Oct. 12 Notes for Review

October 12, 2009
c. Oxygen
-reduces DNA damage
-oxygen: very electronegative:
- attractive to electrons
i. anaerobes- bacteria that does not require oxygen to live
aerobic- environment cells (e.g. ours, all bacterial cells that live in normal Ox2( 20% O2) must have mechanisms for fixing DNA and protein damage caused by electrons, O2

Why does oxygen inhibit the growth of many kinds of bacteria?
Antioxidant: chemical that “soaks up” free electrons
- This helps prevent damage to DNA, proteins caused by electrons bouncing around and breaking DNA strands/ altering protein structure
- Cell in environment with lots of Ox2 is also in the presence of electrons; electrons bounce around , break DNA, proteins
ii.) aerobes – require oxygen to grow
- * use identical ATP –generation mechanism (w/ O2 as terminal electron acceptor) as our mitochondria
- Most skin/ normal flora are aerobes (ex. Staphylococci)
iii.) other atmospheric requirements
1. Microaerophiles – must have approx. 5% O2 to grow, but die with more O2 than that
2. Capnophiles- msut have some O2 and 5-10% CO2 to grow

d. Temperature
i.) psychorophiles : grow best at approximately -5 % C and -10 C
* lots of unsaturated fats in membrane
*little G and C, lots of A and T in DNA
ii.) mesophiles: grow best at app.. 20 degrees-35 degress C
• All bacteria that live in/ on us
iii.) thermophiles : 60 degrees C
hyperthermophiles >, 100 C
• Saturated fat membranes
e.) pH acidophiles live best at low pH’s (1.0-3.0)- cause of stomach ulcers = H pylor
alkalophiles : live at high pH (10.0 +)

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