Actinobacteria or Actinomycetes

Some strains now produce poisonous
hydrogen sulfide (H2S) gas and Necrotizing pneumonia

The Actinobacteria or Actinomycetes are a group of Gram-positive bacteria with high G+C ratio. They
include some of the most common soil life, playing an important role in decomposition of organic
materials, such as cellulose and chitin and thereby play a vital part in organic matter turnover and carbon
cycle. Thus replenishing the supply of nutrients in the soil and is an important part of humus formation.

Actinobacteria are well known as secondary metabolite producers and hence of high pharmacological and
commercial interest. In 1940 Selman Waksman discovered that the soil bacteria he was studying made
actinomycin, a discovery which granted him a Nobel Prize. Since then hundreds of naturally occurring
antibiotics have been discovered in these terrestrial microorganisms, especially from the genus

Other Actinobacteria inhabit plants and animals, including a few pathogens, such as Mycobacterium,
Corynebacterium, Nocardia, Rhodococcus and a few species of Streptomyces.

Actinomycetes: fungus-like bacteria; A. israelii  most commonly associated with actinomycosis

actinomycosis /ac·ti·no·my·co·sis/ (-mi-ko´sis) an infectious disease caused by Actinomyces, marked by
indolent inflammatory lesions of the lymph nodes draining the mouth, by intraperitoneal abscesses, or by
lung abscesses due to aspiration.actinomycot´ic

invasive fungal sinusitis

Clin Exp Obstet Gynecol. 1987;14(2):89-91.

In the last few years actinomyces has aroused great interest in gynecologic practice. Two cases of
preterm delivery in which placental histological examination revealed massive invasion by actinomycetes
accompanied with necrotizing placentitis are described.

The Jekyll and Hyde characteristics of actinobacterial genera are typified by the rhodococci. The
persistent equine pathogen Rhodococcus equi is ubiquitous in the environment, and grows rapidly in
horse manure. It is thought that the main route of infection is via the inhalation of R. equi from
manure-contaminated dust. The infection proceeds in the lungs, causing a pneumonia-like disease,
especially in foals. The genome of R. equi is currently being sequenced at the Sanger Centre in
Cambridge, and the provision of such a resource may aid in the development of a vaccine. Additionally, R.
equi pneumonia is also emerging as a signifi cant human pathogen in patients with HIV, yet currently we
know little about its pathogenicity in humans.