Lecture 2Outline of Last Lecture I. Human microbiome: 10x more bacteria than human cells in our bodies. Microbes are all around us, andin us! II. Scientific nomenclaturea. First name: genus name, capitalizedb. Second name: species name, never capitalizedc. Italicized or underlinedd. Always use scientific nomenclature for living things! e. Strains are identified by numbers after the name. Strains are identified by cell wall and flagella. E.coli 0157:H7f. For viruses (which are not living—therefore do not use scientific nomenclature), they are namedby species name and type of genetic material containedIII. Living organismsa. Bacteriai. Prokaryotesii. Bacteria and archaea both reproduce through nuclear fission, have no nuclear membrane or membrane-bound organellesiii. Have peptidoglycan in cell wallb. Archaeai. Prokaryotes ii. Bacteria and archaea both reproduce through nuclear fission, have no nuclear membrane or membrane-bound organellesiii. Have no peptidoglycan in cell walliv. Extreme conditions—only typically in the oral cavity of the human bodyv. Don’t have the same cell wall or lipid membrane composition as bacteriac. Eukaryai. Prokaryotes ii. Have no peptidoglycan in cell walliii. Non-extreme environmentsIV. Nonliving organismsa. Virusesi. Viruses are obligate intracellular parasitesii. Nonliving b. Viroidsi. Plant pathogensii. Short stretch of RNAc. Prionsi. Protein that will kill you because it is folded inappropriately ii. Spongiform encephalopathy—prion pokes holes in your brain, causes the brain to appear “spongelike” iii. Infectious proteiniv. Can be hereditary—many cases of this appear in those with a family history (genetic link) MCRO 251 1ST Editionv. Mad cow diseaseV. Shapes of bacteriaOutline of Current Lecture I. Bacteria plasma membrane and types of transporta. Transport molecules of membrane help enzymes get into the cytoplasm of a bacteriab. Facilitated diffusion—transporter lets substances move across membrane down concentration gradient. (Doesn’t work much in bacteria)c. Active transport—transporter uses energy generated by electron transport chain (proton motive force) or ATP to bring something in or out against its concentration gradientd. Group translocation—transporter chemically alters substance as it is transported across the membranei. Used for glucose (sometimes)ii. Phosphorylation occurs II. Bacteria cell walla. Peptidoglycan—proteins (peptides) linked with sugars (glycan)b. This molecule is only ever found in bacteria, so if the human body detects it (outside the GI tractwhere there is tons of bacteria), it knows something is wrongc. N-acetylmuramic acid (NAM) and N-acetylgucosamine (NAG) link up. 1 NAM and 1 NAG form upto make a monomer in the cytoplasmd. Then a peptide side chain (five aminos) links to the NAM i. Linked side chain is tetrapeptide (4 aminos). Contains D-amino acids and diaminopimlemic acid. The fifth amino is locked off, energy is used for side chains and sothat’s what takes it from penta to tetraii. Those two amino acids are only found in bacteriaiii. Human aminos are always L-amino acids, so this is another way to differentiate human cells from bacterial onese. This is transported from the cytoplasm to the ECF and begins to form a wall, with the peptide side chain linking rows and rows of the monomers together by linking up NAMsi. Rigid peptide side chain creates a bridge like structure (interbridges) in gram positives. Thick cell wall of peptidoglycanii. Rigid peptides are directly linked in gram negativesf. The peptidoglycan wall gives the organism shapeg. Teichoic acid is in the peptidoglycan wall i. One type of TA is linked around in the wall and can link to things like copperii. Lipoteichoic acid goes all the way down into the lipid bilayer—good for anchoringIII. Gram positive bacteriaa. Contains peptidoglycan with interbridges, with both types of teichoic acid b. Peptidoglycan synthesisi. Autolysin cleaves the peptidoglycan wall. New monomer is madeii. Prenol transfers the new monomer from the cytoplasm and into the ECFiii. Transglycosidases link sugars—NAM and NAG—into cell wall with the other sugarsiv. Transpeptidases link the peptide side chains1. Will make a peptide interbridge in gram positives2. Linked with glycosidic bonds c. Penicillin inactivates one of the transpeptidases, making peptide crosslinking impossible, making the bacteria swell and explode (normally prevented by the cell wall, which kept the bacteria from over expanding). This is why penicillin works on gram positive bacteriaIV. Gram negative bacteriaa. Outside of this cell wall is a second lipid bilayer, which protects the peptidoglycan from antibiotics. b. Also note the peptidoglycan in Gram negatives doesn’t have interbridgesc. Periplasma—space between first lipid bilayer (cytoplasmic membrane, inner membrane) and second (outer membrane)d. Outer membrane is not a normal lipid bilayer because it has lipopolysaccharidese. Lipopolysaccharide—layer outside the external surface of the outer membrane. Lipid with a polysaccharide side chain. Does not exist on the surface of the inner membrane. Lipid A is the lipid, connected to the polysaccharidei. Only in gram negatives, and in every gram negativeii. Lipid A is also something that can cause endotoxic shock, which can be fatal. So lipopolysaccharide=LPS=endotoxiniii. Core polysaccharides on top of the lipid A, can differ by speciesiv. O-side chains—on top of the core polysaccharide, variable even between related species1. This is how you differentiate some strains of the same disease from each other. E.coli O157:H7 is the strain with the 157 O side chainv. Extreme infections caused by gram negatives because of thisf. Porin proteins—only found in outer membrane (so only gram negatives). They let certain molecules through, keep others outi. Penicillin can’t go through porin proteins so it can’t affect gram negatives. Vancomycin is the same—too big to fit through a porin proteinii. This is why Gram negatives aren’t affected by pencillin or vancomycin!V. Glycocalyx, capsule and bacterial slime layera. Glycocalyx—gelatinous, gooey substance made of polysaccharides that surrounds bacteria. Sugar coat. Two kinds: capsule and slime layerb. Capsule—another molecule secreted by some bacteria, outside the peptidoglycan cell wall. Slimy layer lets bacteria adhere to something or avoid white blood cells. Lets them avoid phagocytosisc. Your teeth are slimy after