Microbiology For Dummies by Jennifer Stearns & Julie Kaiser & Michael G. Surette

Author:Jennifer Stearns & Julie Kaiser & Michael G. Surette
Language: eng
Format: epub
ISBN: 9781119544760
Publisher: Wiley
Published: 2019-03-26T00:00:00+00:00

High G + C: Actinobacteria

The phylum Actinobacteria contains many very common soil bacteria and several bacteria that are commensal of the human body, as well as a few notable human pathogens such as Mycobacterium tuberculosis and Corynebacterium diphtheria. Here are three important genera represented in this phylum:

Members of the genus Proprionibacterium ferment sugars into propionic acid and CO2 gas and are the main bacteria used to make Swiss cheese. The gas makes the holes in the cheese, and the acid gives it a nutty flavor.

Colonies of Mycobacteria have a waxy surface because of special acids in their cell walls called mycolic acids that make them difficult to stain in the regular way. Instead, heat and acid are used to stain cells red so that they can be visualized under a microscope. This group has many non-pathogenic members as well as M. tuberculosis.

The Streptomyces were thought for a long time to be a type of fungus because they make big filamentous clusters. They are, in fact, bacteria that, instead of dividing by binary fission into individual cells, form mycelia that make spores, which then pop off to populate new areas (see Figure 12-6). More than 500 different antibiotics have been isolated from this group, many of which are used in medicine today.

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