1 / 97

Microbiology

Microbiology. Prokaryote Architecture. Simple in shape, but genetically and biochemically advanced. General Prokaryote Shapes. Coccus – round or spherical Bacillus – rod shaped Spirila / Vibrio – spiral or twisted, corkscrew, halfmoon. Diplo – groups of 2 Strepto - chains

stormy
Télécharger la présentation

Microbiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Microbiology

  2. Prokaryote Architecture • Simple in shape, but genetically and biochemically advanced

  3. General Prokaryote Shapes • Coccus – round or spherical • Bacillus – rod shaped • Spirila / Vibrio– spiral or twisted, corkscrew, halfmoon

  4. Diplo – groups of 2 • Strepto - chains • Staphlo – grape like clusters

  5. Microscopy • Compound Light Microscope: • Helps to determine cell size and shape • Some internal structures may be seen • Usually need special dye

  6. Microscopy • Electron Microscope (to 150,000X): • Transmission (TEM) – helps to see internal cellular features (DNA, cell wall/membrane, ribosomes, etc.) • Scanning (SEM) – helps to see external features (cell surface, envelope, flagella, etc.) TEM – HIV on lymph SEM – RBC’s in clot SEM – E.coli on sm intestines SEM – intestinal tape worm TEM – flu virus

  7. Typical Prokaryotic Components • Cell membrane – selectively permeable barrier separating inside of the cell from its environment • Cell wall – rigid structure surrounding cell membrane • Gives structural support • Protection from lysing (breaking) • Made of peptidoglycan (sugar protein polymer) • Sensitive to PCN

  8. … 3. Ribosomes – combination of RNA & protein • Site of protein synthesis • Sequence of RNA nucleotide bases is used to identify species 4. Chromosome – DNA of cell • Almost always only 1 per cell • May be 2-4 copies in an actively growing cell 5. Inclusions – single structure of molecules of C, P, S, N • Stockpiles of necessary nutrients for future use in metabolism

  9. Flagella - structure that allows cell to be mobile in an aqueous habitat • Classified based on how many flagella

  10. 2 Major Groups of Bacteria Gram Positive Bacteria Gram Negative Bacteria About 90% of all bacteria Thin cell wall Small amounts of peptidoglycan Pink • About 10% of all bacteria • Thick cell wall • Contains lots of peptidoglycan • Purple

  11. Prokaryotic Cell Walls Diagrams of the cell wall structure of Gram-negative (left) and Gram-positive bacteria. Key: peptidoglycan layer (yellow); protein (purple); teichoic acid (green); phospholipid ( brown); lipopolysaccharide (orange).

  12. Gram Staining • Simple staining technique used to differentiate the 2 groups of bacteria • Uses the differences in the cell walls of different bacteria • Specific Steps to process: • Heat fix slide • Crystal violet (1 min) • Iodine (1 min) • Alcohol (5-10 secs) • Safranin (1 min)

  13. Microbial Growth

  14. ***Bacteria vary from minutes to years in reproduction time!*** • Microbial growth – increase in the number of cells in a population (group of individuals of the same species) • right conditions must exist. • DNA replication, transcription, and translation have to occur • Proteins, lipids, & polysaccharide synthesis all occur simultaneously

  15. Binary Fission: one cell to two cells

  16. Exponential Growth – population increases in number of cells in a fixed time period (1 → 2→ 4→ 8→ 16 → 32…) • Ideal growing conditions must be present • Steady nutrient supply & space • Unchecked / unlimited growth

  17. Growth Curve of Bacteria **Assumes abundant space, food, and no competition!

  18. Lag (acclimation) Phase – culture is transferred to fresh media • Requires time to adjust for growth to begin (synthesize DNA, enzymes) • Log (exponential) Phase – time of rapid growth • Exponential increase • Unlimited resources, ideal growing conditions

  19. Stationary Phase – log ends as nutrients & space are used up and waste products build up • Balance b/w reproduction and death • Cells began to encounter environmental stress • Lack of water, nutrients, & space • Build up of waste • Changes in oxygen and pH • Death Phase – cells cease metabolism; they become inactive or die due to limiting factors in the environment • Some ‘dead’ cells are alive but enter into “suspended animation” or form spores • Both can grow again

  20. Have the growth curve because we can measure the number of total cells in broth culture (blood, tissue, water) • Microscopy • Spread Plating • Turbidity

  21. Microscopy • Direct cell count by counting the cells within a grid (field) then extrapolating to total volume

  22. Spread Plating • Plate counts after a serial dilution, then count colonies, and extrapolate total volume

  23. A plate count may be done on plates prepared by either the pour plate method or the spread plate method.

  24. Turbidity • Use a spectrophotometer • Use a broth culture in a tube and insert in machine • Amount of light blocked by cells is proportional to the number of cells.

  25. Which method is better? • Best approach is to use turbidity after a plate count • Use 2 methods @ 1st, then turbidity

  26. Nutrition & Metabolism • Catabolism – breakdown of chemicals to release energy • Anabolism – “biosynthesis” – building of larger molecules • Requirements for Growth • Physical • Temperature ( -15ْ C to 125ْC) • pH (-0.05 to 13) • Salt (0% to 30%) • Osmotic pressure • Chemical • micro & macro elements • Oxygen (0-21%)

  27. Temperature • Cold • psychrophiles (cold loving) – organisms that grows best -15ْC up to 15ْC. Don’t grow above 25ْC • Psychrotolerant (cold tolerant) - organisms that grows best >20ْC, but can grow at lower temps • Middle • Mesophile organism that grows best b/w 20ْC • Hot • Thermophiles (hot loving) – organisms that grow best above 45ْC but below 80ْC • Hyperthermophiles (extreme thermophiles) grow best above 80ْC

  28. pH • Acidophile – organisms that grow best below pH of 6 • many foods, such as sauerkraut, pickles, and cheeses are preserved from spoilage by acids produced during fermentation • Neutrophile (neutral pH) – anything b/w 6 & 8 • Where most bacteria grow best • Alkalinophile (basic) – grows best pH above 8

  29. Salt • Halotolerant – tolerant to salt, don’t require salt, but can grow in presence of salt • Halophiles – require some salt for growth (up to 10%) • Extreme halophiles- require at least 10% salt for growth

  30. Osmotic Pressure • Microbes obtain almost all their nutrients in solution from surrounding water • Tonicity • isotonic • hypertonic • hypotonic

  31. Many chemicals needed for growth of these organisms

  32. Major Elements & Uses in Cells MACRONUTRIENTS • H (8%), O (20%)– H20 • Carbon (C) 50%– major constituent of all macromolecules; uptaken by cells as organic carbon or as CO2 • Nitrogen (N) 14%– major element in proteins and nucleic acids; uptaken as NH3, NO3-, N2, & organic molecules • Phosphorus (P) 3%– major element in ATP, phospholipids, & nucleic acids; uptaken as PO43- • Sulfur (S) 1%– used in amino acids (cysteine, methionine) & vitamins; uptaken as SO42- & HS

  33. MICRONUTRIENTS • Potassium (K+) 1%– transport of small molecules across the cell membrane, helps in enzyme function, & involved in protein synthesis • Sodium (Na+) 1%– can be used by enzymes & in membrane transport, but it is not required by all species • Magnesium (Mg2+) 0.5%– stabilizes DNA and helps in enzyme function, such as DNA polymerase and in ATP productions • Metals (Fe2+, Fe3+, Cu, Zn) – used in electron transport, used by proteins involved in electron transport processes (metabolism)

  34. Can remember these by: CHOPKNS CaFe all except Mg & Na

  35. Oxygen • There are 4-5 different oxygen requirements for bacteria • Obligate aerobe • Facultative aerobe • Microaerophile • Aerotolerant anaerobe • Obligate anaerobe

  36. Obligate aerobe • Require full level of O2 (20-21%) to grow

  37. Facultative aerobes • Grows best in O2, but can grow without O2

  38. Microaerophiles • Grow at O2 levels <20%, but require less

  39. Aerotolerant anaerobes • Don’t require O2, but can grow in presence of O2

  40. Obligate anaerobes • No O2 required, O2 is toxic

  41. Obligate aerobic • Obligate anaerobic • Facultative aerobe • Microaerophile • Aerotolerant

  42. What does all this mean? • You need to know what the organism you are culturing requires for growth so you can study and treat them!!

  43. Growth control

  44. Methods to Control Growth • Heat Sterilization • Radiation • Filtration • Antimicrobial Agents

  45. Heat Sterilization Sterilization – destruction of all viable life • Incineration (dry heat) – glassware, metal objects • 160ْ – 550ْC • Denatures proteins and makes organic molecules unstable • Takes seconds to hours • Pasteurization (low heat over time) – milk, fluids • 63ْ – 72ْC • Kills up to 99% organisms in milk • 15 seconds – 30 minutes • Autoclave (moist heat) – glassware, metal objects, liquids (sm. Vol.), plastics • 121ْ & 15 psi; pressure is used to increase temp. • Minutes to hours

  46. Radiation • Ionizing radiation (gamma rays) – breaks DNA; disrupts important genes= death • Used for plastics, antibiotics, food • Ultraviolet radiation (ultraviolet rays) – DNA & RNA absorbed and forms strong bonds between thymine; prevents DNA replication • Sterilizes water, air, and surfaces

  47. Filtration • Size of pores or matrix of fibers capture cells while air or fluid passes through

More Related