Biomedical Engineering Reference
In-Depth Information
Nocardiaceae
*Nocardia
*Rhodococcus
Cellulomonadaceae
*Tropheryma
Propionibacteriaceae
*Propionibacterium
Streptosporangineae
Thermomonosporaceae
*Actinomadura
Bifidobacteriales
Bifidobacteriaceae
*Gardnerella
There are two large classes within the Gram-positive group (not all of which
are actually Gram-positive). These are the Firmicutes (containing Class
Bacilli (Chapter 12), Class Clostridia (Chapter 12), and Class Mollicutes
(Chapter 11)) and the Actinobacteria (Chapter 14). The Firmicutes are char-
acterized by low G
C DNA. The Actinobacteria are characterized by high
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G
C DNA.
Members of Class Actinobacteria tend to be filamentous, and this
morphologic feature has led to great confusion. In the past, these filamentous
bacteria were mistaken for fungal hyphae, and many of the diseases caused
by members of Class Actinobacteria were mistakenly assigned fungal names
(e.g., actinomycosis, mycetoma, maduromycosis).
Molecular analysis of the Actinobacteria indicates that they are eubacteria
that share a high degree of sequence similarity among the subclasses [21].
High sequence similarity among sister subclasses is generally interpreted
to mean that the classes are young (i.e., descended from a common ancestor
relatively recently, before their genomes had an opportunity to diverge).
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Actinobacteria
Actinomycetales
Actinomycetaceae
*Actinomyces
*Arcanobacterium
Actinomyces is the cause of so-called actinomycosis (Greek “actino,” ray and
“myco,” fungus), a suppurative condition arising in the oral cavity and naso-
pharynx, characterized by acute and chronic inflammation and the discharge
of so-called sulfur granules. The disease is caused by any of several species of
Genus Actinomyces (e.g., Actinomyces israelii or Actinomyces gerencseriae),
as well as closely related species (e.g., Propionibacterium propionicus). Sulfur
granules are yellow flecks found mixed with inflammation and extruded in
exudate, consisting of numerous bacterial filaments, often radiating from a
