MICR J210 1st Edition Lecture 3Outline of Last Lecture I. Eukaryotes and ProkaryotesA. What is the difference between the two?I. Structural Differences between Eukaryotes and ProkaryotesII. Chromosomal DifferencesIII. Differences in LocomotionIV. Bacterial NomenclatureV. Cell Walls and CapsulesOutline of Current Lecture I. Structure of Prokaryotic cellsII. Gram StainingIII. Structure of Peptidoglycana. Liposaccharides and their Medical RelevanceIV. EndosporesV. Spore formation in FungiVI. Cyst Formation in ProtozoaVII. VirusesVIII. Binomial naming systemCurrent LectureStructure of Prokaryotic cells- Cell wall: gives the bacterium shape and structure- Pili: allow bacterium to adhere to surfacesdo NOT produce locomotion- Flagella: produce locomotion- Cell membrane: contain proper enzymes for oxidative phosphorylation o Function like a mitochondrionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Gram Staining- Gram Positiveo Dark blue/purpleo Uses light microscopy to view the specimeno In general, all bacteria have an inner membraneo Gram positive bacteria have a thick layer of peptidoglycan  Peptidoglycan: sugars linked with peptides Lipoteichoic acids are embedded in the membrane- Gram negativeo Stain pinko Uses light microscopy to view specimeno Inner membrane (phospholipid bilayer) is covered by a thin layer of peptidoglycan  Thin layer of peptidoglycan is located in the periplasmic space that is not anchored to the inner cell membrane like the Gram positive bacteria Not rigidly cross-linked but rather more loosely connectedo Outer membrane (phospholipid bilayer) covers the peptidoglycan Liposaccharides are linked to the outer cell membrane and always face outwards- Composed of lipids and sugars- Known as endotoxins which are responsible for feversGram Staining Procedure- Application of crystal violet on the slideo The crystal violet stains all the bacteriao Both Gram positive and Gram negative cells are stained purple- Application of iodineo Iodine only effects the gram positive cells and forms a complex with the crystal violet - Alcohol washo The alcohol dissolves membranes of the bacteriao Gram negative cells are no longer stained purple—they are now clear- Application of safranino Safranin goes into both types of cell, but the Gram positive cells remain predominantly purple and the Gram negative cells are now pink in colorStructure of Peptidoglycan- Peptidoglycan is a mesh of:o Polysaccharide (sugar) backbone NAM and NAG alternate: NAM NAG NAM NAG NAM NAG- They are both similar in structure to glucose (6-caron structure) but contain varying side chains NAM has amino acid chains dangling down that cross-link laterally NAG does NOT have amino acid chainso Polypeptide cross-bridges Cross-link laterally- Medical Significance of Peptidoglycan (PG)o PG is only present in bacteria Because peptidoglycan is only found in bacteria, it is a good target for many antibiotics Antibiotics that target peptidoglycan work better against Gram positive cells since in these bacteria the bacteria is exposed—unlike Gram negative cells in which the peptidoglycan is covered by a phospholipid bilayero PG keeps the cell from bursting When drugs target the peptidoglycan, the breakdown of the PG causes the osmotic pressure to change- The bacterium then lyse (swell and burst) since water begins moving into the cell to create equilibrium with the lower concentrated environmentLiposaccharides and their Medical Relevance- Liposaccharide is another term for endotoxino Endotoxins are only harmful to humans when they are exposed The only way these endotoxins can be exposed is when the bacteria are broken downo Endotoxins are composed of three parts: Lipid A- Long chain of fatty acid- Source of the toxicity of endotoxins- When exposed they activate macrophageso Too many macrophages circulating the body send humansinto toxic shock- Embedded into the membrane of the bacteria- Lipid A are the same across all bacteria with endotoxins Core- The core changes between different genera of bacteria O-Antigen- Vary between different strains of the same bacteriao Medical Relevance Lipid A is toxic to humans and causes septic shock- Cytokines are released by human macrophages in response to the presence and exposure of Lipid A—this is the cause of septic shock Systemic v Local Infection- Local infection: localized inflammatory response contained in a region of the body (scrape on the knee)- Systemic infection: bacteremia (bacteria in the blood stream) attract macrophages which release the cytokines that cause septic shock (widespread and potentially fatal response)Endospores- Endospores are the most stable living thing known—very durable- Endospores can only be found in certain types of Gram Positive bacteria- Endospores allow the bacteria to produce a dormant and highly resistant cell to preserve the genetic material in times of extreme intolerable conditionso Dormant form of the bacteria, highly resistant and becomes activated once rehydrated and inoculated in nutrientso Endospores germinate and produce the original organism once returned to favorable conditions- How do bacteria grow?o They do NOT undergo mitosis or meiosiso They grow through binary fission Clone themselves and replicate exact copy of original bacterial cell Known as the simplest form of replication DNA attaches to the cell membrane during the splitting of the two cells so that the membrane pull the DNA apart equally into the two cellso Undergo binary fission only as long as nutrients are unavailable Gram-positive bacteria only form endospores under harsh condition- Vegetative cell develops spore coat (made of peptidoglycan)- Everything inside of the spore coat becomes the endospore—therest of the cell (mother cell) disintegrates- Medical Relevance of Endosporeso ONLY Gram + cells produce endospores Example: Clostridium tetani Endospore-forming Gram positive rods are present in soil Step on a dirty nail and spores from the soil germinate deep within human tissue Fully grown bacteria release exotoxins which cause the disease tetanus (Lock jaw) Spore-formation in Fungi- Fungi are eukaryotes and undergo sexual reproduction- Fungi cell walls are not composed of peptidoglycan like bacteria—they are composed of chitin (polysaccharide)o