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Microbiology 315 > Lecture 5 > Flashcards

Lecture 5 Flashcards

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1
Q

DNA supercooling

A

• Gyrase (topoisomerase II)
*gyrase only supercoiling
• Topoisomerase I – removes supercoils (don’t need to know this now)

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2
Q

DNA compacting

A

DNA binding protiens

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3
Q

What are two unique traits of archaeal cell membranes?

A
  • ether bonds (instead of ester)
  • L-glycerol
  • S-layer
  • lipid branching
  • complexity
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4
Q

Which of these is true about the prokaryotic chromosome ?

A

It has a single origin of replication and the DNA is replicated bidirectionally

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5
Q

MICROBIAL NUTRITION
(Things that bacteria need to grow )

Essential nutrients
A

compounds that a microbe must have but cannot make
• Supplied by the environment
• Can differ substantially between organisms

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6
Q

Macronutrients

A

nutrients needed in large quantities

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7
Q

Six major elements in cell macromolecules

A

C,O,H,N,P,S

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8
Q

Cations that serve as cofactors for specific enzymes or signaling molecules

(To fold to function)

A

Mg2+, Fe2+, K+, Ca2+

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9
Q

Micronutrients

A

trace elements
• Necessary for enzyme function
• Co, Cu, Mn, Zn, Mo, Ni

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10
Q

BIOMASS AND ENERGY

All life requires electrons, energy, and material to make _____

A

Cell parts (carbon)

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11
Q

Organisms can be characterized according to how they build ______ and _____

A

Biomass

Obtain energy

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12
Q

Carbon

  • Heterotrophs
  • Autotrophs
A

break down organic compounds acquired
from outside to gain energy and harvest carbon for biomass

build biomass by fixing CO2 into complex molecules

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13
Q

Energy

  • phototrophs
  • chemotrophs
A

light absorption captures energy

chemical electron donors are oxidized

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14
Q

Electrons

  • Organotrophs
  • Lithotrophs
A

organic molecules donate electrons

Inorganic molecules donate electrons

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15
Q

NAMING “-trophs”

Energy-electron-carbon-troph

A
  • Chemo-organo-hetero-troph
  • Chemo-litho-auto-troph
  • Photo-litho-auto-troph
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16
Q

REGARDLESS OF SOURCE

Energy must be stored

A

Chemical energy (ATP)

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17
Q

A membrane potential

A

is generated when chemical energy is used to pump protons outside of the cell

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18
Q

The H+ gradient plus the charge difference form an ________ called the proton motive force

A

electrochemical potential

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19
Q

The potential energy stored can be used to transport nutrients, drive flagellar rotation, and make ATP by the _____

A

F1FOATP synthase

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20
Q

THE NITROGEN CYCLE

_______ is an essential component of proteins, nucleic acids and other cellular constituents

A

NITROGEN

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21
Q

Nitrogen gas makes up nearly _____ of earths atmosphere, but most organisms are unable to use the gas form (N2)

A

79%

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22
Q

Requires _________ bacteria to convert N2 to NH4+ (ammonium) using nitrogenase enzyme

A

Nitrogen-fixing

[pic]

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23
Q

NUTRIENT UPTAKE

Membranes are designed to separate what is \_\_\_\_\_ the cell from what is inside
A

Outside

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24
Q

Selective permeability is achieved in three ways:

A

• Substrate-specific carrier proteins (permeases) in the
membrane
• Nutrient-binding proteins that patrol the periplasmic space
• Membrane-spanning protein channels (pores) that discriminate between substrates

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25
NUTRIENT UPTAKE - DIFFUSION Passive diffusion
• Some molecules pass freely through membranes (O2, CO2) • Follows concentration gradient (Always high to low)
26
Facilitated diffusion
• Transporters pass material into/out of cell • Follows concentration gradient [pic]
27
NUTRIENT UPTAKE - ACTIVE TRANSPORT Coupled transport
Uses energy released from one molecule transported down | gradient to transport a second molecule against its gradient
28
Symport
molecules move in the same direction
29
Antiport
molecules move in the opposite direction | [pic]
30
The largest family of energy-driven transport systems is the ATP-binding cassette superfamily, or ______
ABC Transporters • Found in all domains of life • Important for uptake (sugars, amino acids) and efflux (drugs, hazardous chemicals) [pic]
31
Group translocation
Uses energy to chemically alter the substrate which then | moves down its concentration gradient
32
Example – phosphotransferase system (PTS)
• Uses energy from phosphoenolpyruvate (PEP) to attach a phosphate to specific sugars • E.g. Glucose becomes glucose-6-phosphate upon entry into the cell • Sugars move down their concentration gradient • The system has a modular design that accommodates different substrates • Refer to video posted on Canvas
33
GROUP TRANSLOCATION : PTS
[pic with important info]
34
CULTURING AND COUNTING BACTERIA Culture media has all materials necessary for growth
* Varies for different bacterial species * Energy source * Carbon source
35
Selective media
favor growth of one organism over another
36
Differential media
expose biochemical differences between species
37
EXAMPLE OF MEDIUM THAT IS BOTH SELECTIVE AND DIFFERENTIAL MacConkey medium
• Contains bile salts and crystal violet • Only gram-negative bacteria grow on lactose MacConkey (selective) • Includes lactose, neutral red dye, and peptones • Only species capable of fermenting lactose produce pink colonies (differential) [pic]
38
UNCULTURABLE MICROBES After 120 years of trying to grow microbes in the lab, we have succeeded in culturing less than _____ of the microbes around us
1%
39
How do we know unculturable microbes exist?
* All known microorganisms contain ribosomal RNA (rRNA) * rRNA is highly conserved across the phylogenetic tree * PCR/sequencing of soil and water samples (etc) compared to genes of known culturable organisms reveals that there are MANY undiscovered microbes
40
THE GROWTH CYCLE Most bacteria divide by _______, where one parent cell splits into two equal daughter cells
Binary fission
41
Growth rate
rate or increase of cell numbers or biomass | * Proportional to the population size at any given time
42
Such a growth rate is called “_______” because it generates an exponential curve – a curve whose slope increases continually
Exponential
43
If a cell divides by binary fission, the number of cells is proportional to ___
2n * Where n = number of generations
44
GENERATION TIME
the interval of time from one generation to the next (a.k.a. doubling time) • Varies with respect to many parameters: species, medium, temperature, pH
45
For cells undergoing binary fission, | Remember this is for growth in pure culture
``` Nt =N0 x2n where Nt is the final cell number N0 is the original cell number n is the number of generations ```
46
Generation time, g = t/n
where t = growth time
47
GROWTH RATE
The rate of exponential growth is expressed as the mean growth rate constant, k, number of generations per unit time (usually per hour)
48
k = n/t
``` where n = number of generations t = growth time *Remember generation time g = t/n • So,k=1/g ```
49
GENERATION TIME
Example • Start with 1 cell and let it grow for 3 generations • Nt =N0 x2n =(1cell)x(23)=(1cell)x8=8cells
50
If you put 106 bacterial cells in a broth. How many cells will there be after 2.5 hours of growth if the generation time is 30 min (if we pretend it is all exponential growth)?
(10^6) x 25 = 32,000,000 G=t/n N=t/g
51
STAGES OF GROWTH IN A BATCH CULTURE Exponential growth never lasts ____
Indefinitely
52
The simplest way to model the effects of a changing | environment is to culture bacteria in a ____
Batch culture | • A liquid medium within a closed system
53
The changing conditions in this system greatly affect bacterial physiology and growth
• This illustrates the remarkable ability of bacteria to adapt to their environment
54
THE GROWTH CYCLE
[pic important]
55
CONTINUOUS CULTURE
all cells in a population achieve a steady state • Keep the cells in exponential growth • Allows detailed study of bacterial physiology
56
The _______ ensures logarithmic growth by constantly adding and removing equal amounts of culture media
Chemistat | • Carefully tune flow rates to match growth rate
57
BIOFILMS
specialized, surface attached, collaborative communities
58
Can be ______ by a single species or multiple, collaborating species
Constructed
59
BIOFILMS
* Can form on a range of organic and inorganic surfaces * Form when nutrients are plentiful * Formation can be cued by different environmental signals * Chemical signals enable bacteria to communicate (quorum sensing)
60
BIOFILM DEVELOPMENT
Distinct stages in biofilm development • Form thick extracellular matrix (e.g. EPS) – increase antibiotic resistance of residents within biofilm [PIC]
61
CELL DIFFERENTIATION Bacteria faced with environmental stress undergo ___________ that includes changes in cell structure
Complex molecular Reprogramming
62
Examples include:
* Endospores of gram-positive bacteria * Heterocysts of cyanobacteria * Fruiting bodies of Myxococcus xanthus
63
ENDOSPORES ARE BACTERIA IN SUSPENDED ANIMATION • Certain gram-positive bacteria (Clostridium, Bacillus) have the ability to form dormant ____
Spores • Heat and desiccation resistant • Do not grow and do not need nutrients until they germinate [pic]
64
CYANOBACTERIAL HETEROCYSTS Some autotrophic cyanobacteria make oxygen through photosynthesis and “fix” N2 to make ______
Ammonia
65
Anabaena differentiates into specialized cells called ______
Heterocysts • Allow it to fix nitrogen anaerobically while maintaining oxygenic photosynthesis [pic]
66
FRUITING BODIES Myxococcus xanthus uses gliding motility –
uses pilus to travel on surface
67
Starvation triggers a developmental cycle in which 100,000 or more cells aggregate to form a _______
Fruiting body
68
________within the fruiting body differentiate into thick walled spores and are released into the surroundings (to find nutrients)
Myxococci | [pic]
69
. Many form biofilms (communities) - Enviovmtal signal • When cells go into biofilm, they no longer have their flagellum $ use twitching motility
``` • Micro colony → they communicate by sending 31 Mag-D Quorum relieving chemicals; sensing • Thick slimy material cons its of polysaccharides polymers (Exo polys.) & -3 in t raped in 1 organic materials protects ```

Microbiology 315 (7 decks)

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