Chapter 3: Microscopy and Cell Structure
Chapter 3: Microscopy and Cell Structure MICRBIO 4000 - 0110
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This 8 page Class Notes was uploaded by Victoria Gonzalez on Sunday September 27, 2015. The Class Notes belongs to MICRBIO 4000 - 0110 at Ohio State University taught by Madhura Pradhan,Tammy Bullwinkle in Fall 2015. Since its upload, it has received 18 views. For similar materials see Basic and Practical Microbiology in Microbiology at Ohio State University.
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Date Created: 09/27/15
Chapter 3 Microscopy and Cell Structure Victoria Gonzalez Terms Capsule a distinct thick gelatinous material that surrounds some types of microorganisms sometimes required for an organism to cause disease Chemotaxis directed movement of an organism in response to certain chemicals in the environment Cytoplasmic membrane a thin lipid bilayer that surrounds the cytoplasm and de nes the cell boundary Endospore a kind of resting cell characteristic of species in a limited number of bacterial genera resistant to heat radiation and disinfectants Flagellum in bacteria a long protein appendage composed of subunits of agellum that provides a mechanism of motility Gramnegative bacteria that lose the crystal violent in the gram stain procedure and therefore stain pink their cell wall is composed of a thin layer of peptidoglycan surrounded by an outer membrane Grampositive bacteria that retain the crystal violet stain in the gram stain procedure and therefore stain purple their cell wall is composed of a thick layer of peptidoglycan Lipopolysaccharide LPS a part of the outer membrane of gramnegative bacteria Peptidoglycan macromolecule found only in bacteria that provides strength to the bacterial cell wall Made of alternating NAM and NAG units linked by peptide bonds Periplasm gel that lls the region between the outer membrane and the cytoplasmic membrane in gramnegative bacteria Pili hair like appendages on many gramnegative bacteria that function in conjugation and for attachment Plasmid small extrachromosomal circular DNA molecule that replicates independently of the chromosome often codes for antibiotic resistance Ribosome structure that facilitates the joining of amino acids during the process of translation composed of protein and ribosomal RNA 0 Transport system mechanisms cells use to transport molecules across the cytoplasmic membrane To know How different types of microscopy help better magni cation contrast and resolution How gramstaining and acidfast staining distinguish different types of bacteria General morphology of prokaryotic cells Membrane transport in bacterial cells speci cally the importance of proton motive force and group translocation Structure of bacterial cell wall and basic chemical structure of peptidoglycan Difference between the cell walls of gramnegative and gram positive bacteria Bacterial structures that help with motility and surface attachment Differences between structures and functions of prokaryotic and eukaryotic cells Microscopic techniques a Parameters of microscopy i Magni cation ratio of an object s image size to its real size ii Resolution the measure of the clarity of the image or the minimum distance of two distinguishable points iii Contrast visible differences in brightness between parts of the sample b Light microscopy visible light passes through a series of lenses to produce a magni ed image i Ocular lens eyepiece with 10X magni cation ii Specimen stage iii Condenser focuses on light iv Iris diaphragm controls the amount of light that enters objective lens v Objective lens more magni cation vi Light source vii Rheostat controls brightness of the light viii Types of light microscopy 1 Bright eld illuminates eld evenly 2 Dark eld light is directed at an angle unstained cells are easy to see because they are bright against a black background 3 Phasecontrast increases contrast by amplifying the refractive index difference between the medium and that surrounding it 4 Differential Interference contrast DIC two light beams pass through and then recombine looks 3D 5 Fluorescence cells are stained with a uorescent dye UV light is projected and cells emit different wavelengths colors 6 Scanning laser mirrors scan a laser beam across planes of a specimen computer makes a 3D image c Electron microscopy electron beams are used instead of light can t use living cells Transmission TEM transmits beams of electrons through specimen can observe ne details of cell structure darker is denser Scanning SEM beam of electrons scan back and forth over the surface visible 3D surface details Atomic force probe moves in response to slight forces between it and sample Can see bumps and valleys of atoms on specimen surface 2 Staining techniques a Differential staining distinguishes between two groups of bacteria Gram stain due to different chemistries in cell walls 1 Gram positive remain purple 2 Gram negative turn pink counterstained Acidfast staining 1 Used for cells that do not easily dye 2 Cells that retain the primary red stain are acidfast a Have waxy cell wall 3 Methylene blue is used as the counterstain 3 Morphology of prokaryotic cells a Types I ii iii iv v vi Coccus spherical Bacillus rodcylinder Vibrio bean shaped Spirillum corkscrew Spirochete corkscrew with agellum for movement Pleomorphic can have various shapes b Typical groupings of cells how cells tend to stick together after binary ssion depending on the plane which they divide c Multicellular associations signaling process that allows cells to talk to each other until they can take on multicellular behaviours as a population of bacteria d Parts of prokaryotic cells i Ribosomes free in cytoplasm ii Nucleoid iii Cell wall very different from eukaryotic plant cell walls iv May have capsule made of polysaccharides v May have forms of motility agella pilus e Cytoplasmic membrane i Structure 1 Made up of phospholipid bilayer a Hydrophobic tail b Hydrophilic head 2 Proteins for many functions ii Selectively permeable 1 Passive transport from high to low concentration iii Aquaporins allow passive transport of water 1 Osmosis iv Membrane transport 1 Passive transport move with concentration gradient a Simple diffusion move through plasma membrane b Facilitated diffusion rare in bacteria uses channels 2 Active transport moves against concentration gradient with the use of energy a Pumps especially proton pumps moves H molecules out of the cell important in bacteria b Cotransport 3 Proton Motive Force electrochemical gradient provide energy to power things like transport systems or ATP synthesis 4 Group translocation transported molecule is chemically modi ed by the transporter as it enters the cell a It can be used in the cell and is no longer transported out b Can help with signaling helps cell to monitor how much transported molecule is present so it can turn transporter off 5 Secretion getting things out of the cell a Directed by a speci c amino acid tag or quotsignaling sequencequot f Cell wall i Bacterial cell walls are made of peptidogycan 1 Peptidoglycan structure alternating carbohydrate units making a chain Two chains are combined with a peptide chain made up of amino acids a Amino acid component and carbohydrate component 2 GramPositive stain purple a Thick peptidoglycan layer i Thick layer does not allow the cell to be redyed with the pink stays purple b Contains teichoic acid negatively charged c Gellike material between peptidoglycan and cell membrane periplasm d No outer membrane 3 GramNegative a Thin peptidoglycan layer i Turns pink when dyed because the pink dye penetrates the thin layer b Periplasm space between inner and outer membranes c Outer membrane is present Emma e ti Call it 39ii re rn lF39ulre i nlt Etaiilnedl Eell Helpiresentatiee Bacillus Escherichia Ge ne re Staplny lececem title ssieriler 5trep39 tetetcus Peeti drum nines listingiuislhingi Streaetu resttiem pen elnts Peptid lyean Thick layer ll39hin layer lielentil circle lPrese nt bsent utter membrane Abuse nt F39rese Int Lipepelysaccharide Absent Present lie ndnteein l Putin lrteirle hse nt quotPresent allew unnecessary melecules tn pass tietame titere through enter is no enter membrane membrane e ne rel Eha raeteristies Sensitivity t Generally mere Generally less penicillin suseetiile sunsce ptble with nltable with netailtile exceptional eeeeptien 5 Sensitivity t fes H Iyseyrme peptidoglycan synthesis i Lipopolysachharides LPS 1 Endotoxin when injected into animals it triggers immune system and can be deadly ii Porin proteins are present allow things to go out less selectively permeable d 0 antigen end of polysaccharide that is recognized by our immune system ii Cell walls are permeable to sugars amino acids and other substances iii Penicillin antibiotic that inhibits cell wall 1 Enzymes that are responsible for bridging peptide chains are inhibited 2 More effective on grampositive cells iv Lysozyme an enzyme that breaks down the bonds that link alternating subunits of the glycan chain 1 Found in tears and saliva v Mycoplasma bacteria that causes pneumonia does not have a cell wall so it is not affected by penicillin Capsules and slime layers gellike layer outside of bacterial cell wall that protects the cell or allows it to attach to a surface made of glycocalyx i Capsule distinct and gelatinous ii Slime layer diffuse and irregular h Filamentous protein appendages i Flagella long protein structures that help in bacteria motility 1 6 ln bacteria they spin like propellers 2 Powered by proton motive force 3 Flagella can be arranged differently 4 5 Peritrichous agellar arrangement with Components basal body hook laments agella distributed over the entire surface of the bacterium Monotrichous polar agellar arrangement on one end of the cell ii Chemotaxis motile bacteria can sense and respond to chemicals in their environment can be attractant or repellent 1 Run agella move same direction forming a tight bundle allowing cell to move in one direction 2 Tumble rotation reverses causing cell to stop and tumble allowing it to change direction 3 This is coordinated to allow the cell to move towards or away from a chemical iii Pili 1 Shorter and thinner than agella similar in structure 2 Sex pilus used for conjugation 3 Fimbriae pill that allow cells to attach to surfaces i Internal structures i Chromosome 1 Single circular 2 Tightly packed and supercoiled 3 Found in the nucleoid ii Plasmids 1 Smaller singular circular 2 Not required for the cell can contrain useful genes 3 Horizontal gene transfer iii Ribosomes 1 Site of protein synthesis 2 Similar different from eukaryotes iv Cytoskeleton 1 Less extensive than eukaryotes 2 Less is known 3 Cell division and cell shape 4 Functions of cytoskeleton a Cellular movement b Separation of chromosomes c Maintenance of shape 5 Components a Actin micro laments b Microtubules i Thick long hollow made of ii Made of tubulin iii Make mitotic spindles c Intermediate laments v Storage granules 1 Accumulate and store large polymers or other nutrients vi Gas vesicles 1 Aquatic bacteria 2 Protein bound compartment that provides buoyancy 3 Controlled density vii Endospores and sporulation 1 Unique type of dormant cell produced by some bacterium 2 Resistant to heat chemicals UV 3 Formed during a distinct phase of growth cued by environmental signals
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