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microbial physiology and genetics, mainly focus on the genetic and physiological aspects of microorganism, their way of reproducing and infecting other organism
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Microbial Physiology and Genetics
PART 1
Chapter 7
Microbial Physiology
Physiology – is the study of the vital life processes of organisms, especially how these processes normally function in living organisms
Microbial Physiology – concerns the vital life processes of microorganisms
Advantages of Using Bacteria
Inexpensive to maintain in the laboratory.
Take up little space and reproduce quickly.
Morphology, nutritional needs and metabolic reactions are easily observable.
NutrientsRefers to various chemical compounds that
organisms use to sustain life. Many nutrients are energy sources.Organisms will obtain energy from these
nutrients by breaking chemical bonds.When chemical bond is broken, energy is
released.Nutrients are broken down by enzymatic
actions.
Nutritional RequirementsSix major chemical elements: carbon,
hydrogen, oxygen, nitrogen, phosphorus and sulfur
Lesser amounts: sodium, potassium, chlorine, magnesium, calcium, iron, iodine, and some trace elements
Essential nutrients – materials that organisms are unable to synthesize, but are required for the building of macromolecules and sustaining life.
Categorizing Microorganisms According to Their Energy and Carbon Sources
Terms Relating to Energy SourcePhototrophs- use lightChemotrophs- use either inorganic or
organic chemicalsChemolithotrophs- use inorganic
chemicalsChemoorganotrophs- use organic
chemicals
Terms Relating to Organism’s Carbon SourceAutotrophs- use CO2 as their energy sourceHeterotrophs- use organic compounds as their
carbon source other than CO2
Photoautotrophs- use light energy and CO2 Photoheterotrophs- use light and organic
compounds other than CO2 Chemoautotrophs- use chemicals are energy
source and CO2 as carbon sourceChemoheterotrophs- use chemicals as energy
source and organic compound other than CO2 as energy source
Metabolic Diversity Among Organisms
Nutritional type Energy source Carbon source Example
Photoautotroph Light CO2Oxygenic: Cyanobacteria plants.
Anoxygenic: Green, purple bacteria.
Photoheterotroph Light Organic compounds
Green, purple nonsulfur bacteria.
Chemoautotroph Chemical CO Iron-oxidizing bacteria.
Chemoheterotroph Chemical Organic compounds
Fermentative bacteria.
Animals, protozoa, fungi, bacteria.
Ecology – is the study of the interaction between organisms and the world around them.
Ecosystem – refers to the interactions between living organisms and their nonliving environment.
Phototrophs are producers of food and oxygen for chemoheterotrophs.
Dead plants and animals would clutter the earth if chemoheterotrophic saprophytes and decomposers did not break down dead organic compounds.
Photoautotrophs contribute energy to the ecosystem by trapping energy from the sun and converting it to build organic compound.
Metabolic EnzymesMetabolism is the sum of the chemical
reactions in an organism, Metabolic reaction
Catabolism is the energy-releasing processes.
Anabolism is the energy-using processes.
Metabolic enzymes enhances and regulates metabolic reaction.
A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell.
Metabolic pathways are determined by enzymes.
Enzymes are encoded by genes.
Biologic Catalysts
Biologic catalysts- protein that either causes a particular chemical reaction to occur or accelerates.
Substrate- particular substance in which enzymes act
Apoenzyme- protein (inactive)Cofactor- nonprotein component
Coenzyme- organic cofactor (activator)Holoenzyme- apoenzyme + cofactor
Kinds of Enzymes
Endoenzymes- produce within the cell that remains within the cell (digestive enzymes)
Exoenzymes- produce within the cell and released from the cell (cellulase)
Factors that Affects the Efficiency of Enzymes
Enzymes can be denatured by temperature and pH
Temperature
pH
Substrate concentration
Competitive Inhibition
Non-competitive Inhibition
Metabolism
Metabolite- any molecule that is a nutrient, an intermediary or end product of metabolism
Catabolism- breakdown of carbohydrates to release energy
Anabolism- assembly of smaller molecules to larger molecules
Metabolism
ATP is generated by the phosphorylation of ADP
Biochemical Pathways
Series of linked biochemical reactions that occur in a step-wise manner, leading from the starting material to the end product.
Glucose is the favorite “food” of cells, including microorganisms.
Nutrients- energy sourcesChemical bonds- stored energyWhenever chemical bonds within the nutrients are
broken, energy is released.Aerobic respiration and fermentation reactions.
Catabolism/Aerobic Respiration of Glucose
The breakdown of carbohydrates to release energyGlycolysisKrebs cycleElectron transport chain
Glycolysis
Glycolytic pathway, the Embden-Meyerhof pathway, Embden-Meyerhof-Parnas pathway.
A nine-step biochemical path, involving nine separate biochemical reactions, each of which requires specific enzymes.
Six-carbon molecule of glucose is broken down into three-carbon molecules of pyruvic acid.
Can take place with or without oxygen.Produces very little energy– only 2 ATP.Takes place in the cytoplasm of both prokaryptic
and eukaryotic cells.
Krebs CycleThe pyruvic acid molecules produced during
glycolysis are converted into acetyl-CoA molecules.
The Krebs Cycle is consists of eight separate reactions, each of which is controlled by a different enzymes.
Acetyl-CoA combine with oxalate to produce citric acid (tricarboxylic acid).
Only 2 ATP produced, but a number of products like NADH, FADH2, and H ions.
Mitochondria (eukaryotes); inner surface of cell membrane (prokaryotes).
Electron Transport Chain
Certain of the products produced during the Krebs cycle enter the electron transport chain.
Consist of a series of oxidation-reduction reactions, whereby energy is released as electrons are transferred from one compound to another.
Oxygen is at the end of the chain; referred to as then final or terminal electron acceptor.
Cytochrome oxidase- enzyme responsible for transferring electrons to oxygen.
Produces 32 ATP in prokaryotic cells, and 34 ATP in eukaryotic cells.
Net yield by aerobic respiration: 36 ATP (prokaryotic cells) and 38 ATP (eukaryotic cells).
Aerobic respiration of glucose produces 18-19X ATP than fermentation.
Biochemical Pathway
Prokaryotic Eukaryotic
Glycolysis 2 2
Krebs Cycle 2 2
ETC 32 34
Total ATP 36 38
Number of ATP Produced From One MoleculeOf Glucose by Aerobic Respiration
Pathway Eukaryote Prokaryote
Glycolysis Cytoplasm Cytoplasm
Intermediate step Cytoplasm Cytoplasm
Krebs cycle Mitochondrial matrix Cytoplasm
ETC Mitochondrial inner membrane
Plasma membrane
Fermentation of GlucoseDo not involve oxygenFirst step is glycolysisNext step is the conversion of pyruvic acid into an
end product.Does not use the Krebs cycle or ETCEnd product depends on specific organism
involved: Saccharomyces spp. and Zymomonas spp. convert
pyruvic acid to ethanol and CO2
Lactic acid bacteria convert pyruvic acid to lactic acid.
Alcohol fermentation. Produces ethyl alcohol + CO2
Lactic acid fermentation. Produces lactic acid.Homolactic fermentation. Produces lactic acid
only.Heterolactic fermentation. Produces lactic acid
and other compoundsIn human muscle cells, lack of oxygen during
extreme exertion results in pyruvic acid being converted to lactic acid.
Fermentation produces only 2 ATPAerobes/facultative aerobes Vs. oblgate
anaerobes
Oxidation-reduction Reactions
Paired reactions in which electrons are transferred from one compound to another.
Oxidation- loss of one or more electronsReduction- gain of one or more electronsReducing agent- electron donorOxidizing agent- electron acceptor
Anabolism
Require energy to form chemical bonds.The energy is provided by the catabolic
reactions occurring simultaneously in the cell.Referred to as biosynthetic reactions.
PhotosynthesisChemosynthesis
PhotosynthesisPhoto: Conversion of light energy into chemical
energy (ATP)Light-dependent (light) reactions
Synthesis: Fixing carbon into organic moleculesLight-independent (dark) reaction, Calvin-Benson
cycleOxygenic:
6 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2O
Anoxygenic: CO2 + 2 H2S + Light energy [CH2O] + 2 A + H2O
ChemosynthesisUse energy from chemicals.
Chemoautotroph, Thiobacillus ferroxidans
2Fe2+
2Fe3+
NAD+
NADH
ETC
ADP + P ATP
2 H+
Next topic: Microbial Genetics
Finish!