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Microbiology > Chapter 7 Microbial Growth > Flashcards

Chapter 7 Microbial Growth Flashcards

1
Q

Macronutrients

A

(C,H,O,P,N,S)
Required in large amounts
Metabolism and cell structure
K+,Ca++,Mg++,Fe+++ moderate quantities

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2
Q

Micronutrients

A

(Mn,Zn,Ni,Co,Cu,Mo)
Small amounts - difficult to determine exact requirements (tapwater sufficient)
usually enzymatic function

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3
Q

Chemical requirements for growth

A
  1. Carbon - CO2 or organic
  2. N, S, P - DNA & RNA, protein, some lipids
  3. Trace Elements - Metal ions - only certain cells and in tiny small amounts
  4. Growth Factors - not made by organism
    •purines and pyrimidines: required for synthesis of nucleic acids (DNA and RNA)
    •essential amino acids: required for the synthesis of proteins
    •vitamins: needed as coenzymes and functional groups of certain enzymes
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4
Q

Media formulations

A

Chemically defined media - exact amounts of pure chemicals (research)
Complex media - composition varies (enzymatic)

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5
Q

Specialty medias

A

Selective - inhibit growth of certain species.
Differential - most things will grow- but will look different
Selective and differential - utilizes both aspect

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6
Q

Photoautotroph - Oxygenic

A

Produces oxygen (O2)
(Inorganic)CO2 + H2O + light = (CH2O)n + O2
cyanobacteria, algae, green plants

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7
Q

Photoautotroph - Anoxygenic

A

Does NOT produce oxygen
use inorganic material like hydrogen sulfide (to sulfur) or hydrogen gas (to water)
are obligate anaerobes (O2 toxic)
bacteriochlorophylls - green and purple sulfur bacteria

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8
Q

Photoheterotroph

A

Use light for energy
Use organic compounds like alcohols and fatty acids for carbon source
obligate anaerobes
Green and purple non-sulfur bacteria
Found in bogs, moist soil, paddy fields (light but no O2)

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9
Q

Chemoautotroph

A

Electrons from reduced inorganic compounds used for energy
CO2 used for carbon
remove electrons from H2, H2S, S, or Fe and combine them with CO2, O and H
deep-sea vent bacteria; hot springs

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10
Q

Chemoheterotrophs

A

Use organic molecules for both energy and carbon
Aerobic: uses oxygen as final electron acceptor
Anaerobic: uses sulfate, nitrate, etc. as final electron acceptor
most bacteria, all fungi, all protozoa and all animals, pathogens

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11
Q

Inorganoheterotrophs

A

Use reduced inorganic molecules for energy
Organic molecules for carbon source
some bacteria

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12
Q

Parasites and Saprobes

A 
Parasites: derive nutrients from host
•Pathogens
•Some are obligate parasites
Saprobes: free-living microorganisms that feed on organic waste from dead organisms 
•Opportunistic pathogen
•Facultative parasite
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13
Q

Gas Requirements

A

Oxygen: O2
•Powerful oxidizing agent
•Must be “detoxified”

Carbon dioxide: CO2
•Essential for autotrophs

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14
Q

Oxygen Radicals (Must be neautralized even if organism doesnt use oxygen)

A

Toxic by-products of O2 use and exposure:
•Superoxide O2- superoxide dismutase
•H2O2
catalase, peroxidase
•Singlet Oxygen
photosynthetic organisms have carotenoids which scavenge the singlet oxygen and render it nontoxic

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15
Q

Oxygen Requirements- Obligates

A

Aerobes-
require O2 for growth (21% O2 in air)
they use O2 as a final electron acceptor in aerobic respiration
Anaerobes-
do not need or use O2 (toxic)
anaerobic respiration, anoxygenic bacterial photosynthesis, methanogenesis

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16
Q

Oxygen requirements- Others - Facultative anaerobes

A

Facultative anaerobes- Can switch between aerobic and anaerobic types of metabolism (O2 prefered, fermentation or ana-respiration if not)

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17
Q

Capnophiles

A

require a high level of CO2 and are grown in candle jars

18
Q

Oxygen requirements- Others - Aerotolerant anaerobes

A

Exclusively anaerobic type of metabolism Insensitive to the presence of O2
Produces superoxide dismutase and peroxidase enzymes
Ex: Streptococci

19
Q

Oxygen requirements- Others - Microaerophiles

A

Are aerobic, but need low concentrations of O2
<15% O2
Ex: Helicobacter pylori

20
Q

Anaerobic growth media:Fluid Thioglycollate Medium

A

Anaerobes are killed by exposure to oxygen
Use a reducing medium to deplete available oxygen
Heating the media also drives off oxygen

21
Q

pH Requirements

A

Neutrophiles: Most bacteria grow between pH 6.5 to 7.5
Acidophiles: grow below pH 4.0
Lactobacillus acidophilus (yogurt, ~pH 4)
Some molds and bacteria can tolerate acid (food spoilage)
Alkalinophiles: grow best under basic conditions (not many)

22
Q

Transport: Movement of Chemicals Across the Cell Membrane - Passive transport

A

does not require energy
substances exist in a gradient and move from areas of higher concentration toward areas of lower concentration
Types:
•Simple diffusion – small things slip between the phospholipids (CO2, O2, N2, water)
•Osmosis – diffusion of water
•Facilitated diffusion – requires a carrier

23
Q

Transport: Movement of Chemicals Across the Cell Membrane - Active transport

A

requires energy and carrier proteins
gradient independent
Types:
•Active transport
•Group translocation – transported molecule chemically altered
•Bulk transport – endocytosis, exocytosis, pinocytosis

24
Q

Diffusion

A

Net Movement of Molecules Down Their Concentration Gradient Passive Transport
No addition energy required

25
Q

Osmotic Solutions

A

Isotonic - w or w/o cell wall equilibrium
Hypotonic
Cell wall - wall prevents bursting
w/o cell wall - swelling then osmolysis
Hypertonic
cell wall - membrane shrinks inside wall -plasmolysis
w/o cell wall - shrinking and distortion

26
Q

Facilitated Diffusion

A

Monomer sized molecules need a transport protein to cross the membrane
•Carrier protein
•No additional input of energy required

27
Q

Endocytosis

A

Bringing substances into the cell through a vesicle or phagosome
•Phagocytosis ingests substances or cells
•Pinocytosis ingests liquids

28
Q

Symbiotic Relationships

A

mutualism – obligatory, dependent; both members benefit
commensalism – commensal member benefits, other member not harmed
parasitic – parasite is dependent and benefits; host is harmed

29
Q

Quorum sensing

A

a group of microorganisms coordinate functions (to release digestive enzyme, toxins, transfer DNA, etc.)
Quorum: critical number of cells
Inducer molecules: coordinate some response

30
Q

Counting Bacterial Growth

A

2n, where n is the number of generations
exponential growth
5-10-20-40-80-160-320

31
Q

Phases of Growth: Lag

A

no or slow growth, yet
•culture “waking up”- synthesizing DNA, enzymes, ribosomes, etc.
•or culture so dilute it is below limit of detection

32
Q

Phases of Growth: Log

A
  • Cell division as fast as possible (“balanced growth”)
  • Adequate nutrients and favorable environment
  • Appears linear on a log scale
  • Cells are dividing and growing in geometric progression (2,4,8,16,32,64,128,etc.)
  • Phase used to calculate generation time
33
Q

Phases of Growth: Stationary

A
  • Growth slows such that new cells = dying cells
  • Growth is limited by space, supply of nutrients
  • Depleted nutrients, and waste is accumulating
34
Q

Phases of Growth: Death

A
  • Number of cells dying increases exponentially due to build up of waste products.
  • Some remain viable
35
Q

Direct Measures of Growth - plate counts

A

Plate Counts
•enumeration of bacteria: Assumption that every live bacterium will produce a colony on a plate
•Viable counts

36
Q

Direct Measures of Growth - filtration

A
  • Used when quantity of bacteria is low
  • Need to concentrate bacteria onto filter
  • Transfer bacteria from the filter to an agar dish
  • Touch the filter to an agar dish, then incubate to grow colonies
37
Q

Direct Measures of Growth - Direct Cell Counts

A
  • Petroff-Hausser cell counter
  • Use very accurate counting chamber under microscope (like a hemocytometer)
  • Use grid to establish number of organisms
38
Q

Direct Measures of Growth - Automated Direct Counts

A 
Coulter Counter
•Separate based on charge
•Automatic
•Expensive 
•Breaks easily

Flow cytometry•Can count cells based on fluorescent labels•Separates live from dead•Must be able to manipulate organisms DNA

39
Q

Direct Measures of Growth - Automated Direct Counts

A 
Coulter Counter
•Separate based on charge
•Automatic
•Expensive 
•Breaks easily

Flow cytometry
•Can count cells based on fluorescent labels
•Separates live from dead
•Must be able to manipulate organisms DNA

40
Q

Indirect Measures of Bacteria

A

Turbidity: Use spectrophotometer to measure amount of light scattered by a culture

Metabolic activity: measure amount of product made or substrate used up

Dry Weight: organisms are filtered and then weighed to determine the starting material

41
Q

Preserving Bacterial Cultures

A
  • Refrigeration: for short term storage – what we use in laboratory
  • Deep freezing (-70C): long term (years)
  • Lyophilization (freeze drying): quick frozen cultures then placed under vacuum and sealed (decades)
42
Q

Motility Medium

A
  • Soft agar
  • Inoculate straight in with needle
  • Incubate at room temp

If agar cloudy then microorganisms motile but if they are near injection point non-motile

Microbiology (8 decks)

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