Microbiology Demystified

Endospore-Forming Gram-Positive Rods and Cocci

Endospore forming, gram-positive rods and cocci consist mainly of rod-shaped

bacteria of the genera Bacillusand Clostridium.Another cocci bacteria included

in this group are of the genus Sporosarcina.These bacteria have no clinical sig-

nificance and are saprophytic soil bacteria. Saphrophytes are organisms that feed

on dead organic matter.

These bacteria can be strict aerobes, facultative anaerobes, obligate anaerobes

or microaerophiles. Microaerophiles are bacteria that grow best in an environ-

ment that has a small amount of free oxygen.

The formation of endospores by bacteria is important in medicine and the food

industry because these endospores are resistant to heat and many chemicals.

There are three genera in this section. These are:

• Bacillus: Bacillus consists of the following bacterium:
  
  
  • Bacillus anthracis. Bacillus anthraciscauses anthrax, a severe blood
    infection that infects cattle, sheep and horses and can be transmitted to
    humans. B. anthracisis a non-motile facultative anaerobe and produces
    exotoxin. Anthrax can result in central nervous system distress, respira-
    tory failure, anoxia and death.
  
  
  • Bacillus cereus. Bacillus cereusproduces enterotoxin (a toxin that affects
    the intestine) and causes gastroenteritis (food poisoning).
  
  
  • Bacillus thuringiensis. Bacillus thuringiensisproduces a toxin that attacks
    the digestive system of insects, causing the insects to stop feeding by
    causing paralysis of the insects guts.
  
  
  
  


• Sporosarcina. Sporosarcinaare bacteria that inhabit the soil and receive
  nutrients by feeding on dead organic matter.


• Clostridium. Clostridium are rod-shaped bacteria that exist in water, soil,
  and in the intestinal tract of animals and humans. These bacteria do not
  require oxygen. They release toxins that cause disease. Here are the com-
  mon types of Clostridium:
  
  
  • Clostridium tetani. Clostridium tetani, also known as C. tetani, causes
    tetanus, commonly referred to as lockjaw.
  
  
  • Clostridium difficile. Clostridium difficile, also known as C. difficile,
    causes gastroenteritis.
  
  
  
  

(^162) CHAPTER 10 The Prokaryotes