Microbiology For Dummies
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Unlike the physical requirements where a specific range or concentration is necessary for optimum growth, the chemical requirements just need to be present in the environment and a microbe will use what it needs. Microbes use compounds containing the following elements and vitamins to make everything in the cell including membranes, proteins, and nucleic acids:

  • Carbon: Carbon is necessary for all life. In the microbial world, chemoorganotrophs get their carbon from organic matter, whereas chemoautotrophs get it from carbon dioxide in the atmosphere.

  • Nitrogen, sulfur, and phosphorus: Nitrogen, sulfur, and phosphorus are necessary for protein and nucleic acid biosynthesis. Most microbes get these elements by degrading proteins and nucleic acids, but some capture nitrogen from nitrogen gas or ammonia or get sulfur from other ions in the environment.

  • Trace elements: Trace elements such as iron, copper, molybdenum, and zinc are needed as cofactors for enzymes and must be obtained, in tiny amounts, from the environment.

  • Vitamins and amino acids: Unlike humans, microbes can make vitamins, which also act as enzyme cofactors. Some microbes, however, lack the ability to make one or several vitamins and have to get them from their environment.

    The same is true of amino acids and these along with the vitamins needed are called growth factors. Although most bacteria can make all the amino acids they need, some can’t quite make them all; these bacteria are called auxotrophs.

  • Oxygen: The presence of oxygen affects a few different aspects of microbial growth. Different microbes respond differently to oxygen.

About This Article

This article is from the book:

About the book authors:

Jennifer C. Stearns, PhD, is an assistant professor in the department of medicine at McMaster University. She studies how we get our gut microbiome in early life and how it can keep us healthy over time. Michael G. Surette, PhD, is a professor in the department of medicine at McMaster University, where he pushes the boundaries of microbial research.

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