Skin 200 different kinds of bacteria pH 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 acid 3 methylbutanic acid Sebaceous glands hair follicle glands that secrete sebum fatty acids Abundant on scalp and face Create vitamin E and have some antimicrobial activity Staphylococcus sp Gram positive S epidermitis S aureus Corynobacterium sp Gram positive C diphteriae Propionibacterium sp Gram positive P acnes Pseudomonas aeruginosa Gram negative Acinetobacter johnsonii Gram negative can move Fungi Candida sp Candida albicans Candida balanitis Pityresporum sp in scalp can cause dermatitis The mouth bacteria found as biofilms on teeth and gums Saliva 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 outside Children have different flora Children without teeth Staphylococcus salivus and Lactobacilli pH 5 7 7 After teeth more Staphylococcus species and anaerobic species and filamentous Plaque Biofilm on teeth which is micrometers thick S suberin high affinity for lower parts species Dental carries to the organic layer Lactobacillus sp wears away enamel by fermenting of buildup causes pain when it gets Gastrointestinal tract if gut were to be sterilized by antibiotics pathogens immune to antibiotics can settle in Staphylococcus Yeast 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 birth Intestinal 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 Bacterial Cells Thiamine Vitamin K Vitamin B Ribophorin Glycosidases digestion of unusual steroids Odors H2S NH2 Butyric acid Gases CO2 CH4 H2 Cytoplasm DNA Ribosomes polyribosomes Transcription is coupled to translation RNA protein from RNA simultaneously o RNA made in nucleus transported to cytoplasm o Proteins in cytoplasm Cell membrane in both gram positive and negative has membrane proteins Periplasm in gram negative only has some carrier proteins Cell wall o Gram negative is thin o Gram positive is 20 times thicker o Peptidoglycans Rigidity and shape Protects cell from lysis during changes Peptide is unusual Peptide linkage D amino acids L amino acids DAP in gram negative Diaminopinalic acid L Lys to D Ala in gram positive DAP to D Ala in gram negative Public 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 chain o 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 synthesis RNA synthesis inhibitors DNA synthesis inhibitors Fungi Rifampin Binds to bacterial RNA polymerase and blocks transcription at initiation step Fluroquinolone Interfere with DNA replication by inhibiting the action of DNA gyrase or topoisomerase Beta glucan micafungin caspofungin echinocandins They block beta glucan synthese which is a major component of fungal cell walls Ergosterol Inhibitors of ergosterol synthesis You need an assay Indazoles broad class blocks synthesis of ergosterol required for fungal cell wall integrity Steps for making a library of genes from the pathogen o Cut pathogen s DNA with restriction endonucleases o 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 coli SDS Polyacryhamide gel electrophoresis Suicide plasmid Kanamycin Clean water and water treatment Sewage treatment Vaccines Antibiotics are helpful but should be used with caution How bacteria counter Public health is most responsible for own longevity compared to the 19th century 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 recognized Gram negative has two membranes Cell wall is rigid but porous Porins allow entry of small hydrophilic molecules Disaccharide peptide construction begins inside membrane Gram negative finishes in periplasm Gram positive finishes in cytoplasm Cephalosporin 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 lactamases Beta lactam drugs work best on gram negative Get through porins Get into periplasm and bind to penicillin binding proteins Bacterial counter Cleaving beta lactam ring Not allowing them through porins By excreting them or by producing beta lactamases that are exported into matrix o Gram positive bacteria make beta lactamases