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Skin: 200 different kinds of bacteriapH is low (4-4.5) Bacteria like to live on glands. Endocrine glands: found in hairless places of the sky. Few microbes live there and if blocked then no fluid to allow bacterial growth.Apocrine glands: become active at puberty such as under arms etc. Bacteria responsible for body odor, in sterile conditions there is no odor. Organic acids: propionic acid3-methylbutanic acidSebaceous glands: hair follicle glands that secrete sebum (fatty acids) Abundant on scalp and faceCreate vitamin E and have some antimicrobial activity Staphylococcus sp. Gram positive – S. epidermitis S. aureus Corynobacterium sp. Gram positive- C. diphteriaePropionibacterium sp. Gram positive- P. acnesPseudomonas aeruginosa Gram negativeAcinetobacter johnsonii Gram negative- can move FungiCandida sp. Candida albicansCandida balanitis Pityresporum sp.: in scalp, can cause dermatitis The mouth: bacteria found as biofilms on teeth and gumsSaliva: pH 5.7-7 Organic: Na, H, Ca, Cl and proteins and enzymes Teeth: with living tissue in the inside and calcium phosphate crystals (enamel) on the outsideChildren have different floraChildren without teeth: Staphylococcus salivus and Lactobacilli (pH 5.7-7) After teeth: more Staphylococcus species and anaerobic species and filamentous species.Plaque: Biofilm on teeth which is micrometers thick. S. suberin high affinity for lower parts Dental carriesLactobacillus sp.: wears away enamel by fermenting of buildup causes pain when it gets to the organic layer. Gastrointestinal tract (if gut were to be sterilized by antibiotics, pathogens, immune to antibiotics can settle in.)StaphylococcusYeast – Candida albicans-Inflammatory bowel disease: Linked to excessively good hygiene -Autism links to intestinal fluid: Some bacterial digestive products in excess. Bacteroides fragilis. (gram negative) Stomach-Lumen: pH of 2 and serves as a barrier to many organisms-Walls: Heavily colonized biofilms over epithelial layers Lactobacilli sp. Acid tolerant Streptococci sp. Is in newborn stomachs a week after birthIntestinal tract- Small intestine: Lactobacilli Ectherococci- Large intestine:o Facultative aerobes in the minority E. coli o Obligate anaerobes:  Bacteroides (30 percent of bacteria in gut) Enderococcus fascalis  Bifidobacterium sp. (predominant in infants and goes well on mothers milk) Chlotradia o Colon: Dry weight of feces = 1/3 bacteria. Bacteria are able to modify (bile acid) unfamiliar organic compounds- Carcinogens detoxified- Other compounds continue to promote more toxins - A second liver Vitamins- Thiamine, Vitamin K, Vitamin B, Ribophorin - Glycosidases: digestion of unusual steroids - Odors: H2S, NH2, Butyric acid- Gases: CO2, CH4, H2 Bacterial Cells- Cytoplasm- DNA, Ribosomes, polyribosomes- Transcription is coupled to translation- RNA + protein from RNA simultaneously o RNA made in nucleus transported to cytoplasmo Proteins in cytoplasm - Cell membrane (in both gram positive and negative) has membrane proteins- Periplasm (in gram negative only) has some carrier proteins- Cell wallo Gram negative is thino Gram positive is 20 times thicker o Peptidoglycans  Rigidity and shape  Protects cell from lysis during changes Peptide is unusual- D amino acids + L amino acids- DAP in gram negative ( Diaminopinalic acid) Peptide linkageL-Lys to D- Ala in gram positiveDAP to D-Ala in gram negativePublic health eradicated many previously endemic microbial diseases. Antibiotics inhibit cell wall synthesis in bacteria- They require that a cell be manufacturing a wall and cell growing - Disaccharides of NAM o Fosfomycin blocks- Remove UDP link to a lipid in the membrane o Vancomycin blocks this step- Peptide is crosslinked to peptide in another chaino Penicillin kills the enzyme for crosslinkage Some cells don’t have cell wall: Mycoplasma sp. - No peptidoglycan- Not rigid- Resistant to antibiotics that attack cell wall Protein synthesis- Erythromycin: Bind to ribosome 50S subunit; inhibit protein synthesis at chain elongation step. - Streptomycin: Bind to 30S subunit of bacterial ribosome; cause translational misreading and inhibit elongation of protein chain; kill by blocking initiation of protein synthesisRNA synthesis inhibitors - Rifampin: Binds to bacterial RNA polymerase and blocks transcription at initiation stepDNA synthesis inhibitors - Fluroquinolone: Interfere with DNA replication by inhibiting the action of DNA gyrase or topoisomerase Fungi- Beta glucan (micafungin, caspofungin, echinocandins) They block beta glucan synthese which is a major component of fungal cell walls - ErgosterolInhibitors of ergosterol synthesis- Indazoles (broad class): blocks synthesis of ergosterol required for fungal cell wall integrity You need an assay. - Steps for making a library of genes from the pathogeno Cut pathogen’s DNA with restriction endonucleaseso Close pathogens DNA fragment into plasmid o Transfer into E. coli cells. Made competent by treatment with CaCl2 and heat. o Select for E. coli that received plasmid with gene. Growth on antibiotic  Sometimes one can also screen for insertion of the foreign gene Add bacteria to mammalian cells. Wash away those that invaded lyse and recover.  Plate an antibiotic again. Every colony is a clone for the library of immune genes.o Sequence DNA. o Mutate and re-introduce in E. coliSDS Polyacryhamide gel: electrophoresis - Suicide plasmid - KanamycinPublic health is most responsible for own longevity compared to the 19th century. - Clean water and water treatment - Sewage treatment- Vaccines Antibiotics are helpful but should be used with caution How bacteria counter:- Adapt existing enzymes to recognize and destroy/modify the drug- Block access to drug. Especially Gram -: can mutate porins to prevent entry of drug or entire class of drugs.- Can make protein pumps transport/export drug- Modify the drug’s target so that it is no target recognizedGram negative has two membranes- Cell wall is rigid but porous - Porins allow entry of small hydrophilic moleculesDisaccharide/peptide construction begins inside membrane- Gram negative finishes in periplasm- Gram positive finishes in cytoplasmCephalosporin is less potent than penicillin but it is useful because it lasts longer.- R-groups can be varied. Variations result in unexpected changes. - Bacteria make over 300 beta lactamasesBeta lactam drugs work best on gram negative- Get through porins- Get into periplasm

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USC PHRD 662 - Notes

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