Exam 2
Which microbes grow at an optimum temperature of 15 degrees Celsius?
Psychrophiles
Which microbes grow in temperatures between 37 to 65 degrees Celsius?
Thermophiles
Which microbes grow in at an optimum temperature range of 20 to 37 degrees Celsius?
Mesophiles
What is the maximum temperature for growth of a thermophile?
65 degrees Celsius
Which microbe grows in a temperature range of 20 to 45 degrees Celsius?
Mesophiles
Which microbe grows in a temperature range of 0 to 20 degrees Celsius?
Psychrophiles
At what pH does most bacteria grow?
6.5 to 7.5
What is the optimum pH range of acidophiles?
0 to 5.5
What is the optimum pH range of basophiles?
8.5 to 11.5
How is it that organisms can change the culture media - making it generally more acidic and can be toxic?
Their own waste
Which osmotic pressure has no net movement?
Isotonic
Which osmotic pressure causes water to move into the cell and possibly cause the cell to burst?
Hypotonic
Which osmotic pressure causes water to move out of the cell causing the cell to shrink (plasmolysis)?
Hypertonic
What type of microbe grows in high salt conditions?
Halophiles
What are the macronutrients?
C-H-O-P-N - carbon, hydrogen, oxygen, phosphate, nitrogen
What are trace elements?
Inorganic elements required in small amounts - Fe, Mn, Mg, vitamins (cofactors)
Which element is the backbone nutrient?
Carbon
What is essential for chemoheterotrophs?
organic carbon sources
What is essential for autotrophs and give an example of an autotroph?
CO2; plants
Which type of microbes cannot live without oxygen?
Obligate aerobes
Which type of microbes can live with or without oxygen?
Facultative anaerobes
Which type of microbes cannot live with oxygen?
Obligate anaerobes
Which type of microbes tolerate oxygen?
Aerotolerant anaerobes
Which type of microbes need less oxygen and more carbon dioxide?
Microaerophiles
Complete the equation and name the enzyme to reduce toxicity by removing peroxide (H2O2).
2 H2O2
> 2 H2O +O2; catalase
Complete the equation and name the enzyme to reduce toxicity by removing peroxide.
2 H2O2
> 2 H2O + O2; peroxidase
Complete the equation and name the enzyme to reduce toxicity by removing superoxide free radicals.
O2- + 2H+
> H2O2 + O2; superoxide dismutase
What makes and gets rid of hydrogen peroxide (H2O2)?
Peroxisome
Which medium is made of known amounts of chemicals?
synthetic (defined)
Which medium is made of some ingredients of unknown composition or amounts?
complex
What are some examples of complex mediums?
nutrient broth or tryptic soy broth
What is an example of a synthetic medium?
E. coli minimal salts medium
What is agar?
complex polysaccharide
What is agar used for?
As a solidifying agent for culture media in Petri plates, slants and deeps
What makes agar and ideal medium for microbes?
It is generally not metabolized by microbes
At what temperature does agar liquefy?
100 degrees Celsius
At what temperature does agar solidify?
40 degrees Celsius
Which medium encourages the growth of certain organisms while discouraging the growth of others?
Selective medium
Which medium distinguishes between different groups of bacteria?
Differential medium
Which type of medium contains constituents which cause an observable change (color or pH change)?
Differential medium
What is an example of a selective medium?
crystal violet or basic fuschin dyes selective for Gram-
Which type of medium provides basic needs?
General medium
What is an example of a differential medium?
MacConkey contains lactose and neutral red, lactose fermenters appear pink; blood agar - hemolysis
What is the time required for cells to divide (and thus double the population) and can be as short as 20 minutes or longer than a day?
Generation time
What are the four phases of the growth curve?
Lag
Log
Stationery
Death
Which phase is best for adding anything?
log phase
Which phase is when the growth and death of cells is about even?
stationary phase
Which phase is when the death of the cells exceeds the growth of the cells?
death phase
Which phase is where the bacteria is adjusting to the environment?
lag phase
What is the difference in indirect and direct methods of counting bacteria?
In direct, only live bacteria are measured; in indirect living and dead bacteria are counted
What is a way to measure metabolic activity?
use glucose
Which method of measurement requires the bacteria to be dried in filter paper and weighed?
dry weight
Which method of method of counting bacteria requires the use of a light source, which is measured by whether the light reaches the detector when projected through the bacteria in a tube?
turbidity
Completely destroys all forms of microbial life
sterilization
Limited heat treatment, destroys pathogens but not all bacteria (killing C. botulinum endospores)
commercial sterilization
Destroys vegetative cells on a surface by reducing the number of viable organisms in the material; removal of pathogens
disinfection
Chemical treatment used to disinfect inanimate objects
disinfectant
Treatment of living skin or tissue to kill microorganisms
antisepsis
Physical removal of microbes (alcohol swab, soap) as in cleaning the skin prior to injections
degerming
Microbial contamination
sepsis
The absence of significant contamination
asepsis
What prevents microbial contamination of wounds
aseptic surgery techniques
Systematic cleansing of inanimate objects to reduce the microbial count to a safe level (for public health, used in restrooms, kitchens)
sanitize
Kill all bacteria
bactericidal
Halt the growth of bacteria for as long as the inhibitory substance is present
bacteriostatic
what determines the effectiveness of antimicrobial treatments?
Number of microbes
environment (organic matter, temperature, biofilms)
time of exposure
microbial characteristics
What denatures (unwinds) proteins?
heat
What is the time at a given temperature in which all the microorganisms in a liquid culture will be killed?
thermal death time (TDT)
What is the lowest temperature at which all microorganisms in a liquid suspension are killed in 10 minutes?
thermal death point (TDP)
Steam, pressure and heat - steam alone can reach 100 degrees Celsius but under pressure (15 p.s.i.) can reach 121 degrees Celcius
autoclave
Uses temperature below boiling point to kill pathogens and reduces total microorganism count (doesn't kill all, some harmless microorganisms survive), does not alter food taste
Pasteurization
63 degrees Celsius for 30 minutes
classical Pasteurization
72 degrees Celsius for 15 seconds
high temperature short-time
140 degrees for less than one second
ultra-high temperature
High temperature short-time Pasteurization
flash Pasteurization
Most lethal at wavelength of 260nm; absorbed by DNA, leads to formation of thymine dimers; several methods of repair; used to sterilize air, surfaces (but cannot expose skin); nonionizing radiation
ultraviolet radiation
Xrays, gamma rays, electron beams; penetrates deep into objects; can be used to steriize plastic objects, even foods (microwaves kill by heat; not especially antimicrobial)
ionizing radiation
used with heat-labile samples; physically remove bacteria from liquid or air; .45 or .2 micron pore size
filtration
Where does replication occur?
replication fork
In most bacteria, there are two forks which are moving in opposite directions what is this called?
bidirectional replication
occurs in a specific direction on the DNA (5' - 3')
synthesis
What are the two strands called?
Leading - occurring in the 5'-3' direction
Lagging - cannot synthesize continuously due to direction of DNA
The short pieces on the lagging strand
Okazaki fragments
Which strand requires RNA primers to begin each segment?
lagging strand
Which stand has gaps that are closed by DNA ligase
lagging strand
Each daughter molecule contains one original strand and one newly synthesized strand is called...
semiconservative
What is the sequence of translation?
U C A G down, U C A G across and U C A G going down 4 times or 1st position, 2nd position and 3rd position
Which is starting codon?
AUG
What are the stopping codons?
UAA UGA UAG
Triplets of bases in mRNA form
codons
specifies which amino acid corresponds to each codon
genetic code
is transcribed to make RNA (mRNA, tRNA, rRNA)
DNA
Begins when RNA polymerase binds to the promoter sequence
transcription
Proceeds in the 5' > 3' direction
transcription
Stops when it reaches the terminator sequence
transcrition
Change in the genetic material
mutation
May be neutral, beneficial or harmful
mutation
agent that causes mutation
mutagent
occur in the absence of a mutagent
spontaneous mutation
Identifies potential human carcinogens by measuring mutagenesis in bacteria
Ames Test
A change in the base sequence of DNA - silent if it doesn't cause a change in amino acids (often in the third position)
mutation
Single base substitution
point mutation
What are two types of point mutation?
missense and nonsense
change in one base and results in change in amino acid
missense
no length in code therefore no gene, results in a nonsense codon
nonsense
insertion or deletion of one or more nucleotide pairs
frameshift mutation
Causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone
ionizing radiation (x rays, gamma rays)
Causes thymine dimers
UV radiation
separates thymine dimers
light repair
Any bacteria picks up a "naked" DNA and it attaches to genome of new bacteria
trasnformation (recombination)
Two bacteria conjugate together
conjugation
DNA from one bacteria to another bacteria by virus
transduction
Segments of DNA that can move from one region of DNA to another
transposons "jumping gene"