Popular in Biomedical Microbiology
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This 10 page Class Notes was uploaded by Christinee on Sunday February 7, 2016. The Class Notes belongs to MIC 401 at University at Buffalo taught by Dr. Amy Jacobs in Spring 2016. Since its upload, it has received 298 views. For similar materials see Biomedical Microbiology in Microbiology at University at Buffalo.
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Date Created: 02/07/16
Lecture 1 – Structure Function Bacteria *Disclaimer: these notes are added on notes that were discussed in lecture – basically information that isn’t on any of the slides or notes given on UBlearns. This is to avoid any type of plagiarism/copyrights. Types of Microorganisms All capable of causing disease ALL PATHOGENIC: ability to cause an infection in the host (human) Basic cell types * Can classify cell types as prokaryotic or eukaryotic 1. Prokaryotic: a. Pro: means early b. Karyon: means nucleus c. “Early Nucleus” d. Where do you find prokaryotic organisms? i. Bacteria ii. Algae 2. Eukaryotic a. Eu: means true b. “True Nucelus” c. Membrane bound nucleus d. Where do you find eukaryotic organisms? i. Animals ii. Fungi 3. Prokaryotes & Eukaryotes differ in cell structure & complexity but are similar in other ways as well a. Same metabolic reactions taking place b. Chemically similar Structural Organization of Prokaryotic Cell Cell envelope: outer wrapping of the bacterium that is comprised of different components that make up the envelope 1 General Bacterial Structure A. Appendages: Structures for motility and attachment Flagella: (MOTILITY) true directive movement which means that it changes direction; not just a vibrating back and forth motion (BROWNIAN MOTION) Not all bacteria have flagellum – those with flagella are motile & those without flagella are nonmotile There exist different flagellum arrangements – used for species identification Fimbriae or common pili: (ATTACHMENT) Allow the bacteria to attach to a surface They differ in the number that they would be found on the surface of a bacterial cell Fimbriae: hundreds, always present in a much larger amount than the pili Pili: lesser amounts; can be 13’ Pathogenesis: advantageous for a bacterium to have pili or fimbriae – bacteria/fungi/virus has to find a way into the body, then when it gets into the body it has to first adhere to a surface/attach, once it attaches to a surface it colonizes (grows/replicates/able to set up residence there), when it grows it produces a variety of different factors that aids in its pathogenesis, such as: Toxins Hemolysins Enzymes Pathogenic: means it’s a VIRULENT ORGANISM – it has various factors that aids in its pathogenesis Avirulent: nonpathogenic Sex pilus (specialized pilus): longer pili found on exterior surface used for bacterial conjugation limiting factor: proximity of the two cells 2 B. Cell Envelope: Outer wrapping of bacteria Glycocalyx (two different types: slime layer or capsule – similar composition – protein polysaccharide mix; but also differ) Not all bacteria have to have a slime layer or capsule, but is advantageous if they do Two types of cell envelopes: both aid in pathogenesis – both virulent factors slime layer – not tightly adhered to the bacterium – just a slimy layer that aids in ATTACHMENT; allow to stick capsule – tightly adhered to the bacterium – capsule means ANTIPHAGOCYTIC, allows the bacteria to survive Virulence factors that a bacteria can possess (but not necessary) 1. fimbriae 2. pili 3. slime layer 4. capsule EXAM INFO: know the components of gram positive and gram negative cell wall Cell wall (Exoskeleton of cell) gives SHAPE primary component of cell wall is the heteropolymer peptidoglycan (common component in both gram positive and gram negative) Makeup of cell wall determines what color the gram stain the bacterium will be cross linking is called INTER BRIDGING BETWEEN GLYCAN CHAINS Key Features of the Gram positive cell wall So you have NAM & NAG cross linked by peptide tetralinkers which gives you this interbridging which actually INCREASES RIGIDITY OF CELL WALL there are 40 LAYERS of peptidoglycan in a gram positive cell wall gram positive cell wall consists of 90% peptidoglycan – primary composition acidic polysaccharides – 10% 3 function of teichoic and lipoteichoic acid o they span the peptidoglycan layers – increase rigidity of cell wall & allow the transport of ions across cell wall Key features of the Gram negative cell wall Three layered cell wall – considered to be more complex in nature than a gram positive cell wall (just multiple layers of peptidoglycan) *selectively permeable barrier – components go from the outside to the inside A. Outer membrane – largest part of the multilayered wall – phospholipid bilayer a. intercalated in the outer membrane 1. external to peptidoglycan layer – gram positive more rigid than gram negative cell wall 2. semipermeable 3. typical phospholipid bilayer 4. contains specialized proteins a. lipopolysaccharides – intercalated in outer membrane with hydrophobic and hydrophilic tendencies b. lipoproteins – embedded in outer membrane & attaches to peptidoglycan layer – the function of lipoprotein is to hold this whole entire fluid structure together – the “anchor” – it anchors the outer membrane to the single layer of peptidoglycan c. porin proteins – protein channels – it spans the entire phospholipid bilayer: so it has hydrophilic and hydrophobic tendencies & the purpose of this is going to allow the transport of materials from the outside to the inside irrelevant of their charge (it allows anything to enter) B. Periplasmic space hydrolytic enzymes* (which can break apart 6 carbon sugar unit to single carbon monomers which can be used for synthetic purposes or energy production taking place in the membrane) EXAM INFO: Gram positive and gram negative both share peptidoglycan Need to know what peptidoglycan is 4 Need to know why peptidoglycan gives bacteria cells its rigidity – due to cross linking/inter bridging between glycan chains and muramic acids Need to know that gram negative is more complex cell wall than gram positive Need to know that gram negative cell wall is a 3 unit entity Need to know parts of cell wall and its functions Aka Periplasmic space: contains hydrolytic enzymes which break down the carbohydrates needed for synthetic reactions – energy production – single monomers Cell membrane (Cytoplasmic membrane, protoplasmic membrane, and inner membrane) Primary purpose: useful for synthetic reactions If you’re trying to compare this to membrane bound organelles or eukaryotes – the cellular membrane is considered to be the BACTERIAL ANALOGUE for synthetic reactions that take place in eukaryotic cells Molded around the cytoplasm – allows the materials to be transported into the cytoplasm and out from the cytoplasm embedded in phospholipid bilayer are integral proteins which span the entire bilayer again having hydrophilic & hydrophobic proteins and peripheral proteins which are hydrophilic in nature – the composition of the membrane is variable itself o in the phospholipid bilayer you have phosphate head and lipid tails which gives you the hydrophilic & hydrophobic tendencies (basic composition of outer membrane & inner membrane) secretion of exoenzymes – in a gram negative bacterium these would go to the periplasmic space or transported further out to the exterior for nutrient processing secretion of toxins – toxins are produced when bacteria grow & aids in pathogensis Cytoplasm (Protoplasm) and the internal contents A. Cytoplasm – primary component being water 7080% B. Nucleoid (chromatin) – **non uniform dense region** : its concentrated into an irregular dense area in the center of the cell and consists of a single double strand of DNA minimum genetic requirement needed for bacterial survival 5 C. Plasmids – (extra component – extra chromosomal piece of DNA & AID IN PATHOGENESIS) a. antibiotic resistance is key – is usually coded for on a plasmid – able to develop resistance which can then be transferred from one bacteria to another (can even be different types of bacteria and not even in the same species) because it can pass extra chromosomal piece of DNA (plasmid) b. plasmids either offer a selective advantage or a protective trait Lecture 2 – Bacterial Growth Metabolism **The slides with information on them will be named exactly the same way as it is on the powerpoint slide so you know which slide it belongs too. Only extra information that is NOT included on the powerpoint slides will be included to avoid any plagiarism/copyright infringement. Bacterial Growth (slide 8) o Legionella – bacteria that causes legionnaires pneumonia o Obligate intracellular pathogens – meaning they need cells or tissues to grow on o Mycobacterium leprae – leprosy o Treponema pallidum – causative organism of syphilis Vitamins: growth factors (slide 11) o Bacteria needs these as substrates o FMN – another source of energy for bacteria Nutrients (slide 12) o Ability to use what we give or not use what we give them is sometimes used to describe them o Bacterium that can derive all nutrients that they need from the artificial medium we give them – prototrophs Atmospheric conditions (slide 13) o CO2 – some need and some don’t o Facultative organisms– grow equally well in either situation o Obligate anaerobe – still can grow even if there is a small amount of O2 Bacterial growth phases (slide 15) 6 o Y axis: number of bacteria there is o X axis: time o In the very beginning after they’re inoculated onto a medium, their numbers don’t increase at all during their LAG PHASE of growth. o All of a sudden, they hit a certain threshold in time they grow exponentially called: LOG/EXPONENTIAL GROWTH PHASE. o They hit a peak and exhaust most of the nutrients in the medium and their numbers plateau off and hit a STATIONARY PHASE. o After they really exhaust what there is, and die off called DEATH/LOGARITHMIC DECLINE Bacterial metabolism (slide 16) o The reason they need energy is to form new compounds – the reason they need to form new compounds is to make new bacteria. o Their metabolism is intended to take any constituents they have around them and convert it into energy by usually reaction with substrates by making ADP to ATP. Aerobic respiration (slide 20/slide 21) o Main Goal: generate ATP & metabolic intermediates o In order to accomplish aerobic respiration, most use 3 pathways which are linked to one another o Don’t have to memorize all the intermediates o Glucose + Oxygen – Oxygen is used because in this particular set of reactions it’s the final electron receptor o If its done by its most efficient means, 1 glucose = 38 molecules of ATP Glycolytic pathway (slide 23) o Starts with glucose as the primary substrate o Ends with Pyruvate as the primary end product o Glucose is converted into another substrate by phosphorylation which is converted into another substrate and so on until we get Pyruvate Glycolysis: preparative investment phase (slide 24) o This is the first half of the Glycolytic Pathway o Investment / Preparative Phase o In the total of the entire first half of the pathway, a total of 2 ATP’s are spent o Starts with glucose at the very beginning o Glucose > Glucose 6 Phosphate (ATP has to give up a phosphate in order to phosphorylate that) o And another ATP has to give up a phosphate in order to phosphorylate at the second point as well 7 o Ultimately spending a little gives you more later on o There’s a 6 carbon sugar – and an enzyme cleaves it into two 3 carbon sugars (look almost the same) o There’s an isomerase that makes the two almost identical carbon sugars into the same thing Glycolysis: payoff phase (slide 25) o Payoff Phase o 4 ATP’s gained + 2 NADH’s gained o One of these reactions that effects two 3 carbon sugars ends up letting it release an ATP & NADH o In the end, release 2 more ATP o So lose 2 ATP and gain 4 ATP for a net gain of 2 ATP o 2 NADH are generated – and later on get turned into more energy Krebs cycle overview (slide 27) o Each 1 glucose yields 2 pyruvates in the end because 1 6 carbon sugar got cleaved into 2 3 carbon sugars o Then the pyruvates enter into the Krebs Cycle o However, right before the Krebs cycle, there’s an intermediate/initial step that takes place Initial step krebs cycle (slide 28) o 2 pyruvates for each glucose at the end of the glycolytic pathway o pyruvate dehydrogenase complex (enzyme) changes it into Acetyl CoA o As a consequence of this, an NAD molecule is changed into/decarboxylated into NADH molecule (turns into more ATP) o Before entering Krebs Cycle: another 2 NADH molecule – generated from each of the glucose you started with Krebs cycle – detailed (slide 29) o At one point along the way ADP is phosphorylated into ATP o At three points along the way, NAD+ becomes NADH (gets turned into more ATP/energy later on) o At one point FAD becomes FADH2 by an oxidation reduction reaction (gets converted into more ATP/energy later on) o So, so far, we’ve generated more ATP & a lot more NADH & an FADH2 – which will all be doubled because it’s being kick started with 2 molecules of Acetyl CoA in the beginning Krebs cycle (slide 30) o 1 glucose = 2 pyruvates o Initial step: 2 pyruvates changed into CO2 + 2 Acetyl CoA – 2 NADH’s generated in initial step 8 o Net gain of 2 ATP’s per molecule of glucose o 6 NADH (3 circled in diagram– so doubled means 6, since started with 2 Acetyl CoA) o 2 FADH2’s o *All NADH & FADH2 gets converted into more ATP later on Electron Transport & Oxidative Phosphorylation (slide 31) o 3 place they get converted into ATP is the 3 Pathway – Electron Transport Chain + Oxidative Phosphorylation Electron transport (slide 32) o When one molecule gives up an electron to another, the molecule that gave it up is OXIDIZED, molecule that gains is REDUCED (bc of the charge) Electron Transport & Oxidative Phosphorylation (slide 33) o Image of a cytoplasmic membrane – lipid bilayer – lipid tails and heads pointing to the outside o Different molecules – mostly cytochromes – that shuttle along electrons o NADH that was generated earlier goes to cytoplasm and gives up an electron (so its oxidized) to a carrier that gives it up to another carrier that gives it up to another carrier o Each time the electron is transferred, a little more energy is generated o At the very end, the energy is converted into ATP by an enzyme called ATP SYNTHASE COMPLEX which allows all the energy to convert ADP into ATP as a storage form of the energy o FADH2 also gives up an electron into the electron transport system in the cytoplasmic membrane, HOWEVER, enters the pathway a little downstream o Because of this, there are fewer electron transfers – and because there are fewer electron transfers, you don’t get as much ATP – only 2 o Oxygen is the final electron acceptor Overview – metabolic pathways (slide 34) ************ o Glycolytic Pathway 1 glucose = 2 pyruvates + 2 ATP + 2 NADH o Initial Step 2 Acetyl CoA molecules + 2 NADH o Kreb’s Cycle 2 Acetyl CoA molecules = 9 + 6 NADH + 2 ATP + 2 FADH2 o Electron Transport System +34 ATP molecules total 2 NADH from glycolytic pathway enter 2 NADH from initial step enter 6 NADH from Krebs cycle enter 2 FADH2 from Krebs cycle enter ALL generated into ATP be electron transfers 3 ATP for every NADH 2 ATP for every FADH2 o +38 ATP molecules total 34 from electron transport system 2 from glycolytic pathway 2 from kreb’s cycle metabolic energy (slide 35) o The only difference between aerobic and anaerobic respiration is that in anaerobic respiration, the final electron acceptor is NOT OXYGEN Anaerobic respiration (slide 36) o In the electron transport chain right at the end, instead of an O2 picking up the electron oxygen containing salts pick up the electron o Because in the very end O2 isn’t the last electron acceptor, there might be a dip or variability in the amount of ATP that’s generated Fermentation (slide 38/40) o Primarily used for anaerobic bacteria – bacteria that grow better in the absence of O2 o Organic compound used as terminal electron acceptor o A WHOLE lot less efficient at producing energy o At the end of glycolytic pathway, pyruvate is left over to react with NADH generated to produce lactic acid o Just 2 ATP o 10
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