in Bacteria
Oxygen has a great impact on the metabolism and physiology of microorganisms. It serves as the most efficient terminal electron acceptor to drive the energy conservation process of cellular respiration and is required in many biosynthetic reactions. Bacte
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Metabolic Reprogramming Under Microaerobic and Anaerobic Conditions in Bacteria Yue Shan*, Yong Lai*, and Aixin Yan
Abstract Oxygen has a great impact on the metabolism and physiology of microorganisms. It serves as the most efficient terminal electron acceptor to drive the energy conservation process of cellular respiration and is required in many biosynthetic reactions. Bacteria encounter oxygen fluctuation and limitation during their growth in both natural ecological niches and in laboratory vessels. In response to oxygen limitation, facultative bacteria undergo substantial metabolic reprogramming to switch from the aerobic respiration to either anaerobic respiration, fermentation, or photosynthesis. Two key factors determine the metabolic pathways bacteria adopt under oxygen deprived microaerobic and anaerobic conditions: maximal energy conservation and redox homeostasis. In this chapter, we first describe how the fulfillment of these two key factors governs the metabolic reprogramming of facultative bacteria and how the process is tightly controlled by several global regulatory factors: FNR, ArcBA, as well as NarL and NarP. We then utilizes fermentation of glycerol, a large surplus byproduct of biodiesel industry, as an example to illustrate how environment, process, and strain based approaches can be exploited to manipulate and engineer the anaerobic metabolic pathways so that desirable fermentation products can be achieved with optimal yield. Keywords Aerobic respiration • Anaerobic respiration • Fermentation • Glycerol fermentation • Redox homeostasis
*Yue Shan and Yong Lai are contributed equally Y. Shan • Y. Lai • A. Yan (*) School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China e-mail: [email protected] X. Wang et al. (eds.), Reprogramming Microbial Metabolic Pathways, Subcellular Biochemistry 64, DOI 10.1007/978-94-007-5055-5_8, © Springer Science+Business Media Dordrecht 2012
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Abbreviations Arc ATP ETC FNR NADH TCA cycle
8.1
aerobic respiratory control adenosine-5¢-triphosphate electron transport chain fumarate and nitrite reduction nicotinamide adenine dinucleotide (reduced form) tricarboxylic acid cycle
Introduction
Oxygen (O2) as an atmospheric component has a great impact on the life style of living organisms on earth. It serves as the most efficient terminal electron acceptor to drive the energy conservation process of cellular respiration and is required in many biosynthetic reactions. Owing to its substantial effect on the growth and metabolism of microorganisms, how these organisms respond to the presence and levels of O2 has been an important scenario to categorize microbial species. From this regard, microorganisms are classified as obligate aerobes, facultative anaerobes, aerotolerant anaerobes, microaerophiles, and obligate anaerobes. Facultative anaerobes are those that can grow both in the presence (aerobic) and absence (anaerobic) of O2 and have been an important class of organisms exploited in biotechnology owing to their
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