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Processes in Microbial Ecology$
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David L. Kirchman

Print publication date: 2011

Print ISBN-13: 9780199586936

Published to Oxford Scholarship Online: December 2013

DOI: 10.1093/acprof:oso/9780199586936.001.0001

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Physical-chemical environment of microbes

Physical-chemical environment of microbes

(p.35) Chapter 3 Physical-chemical environment of microbes
Processes in Microbial Ecology

David L. Kirchman

Oxford University Press

Many physical-chemical properties affecting microbes are familiar to ecologists examining large organisms in our visible world. This chapter starts by reviewing the basics of these properties, such as temperature effects and the importance of water for microbes in soils. Another important property – pH – has direct effects on organisms and indirect effects via how hydrogen ions determine the chemical form of key molecules and compounds in nature. Oxygen content is also critical, as it essential to the survival of all but a few eukaryotes. Light is used as an energy source by phototrophs, but it can have deleterious effects on microbes, especially ultraviolet light. In addition to these familiar factors, the small size of microbes sets limits on their physical world. Microbes are said to live in a ‘low Reynolds number environment’. When the Reynolds number is smaller than about one, viscous forces dominate over inertial forces. For a macroscopic organism like us, moving in a low Reynolds number environment would seem like swimming in molasses. The chapter also provides an overview of the physical environment of aquatic and terrestrial habitats, and ends with a discussion of how the physical-chemical environment of microbes in biofilms is quite different from that of free-living organisms.

Keywords:   Arrhenius equation, psychrophile, acidophile, piezophile, redox potential, extracellular polymers, diffusion, chemotaxis

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