Microbiology Lecture 4 Bacterial Metabolism

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•All cells need to accomplish twofundamental tasks

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–Synthesize new parts

–Harvest energy to power reactions

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Sum total of Synthesize new parts –Harvest energy to power reactions is called

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Metabolism

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Metabolism occurs to what end?

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– transcription, translation, enzymatic reactions

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Two Parts to metabolism

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Catabolism and Anabolism

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Define Catabolism

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Processes that degrade compounds torelease energy Cells capture to make ATP

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Define Anabolism

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•Biosynthetic processes

•Assemble subunits of macromolecules

•Use ATP to drive reactions

Anabolic steroids

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Exergonic reactions

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–reactants have more free energy•Energy is released in reaction

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Endergonic reactions

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–products have more free energy•Reaction requires input of energy

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Energy released from where powers what ?

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•exergonic reactions powers endergonicreactions

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what are 3 metabolic pathways

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•linear, branched, cyclical

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ATP is composed of

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Adenine, Ribose and three phosphates

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3 Processes that generate ATP

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–Substrate level phosphorylation•Exergonic reaction powers

–Oxidative phosphorylation•Protonmotive force drives

–Photophosphorylation•Sunlight used to create proton motive force to drive

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The bonds between Phosphate groups in ATP are

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High Energy and UNSTABLE

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–Energy released when electronsmove from

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low affinity molecule to high affinity molecule

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•More energy released when

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differencein electronegativity is greater

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The electron donor is the _________And the Acceptor is the______________

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Energy Source Terminal Electron acceptor

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Substance that loses electrons is

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oxidized

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Substance that gains electrons is

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reduced

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Dehydrogenation

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oxidation

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Hydrogenation

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reduction

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•Role of Electron Carriers

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Electrons transferred to electroncarriers, which represent reducingpower.

–Raise energy level of recipient molecule

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–Threedifferent types of electron carriers

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•Nicotinamide adeninedinucleotide–NAD+•Flavin adenine dinucleotide–FAD

•Nicotinamide adenine dinucleotide phosphate–NADP+•

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•Three central metabolic pathways

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•Glycolysis

•Pentosephosphate pathway

•Tricarboxylic acidcycle

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•Pentosephosphate pathway

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•Primary role is production precursormetabolites, NADPH

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•Tricarboxylic acidcycle is called

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•Oxidizes pyruvates from glycolysis

•Generates reducing power, precursormetabolites, ATP

•Called an amphibolic pathway (has both catabolism andanabolism)

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•Anaerobic respiration

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–Molecule other than O2 as terminal electron acceptor

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Fermentation

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–If cells cannot respire, will run out ofcarriers available to accept electrons

–Uses pyruvateor derivative as terminal electron acceptor to regenerate NAD+

•Glycolysis can continue

Oxygen is not terminal acceptor.......lactic acid

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Respiration has three main steps

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Glycolysis

TCA

Oxidative Phosphorylation

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Glycolysis converts and makes

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–Convertsglucose into pyruvate–MakesATP and NADH

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•Citricacid cycle converts and makes

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–Usesacetyl CoA (from pyruvate) to make NADH, FADH2, and ATP

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•Oxidationphosphorylation

Used and makes

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–Usesthe electrons carried by NADH and FADH2 to make ATP–Protongradient

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Oxidativephosphorylation of prokaryotes final electron acceptor

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can be different from oxygen;

Nitrate-reducers- Sulphate reducers

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critical parts of metabolism

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Transcription and translation

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Glycolysis,citric acid cycle and electron transport chain all contain

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•multipleenzymes of which each is encoded by a gene

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inorder to have metabolism, you require that the genes for these enzymes be

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transcribed and translated

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Theultimate outcome of any metabolism is often measured in terms of

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growthrate

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Growthrate will be affected by various

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parameters’inside the cell

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Globalcellular parameters

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thosethat govern ‘all’ genes, including those directly involved in the metabolism

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constitutive

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•genesthat are always on

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Transcriptionrate increases with

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growthrate

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Transcription rate =

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•amount of mRNA being made per unit time (i.e., hour)

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MoreRNA polymerase is made at faster doubling time – thus

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moremRNA per cell

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Genedosage per cell increases with

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increaseswith growth rate

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Genedosage is a

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measureof DNA replication (cell division)

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•Atvery fast growth rate, DNA replication

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starts before the previous round of cell division has finished

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Translationrate flat lines

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withgrowth rate

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Atfaster growth rates, protein is

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dilutedat faster rates

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Cellvolume increases with growth rate means

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atfaster growth rates, cells are going to be larger

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–limitingstep in industrial processes

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Translation

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Investigation of how cells allocateenergy use on a ‘global’ scale can be studied by

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slowingthe process of translation

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Translation can be inhibited in a

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•graded manner by growing cells in increasing concentrations of the antibiotic chloramphenicol

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More chloramphenicol means

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less translation

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in response to the addition of chloramphenicol and less translation cells will

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Make more Ribosomes

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3 compartments of bacterial cells

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P R Q

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CompartmentP

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GROWING AND CELL RESPIRATION

•(GLYCOLYSIS,KREB,OxydativePHOSPHORYLATION)

–Energydevoted to translation of non-ribosome protein products–Controlsgrowth rate

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•CompartmentR

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–Energydevoted to ribosome production

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CompartmentQ

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•(CELLWALL DNA REP)

–Energydevoted to cell metabolism outside of translation

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Inhibitingbacteria by using antibiotics adjusts how much the cell commits

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toP and R groups

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Bypushing energy towards your new gene (compartment U), you take away fromcompartment

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Pand R BUT ITDOESN’T TOUCHQ

•Reducesgrowth rate as cells have less energy devoted to the P sector

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A contributing factor to bacteria becoming competent is

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Lack of nutrients in surrounding area.

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Homologous recombination is usually about

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DNA Repair

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Steps for "transformation"

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1. Bacteria become competent

2. Picks up DNA from Environment

3. DNA is converted to Singles strand when imported

4. If DNA is foreign looking endonucleases degrade it

4a. if similar DNA is integrated via Homologous recombo.