1. Medical Microbiology Dr. Oruba lec.3

2. Microbial Metabolism

3. Metabolism
Metabolism: Is the sum of all chemical reactions in the body.
metabolism is divided into two types of classes: catabolism and anabolism.

4. Metabolism; It includes all the chemical reactions that occur in the cell, which include two processes;
1- Anabolism; all the chemical reactions that building up of cell structures
and constituents where these reactions require energy.
2- Catabolism; all the chemical reactions that lead to the breaking down of
macromolecules in to small and simpler ones where it leads to
production of energy.Oxidation of carbohydrates to form carbon and
energy source…………………..
Hexoses and pentoses are the major monosaccharides sources………
Funneling into the major pathways……..
Degradation of bigger molecules into smaller ones………..
Formation of end products……

5. Assimulation (anabolism): energy-requiring
Dissimulation (catabolism): energy-acquiring
Glycolysis
Pentose phosphate pathway
TCA cycle
Respiration (aerobic and anaerobic)
Fermentation
Focal metabolites: metabolic intermediates that link anabolic and catabolic pathways.
Microbiology
Dr Saleh

8. The Requirements for Growth: Chemical Requirements
Carbon
Structural organic molecules, energy source
Chemoheterotrophs use organic carbon sources
Autotrophs use CO2

9. *According to the source of energy, organisms are divided into two groups;
Phototrophs; convert radiant energy from sunlight into chemical energy…..
Chemotrophs; transfer energy from organic or inorganic molecules into specific energy molecules………
*According to the source of carbon, organisms are divided into two groups;
Heterotrophs; use organic or inorganic chemicals( other than CO2) as a source of carbon…
Lithotrophs (autotrophs); their source of carbon is by fixation of CO2 from the atmosphere….

10. Therefore, organisms in general, are divided into four groups;
Nutritional group
Carbon source
Energy source
Examples 1- 2- 3- 4-
Chemolithotrophs
Chemoheterotrophs
Photolithotrophs
photoheterotrophs
CO2
Org.comp.
Org. comp.
Chemicals
Light
Sulfur bact., iron bact.,….
Higher animals including human, most eukaryotic organisms,….
Green plants, most algae…..
Some cyanobact., some algae.

11. On the basis of the kind of electron acceptor, energy, in the form of ATP, in
microorganisms is produced by 3 ways;
Fermentation; it is an oxidation-reduction process for the production of energy, where the electron donors and electron acceptors both are organic compounds….and the amount of energy produced is only 2 ATP.
Aerobic respiration; it is an oxidation-reduction process for production of energy where the electron donors are either organic or inorganic compounds, and the final electron acceptor is oxygen….and the amount of energy produce is 36 ATP.
Anaerobic respiration; it is an oxidation-reduction process, where the electron donors are either organic or inorganic compounds, and the electron acceptor is inorganic molecules, such as; NO-3, NO-2, SO4- -, CO2, H2S, …….etc. The amount of energy produced is only
1 or 2 ATP.

12. *Mechanism of electron transport and oxidative phosphorylation is
basically the same in aerobic and anaerobic respiration, but differs in the
followings:
Type of the electron acceptor..
Amount of the energy produced
The terminal enzyme component in electron transport system in
anaerobes is not cytochrome oxidase but other enzymes such as reductases…

13. The Requirements for Growth: Chemical Requirements
Nitrogen
In amino acids, proteins
Most bacteria decompose proteins
Some bacteria use NH4+ or NO3
A few bacteria use N2 in nitrogen fixation
Sulfur
In amino acids, thiamine, biotin
Some bacteria use SO42 or H2S
Phosphorus
In DNA, RNA, ATP, and membranes
PO43 is a source of phosphorus

14. The Requirements for Growth: Chemical Requirements
Trace Elements
Inorganic elements required in small amounts
Usually as enzyme cofactors

15. The Requirements for Growth: Chemical Requirements
Organic Growth Factors
Organic compounds obtained from the environment
Vitamins, amino acids, purines, pyrimidines

16. Agar Complex polysaccharide
Used as solidifying agent for culture media in Petri plates, slants, and deeps
Generally not metabolized by microbes
Liquefies at 100°C
Solidifies ~40°C

17. Culture Media Culture Medium: Nutrients prepared for microbial growth
Sterile: No living microbes
Inoculum: Introducing of microbes into medium
Culture: Microbes growing in/on culture medium

18. Sterile Mannitol Salt Agar

19. Streak Plate
Figure 6.10a, b

20. Nasal swab sample on Mannitol Salt Agar (MSA)
Nasal swab sample on Mannitol Salt Agar (MSA). Non-mannitol fermenter on left. Mannitol fermenter on right, viewed from bottom

21. References:
1- Jawetz, Melnick, & Adelberg’s.( 2013). Medical Microbiology (Twenty-Sixth Edition).
2- Kenneth Todar. (2008).Todar’s Online Textbook of Bacteriology ,University of Wisconsin.

22. Thank you