Microbiology Demystified

thought to be viruses because they lack a cell wall. However, they have a cell

membrane, DNA and RNA, which distinguishes them from viruses.

Mycoplasmas can also resemble fungi because some Mycoplasmas produce

filaments that are commonly seen in fungi. It is these filaments that led scien-

tists to name it Mycoplasma. Myco means “fungus.”

Many Mycoplasmas are unable to move by themselves because they do not

have flagella, but some are able to glide on a wet surface.

Two of the more common types of Mycoplasma are:

• Mycoplasma pneumoniae. Mycoplasma pneumoniaeis the cause of atypi-
  cal pneumonia, commonly referred to as walking pneumonia.


• Ureaplasma urealyticum. Ureaplasma urealyticumis a bacterium that is
  found in urine and one that can cause urinary tract infection.

Gram-Positive Cocci

Within the gram-positive cocci section are two genera. These are Staphylococcus

and Streptococcus,and each has an important role in medicine.

• Staphylococcus. Staphylococcusbacteria have a grape-like cluster appear-
  ance and grow in environments of high osmotic pressure and low moisture.
  Osmotic pressure is the pressure required to prevent the net flow of water
  by osmosis. Infections caused by the Staphylococcus bacteria are typically
  called staph infections. Here are the commonly found Staphylococcus
  bacteria:
  
  
  • Staphylococcus aureus. Staphylococcus aureus, also called S. aureus, is a
    bacterium that forms yellow-pigmented colonies that grows with oxygen
    (aerobically) or without oxygen (anaerobically). S. aureusis the cause of
    toxic shock syndrome that results in high fever, vomiting and sometimes
    death. It produces enterotoxins, which affects intestinal mucosa. S. aureus
    is also the cause of boils (skin abscess), impetigo (pus-filled blisters on
    the skin), styes (an infection at the base of an eye lash), pneumonia,
    osteomyelitis, acute bilateral endocarditis (inflammation of the internal
    membranes of the heart) and scalded skin syndrome in very young chil-
    dren that causes skin to strip off (denude) due to an exfoliative toxin.
    S. aureusis one of the major types of infections that occur in hospi-
    tals because it is resistant to antibiotics such as penicillin. An infection
    of S. aureusis usually identified by the presence of an abscess.
  
  
  
  

(^160) CHAPTER 10 The Prokaryotes