BIOL 2230 Unit 2 weeks 1-2
BIOL 2230 Unit 2 weeks 1-2 BIOL 2230
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This 12 page Class Notes was uploaded by Allison Collins on Sunday February 28, 2016. The Class Notes belongs to BIOL 2230 at Middle Tennessee State University taught by Anthony L Newsome in Fall 2015. Since its upload, it has received 24 views. For similar materials see Microbiology in Biology at Middle Tennessee State University.
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Date Created: 02/28/16
2/16 Microbial growth control Physical means • Based on: o Heat, low temperature, desiccation (dehydration), osmotic pressure, filtration, radiation • Microbial control doesn’t necessarily mean killing the bacteria o For example, putting food in the freezer doesn’t kill bacteria, it only slows its growth o The goal of microbial control may just be to sufficiently inhibit growth • Sterilization -‐ destruction or removal of all forms of microbial life, including spores and viruses o NOT synonymous with disinfecting Types of physical microbial growth control 1. Moist heat • Autoclaves (heat under pressure) o 121C for 15 min at 15lb of pressure; must have moisture present • Boiling water o Kills most vegetative forms of bacteria and most viruses in 10 minutes o Spores and hepatitis can survive several minutes or more in these conditions o Doesn’t achieve sterilization • Pasteurization – mild heating (72C) o Also doesn’t achieve sterilization 2. Dry heat • 170C (340F) for 2 hours • Moist heat is more effective – takes 10-‐15 min at a lower temperature o Heat in fluid transfers heat to the object being sterilized § Especially cooking oils 3. Gas • Ethylene oxide for 4-‐18 hours • Denatures protein • Ideal for sterilizing electronic equipment and other heat-‐sensitive materials 4. Radiation • Ionizing radiation (irradiation) – use of high-‐penetrating gamma rays o Gamma rays have enough energy to disrupt molecules – damages DNA or other cellular structures – kills organism or makes it incapable of reproducing o Used for single use medical supplies, tissue-‐based products, food (i.e. astronaut food) o Kills probiotics too • Non-‐ionizing radiation o Less penetrating – useful for sterilization of surfaces o Ex: microwaves, UV rays Disinfection -‐ the process of destroying vegetative pathogens but not necessarily spores or viruses • Antiseptic vs. disinfectant o Antiseptics are applied to living tissue to prevent infection o Disinfectants applied to inanimate objects, so are stronger 2 Chemical means 1. Phenols • First used by Joseph Lister (Listerine) • Ex: Chlorhexidine (Hibiclens) • Phenolics – phenol derivatives o Damage cell membranes, denature proteins o Ex: hexachlorophene (phisohex), Lysol 2. Halogens • Iodine o Combines with microbial proteins to disable their function o Used as a tincture of iodine – a tincture is an alcoholic extraction o Iodophore – combinations of iodine and organic molecules § Includes Betadine and Isodyne • Contain povidone, a surface active agent • Chlorine o Used as sodium hypochlorite – AKA bleach – most commonly used halogen o Chlorine is used as a gas to control microbial growth in drinking water 3. Alcohols • Proof – measure of amount of ethanol – twice the percent of ABV (alcohol by volume); ex 100 proof = 50% alcohol • Most widely used kind is 70 percent ethyl alcohol (ethanol -‐ EtOH) • Isopropyl alcohol (rubbing alcohol) o Useful in disinfecting skin before injections because it evaporates quickly and leaves no residue 3 4. Heavy metals • Silver – used as silver nitrate to guard against infection and cauterize wounds • Copper – used as copper sulfate to slow growth of algae, also is antifungal agent in paint • Zinc – used as zinc chloride in mouthwash 5. Soaps and detergents • Emulsification agents – break down and suspend fat molecules in the oily film on a surface – easier to wash away oil, debris, and MO 5. Aldehydes • Formaldehyde – used as formalin, a solution of formaldehyde gas o Used for embalming • Glutaraldehyde – used as a liquid for cold sterilization of hospital equipment 6. Oxidizing agents • Kill MO by releasing large amounts of oxygen – alters microbial enzymes • Hydrogen peroxide (H2O2) – wounds, contact lenses • Benzoyl peroxide – treats acne by inhibiting anaerobic growth 7. Quaternary ammonic compounds • Cationic detergents • Break down cell membranes of MO • Ex: Cepacol (mouth wash), Virex128, D.O.C. 64 • Tuberculosis and Hepatitis are top infectious concerns at hospitals – not protected against by quaternary ammonic compounds o EndBac II – does protect against tuberculosis 4 2/23 Nucleic acid recap • Nucleic acids – long polymers of nucleotides o DNA – double stranded o RNA – single stranded • Nucleic acid principles o 2 information storing molecules – primary function o RNA – 80 to 200,000 nucleotide units long o DNA – several million nucleotide units long • Each nucleotide has: phosphate group, pentose sugar, nitrogenous base o In RNA – ribose sugar o In DNA – deoxyribose sugar • Why called deoxyribonucleic acid/2-‐deoxyribonucleic acid? o The nitrogenous bases of nucleic acids belong to 2 chemical classes: § Pyrimidine – 1 ring • RNA: uracil and cytosine • DNA: thymine and cytosine § Purine: 2 fused rings • RNA and DNA: adenine, guanine o **only need to memorize names, not exact chemical structure** DNA details • Important concept: in order to convey info, you must have VARIABILITY o Ex: bar code, alphabet, binary code 5 • What varies in nucleotides? o Nitrogenous bases (A, C, U/T, G) • DNA is double stranded – strands are COMPLEMENTARY & ANTI-‐ PARALLEL o (i.e. not identical) o Pairs: A-‐T, T-‐A, C-‐G, G-‐C o Nucleotides associated via nitrogenous bases o Nitrogenous bases are always at 1’ carbon o Remember – purines (adenine and guanine) only go with pyrimidines (thymine and cytosine) and vice versa • True of all pentose sugars in nucleotides o 1’ Carbon – top right of pentose sugar -‐ connected to nitrogenous base o 2’ Carbon – bottom right of pentose sugar -‐ H (OH in RNA) o 3’ Carbon – bottom left of pentose sugar -‐ shares O with the phosphate group o 4’ Carbon – forms straight line with 3’ and 5’ carbon, top left of pentose sugar o 5’ Carbon – connects to O of phosphate group, not part of the pentagon o 1’ à 5’ is clockwise DNA Replication • DNA unzips – forms a replication fork (handout) o As bases join the “unzipped” strands, eventually 4 strands total are involved (i.e. 2 DNA strands) o Nitrogenous bases are floating loosely and join complementary base on strands 6 • DNA synthesis: 1 chromosome à 2 chromosomes o Is SEMICONSERVATIVE – each chromosome contains 1 of the original DNA strands plus one newly synthesized complemen tary strand • Replication fork o Moves forward due to action of DNA polymera se (enzyme) o DNA grows only in the 5’ à 3’ direction § Nucleotides only added to the 3’ end • 2 new strands o Continuous strand: fast and efficient o Discontinuous strand: not as efficient § Has to wait for fork to open because bases can only be added to 3’ end and is opposite of leading strand § This creates discontinuous fragments that are later joined together by DNA ligase § Discontinuous fragments of lagging strand – called Okazaki fragments § DNA polymerase – other major enzyme involved • Joins the nitrogenous bases • Antibiotics inhibit these enzymes in bacteria • DNA gyrase – only in bacteria o Bacterial DNA is supercoiled – gyrase uncoils it o Antibiotics selectively inhibit it • Eukaryotic cell – large chromosomes allow for multiple replication forks • Prokaryotic cell – circular DNA (single circular chromosome) o Only 2 replication forks (vs. multiple in DNA) 7 2/25 Flow of genetic info • DNA (replicates itself) à transcription à RNA (m, t, r) à translation à protein (AA sequence) à start over • AA sequence in protein has direct relationship to nitrogenous bases in DNA RNA synthesis • Type of nucleic acid synthesis • Uses DNA as a template • Transcription – synthesis of a complementary strand of RNA from a DNA template • RNA is synthesized in the 5’ à 3’ direction o Only add nucleotides to the 3’ end (same as DNA) o At any particular point, only ONE strand is transcribed § This strand is called the “sense strand” § Other strand is the “nonsense strand” § Transcription will not occur in same spot on opposite DNA strand • The RNA transcript from DNA is complementary o DNA to RNA o A à U o T à A o C à G o G à C • Transcription generates 3 types of RNA o Messenger RNA (mRNA) 8 § Bears message for protein synthesis o Transfer RNA (tRNA) § Carries AA to site of protein synthesis o Ribosomal RNA (rRNA) § Are components of ribosomes Gene – DNA segment that codes for polypeptides via mRNA, tRNA, and rRNA • Genes occur on chromosomes • Same in prokaryotes and eukaryotes Transcription differences in bacteria • Occurs in cytoplasm alongside translation o Eukaryotic cells: DNA synthesis in nucleus, protein synthesis in cytoplasm • RNA polymerase binds to specific promoter region on DNA – called the Pribnow box – consists of TATAAT sequence of nucleotides • RNA arises from post-‐transcription modification o After RNA is synthesized, certain segments are removed before it becomes functional o Removed segments: introns o Exons: regions coding for RNA that end up in the final RNA product – i.e. regions of DNA that are transcribed o 90% of our DNA is contained in introns • Translation – the process in which the genetic message carried by mRNA directs the synthesis of polypeptide chains with the aid of ribosomes SO: Translation = RNA à protein Transcription = DNA à RNA 9
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