Chapter 5 Flashcards
(52 cards)
1
Q
“Normal” growth conditions
A
-Sea level atmospheric pressure
-Temperature 20oC–40oC
Neutral pH
-0.9% salt, and ample nutrients
based on one main criterion:
The tolerance of that organism’s proteins and other macromolecular structures to the physical conditions within that habitat
2
Q
extremophiles
A
- Ecological niches far outside this window are called “extreme”
- enzymes are useful for certain scientific investigations and industrial applications
- Such as enzymes that function in extremes of temperature, salt concentrations, or pH.
- may provide insight into extraterrestrial microbes we may one day encounter.
3
Q
Bioinformatic analysis
A
- uses the DNA sequence of a gene to predict the function of its protein product
- Allows us to study the biology of organisms that we cannot culture.
- Global approaches (all genes in a cell) used to study gene expression allow us to view how organisms respond to changes in their environment.
- Knowing which genes and proteins are expressed under different conditions reveals the microbes physiology and how they defend themselves against environmental stresses.
- It can reveal how pathogens interact with their host
4
Q
Environmental Pressure- temperature
A
- Hyperthermophile- growth about 80oC
- Thermophile- growth between 50-80oC
- Mesophile- growth between 15-45oC
- Psychrophile- growth below 15oC
5
Q
Environmental Pressure- pH
A
- Alkaiphile- growth above pH 9
- Include most pathogens
- Neutralophile- growth between pH 5-8
- Are often chemoautotrophs
- Acidophile- growth below pH 3
- Typically found in soda lakes
6
Q
Environmental Pressure- osmolarity
A
halophile- growth in high slat
7
Q
Environmental Pressure- oxygen
A
- aerobe- growth only in O2
- facultative- growth with or without O2 (E. coli)
- microaerophile- growth in small amounts of O2
- anaerobe- growth only without O2
8
Q
Environmental Pressure- pressure
A
barophile- growth at high pressure, greater than 380 atm
-barotolerent- growth between 10 and 495 atm
9
Q
Adaptation to Temperature
A
- Bacteria have the same temperature as their environment.
- Changes in temperature impact microbial physiology, proteins, and membranes
- Each organism has an optimum temperature, as well as minimum and maximum temperatures that define its growth limits.
- Microbes that grow at higher temperatures can typically achieve higher rates of growth
10
Q
Growth Rate and Temperature
A
- The growth rate roughly doubles for every 10oC rise in temperature, within the range appropriate for an organism.
- The same relationship is observed for most chemical reactions.
- Bacterial organisms can typically grow within a range of 30–40 degrees around its optimal growth temperature
- But the range is not symmetric and drops off faster at high temperatures.
11
Q
The Heat-Shock Response
A
- Temperature changes experienced during growth activates stress response genes
- Induced proteins include chaperones that maintain the shape of proteins and enzymes that change membrane lipid composition.
- Stress responses have been documented in “all” living organisms examined so far
12
Q
Adaptation to Pressure
A
- Barophiles or piezophiles (preferred term) are organisms adapted to grow at very high pressures- Up to 1,000 atm
- Barotolerant organisms grow at moderate pressures.
- Note that many barophiles are also psychrophiles because the average temperature at the ocean floor is 2oC
13
Q
Water Activity and Salt
A
-Water activity (aw) is a measure of how much water is available for use.
-Typically measured as the ratio of the solution’s vapor pressure -relative to that of pure water.
Most bacteria require water activity levels > 0.91
14
Q
Osmolarity
A
is a measure of the number of solute molecules in a solution and is inversely related to aw
15
Q
Aquaporins
A
- are membrane-channel proteins that allow water to traverse the membrane much faster than by diffusion.
- Help protect cells from certain types of osmotic stress
16
Q
two mechanisms to minimize osmotic stress
A
- In hypertonic media, bacteria synthesize or importing compatible solutes (e.g., certain sugars, proline, or K+)
- In hypotonic media, pressure-sensitive channels can be used to leak solutes out of the cell (better than blowing up)
17
Q
Adaptation to pH
A
- The concentration of hydrogen ions (H+)—actually, hydronium ions (H3O+)—has a direct effect on the cell’s macromolecular structures.
- Extreme concentrations of either hydronium or hydroxide ions (OH–) in a solution will limit growth.
18
Q
pH Optima, Minima, and Maxima
A
- All enzyme activities exhibit optima, minima, and maxima with regard to pH.
- Bacteria can regulate internal pH, within limits.
- Weak acids can pass through membranes and disrupt cell pH homeostasis thus killing cells
- This phenomenon is used to preserve some foods
19
Q
Oxygen and Other Electron Acceptors
A
- Many microorganisms can grow in the presence of molecular oxygen (O2).
- Some use oxygen as a terminal electron acceptor (TEA) in the electron transport chain.
- process is called aerobic respiration.
- Essentially the same as your mitochondria
20
Q
Oxygen Benefits and Risks
A
- benefit to aerobes, organisms that can use oxygen as a TEA to extract energy from nutrients
- toxic to all cells that do not have enzymes capable of efficiently destroying the reactive oxygen species (ROS)—for example, anaerobes
21
Q
Strict aerobes
A
require oxygen for growth
22
Q
Microaerophiles
A
grow only at lower O2 levels
23
Q
Strict anaerobes
A
die in the least bit of oxygen
24
Q
Aerotolerant anaerobes
A
have a fermentation-based metabolism that does not require oxygen, but they can tolerate oxygen
25
Facultative anaerobes
- can grow with or without oxygen.
| - possess both fermentative metabolism and respiration (anaerobic or aerobic)
26
Superoxide dismutase
- used by reactive oxygen species (ROS)
- converts superoxied to hydrogen peroxide
O2- + H+ --> H2O2
27
Catalase
- used by reactive oxygen species (ROS)
- converts hydrogen peroxide into water and oxygen
2H2O2 --> 2H2O + O2
28
Peroxidase
- used by reactive oxygen species (ROS)
- converts hydrogen peroxide into water and NAD+
2H2O2 --> 2H2O + NAD+
29
Three oxygen-removing techniques are used today
1. Special reducing agents can be added to ordinary liquid media
2. An anaerobe jar
- O2 is removed by a reaction catalyzed by palladium
3. An anaerobic chamber with glove ports
- O2 is removed by vacuum and replaced with N2 and CO2
30
Eutrophication
- the infusion of a limiting nutrient
| - can lead to a “bloom” of some microbes,which can threaten the balance of species in environments
31
Humans have caused nutrient pollution in 2 main ways
- Runoff from agricultural fields, urban lawns, and golf courses
- Untreated or partially treated domestic sewage
32
Sterilization
killing of all living organisms
33
Disinfection
killing or removal of pathogens from inanimate objects
34
Antisepsis
killing or removal of pathogens from the surface of living tissues
35
Sanitation
reducing the microbial population to safe levels
36
Cells Die at a Logarithmic Rate
-Microbes die according to a negative exponential curve, where cell numbers are reduced in equal fractions at constant intervals
37
Decimal reduction time (D-value)
- the length of time it takes an agent or a condition to kill 90% of the population.
- Used to quantify the effectiveness of an antimicrobial method
38
Physical Agents That Kill Microbes- High temperature
- Moist heat is more effective than dry heat.
- Boiling water (100oC) kills most cells but not all.
- Killing spores and thermophiles usually requires a combination of high pressure and temperature.
- Steam autoclave
39
Physical Agents That Kill Microbes- Pasteurization
- Limited heat treatment that kills pathogens but not all microbes; does not damage the food item very much
- does not sterilize
- Used for milk, beer, and other foods
- Different time and temperature combinations can be used.
40
Physical Agents That Kill Microbes- Cold
- Low temperatures slow bacterial growth
- freezing stops growth and kills some cells
- Refrigeration temperatures (4oC–8oC) are used for food preservation.
- Also used for long-term storage of bacterial cultures
- Cells in solutions of glycerol (cryoprotectant) frozen at –70oC
- Some bacteria can be lyophilized (freeze-dried)
41
Physical Agents That Kill Microbes- Filtration
- remove all cells
- Micropore filters with pore sizes of 0.2 mm can remove all microbial cells, but not viruses, from solutions.
- Samples from 1 ml to manyliters can be drawn through a membrane filter by vacuum or can be forced through the filter using a syringe
42
Laminar flow biological safety cabinets
- Air and gasses can be sterilized by filtration
| - force air through HEPA filters, which remove > 99.9% of airborne particulate material 0.3 μm or large
43
Physical Agents That Kill Microbes- Irradiation
-damages biological macromolecules
Ultraviolet (UV) light
- Has poor penetrating power
- Used only for surface sterilization
Gamma rays, electron beams, and X-rays
- Have high penetrating power
- Used to irradiate some medical supplies, foods, and other heat-sensitive items
44
Antimicrobial agents
- microbicide, bactericide, algicide, fungicide, virucide, germicide
- Bacteriostatic agents inhibit growth but do not immediately kill
- Bactericidal agents kill
45
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
46
Disinfectants and Antiseptics
- Ethanol and other alcohols
- Iodine (Wescodyne and Betadine)
- Chlorine
- Ethylene oxide (a reactive gas sterilant)
- surfactants (for example, detergents)
- These damage proteins, lipids, and/or DNA
- Are used to reduce or eliminate microbial content from objects
47
Antibiotics
- compounds synthesized by one microbe that kill or inhibit the growth of other microbial species
- kill bacteria without harming the host
48
penicillin
- antibiotic
- mimics part of the bacterial cell wall and binds to peptidoglycan biosynthetic proteins.
- Prevents cell wall formation and is bactericidal for growing cells
49
antibiotic targets
- Protein synthesis
- DNA replication
- Cell membranes
50
Biocontrol
use of one microbe to control the growth of another
51
Probiotics
contain certain microbes that, when ingested, restore balance to intestinal flora by competing with pathogens
52
Phage therapy
- treats bacterial diseases with a virus targeted to the pathogen
- A possible alternative to antibiotics in the face of rising antibiotic resistance
- Very specific for the target organism
