Lecture 3: Prokaryote = Bacteria

Lecture 3 Prokaryote = Bacteria ↳ small unicellular organisms ↳ all proteins begin with the amino acid, formylmethionine Eukaryote = Fungi, plant cells, protozoa, metozoa, human cells ↳ all proteins begin with the amino acid methionine Viruses, viroids (incomplete virus), and prions (infections proteins) are not cells and are in neither category Prokaryote means before nucleus · DNA not in enclosed envelope · DNA not associated with histones · Lack membrane -enclosed organelles · Peptidoglycan in cell wall · smaller ribosomes 70s · Divide by binary fission · no meiosis Eukaryote means true nucleus · DNA in nucleus · DNA associated with histones · Membrane -enclosed organelles · simple cell walls · larger ribosomes 80s · Divide by mitosis · Meiosis Endosymbiotic Theory: bacterial origin of mitochondria in Eukaryotic cells Mitochondria and chloroplasts were eaten by larger cells and they evolved to be in cells today b/c it’s beneficial to have structures that produce ATP/energy (That’s why there’s two membranes around them) Bacteria not stained by Gram's stain · Mycobacterium (M. tuberculosis) - causes TB ↳ cell wall has peptidoglycan but large amounts of mycolic acid which prevents stain penetration · Mycoplasma (M. pneumoniae) - causes pneumonia ↳ no cell wall and no peptidoglycan; contains large amounts of sterols Ziehl-Neelsen or "acid-fast" stain is for organisms with a high lipid/wax content in cell wall Acid-fast Stain - Mycobacterium, Nocardia, etc. ↳ these bacteria have waxes in their cell walls. Carbol fuchsin is added to smear and heated or treated with phenol, which enhances the penetration of the dye through the wax. ↳ decolorization is done by exposing the smear to acid alcohol, removing the red stain from the organisms that are not acid-fast. ↳ counter stain with methylene blue, then colour the background so that its easier to see the red-stained acid-fast organisms Negative staining for capsules Gram(-) = pink with a halo around the cell where the stain cannot reach Acid-Fast = red (w/blue background) ↳ background is stained and the organism appears as a particle Bacterial Structures and Function · Motility ↳ Flagella - one or many rotate around to help cell move ↳ Axial filament - flagella inside of cell wall (spirochaetes) allowing the cell wall to rotate like a corkscrew · Attachment and conjugation ↳ conjugation: horizontal transmission of genes from one bacteria to another ↳ Pili/Fimbriae ① attachment to cells/tissues ② can pull bacteria along the surface of cells (kinda) ③ sex pilus (transfer of plasmid) · Protection ↳ capsule/glycocalyx: surrounds bacterium and helps to evade from WBC, sometimes also helps w/attachment Capsule Bacterium Gram(+) = purple Negative stain: any colour? Cell Wall Structures · Gram (-) cell walls have a lot of waxy phospholipid layers, thin peptidoglycan layer · Gram (+) cell walls have lots of waxy peptidoglycan layers · Peptidoglycan: lattice structure like a mesh · Lipopolysaccharide (LPS): outer membrane (only G-) ↳ Lipid A: "endotoxin" anchors in bacterial outer membrane ↳ Polysaccharide = "O" antigen projects out of cell · Teichoic and Lipoteichoic acids (only G+) ↳ attached to peptidoglycan layer, projects outwards and creates (-) charge, (adhesion) Plasma membrane/Cytoplasmic membrane · Prokaryotes = phospholipid CM, usually no sterols · Eukaryotes = some phospholipids, carbohydrates, sterols in CM Human cell membrane contains cholesterol Fungi cell membrane contains ergosterol Cytoplasm of Bacteria · Nuclear area = nucleoid ↳ 1 chromosome in bacteria, 46 in humans · Ribosomes: site of protein synthesis (70s) · Inclusions: reserve deposits of nutrients in membrane bounded vacuoles · Plasmids: small circular pieces of DNA that code for a restricted number of proteins Endospores: resting cells with a coating around a pocket of DNA ↳ resistant to heat, drying, UV radiation, chemicals ↳ helps with survival ↳ NOT LIKE A CAPSULE!!! Clostridium difficile · A major cause of nosocomial (hospital acquired) infection globally · Anaerobic, Gram+, rod, bacillus, produces endospores and exotoxins ↳ spores are not "living", and cannot be inactivated by alcohols or antibiotics ↳ spores can survive for months · Transmission: fecal-oral transmission · Virulence Factors: TcdA (toxin A), TcdB (ToxinB), CDT- C. difficile binary toxin · Pathogenicity: - spores are ingested and unaffected by stomach acid - germinate in intestine after contact with bile acids - Exotoxins made by vegetative bacteria damage intestinal mucosa, kills cells, and causes epithelium to leak, leading to watery diarrhea (both are cytotoxins). Treatment: Syndromes Associated: · Conventional · Dehydration · Nonconventional · AAC (antibiotic associated colitis) ↳ antibiotics like vancomycin and metronidazole · AAD (antibiotic associated diarrhea) ↳ probiotics · CDAD (Clostridium difficile associated diarrhea) ↳ fecal implants (best success rate at 93% ) Prevention: · PMC (pseudomembranous colitis) · Toxic megacolon (gangrene of intestines) · Death ① Avoid hospitalization ② Keep environment clean (wash hands) ③ Reduce excess microbials ④ Restore flora ⑤ Vaccines or antibodies ⑥ Antibiotics and treatment IMPORTANT: Children < 2 years never have symptomatic C. difficile infection but they may harbour the bacterium