Exam 2 Flashcards
(91 cards)
1
Q
5 phases of microbial growth curve
A
- Lag phase
- Exponential phase
- Stationary phase
- Death phase
- Long-term stationary phase
2
Q
What happens in lag phase?
A
- Cell synthesizing new components
- Varies in length - in some cases can be very short or even absent
3
Q
What happens in exponential phase?
A
- Also called log phase
- Rate of growth and division is constant and maximal
- Population is most uniform in terms of chemical and physical properties
4
Q
What happens in the stationary phase?
A
- Closed system population growth eventually ceases, totally number of viable cells remain constant
- Active cells stop reproducing or reproductive rate is balanced by death rate
- Population may cease to divide but remain metabolically active
5
Q
Possible reasons for stationary phase
A
- nutrient limitation
- Limited oxygen availability
- Toxic waste accumulation
- Critical population density reached
6
Q
What happens during the death phase
A
- The cell cannot be supported and they die
- Cells dying at a constant rate from environmental factors
- Two alternative hypotheses: cells are viable but not culturable, or programmed cell death.
7
Q
What happens during the long-term stationary phase
A
- Continually evolves
- Successive waves of genetically distinct variants
- Natural selection occurs
8
Q
What is culture media used for?
A
To grow, transport, and store microorganisms in lab
9
Q
Types of media
A
Defined/synthetic
Complex
10
Q
Defined/synthetic media
A
- Each ingredient can be defined with a chemical formula
- Use if you want to know the metabolism
11
Q
Complex media
A
Contain some ingredients of unknown chemical composition
12
Q
What are the two types of functional media and what do they do?
A
- Supportive or general purpose media - support the growth of many microorganisms
- Enriched media - general purpose media supplemented with special nutrients (ex. Blood agar - adding something in tot see what it does to it)
13
Q
Selective Media
A
- Allow the growth of particular microorganisms while inhibiting the growth of others
- Select for gram positive or negative
14
Q
Differential Media
A
- Distinguish among different groups of microbes and even permit tentative ID phase don their biological characteristics
- Helps identify them by what they do
- Select for gram negative and differentiate them
15
Q
Strict anaerobic microbes
A
- lack or have very low quantities of superoxide dismutase and catalase.
- cannot tolerate O2 and must be grown without O2.
16
Q
Isolation of pure cultures
A
Allows for the study of single type of microorganism in mixed culture
17
Q
Streak plate
A
- Technique of spreading a mixture of cells on an agar surface so individual cells are well separated.
- Each cell can reproduce to form a separate colony.
18
Q
Spread plate
A
- Small volume of diluted mixture containing 25-250 cells
- Spread evenly over surface with a sterile bent rod
- Pre diluted
19
Q
Pour plate
A
- Serially diluted
- Mixed with liquid agar
- Poured into sterile culture dishes
20
Q
Continuous culture of microorganisms
A
- Growth in an open system
- continual provision of nutrients and removal of wastes.
21
Q
Continuous culture of microorganisms maintains the cells in
A
Log phase at a constant biomass concentration for extended periods
22
Q
What are continuous cultures used for?
A
- Microbial growth at very low nutrient concentrations
- Interactions of microbes under conditions resembling those in aquatic environments
- Food and industrial microbiology
23
Q
Direct measurement of cell numbers
A
- Counting chambers
- Membrane filters
- Flow cytometry
- Electronic counters - the coulter counter
24
Q
Measurement of cell mass
A
- Dry weight
- Spectrophotometry
- Concentration of a particular cell constituent (ex protein, DNA, ATP)
25
Most microorganisms prefer
Neutral environmental conditions
26
Extremophiles are
Permanently living in extreme conditions and often require the extreme condition for optimal growth
27
Most common mechanisms used by extremophiles
- Synthesizes specialized enzymes and proteins
- Altering genomic material
- Altering membrane composition
- Opening/closing channels or similar mechanism to acquire or remove substances to balance intracellular environment
28
Osmotic concentration
- Outcome - there will be an influx of water in or out of the cell causing it to either shrink or burst
- Adaptation - trigger channels in the membrane to open allowing solute to leave or increase their internal osmotic concentration
29
PH
- Outcome - cytoplasmic pH becomes acidic or alkalaine, cause cell death
- Adaptation - utilize mechanisms that maintain a neutral cytoplasmic pH. - exchanging protons, synthesize specialized proteins, produce waste products to balance environmental pH
30
Temperature
- Outcome - microbes cannot regulate their internal temperature. Enzymes do not function well outside of optimal range
- Adaptation - utilize means to stabilize proteins and membrane.
31
Oxygen concentration
- Outcome - orgs can be obligate (strict) or facultative (either) aerobes or anaerobes. Anaerobes utilize O2 for metabolic processes to generate energy. O2 is toxic to anaerobes and they employ other means for to generate energy.
- Adaptation - obligate anaerobes associate with facultative anaerobes that will remove any oxygen from the environment. - Many also utilize enzymes that scavenge and neutralize reactive oxygen byproducts.
32
Pressure
- Outcome - organisms on land and water surfaces are always at a pressure of 1 atm.
- Adaptation - only extremophiles need adaptation mechanisms
33
How do microbes adapt to changes in osmotic concentrations?
Mechanosensitive (MS) channels in plasma membrane allow solutes to leave
34
Halophiles
Grow optimally in the presence of salts at a concentrate above about 0.2 M
35
Extreme halophiles
Require salt concentrations between 3M and 6.2M
36
PH preference in fungi
Most fungi prefer more acidic surroundings (ph 4-6)
37
Many archaea are
Acidophiles
38
Most bacteria and protists are
Neutrophiles
39
Ph tolerance
- Using mechanisms that maintain a neutral cytoplasmic pH
- neutrophils exchange potassium for protons
40
Acidic tolerance response
- Pump protons out of the cell
- Some synthesize acid and heat shock proteins that protect proteins (cellular components)
41
Many microorganisms change the pH of their habitat by
producing acidic or basic waste products
42
High temperatures may ____ enzyme functioning and be _____
- inhibit
- Lethal
43
Adaptations of thermophiles
- More chaperone proteins, H binding proteins
- More saturated, more branched and higher molecular weight lipids
- Ether linkages (archaeal membranes)
44
Barotolerant
adversely affected by increased pressure, but not as severely as nontolerant organisms
45
Barophillic
- Require or grow more rapidly in the presence of increase pressure
- Change membrane fatty acids to adapt to high pressures
46
What has the greatest impact on microbial growth?
Oxygen
47
Microbes fall into one of three categories:
- Those that use oxygen and detoxify it
- Those that can neither use oxygen nor detoxify it
- Those that do not use oxygen but can detoxify it
48
How microbes process oxygen
- Transformed into several toxic products:
Singlet oxygen - highly reactive - can damage and destroy a cell by oxidation of membrane lipids
Superoxide ion - highly reactive
Hydrogen peroxide - toxic to cells - disinfectant
Hydroxyl radical - highly reactive
49
How microbes protect themselves against damage from oxygen by-products
- Superoxide ion is concerted into hydrogen peroxide by superoxide dismutase
- Hydrogen peroxide is concerted into harmless water and oxygen by catalase
50
Aerobes can use ___ in their metabolism and possess the enzymes needed to process toxic products
Oxygen
51
Facultative anaerobes do not require ____ for metabolism but use it when it is present
Oxygen
52
Anaerobes lack the ______ _______ _______ for using oxygen in respiration
Metabolic enzyme systems
53
Most microbial live in _____ ______ states
Growth arrested states
54
Most microbes inhabit ______ environments
Oligotrophic
55
Microbes have evolved many responses to starvation and environmental stress. What are they?
- Morphological changes (endospore formation)
- Enter stationary phase
- Use cellular components as nutrients
- Numerous genes and proteins that help
- Viable but not culturable state
56
Quorum sensing
Controls genes that direct activities that are beneficial when performed in synchrony.
57
What is controlled by quorum sensing?
Bioluminescence, sporulation, competence, antibiotic formation, biofilm formation
58
What does quorum sensing require?
An autoinducer
59
Biofilm formation process
1. Reversible attachment of planktonic cells
2. First colonizers become irreversibly attached
3. Growth and cell division
4. Production of EPS and formation of water channels
5. Attachment of secondary colonizers and dispersion of microbes to new sites
60
Heterogeneity in biofilms
- Differences in metabolic activity and locations of microbes
- Exchanges take place metabolically, DNA uptake and communication
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Surfaces that most microbes grow attached to
Sessile
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Free floating
Planktonic
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Psychrophile
Cold loving
Optimal growth in 15C or less
- produce proteins and enzymes that function at low temperatures
- membrane contains more unsaturated fatty acids and genome is higher in G-C content
64
Thermophile
Heat loving
Growth above 45C
- produces proteins and enzymes that are stable at high temperatures
- cytoplasmic membrane has more saturated fatty acids to remain stable
- utilizes gene transfer
65
Acidophile
Acid loving
Thrive at low pH
- impermeability of cell membrane restricts the influx of protons into the cytoplasm
- reduce pore size in membrane
- specialized mechanisms prevent entry of proton into the cell and acid hydrolysis of membrane
66
Alkaliphile
Alkaline loving
Thrive at High pH (9+)
- utilize mechanisms to acquire H+ from extracellular environment and reduce H+ leakage
- atp synthesis contributes to pH homeostasis (prevents the release of protons during the ETC)
- produce metabolic acid (increase H+ in cytoplasm)
67
Xerophile
survive in very dry environments
- dormancy (sporulation)
- biofilm formation
- increased fatty acid content in cell meme range
- product proteins that counteract the effects of low water activity
68
Osmophiles
Survive in environments with high osmotic pressures (sugar concentration)
- produce different alcohols and amino acids that prevent change in osmotic pressure inside the cell
- protein and enzymes have more protein charges and hydrophobicity that protects against the change in solute composition In the cytoplasm
69
Piezophiles/barophiles
Pressures greater than 1ATM
- high pressure can cause formations of gel like membrane with decreased nutrient uptake and processing and reducing membrane fluidity
- protein structure/composition proves high flexibility, preventing conformational changes that would inhibit function
- changing membrane fatty acids to make them tolerant to pressure
70
Sterilization
Destruction or removal of all viable organisms
71
Disinfection
Killing, inhibition, or removal of disease causing organisms.
72
Disinfectants
Used on inanimate objects
73
Sanitization
reduction of microbial population to levels deemed safe (based on public health standards)
74
Antisepsis
prevention of infection of living tissue by microorganisms
75
Antiseptics
Applied to tissue
76
Chemotherapy
Used of chemicals to kill or inhibit growth of microorganisms within a host tissue
77
Cidal
Kill
Include bactericides, fungicides, and viricides
78
Static
Inhibit growth
Include bacteriostatic and fungistatic
79
Microbial control methods
Mechanical, physical, chemical, biological
80
Mechanical methods
Filtration:
- Liquid - membrane filters - used in water recycling
- Air - high efficiency particulate air (HEPA) filters - used in some enclosed barns
81
Physical agents
heat and radiation
82
Moist heat (physical agent)
- Autoclave - effective against all types of organisms including spores.
- Pasteurization, boiling, steam
- Destroys viruses, bacteria, fungi
- Boiling will not destroy endospores and will not sterilize.
- Degrades nucleic acids, denatures proteins, disrupts membrane
83
Pasteurization (physical agent)
Does not sterilize but does kill pathogens and reduce bad organisms
84
Dry heat (physical agent)
- Less effective
- Oxidize cells and denature proteins
- Does not corrode glassware and metal but you have to use it at lower heat for longer time
85
Ionizing radiation
Gamma rays
86
Ultraviolet radiation
- Used for water treatment
- Creates thymine diners that prevent replication
87
Chemical agents
Disinfectants, antiseptics, sterilization
88
Disinfectants
- Phenolics- denature proteins and disrupt membranes
- Common hospital use
- Alcohols - most widely used
- Bacterial, spongicidal, but not sporicidal
89
Antiseptics
- Overuse concerns because it can select for resistant bacteria
- Halogens (iodine) - skin antiseptic - oxidizes cell conditioners and iodinates endospores
- Chlorine - oxidizes cell constituents and destroys vegetative bacteria and fungi - chlorine gas is sporicidal
90
Sterilization
- Heavy metals - effective but usually toxic
- Quarternary ammonium compounds (detergent) - some can kill bacteria but not endospores
- Aldehydes - Sporicidal and can be used as chemical sterilant
- Sterilizing gas - microbial and sporicidal but DANGEROUS
91
Biological agents
Natural control mechanisms - viral mediated lysis (release toxin into bacteria and destroys- used mostly in food)
