Chapter 7
Microbial Physiology and Genetics PART 1
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 Advanta ges 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.
Nutrients Refers 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 Requirements Six 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 Source PhototrophsPhototrophs- use light ChemotrophsChemotrophs- use either inorganic or organic chemicals ChemolithotrophsChemolithotrophs- use inorganic chemicals Chemoorganotrophs Chemoorganotrophs-- use organic chemicals
Terms Relating to Organism’s Carbon Source Autotrophs- use CO as their energy source 2
Heterotrophs- use organic compounds as their carbon source other than CO 2
PhotoautotrophsPhotoautotrophs- use light energy and CO 2
PhotoheterotrophsPhotoheterotrophs- use light and organic compounds other than CO 2
ChemoautotrophsChemoautotrophs- use chemicals are energy source and CO 2 as carbon source
Chemoheterotrophs- use chemicals as Chemoheterotrophsenergy source and organic compound other than CO2 as energy source
Metabolic Diversity Among Organisms Nutritional type Photoautotroph
Energy source Light
Carbon source CO2
Example Oxygenic: Cyanobacteria plants. Anoxygenic: Green, purple bacteria. Green, purple nonsulfur bacteria.
Photoheterotroph
Light
Organic compounds
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 Enzymes Metabolism 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 Enzymes are encoded by genes 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 Apoenzyme- protein (inactive) Cofactor- Cofactor- nonprotein nonprotein component Coenzyme- Coenzyme- organic organic cofactor (activator) Holoenzyme- Holoenzyme- apoenzyme 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 Metabolitenutrient, an intermediary or end product of metabolism Catabolism Catabolism-- breakdown of carbohydrates to release energy Anabolism 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 sources
Chemical bonds- stored energy
Whenever 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 energy
Glycolysis Krebs cycle Electron 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 of pyruvic acid. acid. Can take place with or without oxygen. oxygen.
Produces very little energy– only 2 ATP. ATP.
Takes place in the cytoplasm of both prokaryptic and eukaryotic cells.
Krebs Cycle The 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. 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. chain. Consist of a series of oxidation-reduction reactions, 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 pr oduces 1819X 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 Molecule Of 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 Fermentati on of Glucose Do not involve oxygen
First step is glycolysis
Next step is the conversion of pyruvic acid into an end product. Does not use the Krebs cycle or ETC
End product depends on specific organism involved:
Saccharomyces spp. spp. and Zymomonas spp. convert pyruvic acid to ethanol 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 compounds
In human muscle cells, lack of oxygen during extreme exertion results in pyruvic acid being converted to lactic acid. acid. Fermentation produces only 2 ATP
Aerobes/facultative anaerobes
aerobes
Vs.
oblgate
Oxidation-reduction Reactions Paired reactions in which electrons are transferred from one compound to another. Oxidation- loss of one or more electrons Reduction- gain of one or more electrons Reducing agent- electron donor Oxidizing 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.
Photosynthesis Chemosynthesis
Photosynthesis Photo: Conversion of light energy into chemical energy (ATP)
Light-dependent Light-dependent (light) reactions
Synthesis: Synthesis: Fixing carbon into organic molecules
Light-independent Light-independent (dark) reaction, Calvin-Benson cycle
Oxygenic:
6 CO2 + 12 H2O + Light energy → C6H12O6 + 6 O2 + 6 H2O
Anoxygenic:
CO2 + 2 H2S + Light energy → [CH2O] + 2 A + H2O
Chemosynthesis Use energy from chemicals.
Chemoautotroph, Thiobacillus Thiobacillus ferroxidans
2Fe2+
NAD+ ETC
2Fe3+
NADH 2 H+
ADP + P
ATP
Finish! Next topic: Microbial Genetics
