117 Cards in this Set
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How do microbes grow?
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By increased number of cells (not by size)
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What are the 3 growth patterns of microbes?
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1. Discreet colony: Cells visible on surface of solid media
2. Dispersed cells: Single cells in liquid media
3. Complex biofilm: community of one or more species of bacteria
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What are the four steps of Binary Fission?
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Step 1: Cell Replicates it's chromosome (DNA molecule), then attatches to cytoplasmic membrane (In prokaryotes) to microtubules (in eukaryotes)
Step 2: Cell stretches and chromosomes separate. (Eukaryotes segregate by mitosis!)
Step 3: The cell forms a new cytoplasmic membra…
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Microbes uses what type of rate to multiply?
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Doubling
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Which growth pattern allows for hundreds to millions in hours through binary fission? arithmetic or logarithmic
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Logarithmic- Exponential Growth (2^n) - N= # of generations
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What is clinical sampling and what must be considered with this?
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Taking human specimens and testing it
Considerations:
-Proper specimen
-Technique
-Timely delivery
-Proper culture methods
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True or false: Have all microorganisms been grown in culture media?
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False- Majority of microorganisms HAVE NEVER BEEN GROWN in ANY culture medium
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What is selective media, give an example.
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A selective media contains substances that either favor the growth of a particular microorganism or inhibit the growth of unwanted ones.
Example: Eosin, methylene blue, and crystal violet inhibit growth of gram positive bacteria
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What is differential Media, give an example
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Differential media helps differntiate betweem different kinds of bacteria by being formulated to show visible changes in the medium or differences in appearence.
Example: Blood Agar plate inocculated with different pathogens to differentiate the amount of red blood cells used by …
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What are the phases of microbial growth? (4)
And which phase will be MOST sensitive to antimicrobials?
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-Lag Phase: Cells adjust to new enviroment, no growth
-Log Phase: Cells enter rapid chromosome replication, growth, and reproduction *** MOST SUSCEPTIBLE TO ANTIMICROBIALS!
-Stationary (Number of dying cells = number of cells being produced.)
-Death (exponential decline…
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What is microbal growth classified by?
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Nutritional and Physical:
Nutritional: Where it obtains it's energy
Physical: Temperature, pH, osmotic pressue, other microbes present
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Where does a microbe obtain their energy (two types)?
Where do microbes aquire their carbon from (two main sources)?
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Microbes obtain energy as:
-Phototrophs (Aquire energy from sunlight)
-Chemotrophs (Aquires energy from organic/inorganic molecules)
Microbes obtain carbon from:
1. Autotrophs: "Self-feeders" Make their own food (fixing CO2 via Calcin Bensen Cycle)
2. Heterotrophs: "D…
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What is a phototroph?
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Energy from sunlight
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What is a chemotroph?
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Break chemical bonds to make ATP
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What is an autotroph?
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using CO2 by the Calvin benson to make glucose
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What is a heterotroph?
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uses carbon remnants from other substances
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Toxic forms of oxygen tend to be what?
What are not toxic forms of oxygen?
What is toxic oxygen a by-product of?
Why?
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-Oxidizing agents are toxic
-O2 or oxygen covalently bound to another molecule is not toxic
-Oxidizing agents are toxic because they intiate chains of oxidation that causes irreperable damage to a cells proteins and lipids
-They are a by-product of aerobic respiration
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4 toxic forms of oxygen
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-Singlet oxygen: Oxygen where the electrons are boosted to a higher energy state. (Generated in photsynthesis and aerobic metabolism)
-Superoxide radicals: Formed during incomplete reduction of oxygen. Removed by: superoxide dimutase (SOD) enzyme .
-Peroxide anion: Formed du…
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Toxic forms are byproducts of what type of respiration?
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aerobic
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Name the Oxygen Dependency Classifications (5)
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1. Obligate aerobe
2. Facultative anaerobe
3. Aerotolerant anaerobe
4. Strict Anaerobe
5. Microanaerophile
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What is an aerobe?
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Uses oxygen for metabolism (detoxifies toxic forms of oxygen)
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What is an anaerobe?
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Organism that does not require oxygen to survive (fermentation)
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What is a facultative anaerobe?
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utilizes oxygen but can also grow in its absence
(Can use: fermentation, anaerobic respiration and aerobic respiration)
ability to detoxify toxic forms of oxygen
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Insufficient nitrogen can lead to what? Why?
Where is nitrogen aquired from?
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Anabolism to stop because nitrogen is needed for protein and nucleotide synthesis
Nitrogen is aquired from organic and inorganic sources, and recycling from uneeded nucleotides
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Toxic oxygen and 4 characteristics:
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-created via metabolism
-very reactive
-chains of oxidation reactions
-byproduct of aerobic respiration
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True/False: Can a catalase be used as a defense mechanism?
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True
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What is Nitrogen Fixation?
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Process of converting nitrogen gas into nitrogen compounds that plants can absorb and use (ie into ammonia NH2--> NH3)
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Name 4 "other" chemical requirements for microbial growth?
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-Phosphorus
-Sulfur
-Trace elements
-Growth Factors
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What type of energy plays a crucial role in structure and function of a cell's proteins and membranes?
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Thermal Energy.
Most microbes have maximal growth at a specific temperature
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Psychrophile
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-5 to +20 C
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Mesophile
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+15 to +45 C
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Thermophile
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+40 to +80 C
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Extreme Thermophile
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+80 to +121 C
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Neutophiles
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6.5 to 7.5 pH
*This is most bacteria and protozoa
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Acidophiles
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The bacteria and many fungi which grow best in acidic environments
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Alkalinophiles
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Live in basic enviroments- water and soils up to 11.5 pH
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What is an obligate halophile?
What is a facultative halophile?
What is a barophile?
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Obligate Halophile: Can grow in up to 30% salt
Facultative Halophile: Can tolerate high salt concentrations
Barophiles: Organisms that live under extreme pressure
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Define biofilm
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A microbial community attatched to a surface. A biofilm is 1000x more resistent to antibiotics.
*** 60-80 % of all bacteria infections are caused by bacteria in the biofilm form
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Define sessile
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microbes attached to a surface
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Define planktonic
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microbes that are free living (not attatched to a surface)
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True/False:
Pure cultures are present in nature
Who invented methods to isolate microorganisms in pure cultures?
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False. They are absent in nature.
-Robert Koch
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What are the 5 characteristics of biofilms?
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1. Attach to surface
2. Complex social structure
3. Resistant to antibiotics
4. Biofilm is a filter
5. Low metabolism of cells within the biofilm
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Biofilm associated with pacemakers
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S. aureus
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Biofilm associated with catheters
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E. coli
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Biofilm associated with contact lenses
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gram + bacteria
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What % of all bacterial infections are caused by bacteria in the biofilm form?
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60-80%
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True/False:
biofilms are homogenous
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False. Hetergenous
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What is the habitat of a biofilm dependent on? (3 things)
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Oxygen
pH
Growth Factors
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What are the 5 steps of biofilm formation?
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1. Initial interaction (contact/release until adhesion)
2. Stable adhesion (irreversable attatchment)
3. Microcolony formation (attached, more cells, loss of genes/expression)
4. Exopolysaccharide Synthesis (capsule)
5. Mature biofilm
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How is gene regulation controlled in biofilm development?
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By quorum sensing
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What is quorum sensing?
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This is how biofilms often form.
Quorum sensing uses cell to cell signaling that allows an individual bacterium to monitor the density of cells nearby, receptors bind signaling moleucules and this makes a biofilm.
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What is an autoinducer?
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An autoinducer will allow the regulation of specific genes by monitoring the cell density of the population of bacteria
Example: Switching between flagella gene and the gene for capsule for the development of a biofilm
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What is the unique signaling molecule of bacterial species?
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Homoserine lactone
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Which type of density population in biofilms is aggressive and will produce biofilms and toxins?
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High population density
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What prevents and blocks quorum sensing in biofilm production?
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Furanones from red algae
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Define genome, how is it organized?
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Entire genetic complement of an organism
*** Includes nucleotides sequences and genes.
Organized into genes that carry out instructions for synthesis of both RNA and proteins
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Define DNA
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Deoxyribonucleic acid
Master Copy/ Genetic material
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Define genotype
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complete set of genes in the genome
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Define phenotype
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Physical features and functional traits
that are a result of gene expression
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Define Replication
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Exact duplication of entire genome for purposes of reproduction (cell division).
Simple discription: A cell seperates the two original strands and uses each one as a template for synthesis of a new complimentary strand
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Define Transcription
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Copying of DNA information into RNA nucleotide sequences
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Define Translation
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Ribosomes synthesize polypeptides (proteins) by using the genetic information of nucleotide sequences
*interpretation of mRNA nucleotide
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What are the 3 parts of the nucleotide structure?
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1. Phosphate group (neg. charge)
2. Pentose sugar
3. One base: -Adenine
-Guanine
-Cytosine
-Thymine
-Uracil
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How do you differentiate between DNA and RNA?
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DNA= H (deoxy)
RNA= OH
***Found at the 2 prime
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Name the 5 base pairs? Indicate RNA/DNA.
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T-A (DNA)
U-A (RNA)
C-G (DNA and RNA)
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How are monomers linked in nucleotides?
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5' to 3'
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What are two key features of a double helix?
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Complementary and antiparallel
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Where is the genome structure of prokaryotes?
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In Prokaryotes the Genome is found in:
-Chromosomes: A circular molecule of DNA that folds upon itself to form a messy clot within the cytoplasm called a nucleoid. Need protein and RNA for replication and transcription
-Plasmids: Small Circular molecules of DNA that replicate in…
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Name this structure: main portion of DNA, one per cell, circular molecule, nucleoid, associated with proteins
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chromosomes
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Name this structure: small, circular, replicate independently, many types, survival advantages...
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plasmids
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Where is the genome of eukaryotes?
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Nuclear chromosomes and extranuclear DNA
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Name this structure: more than one per cell, linear
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nuclear chromosome
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name this structure: DNA is circular, resembles prokaryotes
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Extranuclear DNA
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Define DNA replication
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An anabolic process that gets energy from phosphates creating 2 identical DNA models by using complementary base pairing
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Define semiconservative
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New helicies pair with daughter strand
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What are the 6 steps of DNA replication?
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1. remove DNA
2. Unwind and seperate strands
3. Synthesize RNA primers (primase)
4. Extend primers with DNA polymerase III (synthesis of DNA in the 3' direction)
5. Degrade RNA primers and fill in the gaps with DNA POLYMERASE 1
6. rewind new hybrid strands
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What does primase do?
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Binds to DNA and creates short sequence of RNA that is complementary to DNA
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What does DNA polymerase III do?
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Binds to 3' and extends and reads. Places appropriate nucleotides dictated by the DNA
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What does polymerase I do?
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removes the initial RNA sequence and replaces it with DNA
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True/False: Bacteria cells do not have to finish replication to start a new replication.
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True
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Bacteria use what to relieve strain on chromosomes during replication?
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topoisomerases
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Where does transcription take place in prokaryotes?
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nucleoid
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Where does transcription take place in eukaryotes?
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nucleus, mitochondria, choloplasts
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What is messenger RNA?
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contains sequence message to build protein; translated for protein synthesis
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What is ribosomal RNA?
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Combines with proteins to form ribosomes --> platform for synthesizing new proteins
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What is transfer RNA?
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sequences used to transport amino acids to the ribosomes
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Transcription uses what type of start and stop signal?
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Promoter and terminator
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What is the binding site on DNA for RNA polymerase?
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at the promoter
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What aids RNA polymerase to locate a promoter?
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Sigma Factor
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Define Transcription Initiation
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RNA polymerase recognizes and binds to promoter with aid of sigma factor
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Define Transcription Elongation
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Sigma is released, and the RNA polymerase keeps moving down, occurs in complementary nature of DNA
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Where and what does translation mRNA?
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By the ribosomes in the cytosol
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What is a codon?
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cluster of 3 nucelotides coding for a specific amino acid
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True/False: tRNA does have a secondary structure
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True
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Define acceptor stem
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tRNA linked to amino acid by aminoacyl-tRNA synthetase
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Define anticodon
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nucleotide triplet complementary to the mRNA codon for a given tRNA's amino acid
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What makes up ribosomes?
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rRNA + protein
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What carries the anti codon to the start codon?
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tRNA
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Define translation initiation
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Ribosomal subunits assemble on mRNA transcript and recruit initiator tRNA molecule
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Define translation elongation
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Ribosome recruits amino acid bound tRNAs according to mRNA template
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Translation elongation does not create a peptide bond. True/False
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False
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Define translation termination
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Stop codons prompt release of of polypeptide from last tRNA/ Ribosome dissociates
mRNA= degraded or reused
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True/False: Transcription must be done in order to do translation
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False
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What controls genetic processes and are expressed at all times? Where are they kept?
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House keeping genes and in the chromosome
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Where do cells stop protein synthesis when they want to shut down?
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Transcription of corresponding protein
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Where are genes with similar functions grouped in prokaryotes?
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Operons
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What carries info of several genes in prokaryotic gene organization?
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Polycistronic mRNA
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Define a prokaryotic operon
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cluster of genes on a chromosome whose expression is regulated by common promoter and operator (area on DNA) elements
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Define inducible operon
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must be activated by inducers
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Define repressible operon
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transcribed continually until deactivated by repressors
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True/False: The regulatory gene is always off
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False. It is on
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What is a mutation?
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change in nucleotide base sequence of an organism's genome
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What are the 2 types of mutations?
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Point and Frameshift
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Define the 4 effects of mutation
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1. Silent- no change in AA sequence
2. Missense- slightly different AA sequence
3. Nonsense- creates stop codon and halts protein synthesis
4. Frameshift- major difference in AA sequence
*all can be detrimental
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What are radiation mutagens?
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Potent
High energy= breaks in chromosomes
Low energy= induce crosslinks
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What are chemical mutagens?
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-disrupt DNA and RNA replication
-result in base pair substitution mutations
-missense mutations
-frameshift mutagen- result in nonsense mutation
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Explain bacterial DNA repair mechanisms?
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Direct/Excision: precisely find mutated base(s) and fix
Post/SOS/Error: Last resort, remove to save it
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MIC 205: Final Exam