Presentation on theme: "الجامعة الإسلامية - غزة كلية العلوم قسم التحاليل الطبية الجامعة الإسلامية - غزة كلية العلوم قسم التحاليل الطبية Bacterial Oxygen Requirement By / Shadi."— Presentation transcript:
الجامعة الإسلامية - غزة كلية العلوم قسم التحاليل الطبية الجامعة الإسلامية - غزة كلية العلوم قسم التحاليل الطبية Bacterial Oxygen Requirement By / Shadi F. Alashi DR. Abdelraouf ELmanama
INTRODUCTION One of the most prominent differences among bacteria is their requirement for, and response to, atmospheric oxygen (O2).
Bacterial Oxygen Requirement Bacteria can be divided into four groups based on requirement of gaseous oxygen: 1. Aerobes - require the presence of gaseous (molecular) oxygen.
Bacterial Oxygen Requirement 2. Anaerobes - require absence of gaseous oxygen (utilize O in oxygen containing compounds - chemical oxygen). 3. Facultative - either condition (Facultative anaerobes, facultative aerobes). 4. Microaerophilic - require the presence of small amounts of oxygen (2% - 10%) - reduced oxygen tension
Bacterial Oxygen Requirement a. Obligate Aerobes : Microbes that are use molecular oxygen produce more energy from nutrients than microbes that do not use oxygen ( anaerobes ).
Bacterial Oxygen Requirement Obligate aerobes are at a disadvantage in the oxygen poorly soluble in the water of their environment, therefore, many of the aerobic bacteria have developed, or retained, the ability to continue growing in the absence of oxygen.
Bacterial Oxygen Requirement b. Obligate anaerobes : Are bacteria that are un able to use molecular oxygen for energy – yielding reactions. For example : Clostridium tetani, botulism
Bacterial Oxygen Requirement Clostridium cause botulism
Bacterial Oxygen Requirement c. Facultative anaerobes : Can use oxygen when it is present but are able to continue growth by using fermentation or anaerobic respiration when oxygen is no available. However, their efficiency in production energy decreases in the absence of oxygen.
Bacterial Oxygen Requirement For example Escherichia coli
Bacterial Oxygen Requirement d. Aerotolerant anaerobes : Cannot use oxygen for growing, but they tolerate it fairly well. On the surface of a solid medium, they will grow without the special techniques required for obligate anaerobic
Bacterial Oxygen Requirement Example : lactobacilli
Bacterial Oxygen Requirement e. Microaerophilic : are a specific type of bacteria that requires oxygen to survive, but requires environments containing lower levels of oxygen than are present in the atmosphere (~20% concentration
Bacterial Oxygen Requirement Examples include Borrelia burgdorferi, a species of spirochaete bacteria that causes lyme disease in humans, and Helicobacter pylori, a species of prpoteobacteria that has been linked to peptic ulcers and some types of gastritis
Bacterial Oxygen Requirement In a test tube of solid nutrient medium, they growth only at a depth where a small amounts of oxygen have diffused in to the medium; they do not grow at the oxygen rich surface or below the narrow zone of adequate oxygen.
Bacterial Oxygen Requirement The tests : The oxygen requirements of bacteria can be testing by inoculating them in to a medium with an oxygen gradient. The oxygen gradient will be produced by heating an agar medium to drive off any dissolved oxygen.
Bacterial Oxygen Requirement so, the top of the deep will become oxygenated, while the bottom will remain anaerobic. After inoculation, growth only at the top of the deep in indicates an obligate aerobe. Growth just under the surface of the deep indicates a micriaerophile.
Bacterial Oxygen Requirement While growth only at the bottom of the deep indicates an obligate an aerobe anaerobe. Growth throughout the deep indicates either a facultative anaerobe or an aerotolerant anaerobe.
Fluid thioglycollate broth 0.075% agar to prevent convention current from carrying atmospheric oxygen throughout the broth. Thioglycolic acid acts as a reducing agent
Bacterial Oxygen Requirement Many nutrients factors such as: casein, yeast, beef extract & vitamins. Oxidation- reduction indicator (resazurin) : Present of o 2 pink Absent of o 2 colorless
Bacterial Oxygen Requirement Strick aerobic tend to grow in a thin layer on the surface of the broth. Sodium thioglycolate combined with dissolved oxygen lead to depletion dissolved oxygen in culture media
Bacterial Oxygen Requirement Anaerobic jar Perform for an anaerobic environment. Chemical in the envelope produce hydrogen gas and co2. The hydrogen combined with the oxygen in the chamber to yield H2O. A methylene blue when the O 2 has been removed turn to colorless
Bacterial Oxygen Requirement sodium bicarbonate + sodium borohydride + water H 2 +CO 2 + O 2 palladium catalyst H 2 o