Chapter 5 Flashcards
What are the “normal” growth conditions?
- Sea level
- 20ºC-40ºC
- A near-neutral pH
- .9% salt and ample
nutrients
What are organisms that inhabit ecosystems outside of the “normal” conditions called?
extremophiles
What allows us to study the biology of organisms that we cannot culture?
Bioinformatic Analysis
A bacterial cell’s temperature matches that of..?
its immediate environment
True or False. Changes in temperature impact only some aspects of microbial physiology.
False. It impacts every aspect
Microbes that grow at higher temperature can typically…
higher rates of growth
The growth rate roughly doubles for every___ ºC
10ºC
Thermophiles’ Characteristics
1. They are not easily
unfold as those of
mesophiles
2. They do not have
high amount of
glycine
3. The N-terminus of
the enzyme is
anchored to the
other parts of the
enzyme
4. They have
chaperones
5. They have DNA-
binding proteins.
6.They have more
saturated fatty acids
in the membrane.
7. They have
monolayers.What organism’s regular growth temperature is 0ºC-20ºC?
Psychrophiles
What organism’s regular growth temperature is 15ºC-45ºC?
Mesophiles
What organism’s regular growth temperature is 40ºC-80ºC?
Thermophiles
What organism’s regular growth temperature is 65ºC-121ºC?
Hyperthermophiles
What causes heat-shock response?
Rapid temperature changes experienced during growth activates batcher of stress response genes.
What does chaperones do?
maintain protein shape
What do enzymes do?
change membrane lipid composition
What are psychrotolerants?
- grow on old food in the fridge
2. Spoils milk
What are organisms that have adapted to grow at very high pressures? (up to 1,000 atm or 101 MPa or 14,600 psi)
Barophiles or piezophiles
What are organisms that grow well over the range of 1-50 MPa, but their growth falls off thereafter?
Barotolerant
Barophiles are also ________ because the average temperature at the ocean floor is 2ºC.
Psychrophiles
What reduces membrane fluidity?
- increased hydrostatic
pressure - Cold temperature
What can counter act the reduction of membrane fluidity?
protein structures
What is a measure of how much water is available for use?
Water activity (aw)
Most bacteria require water activity levels>__.
.91
Fungi can tolerate water activity levels>___.
.86
What is water activity typically measured as?
the ratio of the solution’s vapor pressure relative to that of pure water
What is a measure of the number of solute molecules in a solution and is inversely related to aw?
Osmolarity
Why is osmolarity important to the plasma membrane in cells?
1. Allows water to pass
but not solutes
2. For a cell in a
hypertonic medium,
water will leave the
cell in an attempt to
equalize osmolarity
across the membrane
3. In contrast,
suspending a cell in a
hypotonic medium
will cause an influx of
waterWhy is osmolarity important to the plasma membrane in cells?
1. Allows water to pass
but not solutes
2. For a cell in a
hypertonic medium,
water will leave the
cell in an attempt to
equalize osmolarity
across the membrane
3. In contrast,
suspending a cell in a
hypotonic medium
will cause an influx of
waterWhat are membrane-channel proteins that allow water to transverse the membrane much faster than by diffusion?
Aquaporins
Hypertonic
- solute concentration is
higher outside the cell
-water rushes out of the
cell
Hypotonic
- solute concentration is
higher inside the cell - water rushes into the
cell
What are two mechanisms microbes have to minimize osmotic stress?
1. In hypertonic media, bacteria protect their internal water by synthesizing or importing compatible solutes 2. In hypotonic media, pressure-sensitive or mechanosensitive channels can be used to leak solutes out of the cell.
What causes the two mechanisms to become ineffective at controlling internal osmolarity?
When they are outside their osmotic comfort range
What type of microbe requires high salt concentrations?
Halophiles
Halophiles need _____ % NaCl while the seawater is ___ % NaCl
10-20%
3.5%
What is the normal salt requirement?
.5-5%
How do halophiles achieve a low internal concentration?
They use special ion pumps to excrete sodium and replace it with other cations, such as K+
What organisms grow at pH 5-8?
Neutralophiles (include most pathogens)
What organisms grow at pH 0-5?
Acidophiles(are often chemoautotrophs)
What organisms grow at pH 9-11?
Alkaliphiles (typically found in soda lakes)
Is moist heat or dry heat more effective at killing microbes?
Moist Heat
What temperature does water have to be to kill most cells?
100ºC (Boiling temp)
What does killing spores and thermophiles usually require?
a combination of high pressure and temperature.
How does the steam autoclave kill microbes?
- 121ºC at 15 psi for 20
minutes - Conditions produced in pressure cookers when canning vegetables
How does Pasteurization kill microbes?
- LTLT(low temperature/ long time) : 63ºC for 30 minutes
- HTST(high temperature/ short time): 72ºC for 15 seconds
How does Cold kill microbes?
- low temperatures slow growth and preserve strains Refrigeration Temperatures(4ºC-8ºC) are used for food preservation - For long-term storage of cultures (lyophilization or freeze-drying)
How does filtration kill microbes?
- Micropore filters with pore sizes of .2 um can remove microbial cells, but not viruses, from solutions.
Can air be sterilized by filtration?
Yes, this process forms the basis of several personal protective devices.
What are Laminar flow biological safety cabinets?
- force air through HEPA filters, which remove > 99.9% of airborne particulate material .3 um in size or larger.
What does newer technologies embed in the fibers of the filter?
- Antimicrobial agents or enzymes
How does Irradiation kill microbes?
- Ultraviolet light: poor penetrating power; used only for surface sterilization - Gamma Rays, electron beams, and X-rays: high penetrating power; used to irradiate foods and other heat-sensitive items
What bacteria is nickname “Conan the bacterium” and why?
- Deinococcus radiodurans
- has the greatest ability
to survive radation of
any known organism - Has exceptional
capabilities for
repairing DNA
damaged by radiation - Was genetically
engineered for use in
bioremediation
What are the factors that influence the efficacy of a given chemical agent?
- presence of organic matter - the kinds of organisms present - Corrosiveness - Stability, odor, and surface tension
What is the test called that compares the effectiveness of disinfectants?
- Phenol coefficient
Test
What are examples of commercial disinfectants and antiseptics?
- Ethanol
- Iodine (Wescodyne
and Betadine)
-Chlorine
-Ethylene Oxide (a gas
sterilant)
What do commercial disinfectants and antiseptics do?
- Damage proteins, lipids, and/or DNA - Are used to reduce or eliminate microbial content from objects
Can bacteria develop resistance to disinfectants?
Yes
What are the mechanisms that bacteria use to become resistant to disinfectants?
- Altering the fatty acid synthesis protein normally targeted by triclosan
- Producing membrane- spanning, multidrug efflux pumps
- Forming multi-species biofilms, which offer collaborative protection
What are chemical compounds synthesized by one microbe that kill or inhibit the growth of other microbial species?
Anitbiotics
What prevents cell wall formation and is bactericidal?
Penicillin
What mimics a part of the cell wall to kills the cells?
Penicillin
What is the use of one microbe to control the growth of another called?
Biocontrol
What contains certain microbes that, when ingested, to aim to restore balance to intestinal flora?
Probiotics
What aims to treat infectious diseases with a virus targeted to the pathogen?
Phage therapy
