EBIO 3400 1st Edition Lecture 10Outline of Last Lecture I. Logistic growth of bacteria Outline of Current Lecture II. Importance of growth III. BioluminescenceIV. PseudomonasV. How do microorganisms obtain energy? VI. Fermentation vs. RespirationVII. Electron transport chain Current LectureI. Importance of growth- In medicine and the environment- Microbes found in rich environments often form biofilms- Biofilms: colonial microbes attached to a surface - Found in: catheters tubes, ventilators, on teethA. Quorum sensing: how cells in biofilm talk to each other, Microbes express different genes when they are in biofilms - they sense their degree of crowdedness using this sensing mechanism B. Very important to microbes that act in unison (e.g. pathogens, decomposers, predatorsC. How Quorum Sensing works: Cells of a given species make basal levels of low molecular weight compounds (e.g. homoserine lactones or HSLs) that diffuse out of the cell. The cell can sense these compounds (with surface receptors). When con-specific cells are densely packed (e.g. in a biofilm) their receptors are full and they express genes that are advantageous for the group (e.g. pathogenicity genesD. Group genes off: Not interacting enough with the auto inducer to turn on genesII. Bioluminescence - Turned on via quorum sensingThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Many oceanic Vibrio (and Photobacterium) species are capable of bioluminescence- Live symbiotically with squid or fish.- Enzyme luciferase (same as in fire flies) - The reaction involves shuttling electronsto O2 without an e- transport chain - energy is released as light instead of heat orgoing to ATP production- Only make extracellular proteases when they are crowded- Releasing HSL- Attack protein release amino acids then they will then eatIII. Pseudomonas - Very metabolically diverse, but strictly respiratory (no fermentations), Gram- Gammaproteobacterium- Fast growing / opportunistic / not fastidious- Plant and animal pathogens, P. syringae and P. aeruginosa, respectively- P. aeruginosa is so metabolically versatile that it can grow in distilled water. It is also found in soil and on plants, including flower petals. Very common as an opportunistic pathogen and in nosocomial infections (infections acquired in the hospital)- On low iron media – diffusing, green fluorescent pigment (Pyoverdin - a siderophore) produces a siderophore that binds with iron - P. aeruginosa has also been studied extensively because it utilizes Quorum Sensing- Only turns on virulence genes if it is in a biofilm. - This allows it to avoid detection until its numbers are high enough to do real harm- Most microbes that use Quorum Sensing lead double lives- Lone cells (planktonic) don’t need group genes turned on- Cells in biofilm need can cause macroscopic effects such as disease or light productionIV. How do microorganisms obtain energy? - Chemical energy is the energy released from organic or inorganic compounds when they are oxidized: burn something releasing CO2 and heat - Some is lost as heat, but some of the energy of a chemical reaction is free energy(G), that is the energy that is available to do work- The change is free energy during a reaction is expressed as DG- If in the reaction:A + B à C + DThe Delta G is negative, the reaction proceeds with a release in energy = exergonic- If the DG is positive, then the reaction requires energy in order to proceed = endergonic- These energy releasing (catabolic) reactions involve the oxidation and reduction of molecules- Oxidation = loss of electrons froma substance (ole-)- Reduction = addition of electrons to asubstance (reduction in positive valence)- Oxidation/reduction reactions all involve pairs of electron donors and electron acceptors (Work is done as the electrons move from one to the other)- The substance that is oxidized (e.g. H2) is known as the electron donor- The substance that is reduced (O2) is known as the electron acceptor- Most molecules can be either electron donors or electron acceptors, but vary in their tendency to be oxidized or reducedV. Fermentation vs. Respiration- Fermentation - redox reactions take place in the absence of terminal electron acceptors, ATP is produced by substrate-level phosphorylation- Respiration - oxygen or another oxidant serves as the terminal electron acceptor, ATP is generated via oxidative or electron transport phosphorylation using a proton motive forceVI. Electron transport system (chain)- Main goal of this system: energy from these electrons, e acceptor more electronegative (more affinity for electrons) to pump protons across the membrane- More positive ions outside than insideKnow that movement of electrons down the chain leads to:1) Pumping of protons across the membrane This establishes the “Proton Motive Force”2. The reduction of oxygen at the end of the chain forming water
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