Midterm 2 Flashcards
1
Q
Flagella
A
Long filamentous appendages which propel bacteria
2
Q
Four possible flagella arrangements
A
Monotrichous
Amphitrichous
Lophotrichous
Peritichous
3
Q
Monotrichous
A
Single, Polar
4
Q
Amphitrichous
A
Tuft at each end
5
Q
Lophotrichous
A
Two or more at one pole
6
Q
Peritichous
A
Distributed over entire cell
- They move faster because of the amount of flagella
7
Q
Flagellar structure
A
Filament, Hook, Basal Body
8
Q
Filament
A
Consists of flagellin protein arranged in chains intertwined around a hollow core
9
Q
Hook
A
Protein to which filament is attached
10
Q
Basal body
A
Anchors flagellum to the cell wall and cytoplasmic membrane; consists of a central rod inserted into a series of rings
11
Q
Mot protein
A
Motor for the flagella and spins the rings
12
Q
Gram-negative Basal body
A
Gram-negative bacteria contain two pairs of rings in the basal body; outer pair anchored to the cell wall and inner pair anchored to the plasma membrane
13
Q
Gram-positive Basal body
A
Gram-positive bacteria has two rings, one in the cell membrane and one in the cell wall
14
Q
How do bacteria move
A
Movement is achieved through the rotation of the flagellum from the basal body either clockwise or counterclockwise
15
Q
Run / Swim
A
Continuous movement in one direction which can be interrupted by a “tumble”
16
Q
Tumble
A
An abrupt change in direction of the bacteria.
17
Q
What can cause a bacteria to tumble
A
Bactria are usually moving towards a nutrition source or moving away from something toxic.
18
Q
Taxis
A
Movement of a bacterium toward or away from a stimulus
19
Q
Chemotaxis
A
Movement towards or away from a chemical
20
Q
Phototaxis
A
Movement toward or away from light
21
Q
Magnetotaxis
A
Movement toward or away from a magnetic field
22
Q
Fimbriae & Pili
A
- Typically found on Gram-negative bacteria
- Hairlike projections; shorter, straighter, thinner than flagella
- Consist of a protein: pilin
They are not responsible for any movement but come out of the cell wall
23
Q
Fimbriae
A
Occur at bacterial cell poles or evenly distributed over entire cell surface
Few or several hundred per cell
Primary role in adherence to surfaces or other cells
e.g. Neisseria gonorrhoeae
24
Q
Pili
A
Usually longer than fimbriae
One or two per cell
25
Macronutrients
C, N, P, S, K, Mg, Ca, Na
26
Nutrients
Required substances for growth
27
Chemically defined
Exact chemical composition is known
28
Undefined (complex)
Uses digests of animal or plant products, exact composition not entirely known
- Undefined medium are easier to use in a lab because they can grow faster
29
Selective medium
Contains compounds that selectively inhibit the growth of some microorganisms and not others
30
Differential medium
Contains an indicator which distinguishes between chemical reactions generated by different species of bacteria.
- Will not inhibit growth but will allow you to distinguish
31
Pure culture
Contains one single type of microorganism
32
Amphibolic pathways
Reaction pathways that utilize roles of both catabolism (a break down) and anabolism (a build up)
- Transfer of ATP provides a link between catabolic and anabolic reactions
33
Energy
Ability to work
34
Free energy
Energy released that is available to do useful work
35
Delta G not prime
Change in free energy under standard conditions of pH and temperature
pH -7.0
Temp 25C
36
Negative delta G not prime
Exergonic, releases energy
Spontaneous
37
Positive delta G not prime
Endergonic, takes in energy
38
G not sub F
Free energy of formation, energy that is released or required for the formation of a molecule
39
Activation energy
Amount of energy needed to disrupt the stable arrangement of a given molecule
40
Reaction rate
Frequency of collisions containing sufficient energy to create a reaction
(the speed at which a chemical reaction takes place)
41
Enzymes
Biological catalysts which speed up a reaction and act on a specific substrate at its active site
42
Enzyme-substrate complex
A temporary molecule formed when the substrate binds to the enzyme, lowers the activation of a particular reaction
43
What is enzyme activity affected by
- Temperature
- pH
- Substrate concentration
- Inhibitors
44
Feedback inhibition
Prevents the cell from wasting chemical resources
End product of a reaction can inhibit one of the enzymes earlier in the pathway
45
Oxidation reaction
Oxidation reactions are chemical processes where a substance loses electrons, increasing its oxidation state.
- Generating energy
- Mostly have dehydrogenation reactions
46
Reduction reaction
A reaction where a substance gains electrons oand decreases its oxidation state
Gain of one or more electrons
47
Dehydrogenation reaction
A type of oxidation reaction involving the loss of hydrogen atoms
48
ATP generation
Formation of ATP allows the cell to store potential energy
49
Phosphorylation
Addition of P to a chemical compound A(help generate energy)
50
Substrate-level phosphorylation
The direct transfer of a phosphate group to ADP to form ATP
ATP is generated after a high-energy phosphate group transfers from a phosphorylated substrate to ADP
51
Oxidative phosphorylation
The process of forming ATP via the transfer of electrons
Involves the ETC that is a series of compunds that pass electrons from one to another
- The electron carrier is usually NAD
- Occurs in plasma membrane of prokaryotes
52
Photophosphorylation
Occurs only in photosynthetic cells
Light energy is converted to chemical energy of ATP and NADPH
- Light trapping pigment is chlorophyll
53
Carbohydrate Catabolism
Breakdown of carbohydrate molecules to produce energy
54
Processes used in glucose catabolism
Cellular respiration
Fermentation
55
Alternatives to classic glycolysis
Pentose phosphate pathway
- only one (E.coli)
Entner-Doudoroff pathway
- More common in gram-negative (Rhizobia)
56
Aerobic respiration
Aerobic respiration is the process by which cells generate energy (ATP) in the presence of oxygen. It is the most efficient way for cells to produce energy and occurs primarily in the mitochondria of eukaryotic cells
- Krebs cycle (citric acid cycle)
- Potential energy in acetyl CoA is released throughout a series of reactions
- Final electron acceptor must be an inorganic compound other than oxygen
e.g. Pseudomonas can use nitrate
Desulfovibrio uses sulfate
57
Electron Transport Chain
Sequence of carrier molecules capable of both oxidation and reduction
Stepwise release of energy as electronsare passed through the chain
Three classes of carrier molecules (flavoproteins, cytochromes, ubiquinones)
58
Chemiosmosis
The process used by cells to generate energy in the form of ATP, which is essential for powering cellular activities.
This process takes place in the mitochondria during cellular respiration and in the chloroplasts during photosynthesis.
Energy released when protons moving along a gradient used to synthesize ATP
This mechanism is used in both prokaryotes and eukaryotic cells
59
Fermentation
Conversion of sugars (mainly glucose) into other compounds in the absence of oxygen
Does not require oxygen
Does not require use of Kerbs cycle or electron transport chain
Uses an organic as the final e acceptor
Produces small amounts of ATP
60
Lactic acid fermentation
Following glycolysis pyruvate is reduced to lactic acid
Energy generated remains stored in lactic acid
e.g. Streptococcus and Lactobacillus (suicide bacteria, don’t stop producing acid and it can exceed the buffer)
- Lactic acid fermentation is generating lactate
61
Alcohol fermentation
Following glycolysis reduction of pyruvate leads to formation of acetaldehyde and then ethonal
Low energy yield as energy is in ethanol
62
Heterolactic
Heterolactics produce lactic acid as well as other alcohols or acids
- Produce more than one end product
- Can be unique to prokaryotes and there environmental conditions, so they can have many end products
- E Coli is a heterolactic
63
Lipid and Protein Catabolism
Use lipases to break down lipid material to fatty acid and glycerol components
- Can be used to clean up spills
- If there is an oil spill and a bacteria works for awhile then stops, that means the environmental conditions changed. The change might be really small but can affect the bacteria.
Krebs cycle will function in oxidation of glycerol and fatty acids
e.g. beta oxidation of petroleum
Extracellular production of proteases and peptidases break proteins down into amino acid components
Amino acids readily pass through prokaryotic membrane but require further conversion in order to be catabolized
e.g. deamination, decarboxylation, dehydrogenation
64
Bacterial growth
Bacterial growth refers to the process by which bacteria reproduce and increase in number over time
Need to graphically represent large populations
Need to determine microbial numbers
Growth has traditionally been defined as an increase in cell numbers in microbiology
65
Why do we need to know why bacteria grow
Because we need to control disease, and to control them we need to know how they grow
66
Bacterial division
Bacterial growth results in an increase in cell number via binary fission (1 into 2)
67
How do enormous populations of bacteria happen
Result from doubling growth pattern
The daughter cell is the same size as the mother cell
68
Min protein
Min proteins in bacteria control the timing of cell division by regulating the location of FtsZ, a protein that forms the septal ring
They prevent FtsZ from binding to cell poles.
Min proteins inhibit FtsZ from binding to the cell pole membrane, ensuring that bacterial cell division occurs in the middle of the cell.
69
Fts protein
Filmentes temperature sensitive protein
Fts protein interaction results in the formation of a divisome
Assisted by series of Min proteins
70
Divisome dictates what?
Divisome dictates synthesis of new cytoplasmic membrane and cell wall material in both directions until cell length has doubled
71
Invagination
When the proteins build a bridge to start division
72
MreB
Major shape-determining protein
Coccus-shaped bacteria (the default shape for prokaryotes) lack MreB
73
New wall synthesis
Small openings in the wall are created by autolysins at FtsZ ring point
New wall material is added across openings assisted by bactoprenol
74
Transpeptidation
The formation of new peptide cross-links
- Penicillin interferes with transpeptidation, it helps control bacteria growth and prevents them from multiplying
- Strengthens the cell wall
75
Generation time (doubling time)
Time required for a cell to divide and its population to divide
Environmental conditions will influence generation time and vary with the specific organism
- Everything from the original cell has to double, not every organism is going to reproduce itself at the same rate
76
Phases of bacterial growth
Bacterial growth phases can be represented in a batch (closed) system using a growth curve
Four basic phases of growth: lag, log, stationary and death
- To see these phases batch conditions are needed
- In a closed system there is only a certain amount of nutrition
77
Lag phase
Period of little or no cell division when cells freshly inoculated into new media
Intense metabolic activity including synthesis of enzymes
78
Log phase
Once cell division begins, a period of exponential growth follows during which generation time is constant
Logarithmic plot results in a straight line
Cells are more sensitive to adverse conditions during this period
- Because they are going through reproduction and are the most vulnerable
79
Stationary phase
Growth rate slows during this period (in response to some physical or chemical limitation)
Number of deaths balance number of new cells produced
- Number of cells dying match the number of cells growing, it’s a net number
80
Death phase
When the number of deaths in the population exceeds the number of new cells formed
Also called logarithmic decline phase
Continues until population dies out or greatly diminishes
81
Continuous growth
Continuous culture is an open system (e.g. chemostat)
- Constant/continuous flow of nutrients into the system
- There is an in and an out (humans are kind of like chemostats)
- To control a chemostat we can decided the dilution rate, the rate at which the nutrition reaches them.
- The one thing you can control is the dilution rate
82
Batch culture
Fixed volume and closed system
83
Chemostat
Controls both growth rate and population density
84
5 main things that effect bacteria growth, how you can control there growth
pH, Temperature, Oxygen, Nutrients, Water activity
85
Microbial Growth - Temperature
Can affect microbial growth positively or negatively
Temperature classes of microorganisms can be defined by cardinal temperatures
Psychrophile
Mesophile
Thermophile
Hyperthermophile
Each species has its own minimum, optimum and maximum growth temperature (cardinal growth temperatures)
86
Psychrophile
Favour cold temperature
(15 or less)
87
Mesophile
Favour moderate temperature
(25-40)
88
Thermophile
Favour higher temperatures
(above 45)
89
Hyperthermophile
Favour extremely high temperature (above 80)
90
Cold environments
Isolate psychrophiles where environment is constantly cold
Psychrotolerant microorganisms are more widely distributed; important in food spoilage
Spoilage cold-active enzymes have greater amounts of alpha-helix and lesser amounts of beta- sheet secondary structure
Active transport occurs optimally at low temperatures
Cytoplasmic membrane contains higher concentrations of concentration fatty acids
Freezing temperatures may prevent cell growth but do not necessitate cell death
91
Thermal environments
High temperature environments are restricted in nature
Soils in full sunlight may be heated above 50oC
Intracellular enzymes and proteins thermostable
Cytoplasmic membrane richer in saturated fatty acids to optimize stability and function at higher temperatures
Hyperthermophiles (Archaea) have C40 hydrocarbons instead of fatty acids in the membrane
92
Microbial Growth - pH
Optimal growth pH refers to the external environment
Most bacteria grow optimally in a narrow pH range (6.5-7.5)
Most natural environments have pH values between 5 and 9
Recall: acidophile and alkaliphile
Buffers are added to microbial culture media to assist in pH stability during growth
Intracellular compensating systems if pH is away from the optimum
93
Microbial Growth - aw
Water activity is a measure of the available water in a substance for microbial growth, and it directly influences the ability of bacteria to survive and reproduce. It ranges from 0 (completely dry, no available water) to 1 (pure water). Bacteria require a certain level of water activity to grow, as they rely on water for cellular processes, nutrient absorption, and waste removal.
Usually cell experiences equal water balance
Environments with high salt concentrations require tolerance to lower aw
Xerophiles
Osmophiles
Intolerant bacteria may suffer loss of water internally to the external environment resulting in plasmolysis
94
Xerophiles
Capable of growth in very dry environments
95
Osmophiles
Can grow in the presence of high sugar concentrations
96
Obligate aerobes
Microorganisms requiring oxygen to live
97
Toxic forms of oxygen
Singlet oxygen
Superoxide anion
Hydrogen peroxide
Hydroxyl radical
98
Facultative anaerobes
Microorganisms that use oxygen when it is present but can continue to grow in its absence
99
Obligate anaerobes
Bacteria cannot use oxygen for energy-yielding reactions and are often harmed by it
Obligate anaerobes do not produce enzymes to neutralize
100
Microbial Growth - Oxygen
Tolerant microorganisms require enzymes such as superoxide dismutase (SOD) to neutralize toxic intermediates
Obligate anaerobes do not produce enzymes to neutralize
101
Aerotolerant anaerobes
Cannot use oxygen for growth but tolerate its presence
102
Microaerophiles
Grow only at low oxygen tension but do require it for growth
103
Enzymes that destruct toxic oxygen
Catalase
Peroxidase
Superoxide dismutase
104
Microbial Growth - N, S, P
Required for synthesis of cellular material
Nitrogen used to form amino acids
Sulfur used in amino acids and vitamins
Phosphorus is essential for nucleic acid synthesis and phospholipid membrane structure
105
Superoxide dismutase (SOD)
Enzyme used by tolerate microorganisms to neutralize the toxic parts of oxygen
Obligate anaerobes don't have these enzymes
