Microbial Physiology And Genetics Part 1

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 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 Phototrophs- use light Chemotrophs- use either inorganic

or organic chemicals Chemolithotrophs- use inorganic chemicals Chemoorganotrophs- use organic chemicals

Terms Relating to Organism’s Carbon Source Autotrophs- use CO2 as their energy source Heterotrophs- 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 source Chemoheterotrophs-

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

CO2

Photoheterotroph

Light

Organic compounds

Chemoautotroph

Chemical

CO

Iron-oxidizing bacteria.

Chemoheterotroph

Chemical

Organic compounds

Fermentative bacteria. Animals, protozoa, fungi, bacteria.

Oxygenic: Cyanobacteria plants. Anoxygenic: Green, purple bacteria. Green, purple nonsulfur 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 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 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 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 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. 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 1819X ATP than fermentation.

Biochemical Prokaryotic Pathway Glycolysis 2

Eukaryotic 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 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. 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 compounds In human muscle cells, lack of oxygen during

extreme exertion results in pyruvic acid being converted to lactic acid. Fermentation produces only 2 ATP Aerobes/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 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) reactions

Synthesis: Fixing carbon into organic molecules 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 ferroxidans

2Fe2+

NAD+ ETC

2Fe3+

NADH 2 H+

ADP + P

ATP

Finish! Next topic: Microbial Genetics