1. Bacterial oxygen requirement

2. Introduction
Bacteria in various environments have different behavior with oxygen according the enzymatic system which bacteria own.
Oxygen Species is harmful if :
1- bacteria have no enzyme
system to eliminate it.
2- Oxygen Species concentration
is very high in media or air.

3. Oxygen Species
Singlet oxygen (O2) : is in high energy state and extremely reactive, exists in phagocytes.
Superoxide free radical (O2-) & hydrogen peroxide (H2O2): is so toxic to cell , formed in small amount in cellular respiration.
Peroxide anion (O2-2) : used as antimicrobial agent.
Hydroxyl radical (OH-) : the most active form, form in the cytoplasm from respiration.

4. Enzyme systems Super oxide dismutase
Converts the superoxide ion to hydrogen peroxide in the existence of hydrogen ion 2

5. 2. Catalase : breaks up hydrogen peroxide to water and oxygen.
3. Peroxidase : converts hydrogen peroxide to water in presence of hydrogen ions (NADH).

6. Other protective factors :
ß –carotene : acts as anti-oxidant & is composed from simple lipids , quench singlet oxygen.
Phenolic Glycolipids : scavengers of hydroxyl and superoxide anions (complex lipid).
Dimethylsulfoxide : a hydroxyl radical scavenger.
Tryptophan (A.A.) : a hydroxyl radical scavenger.

7. Taxonomy
Bacteria are classified according to oxygen requirement into five classes :
Obligate aerobes : growth occurs only
when high concentration of oxygen
diffused into the medium.
2. Facultative anaerobes : grows in best
where most oxygen is presented, but
occur throughout tube.

8. 3. Obligate anaerobes : growth occurs
only when there is no oxygen.
4. Aerotolerant anaerobes : growth
occurs evenly, oxygen has no effect.
5. Microaerophiles : growth occurs only
where a law concentration of oxygen
has diffused into medium.

9. Facultative anaerobes Obligate anaerobes Aerotolera -nt anaerobes
class
Aspects
Obligate aerobes
Facultative anaerobes
Obligate anaerobes
Aerotolera -nt anaerobes
Microaerop-hiles
Energy source
cellular respiration
respiration, fermentation
fermentation, autotrophy
fermentation
aerobic
anaerobic
SOD enzyme
Peroxidase
catalase
example
Bacillus, Pseudomonas
E. coli, Staphylococcus
Clostridium tetani,Bacteroides
Lactobacillus
Campylobacter & Heliobacter pylori
+ growth region
Microaerophiles have just few amount of either Peroxidase or catalase or none

10. Methods for excluding oxygen

11. Fluid Thioglycollate Media (FTM)
supports aerobic & anaerobic bacteria
– Sodium thioglycollate and cyctine
removes O2 from the medium
– Resazurin as an oxidation reduction indicator
turns pink in presence of O2
Small amount of agar presented to retard gases

12. Gas Pack System : Anaerobic Jar

14. Gas Pak Pouch Procedure for GasPak Pouch.
(a) Dispense GasPak liquid activating reagent into channel of pouch.
(b) Place plates inside the pouch.
(c) Lock in anaerobic environment with sealing bar and incubate.

15. Candle jars
The candle flame will consume most of the oxygen in the jar.
Produce an elevated level of carbon dioxide.
These conditions are ideal for the growth of campilophilic and microaerophilic organisms.

16. CO2 Generating Packet

17. Anaerobic Chambers
The Vinyl Anaerobic Chambers provide a strict anaerobic atmosphere using a palladium catalyst and hydrogen gas mix of 5%.