Lecture 11 [Exam 3] Flashcards
Microbes have both __________ and ___________ growth rate.
fastest and slowest
True or False: Some hot springs bacteria can double as fast as 10 minutes while some deep sea sediment bacteria can double in as long as 100 years.
True
These differences are determined by ____________ and ____________.
Nutrition and Niche-specific physical parameters, ex. temperature and pH
What are normal growth conditions?
- Sea level
- Temperature 20°C–40°C
- A near-neutral pH
- 0.9% salt
- ample nutrients
Any habitat outside this window is called “extreme,” and organisms
inhabiting them are called ________________.
extremophiles
What are extremophiles?
Microbes (bacteria, archaea, and a few eukaryotes) that are able
to grow in conditions very different from those for humans.
What are polyextremophiles?
Microbes that can survive many extreme environments.
True or False: The bacteria cell temperature matches its immediate environment.
True
True or False: Bacteria have an optimal temperature in which they grow the quickest.
True
Psychrophiles:
~0°C–20°C
Mesophiles:
~15°C–45°C
Thermophiles:
~40°C–80°C
Hyperthermophiles:
~65°C–121°C
True or False: The thermophile, Thermus aquaticus was the first source of a high temperature DNA polymerase used for PCR
True
Who discovered Thermus aquaticus at Yellowstone National Park?
Thomas Brock
What is sterilization?
process of killing of all living cells, spores, and viruses on an object
What is disinfection?
killing or removal of PATHOGENS from inanimate surfaces (does not always result in sterilization)
What is antisepsis?
killing or removal of pathogens from the surface of living tissues
(ex. Skin)
What is sanitation?
-reducing the microbial population to safe levels which includes cleaning and disinfection
What does bacteriostatic mean?
Having the ability to inhibit the growth of bacterial cells
What does bactericidal mean?
Having the ability to kill bacterial cells
What does germicidal mean?
Chemical substances that kill pathogens (and many nonpathogens). Does not kill some spores.
What are the 5 physical means of killing bacteria?
- High temperature and pressure
- Pasteurization
- Cold
- Filtration
- Radiation
What temperature and pressure is used in a steam autoclave?
121°C (250°F) at 15 psi for 20 min
What is pasteurization?
The heating of food at a temp. and time
combination that will kill Coxiella burnetii
LTLT (low temperature/long time):
63°C for 30 minutes
HTST (high temperature/short time)
72°C for 15 seconds
UHT (ultra-high temperature):
138°C for 1 to 2 seconds
20
Low temp. have 2 basic purposes in microbiology to _________ and ___________.
To slow growth and preserve strains
True or False: Gram-positive bacillus Listeria monocytogenes grows well in the cold and can cause disease when ingested.
True
What happens in cryopreservation?
Bacteria are suspended in a glycerol solution and stored at -80°C which suspends growth and preserves the strains from dying.
What happens during Lyophilization/freeze-drying?
Lyophilized bacteria (powder form) are preserved at 4°C
What happens during filtration?
Micropore filters with pore sizes of
0.2 μm remove microbial cells (not
viruses) from liquid solutions.
What is the advantage of filtration?
It does not use heat (heat can cause damage to materials)
What do Laminar flow biological safety cabinets do?
force air through high efficiency particulate air (HEPA) filters
that removes >99.9% of airborne particulate material 0.3 μm in size or larger
True or False: Newer technologies embed antimicrobial agents or enzymes into the fibers ofthe HEPA filter.
True
What types of materials have the FDA approved for irradiation?
beef, pork, fruits, vegetables, eggs, spices, seeds
What is ultraviolet used for?
Since it has poor penetrating power, it is mainly used on surface sterilization
What type of radiation has high penetrating power and can be use to irradiate foods and other heat-sensitive items?
Gamma rays, electron beams, and X-rays
How does radiation kill bacteria?
forms very short-lived reactive chemicals (reactive oxygen species) that damage DNA and proteins
Sensitivity to irradiation, depends on multiple factors including:
- the size of the genome of the bacteria
- the rate at which bacteria can repair damaged DNA
- condition of the food - takes a higher dose of radiation to kill
microbes in frozen foods
28
True or False: Deinococcus radiodurans has the greatest ability to survive radiation of any known organism.
True
What properties account for Deinococcus radiodurans
amazing resistance to radiation?
- highly efficient double-strand-
break DNA repair system requiring
homologous recombination - 4-6 copies of its two chromosomes
and two plasmids - aggressively protect its proteins
A number of factors influence the efficacy of a given chemical agent including:
*The presence of organic matter – lowers the agent’s
effectiveness against microbes
* The kind of organisms present – should be effective against
broad range of pathogen
* Corrosiveness - should not corrode the surface or, in the
case of an antiseptic, damage skin
* Stability, odor, and surface tension
31
____________ uses the high potency of phenol as the benchmark against other disinfectants to be measured.
The phenol coefficient test
_________ is a toxic liquid that is no longer used as a routine disinfectant.
Phenol
Derivatives, cresols and orthophenylphenol are still in use because they are:
*Very effective
*Denature protein
* Effective in the presence of organic matter
* Remain active on the surface long after application
Examples of derivatives, cresols, and orthophenylphrenol that damage DNA and proteins:
- Ethanol
- Iodine
- Chlorine
- Detergents
Altering the fatty acid synthesis protein (normally targeted by triclosan) can ________________.
Enable bacteria to develop a resistance to certain disinfectants
True or False: Pseudomonas can pump several biocides, detergents out of the cell, reduce
efficacy. This is an example of bacteria being able to reduce efficacy by producing membrane-spanning, multidrug efflux pumps.
True
True or False: Forming multispecies biofilms offer collaborative protection against certain disinfectants.
True
__________ binds disinfectants, slowing their penetration.
Extracellular matrix
_________________have time to activate protective stress response
system.
Cells in the deeper biofilm area
__________ are chemical compounds synthesized by one microbe to either kill (bactericidal) or stop the growth of (bacteriostatic) other competing microbial species.
Antibiotics
True or False: Antibiotics are classified according to their modes
of action.
True
The four functions/structures that antibiotics target:
*cell wall synthesis
* b. protein synthesis
* c. DNA replication
* d. cell membrane structure
_______________ is bactericidal because it prevents peptidoglycan synthesis and cell wall formation (bacteria cant live without support of the cell wall).
Penicillin
How do antibiotic-producing microbes avoid suicide?
a. lacks the target molecule (Penicillium mold lacks peptidoglycan)
b. modify its own receptors (some bacterial colicins).
c. modify the antibiotic if it renters the cell (streptomycin produced by Streptomyces griseus).
______________ is the use of one microbe to control the growth of another
Biocontrol
True or False: Presence of harmless microbes retard the growth of pathogenic strains.
True
______________ are food or supplements that contain live microbes. When ingested, they can restore balance to intestinal flora.
Probiotics (ex. Lactobacillus and Bifidobacterium)
True or False: Every bacterial species is susceptible to a limited number of specific phages.
True
_______________ are viruses that prey on bacteria. Can cause bacterial lysis and serve as a possible way to treat infectious diseases.
Bacteriophages
Commercial phage products target a __________ food-borne pathogens.
few
A ________________ contains several phages.
Phase product
True or False: Phase products are sprayed onto the hides of cattle 1-4 hrs before slaughter.
True
Using ___________ phages in each preparation eliminates the risk that phage resistance will develop in the pathogen.
multiple
