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Date Created: 10/16/14
Microbiology the study of microorganisms Studied as pure and applied science Pure science is the basic biological processes studed such as photosynthesis etc Robert Hook built first compound microscope and used it to observe mold Micrographia published and coined the term cell Antoni Van LeeuWenhoek built single lens magnifiers with sample holder and focus adjustment First to observe single celled microbes and called them wee animalcules Louis Pasteur ash experiment demonstrate that microorganisms are in the environment Put cap on spontaneous generation Robert Koch demonstrated link between microbes and infectious diseases Developed Koch s postulates Developed techniques for obtaining pure cultures of microbes Koch s postulates 1 The suspected pathogen must be present in all cases of the disease and absent from healthy animals 2 The suspected pathogen must be grown in pure culture 3 Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal 4 The suspected pathogen must be reisolated and shown to be the same as the original Viruses can not be grown in a pure culture ltl can be pure culture of bacteria Microbes are important in health and disease Lecture 2 Prokaryote cell structure cell wall cytoplasmic membrane nucleoid cytoplasm plasmid ribosomes Diversity in shapes of microbes 1 coccus 2 rod 3 spirillum 4 spirochete 5 budding and appendages bacteria stalk or a hypha 6 filamentous bacteria Size range for prokaryotes 02 micrometers to 700 micrometers in diameter Most btw 0 and 4 wide and 15 long Size range for eukaryotic 10 to 200 micrometers Advantages to being small 1 More surface area relative to cell volume 2 Support greater nutrient exchange per unit cell volume 3 Grow faster than large cells 4 Easy to manipulate Cytoplasmic membrane 8 to 10 nanometers thick highly selective permeability barrier Bacterial membranes phospholipid bilayers two layers of phospholipids each with hydrophilic and hydrophobic end a Hydrophobic two chains of fatty acids b Hydrophillic PO4 bound to a glycerol Hydrophobic inside of membrane like a fluid allows thing to move around in the membrane fatty acids dissolve into one another Outside environment is aqueous and charged and interacts with phosphoglycerol hydrophilic ends THE MEMBRANE IS HELD TOGETHER BY HYDROPHILLIC AND HYDROPHOBIC INTERACTIONS Polarity causes the structure Membranes are a selective barrier by only letting in certain molecules which are small and uncharged like water sulfide nitrogen etc Small diffuse across cell They get larger things in by using proteins that move them across the phospholipid matrix These proteins are crucial to the function Two types of proteins 1 integral membrane proteins embedded in membrane inside membrane 2 Peripheral membrane proteins one end in anchored in membrane and one exposed to environment Membrane Strengthening molecules Need these because otherwise the cell wall would be easily destroyed Eukaryotes have sterols rigid planar lipids that strengthen and stabilize membranes like cholesterol Some Prokaryotes have hopanoids like sterols Archaeal Membranes Hydrophobic hydrophilic Do NOT have fatty acids but have ISOPRENES that are bound to glycerol with ETHER linkage BACTERIA AND EUKARYA HAVE ESTER LINKAGES fatty acid to glycerol 2 classes of archaeal membranes 1 glycerol diethers form membrane bilayers 2 Glycerol tetraethers form membrane monolayers with glycerol PO4 on each side of membrane covalently bonded One layer of molecules is very strong so this is common in extremophiles because extreme environments pull molecules apart temp etc Cytoplasmic membrane function permeability layer prevents leakage and functions as gateway for transport of nutrients into and wastes out of cell transport site of holding proteins protein anchor Energy conservation site of generation and dissipation of the PMF 0 Moved particles depend on the relative concentration of substance on each side of membrane difference in concentration you move towards a lower concentration Concentration gradients is a kind of power or energy Diffusion is passive 0 Water is moved by osmosis from areas of high and low solutes Rigid cell walls prevent too much water from owing in and causing the cell to burst counteracts the pressure Aquaporins are a type of protein that increase the movement 0 Charged ions get stuck interacting with hydrophilic parts Like hydrogen ion They get bound and can not pass through the hydrophobic interior 0 Cells get in sugars organic acids amino acids and other things by actively movingtransporting them across gradients Transport systems allow cells to concentrate substances against concentration gradient Usually transport proteins are specific and only transport one substance and their synthesis is regulated by the cell This is faster than diffusion because of the energy Good for moving limited nutrients 0 Once the transporter is saturated the process will slow down after a steep curve of fast transport it will level off whereas simple diffusion will be one steady slope upward Transport systems energy required to transport against gradient Simple transport driven by concentration gradient and some channel that Will let it move Proton or other ion gradient PMF Requires one membrane spanning protein Made of 12 helices Energy from gradient across membrane Group translocation Substance transported is chemically modified you change concentration gradient Chemical modification with a high energy compound Driven by PEP Chemically changes by adding on phosphate compound Requires set of proteins Common type is the phosphotransferase system With PO4 from PEPdonor molecule transferred to substance transported Phosphotransferase is used to transport glucose mannose fructose energycarbon sources They are phosphorylated chemically modified during transport P04 is passed to each protein phosphate cascade and final transfer is to sugar Packaged energy 45 enzymes are cytoplasmic Specificity Within the enzymes refers to the phosphate transfer and only being able to donate to the glucose transport The nonspecific are constantly getting high energy phosphate that was removed from PEP and interacting with HPr then transferring to specific components When glucose gets to Enz IIc a conformational change occurs and moves glucose across membrane and phosphorylation phosphorylated glucose is the first step of glucose metabolism ABC ATP binding cassette system the periplasmic binding proteins Changing conformation of the protein one end will sense by other part of protein and then interact with ATP to cause changes Requires a substrate binding protein a membrane transport protein an ATP hydrolyzing protein splits ATP and ATPenergy source Used to transport sugars amino acids inorganic nutrients and trace metals HIGH substrate specificity substrate first bound by periplasmic binding protein gram or by protein on outer cytoplasmic membrane gram These proteins are specific for each substrate Substrate then transferred to membrane spanning protein Energy from ATP used to move it across membrane and into cytoplasm 0 Translocases are used to insert proteins in to the membrane itself Structures of membrane transport proteins 1 2 Uniporters move one substance in one direction across membrane Symporters cotransporters moves two substances at same time in same direction Usually because a second substance if required to move the first usally depending on concentration gradient of second Antiporters moves one substance in one direction and a second substance in the opposite direction One substance could be taking advantage of conc Gradient LECTURE 3 Cell walls outside cytoplasmic membrane gives rigidity and counteracts osmotic effects All bacteria is divided into gram and gram Gram staining procedure need to stain to see small cells Gram retains the stain and gram does not because of the difference in peptidoglycan gram has thick peptidoglucan rigid Peptidoglycan rigidity and only in bacteria Composed of N ACETYLGLUCOSAMINE and N ACETYLMURAMIC ACID They ALTERNATE to form backbone chains that are cross linked Three dimensional latticework One big molecule surrounding the cell Each sugar has amino acid side chain that form links between peptidoglycan chains gram have two parallel strands glycine bridge 5 glysine residues and then another chain Gram walls multilayered complex stain pink thin peptidoglycan inside periplasmic space 10 second outer membrane LPS Lipopolysaccharid layer Aquaporins in the cytoplasmic membrane PMF is concentrated in the periplasmic space And protons Cells are actively transporting protons outside of cell Use for energy Lumpy surface Perplasmic space has three types of enzymes 1 Hydrolytic degrade and lyse large organic matter that comes thru porins Turns big molecules to small ones 2 Binding proteins ABC transport takes molecule to membrane spanning proteins for transportation 3 Chemoreceptors LPS more permeable than cytoplasmic Has porins proteins with channels that let large molecules sugars etc through even charged ones Hydrophobic and hydrophilic interactions Made of two polysaccharides Opolysaccharide and corepolysaccharide Lipids in LPS are fatty acids all lipid A with glucosamine phosphate head Also lipid A is a toxin Proteins anchor LPS to peptidoglycan Order of structure 0 Core Lipid A Glucosamine phosphate head and two fatty acid chains 0 and Core sit in the environment and toxic part is in hydrophobic part of membrane All held together by hydrophilic and hydrophobic interactions Lipoproteins are also on the bottom half of outer membrane and are covalently bonded to the peptidoglycan Differences between LPS and cytoplasmic more permeable porins functionally the same hydrophobicphillic More comples with lipid A and lipoproteins Gram wall simple thick peptidoglycan 90 no outer membrane no LPS no periplasmic space Teichoic acids negatively charged to maintain protons of PMF different cross linkages glysine bridge May have binding proteins on cell membrane ABC Lipoteichoic acids covalently bonded to membrane fatty acids Go through peptidoglycan and into cytoplasmic membrane Smooth surface Stain purple Gram Stain procedure U 4gtP gt Stain with crystal violet 1 min Wash with distilled Water Iodine solution 1 min Decolorizing agent then Water Counterstain with safranin for 15 sec Archaea Walls Can t stain Don t have peptidoglycan Some have PSEUDOMOUREIN like peptidoglycan composed of two sugar derivatives NACETYLGLUCOSAMINE AND N ACETYLALOSAMINURONIC ACID Amino acid side chains that cross link 3 amino acids then 4 amino acids Some resistant to acids and high temp Can have pure protein Walls Most common is S LAYER paracrystallin surface made of protein or glycoprotein acts as sieve keeps proteins near cell surface 0 Some prokaryotes have no cell Walls Ones that live in animal bodies hot springs monolayer 0 Eukarya animals have no cell walls Plants algae fungi all have Walls Highly variable LECTURE 4 Inclusions for storage of carbon or nutrient compounds Made for a critical nutrient required for sustaining life Surface associated functional structures Large structures that tie into cel metabolism Inside the cell intracellular Made of only ONE substance Often surrounded by single layer membrane Carbon stored as PHB or glycogen Only gets storage when thing is in excess Nutrients include nitrogen phosphorus and sulfur energy or nutrient Lots of competition Internal biomineralization magnetosomes Some cyanobacteria precipitate carbonate minerals these keep cell deep in water Magnetotactic bacteria magnetosomes made of magnetite or greigite surrounded by a membrane Allow cells to orient to magnetic field magnetotaxis Low oxygen environments 0 Cell capsules or slime layers surround some cells Made of polysaccharide They attach to surface such as pathogens to host or biofilms rock in aquatic environment The protect 0 Fimbriae and pili Made of protein Shorter than agella Extend from cell surface Functions include attachment to surface receptors for viruses gene exchange conjugation Twitching motility extend attach retract powered by ATP Gas vesicles Allow cells to move up and down water column Good for photosynthetic bacteria Buoyancy Too much light is harmful Made of pure proteins GVPA and GVPC hydrophobic Cone shaped Pure hydrophobic proteins that only allow gas molecules to pass through membrane by diffusion through a conc gradient Synthesized in cytoplasm and the center elongates As cells float more light is available When accumulate photosynthate or DOC in the cytoplasm it increases turgor pressure which makes the gas vesicles collapse Endospores Produced by some gram Intracellular Allow cells to survive harsh periods of heat radiation etc Generate to form new vegetative cells when conditions are better Released from cell and germinate into new cells Vegetative cell dies Good for dispersal Need carbon and nutrients to start growing Four different layers DNA cortex core wall and spore coat Microbial Motility In liquid flagella On surface twitching or gliding Magnetic and gas vesicles too Flagella Flagella have three arrangements 1 Peritrichous all over body 2 Polar one on one side of body 3 Lophotrichous multiple on one side Tufts on one end 4 Amphitrichous coming from opposite ends Flagella are long thin rigid and hollow 1520 nm in diameter Helices with different spaces between curves between different species Composed of protein subunit agellin Flagellin is attached to hook Synthesized in cytoplasm moved to flagellum move along hollow center and added to tip Grow until species max length is reached Grow from the inside to outside PMF powers it Protons come from periplasm Cell increases or decrease speed based on strength of PMF concentration gradient Structure 0 Rod holds ring together 0 Hook anchors to cell wall 0 Filament made of agellin 0 MOT proteins are motility proteins Spin Connected to MS ring 0 Fil proteins are the motor switch and what direction the agella will rotate Rings are negatively charged Gram two rings MS and C ring Gram C ring is the cytoplasm P is the periplasmic L is LPS Movement by agella alternate runs and tumbles Runs are CCW flagella is bundled in peritrichous Tumbles are CW agella is pushed apart When they switch direction they tumble Archaeal flagella 1013 nanometer wide Smaller than bacterial Made of several types of protein not agellin May be powered by ATP Gliding motility Occurs on surface No agella Filamentous microbes Excretion of slime Twitching by extracting and retracting pili Movement of proteins on surface of cells LECTURE 5 Cells need macro and micro nutrients These are provided in media Growth factors such as vitamins or specific amino acids that bacterial strain can not synthesize Macronutrients needed in large amounts Used to build cell constituents Needed for proteins RNA etc These make up the cell Make up physical body Include COHNPSKMgCa Na COH form most cell material 700 of cell is water Micronutrients needed in smaller amounts Usually coenzymes cofactors etc Also critical to cell Include B Cr Co Cu Fe Mn Mo Ni Se W V Zn Liebig s Law of the Minimum Whatever is present in the lowest amount will limit growth The barrel analogy The shortest slat determines how much water is in the barrel Could be macro or micro Two classes of culture media 1 Defined everything is known in media in precise amounts 2 Complex undefined Not specifically known what is in there Ex Yeast extract Also use Enriched media selects for specific type of microorganism Selective has compounds which selectively inhibit growth of some microbes Targets an organism This inhibits the ones you don t want Differential indicator usually a dye tells when diagnostic chemical reaction occurs to see If work is correct Other things needed for growth pH oxygen salinity temperature light etc microaerophillic need low oxygen Microbial max photosynthetic Pure culture derived from single organism called AXENIC To get pure culture enrichments streaking picking colonies gliding technique sterile technique Now it must be maintained by transferring into fresh media or stored in glycerol etc Metabolism all chemical processes taking place in cell Classified by energy source and carbon source Energy source can be light or chemicals Carbon source can be CO2 or organic Energy source Light PHOTOTROPHY Chemicals CHEMOTROPHY Carbon source CO2 AUTOTROPHY when CO2 is the energy source Reduced organic carbon HETEROTROPHY or ORGANOTROPHY Organic carbon organo Inorganic carbon litho Categories of metabolic process 1 Anabolism cell is built from chemicals from environment biosynthesis building up cells 2 Catabolism chemicals are broken down to release energy for cell function breaking down cells Bioenergetics kJ Free energy G is energy available for cells to work OXidation removal of an electron from substrate Reduction addition of electron to substrate An oxidant removed electrons A reductant adds electrons Oxidation reduction potential Eh or E0 This is the tendency of a substance to accept or give up electrons volts Top of tower has the greatest amount of potential energy because donor wants to donate electrons LECTURE 6 Metabolic pathways 1 Fermentation chemoorganotrophy 2 Aerobic respirationelectron transport chemoorganotrophy 3 Oxygenic photosynthesis electron transport phototrophy Reducing power NADH H and ATP Both are present in pools in the cytoplasm and NAD AMP ADP All three forms of energy is present Fermentation Common anaerobic energy yielding metabolic pathway Not membrane associated in the cytoplasm Energy source from reduced organic carbon that is partially oxidized So not CO2 Cannot occur with oxygen ATP is formed enzymatically by transfer of phosphate PO4 high energy phosphate from phosphorylated compounds in fermentation pathway to ADP in the cytoplasmic pool Called SUBSTRATE LEVEL PHOSPHORYLATION Internally balanced redox reaction Only small amount of potential energy Uses NADH because it is high on electron tower and can serve as a donor 0 3 Stages 1 2 ATP is used to produce 2 molecules of glyceraldehyde3PO4 from glucose Glucose is splitactivated and sticks phosphates on it no redox reactions 2 An oxidation occurs with NAD the oxidant produces NADH H to produce pyruvate get 4 ATP 3 A reduction occurs to reoxidize NADH and this is required total ATP is 2 The fermented substance will serve as both an electron donor and an electron acceptor as it is metabolized Fermentation of one glucose to 2 pyruvate is called GLYCOLYSIS Yields a small amount of energy Biproducts are consumed Pyruvate gets recycled Fermentation 2 ATP Aerobic Respiration 38 ATPglucose Aerobic Respiration membrane associated energy yielding pathway Energy source is an electron donor which is usually an organic carbon compound Electron is transferred to terminal electron acceptor which is 02 Oxygen is around Energy source can be fully oxidized The PMF generated is used to produce ATP and as it carries electrons along it pushes protons across in the electron transport pathway and moved across membrane The donors and acceptors chain of them are held in place in the membrane by combination of hydrophobic and hydrophilic interactions Electron chains consist of an initial or primary electron donor and a final or terminal electron acceptor Intermediate electron carriers in between the primary donor and the terminal electron acceptor Energy released is the difference between the primary electron donor and the terminal electron acceptor Most important electron acceptor is 02 It is electro positive Most electron carriers are in the membrane but there are also some that free oat around in the cytoplasm Electron transport chain 5 types of membrane associated electron carriers 1 NADH dehydrogenases important hydrogen carrier because if is cytoplasmic and can move between compounds associated with metabolic pathways in cytoplasm 2 Flavoproteins 3 Cytochromes associated with iron and iron is a transition ion which means that it can be oxidized or reduced 4 Nonheme iron sulfur proteins 5 Quinones Freely diffusible in membrane Cytochrome to a quinone will produce the most PMF Two categories of electron carriers 1 Electron carriers only accept and donate electronsnon heme iron sulfur proteins cytochromes Both are associated with iron If it passes an electron to a hydrogen carrier a proton must be picked up from the cytoplasm enhance PMF contributes to the PMF gradient across the membrane 2 Hydrogen carriers have to take proton along with electron NADH dehydrogenase avoproteins quinones If it passes electron to electron carrier the proton is usually donated to side of membrane in increase PMF How this Works Electrons enter the chain from primary electron donor Protons are moved across the membrane when an electron is transferred from an electron carrier to a hydrogen carrier or from a hydrogen carrier to an electron carrier It is organized so that protons are picked up from the cytoplasm and released to the outside PMF is produced by these protons being picked up in the cytoplasm Electrons exit the chain by reducing the terminal electron acceptor 02 Overall Removal of electron from primary electron donor transfer of electron to intermediate electron carriers and then addition of the electron reduction of the terminal electron acceptor LECTURE 7 PMF is composed of two forces 1 concentration gradient of protons 2 difference in electrochemical charges on each side of the membrane protons are charged Chemical energy released in redox reactions is stored in certain phosphorylated compounds package and store energy ATP most importantO 2 high energy phosphate bonds when they are broken there is energy for the cell PEP Glucose 6 phosphate For long term storage there is cellular inclusions made of substance that can be oxidized to generate ATP such as glycogen PHB Elemental sulfur Formation of ATP ATP is produced from AMP or ADP Process is phosphorylation Three types 1 oxidative phosphorylation PMF 2 photophosphorylation PMF light powered 3 substrate level phosphorylation enzymatic 1 and 2 using energy of proton motive force are carried out by a membrane spanning protein called ATP synthase or ATPase F0 and F1 ATPase Fo spans membrane as a channel that allow protons to ow along gradient F1 is on cytoplasmic side is catalytic and carries out the phosphorylation reaction using energy from protons moving through Fo Cells can also do reverse and use the ATP to generate more PMF to move agella etc LECTURE 8 Genome the entrie complement of genes in cell or virus Chromosome main genetic element in eukaryotes and prokeryotes not viruses Circular in prokaryotes tightly coiled Plasmids small covalently closed circular pieces of DNA carry important genes 0 Bacterial DNA replication is bidirectional two replication forks move in opposite directions around chromosome more efficient 0 Replisome pulls DNA through the chromosome while it replicates protein complex Three natural methods of genetic recombination for bacteria 1 Transformation 2 Transduction 3 Conjugation Transformation free DNA taken up Only some strains can be transformed called competent Four steps 1 small piece of DNA bind to competent cell at membrane bound binding protein 2 One strand passes into competent cell and nuclease degrades other strand 3 One strand in cell bound by proteins Moved DNA to chromosome and recombines with homologous region of chromosome By RecA 4 New DNA incorporated and cell is transformed If new DNA is viral it is called Transfection Transduction DNA transferred from one cell to another via bacteriophage virus that infects bacteria Infect recombination new DNA in bacterial chromosome Two types 1 Specialized specific group of bacterial genes is packaged into virus and carried to another bacterium 2 Generalized any part of host gene can be carried by virus Specialized Transduction moves part of actual bacterial chromosome When it inserts into bacterial chromosome and goes to form a new virus it takes some of the bacterial DNA with it New viruses have little piece of host Conjugation DNA transfer occur via cell to cell contact by chromosome transfer or plasmid transfer plasmid moves between cells and takes part of bacterial chromosome with it Passes through conjugation bridge Pilus will grow and DNA or plasmid will pass through there Membrane fusion allows it to pass The donor has a conjugative plasmid called F fertility Recepient is F Rolling circle replication During transfer DNA enters the recipient cell the complementary strand is replicated Rolls in the opposite direction HFR strains high frequency of recombination F is an episome a plasmid that can become integrated into host chromosome Can bring a whole chromosome Transfer of host DNA in an Hfr cell At one site strand will open up at plasmid DNA starts moving across pulls hromosome to other side because It is covalently bonded Only gets first bunch of genes It will keep moving through until the tube breaks The plasmid DNA is transferee and replicated first any chromosomal DNA that comes in after that depends on how long until the bridge breaks LECTURE 9 Most microbes grow by binary fission cell size increase and cell divides into two new cells daughter cells divides at the septum Requires cleavage of peptidoglycan between NAM and NAG Increase in the number of cells in the population is exponential and called the population growth When measuring growth look at growth rate change in cell concentration over time and generation time doubling time These are dependent on what is available in the environment Four phases of growth 1 Lag alive adapting to new environment need some time 2 Log exponential 3 Stationary limited growth because of using something up etc Alive but not growing they are waiting for nutrient or whatever they need Can t stay in this phase too long 4 Death If in stationary stage too long they form endospores and die IN lab normally grow bacteria in batch groWth media is in container with a fixed volume no new media added or continuous the growth container is an open system fresh media is continually added culture Optical density is the absorbance Chemostat Culture reservoir Continually drips media and letting media flow out Volume stays constant When cells get continuous medium they will grow to the maximum Growth rate is defined by rate at which new media drips in If they do not divide fast enough they get flushed out Starts off as batch culture so that they can adapt so they don t get ushed out Dilution rate growth rate Environment Psychrophiles cold loving more polar and less hydrophobic fewer weak bonds Thermophiles heat loving 4580 C Hyperthermophile very hot over 80 in hot springs chemoorganotrophy and chemolithotrophy high diversity Mesophiles US Each has an optimal temperature for growth as well as temperature minimum and maximum At upper limits they grow endospores Enzymes perform better at higher temperatures then crash At minimum you can barely function In super extreme conditions you have monolayers In less extreme you have mixed layers Also for pH has minimum optimal and maximum Alkalphiles gt9 use sodium motive force in natural gradient rather than PMF neutrophiles and acidophile lt6 INTERNAL pH MUST STAY RELATIVELY CLOSE TO NEUTRAL even in acidic or basic conditions Usually positive water balance Most solutes inside cell in cytoplasm than environment so water moves in Plasmolysis cell shrinks away from wall and dies 0 Halophiles grow at reduced water potential and need NaCl Above normal water a little 0 Extreme halophiles require high level of NaCl for growth Will see crystals of salt in microscope 0 Halotolerant can tolerate some reduction in water potential but grow best in absence of added solute 0 Aerobes require oxygen to live 0 Anaerobes do not require oxygen and may be killed by exposure 0 Facultative organism can live with or without oxygen 0 Aerotolgerant anaerobes can tolerate oxygen and grow in presence but can t use it 0 Microaerophiles can use oxygen only when present at levels reduced from that in air LECTURE 10 Major levels of metabolic regulation in cell 1 control of activity of preexisting enzymes control rate etc 2 Control of amount of an enzyme Two types of regulation 1 negative repression turns off or slows down 2 Positive activation turns on or speeds up Two component regulatory systems External signal is transmitted to target in cell to manipulate a process Signals detected by sensors and transmitted to regulatory machinery signal transduction Consists of two different proteins 1 sensor kinase histidine located in cytoplasmic membrane detects environmental signal and autophosphorylates Spans the membrane transmembrane 2 Response regulator located in cytoplasm DNA binding protein that regulates transcription of specific target when it is phosphorylated by sensor kinase signal cascade Can move in cytoplasm Moves to the chromosome and interacts with a gene represses or induces Kinase an enzyme that adds high energy phosphate group to another substance Feedback because of phosphatase either response regulator itself or another enzyme It removes the phosphate group from phosphorylated response regulator turning it off Chemotaxis directional movement towards or away from a chemical taxis directional movement move toward an attractant or away from a repellent Involves 1 response to signal transmitted to cellular response 2 Controlling direction of rotation of flagella etc 3 Adaptation to concentration of signal in environment Phototaxisz move toward light MagnetotaXis move toward magnet Gliding cell toward or away by reversing direction of gliding For agella moving it is more difficult and you have to change ratio of runs to tumbles CCW is forward and CW is reverse tumble It will become bias Also length of runs will increase for an attractant Called biased random walk Bacteria can not sense spatial gradient but CAN sense a temporal gradient concentrations Chemotaxis movement attractant or repellent gets bound to a sensory protei or MCP methyl accepting chemotaxis protein and trigger phosphorylation of CheA CheW complex CheA CheW membrane associated phosphorylate CheY and CheB CheA is a sensor kinase MCPs translate signal from chemoreceptor to agellar motor to control direction of rotation CheYP binds to agellar switch MCP is methylated and demethlylated CheR adds methyls 4 methyls can be on at one time This allows adaptation CheZ removes phosphate on CheY on agella switch Phosphorylation increases with repellent decrease with attractant Methylation increases with attractant Fully methylated they do not respond to attractants but DO respond to repellents This also controls movement to OXYGEN or LIGHT Quorum sensing type of bacterial signaling system Up or down regulation of physiological or genetic processes based on detection of a signal produced by bacteria They produce the signals themselves Only occurs when population of bacteria is dense enough for signal to accumulate When they accumulate they AHLs can diffuse back into the cell and elicit a response This turns genes on or off
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