Micro Chapters 6, 7, 8
6 Which of the following is NOT a characteristic of biofilms? antibiotic resistance; hydrogel; iron deficiency; quorum sensing
6 The Spectrophotometer can be used to measure ________
6 An organism that uses O2 but can grow without it:
6 Organisms that require high heat for growth are called:
6 The culture media designed to suppress unwanted mirobes while encouraging desired microbes?
7 The removal or destruction of all forms of microbial life is called?
7 Which of these disinfectants does not act by disrupting the plasma membrane? Phenolics; phenoll Quat ammonium compounds; halogens; biguanides
7 Which disenfectant would be effective against all 3 bacteria? S. aureaus; E. Coli; Pseudomonas aeruginosa
7 Which is not used to preserve food? Nisin; sodium nitrite; Potassium sorbate; Biguanides
7 In what situation is filtration the only practical way to eliminate undesireable microbes?
When heat or other methods cannot be used (ex, liquids)
8 E. coli is found naturally in the large intestines. Normally this is no problem, but E.coli 0157:H7 produces shiga toxin. How did E.coli get this gene from Shigella and what is this process called?
From bacteriophage, process is called transduction
8 In DNA replication, the newly added nucleotide is joined to the grouwing strand by
8 Bacteria can acquire antibiotic resistance through all of the following except...? Mutation, integration of transposons; conjugation; snRNPs; transformation
8 A group of 3 nucleotides is called?
8 Which is not a method of horizontal gene transfer? binary fission; conjucation; integration of transposons; transduction; transformation
6 Name the 3 primary classifications of microorganisms based on preferred range of temperature and give the range for each. Which classification is most likely to be pathenogenic to humans?
Psychorophiles -10 to 20
Mesophiles 10 to 50 ****most pathenogenic****
Thermopiles 40 to 70
6 Halophile, extreme halophile
Organsims highly adapted to high salt concentrations. If obligate, they require nearly 30% salt.
6 Hyperthermophiles (aka extreme thermophiles)
Members of Archaea have optimum growth temp. of 80 deg C or higher. Sulfur is usually important in their metabolic activity
acid tolerant. Ex: chemoautotrophic bacteria, found in drainage water from coal mines. Oxidizes sulfur to form sulfuric acid. Survives at pH 1
6 pH range at which most bacteria grow best
6 Optimum pH of molds and yeasts
6 How do salt and sugar preserve foods?
By creating a hypertonic environment unfriendly to microbes
What you innoculate media with
6 (t/f) All bacteria reproduce by binary fission
False. Some bud
6 What type of media grows only gram + and has a yellow halo.
Selective and differential
6 An enrichment culture is used to encourage growth of_____?
bacteria present in small numbers (used ofr soil or fecal samples )
6 Name they 6 Oxygen growth-classified bacteria, how they grow and what they look like in a deep.
Obligate aerobes-Only aerobic growth, O2 required
*Growth at top of tube
Facultative Anaerobes-Both aerobic and anaerobic
growth. Greater in presence of O2
*Growth is best where O2 is present, but
occurs throughout tube
Obligate Anaerobes-Only anaerobic/cease in
presence of O2
*Growth only at bottom of tube
Aerotolerant Anaerobes-only anaerobic growth; but
contues in presence of O2
*Growth occurs evenly through culture
Microaerophiles-Only aerobic growth; O2 required in
*smack dab in the middle of the tube
6 Name an example of an obligate anearobe
The genus Clostridium (contains tetanus & botulism)
6 What is a reducing media used for?
Used for growth of obligate anaerobes
6 What are organic growth factors?
Vitamins, amino acids, purines/pyrimidines (the bases ATGC). They are essential organic compounds an organism is unable to synthesize.
6 Type of media that has beef part extract, agar, peptone
Complex Media (growth of chemoautotrophs organisms)
Uses an inorganic chemical as an energy source and CO2 as a carbon source
Uses organic molecules as a source of carbon and energy
6 Enzyme that breaks H2O2 into water & O2
6 Enzyme that breaks H2O2 into water only
6 What is a singlet and why is it important?
Normal molecular O2 that has been boosted into a higher-energy state & is extremely reactive
6 What is a Superoxide radical and why is it important?
Highly instable anion, formed in small amounts during normal respiration, is so toxic to cellular components that ALL organisms attempting to grow in atmospheric O2 must produce enzyme superoxide dismutase (SOD)
6 Superoxide dismutase (SOD)
enzyme produced by ALL organisms attempting to grow in atmospheric O2. It helps to neutralize superoxide radicals
6 What is a buffer and what does it do?
Chemical buffers are included in growth medium to neutralize the acids and maintain proper pH. Expeptones, aa's phosphate salts
6 Name 3 ways to store microbes
Refrigeration-good for short term storage
Deepfreezing- pure culture into a suspending liquid and quick-frozen under -50degC. Can usually be thawed & cultured even several yrs later
Lyphilizaiton-freeze drying, quick frozen then H2O removed by high vacuum. Organisms can be revived at any time by hydration
A small piece of DNA that can move from 1 DNA region to another
8 Difference between generalized transduction and Specialized transduction
Bacteriophages that transport DNA to other cells. Generalized in the lityc cycle, Specialed in the lysogenic cyle.
Self-replicating circular molecules of DNA, not essential for survival
encodes for anibiotic resistance
encodes for sex pili & transfer of the plasmid
A cancer causing agent
An agent that causes mutations. Can be chemical or radiation.
Auxotroph-mutant microorganism w/a nutrional requirement that's absent in the parent
Autotroph-An org that uses CO2 as it's principle carbon source.
8 Name the different types of mutation
Point Mutation (base substitution mutation: 1 base changed
Missense Mutation: results in change in amino acid
Nonsense Mutation: results in a stop codon where it shouldnt be
Frameshift: Insertion or deltion of 1 or more nucleotide pairs. shifts 1 entire side of DNA
Made up of promotor, opperator and structural gene
Gene always off until induced
Gene always on until repressed
8 Is the lac operon inducible or repressible?
Inducible. When no lactose it is off. When there is lactose alalactose is present * binds to repressor & innactivates it so the protein to break down lactose is made
8 A repressor binds to?
Free floating, has anticodon that binds to mRNA codon. Grabs proteins to translate the mRNA into a polypeptide chain.
8 DNA is copied by what and in which direction?
By DNA polymerase 5'->3' direction
Removes entrons. mRNA has exons only. Only humans have entrons
8 Constitutive genes
These are expressed at a fixed rate--always "on"
Repair mechanism, uses visible light to separate the thymine dimer caused by UV damage
8 Nucleotide excision repair
enzymes cut out the incorrect base & fills in gap w/new DNA
High heat w/high temp. Steam must touch surface. Sterylization technique
7 What is ethylene oxide?
a gaseous sterilant, no high temp needed
7 Name Physical ways to reduce/remove bacteria
Heat-moist heat kills by coagulating proteins cause by breakage of H bond; pasteurization; dry heat sterilization kills by oxidation effects
Filtration-HEPA filter, membrane filter
Low Temp-can inhibit or kill with freeze/thaw
High pressure-if applied to liquid suspension can alter protein s of carbs
Dessiccation-Viruses, TB, endospores resistant
Osmotic pressure-uses high salt/sugar. Molds are resistant
Radiation-kills. Ionizing-gamma rays/Xrays, shorter wavelength. Radicals react w/organic cell components. Non ionizing, causes bonds to form betw adjacent purimidine bases (usually T)
7 Name chemical microbial controls
Phenol/phenolics (lysol) injurs lipid-containing plasma membranes; Bisphenols, used for surgical & hostpital control procedures. Gram+ staph & strep very susceptible. Biguanides affect all cell membranes, especially gram+. Halogens (iodine) impairs protein synthesis
Genes of the organism
Expression of the genes
DNA exchange through pilli
The DNA for mating bridge. HFR=the plasmid that encorporates into the genomve
8 Important Enzymes in DNA replication, expression and repair
-DNA Gyrase: relaxes supercoiling ahead of replicatoin fork
-DNA Ligase:makes covalent bonds to join DNA strands. Okazaki fragments in excision repair
-DNA Polymerase: synthesized DNA, proofreads & repairs