BIMM120 Week 7.pdf - BIMM120 Week 7 Discussion Lecture 10...

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: BIMM120 Week 7 Discussion Lecture 10 Microbial trophic dynamics: Carbon and energy Classification of microorganisms ⊷ Mechanism of energy conservation ⊷ C, N, S, P utilization ⊷ Growth factor requirements ⊷ Extracellular enzyme production 3 Basic composition of most cells Macronutrients ⊷ ⊷ ⊷ ⊷ 4 C : all macromolecules are carbon-based N: proteins, nucleic acids P, O, S, H, K, Na, Mg, Ca Fe: cytochromes, electron transport Micronutrients ⊷ ⊷ Mn, Zn, Co, Cu, Ni: coenzymes Se, W, Mo “ 5 Defined media: elaborate recipes with precise, known composition Complex media: heterogeneous stuff Accessing energy and nutrient sources: heterotrophs ● ● ● ● ● 6 Heterotrophs: take up reduced carbon compounds via passive and active transport process Osmotrophy: uptake of dissolved organic matter Ectoenzymes: extracellular enzymatic degradation of particulate organic matter Biosurfactants: excreted or cell surface emulsifying agents that enhance hydrocarbon availability and mobility by altering surface tension at oil:water interface Siderophores: excreted compounds that chelate ions for transport into cell The Quest for Iron (Fe) ● Oxygen present: Fe in mineral phase and is inaccessible ● Solution: produce Fe chelating molecules to scavenge it ○ Siderophores 7 Accessing energy sources: phototrophs Phototrophs: harvest life energy via redox-active chromophore molecules Oxygenic phototrophs: evolve oxygen (cyanobacteria; plants) ⊷ Calvin-Benson cycle Anaerobic anoxygenic phototrophs: purple, green sulfur/non-sulfur bacteria and heliobacteria ⊷ 8 Reverse TCA Cycle: Hydroxyproprionate Pathway Vocabulary of Primary Trophic Classifications Energy ⊷ ⊷ 9 Phototroph: energy source is light chemotroph: energy source derived from redox reactions involving organic or inorganic compounds Electrons (H+ ions) ⊷ ⊷ Organotrophs: organic compounds source of electrons Lithotrophs: inorganic compounds are source of electrons Carbon ⊷ ⊷ Autotrophs: carbon source is CO2 Heterotrophs: carbon source is reduced organic compounds “ 10 Oxidations = removal of electrons Reductions= addition of electrons to a substance Aerobic Respiration 1. Glycolysis: glucose + 2 NAD+ + 2 ATP → 2 pyruvate + 4 ATP + 2 NADH a. Glucose is the electron donor b. NADH is electron carrier c. The electron acceptor is oxygen in oxidative phosphorylation 2. Citric acid cycle: pyruvate + 4 NAD+ + GDP + FAD → 3 CO2 + 4 NADH + FADH + GTP 3. Sum: 38 ATP per glucose a. Chemoorganoheterotrophy is very efficient 11 Lecture 11 Microbial Diversity Aerobic vs Anaerobic Respiration ⊷ Aerobic respiration uses oxygen as electron acceptor ⊷ Anaerobic uses sulfur, NO3-, SO42-, and organic electron acceptors 13 “ Obligate aerobes: require oxygen for respiration Facultative anaerobes: in the absence of oxygen, many microbes can respire alternative electron acceptors via anaerobic respiration Obligate anaerobes: microbes that can’t use oxygen for respiration and must use alternative electron acceptors or exclusively fermentation 14 Anaerobic respiration ⊷ Oxygen is preferred but other electron acceptors can be used ⊷ Use of these compounds is called dissimilative metabolism ⊷ Some can’t exist in presence of O2 15 16 O2 vs. NO3 respiration in E. coli (nitrate reduction) ⊷ ⊷ ⊷ ⊷ ⊷ 17 Get two more protons from aerobic respiration Nitrate reductase = enzyme used in anaerobic respiration Anaerobic respiration repressed by O2 Denitrification = reduction of fixed Nitrogen (NO3) to gaseous products (N2) E. coli is an example of a facultative anaerobe Breathing metals ⊷ ⊷ ⊷ 18 Several metals can act as excellent electron acceptors Metal reduction processes: ⊶ Mineral solubilization ⊶ bioremediation : soluble to immobile mineral phase Microbes reduce toxic compounds → immobilization → prevents further transport through environment Respiring sulfur compounds ⊷ ⊷ ⊷ ⊷ ⊷ 19 Sulfate-reducing bacteria (SRBs): dissimilatory sulfate reduction Strictly anaerobic Electron donors: small organic acids or H2 One ATP generated for each SO42reduced to H2S Must activate SO42- to APS to have a more positive electron acceptor Methanogenesis ⊷ ⊷ ⊷ ⊷ ⊷ ⊷ 20 Dissimilative CO2 reduction Found only in Archaea Strict anaerobic CO2 is electron acceptor Electron donor: Some use H2 and others use organics Not much energy yield because reduction potentials are close Fermentation Respiration ⊷ Utilizes proton motive force for ATP generation Fermentation ⊷ ⊷ 21 Does not require proton motive force Example: glycolysis Fermentation ⊷ ⊷ ⊷ ⊷ 22 Substrate fermented is both the electron donor and acceptor Energetically weak compared to aerobic and anaerobic respiration Fatty acids can’t ferment because they are too reduced Uses substrate-level phosphorylation: energy-rich P bonds transferred directly to form ATP ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern