BB/HAPPIPITOISUUS

[Bb]

Lähettäjä: Soijuv Lähetetty: 14.10.2005 9:58

Borreliabakteeri elää vähähappisessa ympäristössä. Se ei kykene kasvamaan normaalissa ilmassa jonka happipitoisuus on 20 % vaan vaatii kasvaakseen 2 - 10 % happea. Se selviytyy suolenseinämässä.


http://www.mansfield.ohio-state.edu/~sa ... m#anaerobe
----Microaerophile

1. Low O2 requirement and tolerance:
1. Microaerophiles are microorganisms which are unable to grow when oxygen concentrations reach those found in air (20%) but nevertheless whose growth requires the presence of some oxygen (e.g., 2 to 10%).
2. "Microaerophiles appear to grow best in the presence of a small amount of free oxygen. They grow below the surface of the medium in a culture tube at the level where oxygen availability matches their needs." (p. 147, Black, 1986)

2. The enzyme nitrogenase is poisoned by normal atmospheric oxygen levels thus rendering nitrogen fixation nonoperative. Nitrogen fixing bacteria have a consequent growth preference for lower than normal atmospheric levels of oxygen.

3. Examples:
1. Borrelia burgdorferi
2. Helicobacter pylori
3. Lactobacillus spp. (can also be a facultative anaerobe)
4. Treponema pallidum (can also be an anaerobe)

4. The in many ways similar Treponema pallidum and Borrelia burgdorferi spirochetes are also both examples of microaerophilic bacteria. Note, however, that Bergey's classifies T. pallidum as "Anaerobic or microaerophilic." (p. 30, 1994, Nineth Edition)

5. Microaerophilic conditions, though not necessarily just microaerophilic microorganisms, may be found in some environments particularly at the interface between the anaerobic and the aerobic such as those found in soil, water, or part of the bodies of animals and some plants.

6. The colon is maintained anaerobic by the scavenging of oxygen by facultative anaerobes living near the intestinal wall (and thus the source of oxygen in this system). Areas close to the intestinal wall (especially, intimately in contact with it) are therefore maintained in a microaerophilic state.