Microbiology Study Guide Test 2 PDF

CH6. Microbial Growth 1. The requirements for growth -Physical requirements: temperature (psychrophiles; mesophiles; thermophiles); pH (acidophiles; alkaliphiles; neutrophiles); osmotic pressure (halophiles). -Chemical requirements: carbon; nitrogen; sufur; phosphorus; trace elements; oxygen (obliga...

CH6. Microbial Growth 1. The requirements for growth -Physical requirements: temperature (psychrophiles; mesophiles; thermophiles); pH (acidophiles; alkaliphiles; neutrophiles); osmotic pressure (halophiles). -Chemical requirements: carbon; nitrogen; sufur; phosphorus; trace elements; oxygen (obligate aerobes; facultative anaerobes; obligate anaerobes (different toxic forms: singlet oxygen; superoxide free radicals; hydrogen peroxide; hydroxyl radical); aerotolerant anaerobes; microaerophiles); organic growth factors. 2. Culture media Culture medium; inoculum; culture; agar; test tubes (slants; deep); culture plates (Petri dishes); colony. -Chemically defined media -Complex media: nutrient broth; nutrient agar. -Selective media: bismuth sulfite agar; mannitol salt agar (MSA); MacConkey agar. -Differential media: blood agar; eosin methylene blue (EMB); mannitol salt agar (MSA); MacConkey agar. -Enriched media 3. Obtaining and preserving pure cultures Colony; streak plate method; sterile inoculating loop; deep-freezing; lyophilization. 4. Growth of bacterial cultures Bacterial division (asexual reproduction: binary fission); generation time; phases of growth (lag phase; exponential phase; stationary phase; death phase); chemostat; measurement of microbial growth by direct methods (plate counts (colony-forming units (CFU)); serial dilution; direct microscopic count (electronic cell counters)); measurement of microbial growth by indirect methods (turbidity (spectrophotometer; absorbance or optical density); metabolic activity; dry weight). CH.7 Control of Microbial Growth 1. The terminology of microbial control Definitions: sterilization (destruction of all forms of microbial life and the most common method is heating (to know other methods); disinfection (process of reducing or inhibiting microbial growthon a nonliving surface); antisepsis (against bacterial infection; process of reducing or inhibiting microbial growth on a living tissue); degerming (consists of a mechanical removal by an alcohol-soaked swab); sanitation (treatment intended to lower microbial counts on eating and drinking utensils to safe public health levels); suffix –cide (means to kill) (cidal agent); suffix –static (means to inhibit) (static agent); sepsis (bacterial contamination); nosocomial infections (hospital-acquired infections). 2. Actions of microbial control agents Alteration of the membrane permeability, damaging proteins and nucleic acids. Factors that influence the effectiveness of antimicrobial treatments (number of microbes, environmental influence, time of exposure, and microbial characteristics). 3. Physical methods of microbial control -Heat moist heat: autoclaves; pasteurization; ultra-high-temperature (UHT) treatments dry heat sterilization: flaming; incineration -Filtration: membrane filters -Low temperatures -High pressure -Desiccation: lyophilization -Osmotic pressure -Radiation Ionizing radiation: gamma rays; X rays Nonionizing radiation: UV light Microwaves 4. Chemical methods of microbial control To know certain chemical agents used to control the microbial growth. 5. Microbial characteristics and microbial control A simplified hierarchy of relative resistance of major microbial groups to biocides: (most resitant)- prions- endospores of bacteria (it is important and difficult to eliminate them; two common producing-endospores genera are Clostridium and Bacillus)- mycobacteria- cysts of protozoans- vegetative protozoans- G- bacteria- fungi and fungal spores- viruses without envelopes- G+ bacteria- viruses with lipid envelopes- (least resistant). CH.20 Antimicrobial Drugs 1. The spectrum of antimicrobial activity Chemotherapy; antimicrobial drugs; selective toxicity; antibiotics; bactericidal; bacteriostatic; broad- spectrum antibiotics. 2. The action of antimicrobial drugs -Inhibition of cell wall synthesis: peptidoglycan (PG) -Inhibition of protein synthesis: 70S in prokaryotes (50S and 30S) and 80S in eukaryotes (60S and 40S). -Injury to the plasma membrane -Inhibition of nucleic acid synthesis -Inhibition of essential metabolites synthesis 3. Commonly used antimicrobial drugs -Inhibition of cell wall synthesis: -β-lactams: penicillin (amoxicillin, ampicillin, methicillin), cephalosporins, monobatams, carbapenems; clavulanic acid: inhibitor of β-lactamases. -polypeptide antibiotics (or glycoproteins) (vancomycin, bacitracin) -antimycobacterial antibiotics -Inhibition of protein synthesis (inhibition of translation): -chloramphenicol -aminoglycosides (gentamycin, kanamycin, neomycin, apramycin, tobramycin, streptomycin) -tetracyclines (doxycyclin) -macrolides (erythromycin) -streptogramins -oxazolidinones -Injury to the plasma membrane: -polymixin B -Inhibitors of nucleic acid synthesis: -rifamycins (rifampin): inhibition of transcription -quinolones (nalidixic acid) and fluoroquinolones (norfloxacin, ciprofloxacin): inhibition of replication -Competitive inhibitors of the synthesis of essential metabolites: -sulfonamides -Antifungal drugs (agents affecting fungal sterols (polyenes (amphotericin B), azoles, and allylamines); agents affecting fungal cell walls; agents inhibiting nucleic acids; other antifungal drugs). -Antiviral drugs (nucleoside and nucleotide analog, antiretrovirals, other enzyme inhibitors, and interferons). -Antiprotozoan (quinine, cloroquine, mefloquine, metronidinazole) and antihelminthic (niclosamide, mebendazole, albendazole) drugs. 4. Tests to guide chemotherapy Disk-diffusion method (or Kirby-Bauer test); zone of inhibition; minimal inhibitory concentration (MIC); minimal bactericidal concentration (MBC). 5. Effectiveness of chemotherapeutic agents Bacteria become resistant to chemotherapeutic agents by four mechanisms: -destruction or inactivation of the drug. -prevention of penetration to the target site within the microbe. -alteration of the drug’s target sites. -rapid efflux (ejection) pumping the drug out preventing its action. Role of plasmids and transposons; horizontal and vertical transmission. CH.8 Microbial Genetics 1. Structure and function of genetic material Definitions: DNA (model of Watson and Crick); RNA; protein; genetics; genome; gene; chromosome; haploid; diploid; genotype; phenotype. We can define a gene in many ways: -chromosomic fragment encoding a protein or RNA molecule -sequence of DNA containing the information for a particular trait -unit of hereditary information -sequence of nucleotides that determines the amino acid sequence of a protein -segment of DNA (or RNA in some viruses) that codes for functional products (BOOK) 2. DNA replication Semiconservative and bidirectional; carry out by DNA polymerase; process taking place during the S phase in the cell cycle; differences prokaryotes vs. eukaryotes. 3. Gene Expression (DNA RNA protein) Transcription (carry out by RNA polymerase) and translation (carry our by ribosomes); genetic code (correspondence between codons and amino acids); differences prokaryotes vs. eukaryotes. 4. Regulation of bacterial gene expression Understand why is gene expression a very accurate process and what constitutive genes are. 5. Mutation: change in the genetic material Mutations modifications of the DNA sequence: point mutations (base substitution, deletions and additions); chemical modifications; DNA breaks. Mutagen (any agent that can alter the DNA sequence) vs. carcinogen (agents that can cause cancer in animals) Ames test (to test which substances can be mutagens) Mutation rate 6. Genetic transfer and recombination Genetic recombination; genetic variation; vertical transfer; horizontal transfer; recipient cell; transformation; competence; conjugation; transduction; plasmids; transposons. All these mechanisms (mutation, transformation, conjugation, transduction, recombination, and transposition) provide gene diversity that finally leads to evolutionary improvements in those individuals that undergo these processes, allowing a better adaptation to environment. CH.9 Biotechnology and Recombinant DNA 1. Introduction to Biotechnology Definitions: biotechnology; recombinant DNA (rDNA) technology 2. Tools of Biotechnology Site-directed mutagenesis; restriction enzymes; vectors (plasmids and phages); polymerase chain reaction (PCR); Southern blotting. 3. Applications of rDNA Pharmaceuticals; vaccines; gene therapy; agricultural applications; farm animals. QUESTIONS 1. Clostridium and Streptococcus are both catalase-negative. Streptococcus grows by fermentation. Why is Clostridium killed by oxygen, whereas Streptococcus is not? 2. Explain the different phases of bacterial growth. Draw a diagram indicating the different phases. 3. Indicate at least three factors that influence the effectiveness of microbial treatments. 4. Indicate at least three chemical agents affecting the microbial growth. 5. The bacterial enzyme streptokinase is used to digest fibrin (blood clots) in patients with atherosclerosis. Why doesn’t injection of streptokinase cause a streptococcal infection? 6. By which mechanisms do bacteria become resistant to chemotherapeutic agents? 7. Indicate at least three differences in the process of gene expression between prokaryotes and eukaryotes. 8. Indicate three mechanisms allowing bacteria to provide gene diversity and briefly explain them. 9. Which are good targets on bacteria for chemotherapeutic agents? 10. Classify the different groups of bacteria according their sensitivity to the oxygen. 11. Categorize two methods as either direct or indirect method to measure bacterial growth. 12. Why can high concentrations of salt or sugar be used to preserve food? 13. Describe the principle of the Ames test for identifying chemical carcinogens. 14. How can antibiotic treatments cause secondary infections? 15. Explain how frequent and inappropriate use of antibiotics can cause bacteria or other microorganisms to change so antibiotics don't work against them. 16. What is the purpose of the WAAW? And why is it important? DEFINITIONS 1. Gene, chromosome, genome 2. Genotype, phenotype, 3. Genetics 4. DNA replication 5. Gene expression (transcription, translation) 6. Horizontal gene transfer 7. Transformation, conjugation, transduction 8. Sterilization, disinfection (disinfectant), asepsis (antiseptic), sepsis, suffixes - cidal and -static 9. Pasteurization 10. Autoclave, chemostat 11. Antibiotic, MIC, MBC 12. Chemotherapeutic agent 13. Culture medium (selective medium, differential medium, synthetic medium, complex medium) 14. Inoculation, incubation, colony, CFU 15. Mutation, mutagen, carcinogen 16. Biotechnology 17. Mesophile, thermophile, psychrophile 18. Alkaliphile, acidophile, neutrophile 19. Halophile 20. Quorum sensing