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MICR222 > Labs 1-4 > Flashcards

Labs 1-4 Flashcards

1
Q

Why was 1g cellulose powder added to the winogradsky column

A

Provided a C source

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2
Q

Why was 1g of calcium sulfate added to the winogradsky column

A

Provided a source of sulfur

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3
Q

Features of cyanobacteria, algae, diatoms and protists in winogradsky column

A

Photoautotrophic/ photoheterotrophic/ photosynthetic
Use light as energy source, release O2= causes the O2 gradient
Use energy from sun to fix CO2 and release organic molecules

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4
Q

Features of Beggiatoa

A

Sulfur oxidising
Non-photosynthetic chemolithotrophic, facultative anaerobes
Oxidise hydrogen sulfide to sulfuric acid, energy released used to fix carbon and release organic molecules

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5
Q

Features of Rhodomicrobium

A

Purple non-sulfur
Mixotrophic- can do photosynthesis to fix carbon or simply take it up as a heterotroph
Photoheterotroph
When given light and lacking O2, use this for photosynthesis
Organic molecules or ethanol as electron donor

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6
Q

Features of Chromatium

A

Purple sulfur
Photoautotrophic
Use CO2 as C source from CaCO3-
Light as energy source= photosynthetic
Use H2S as electron donor, tolerate at low amounts (from Desulfovibrio)

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7
Q

Features of chlorobium

A

Green sulfur
Photoautotrophic obligate anaerobes
CO2 from CaCO3- as C source
Light as energy source= photosynthetic
H2S as electron donor, tolerate at higher amounts (from Desulfovibrio)

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8
Q

Features of Desulfovibrio

A

Sulfur reducing
Chemoheterotrophic obligate anaerobes
Use organic molecules as C source
Sulfate as final electron acceptor so creates H2S leading to the gradient in the column

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9
Q

Features of clostridium

A

Fermentative obligate anaerobes
Breakdown cellulose into glucose molecules
Takeup glucose and partially ferment it
Breakdown fermented glucose for energy
Makes ethanol and organic acids as byproducts- react with carbonate to provide the CO2 for the photosynthetic microbes

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10
Q

What does plant made leghaemoglobin do

A

Acts as an oxygen buffer- has high O2 affinity
Supplies oxygen to the bacteroids for ATP production and protects oxygen-sensitive nitrogenase system- bonds oxygen to it to maintain the microaerobic conditions
Reduces N2 to ammonia

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11
Q

How is CFU/mL calculated

A

No of colonies x 1/plated vol in mL x df

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12
Q

How to figure out what dilution is needed for a good plate count

A

No of colonies/CFU/mL x 1/plated vol in mL

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13
Q

Nodulation, if seen and continuation

A

If seen means the plant is an effective strain
Plant supplies C, rhizobia supplies N
Continued successful growth depends on efficiency of symbiotic relationship as C and N can be in trace amounts in the synthetic medium

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14
Q

Viable plate count and PCA in the lab

A

Excludes many bacteria
PCA meant to provide a wide range of growth, still estimated to only lead to 1-10% of growth

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15
Q

Fungi and plant mutualistic relationship

A

Fungi gets fixed carbohydrates, plant gets minerals and water

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16
Q

Why was sabouraud dextrose agar used for fungi growth

A

The fungi will eat the sugar to grow and also has a low pH of 5.6 which bacteria cant grow on but fungi can

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17
Q

Why was penicillin and streptomycin added to the plate for fungi growth

A

Eliminates bacterial growth

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18
Q

Three features of endospores which protect from heat, desiccation, UV and toxins

A

Outer walls tightly bonded due to high amount of cystiene which works to bind proteins
Dry core
Dipicolinic acid and small acid soluble proteins in the cortex

19
Q

Why were endospore plates heated at 80degC for 20 min

A

To kill any bacteria and fungi
These things die at about 65degC

20
Q

Competition outcome depends on…

A

Rate of nutrient uptake, inherent metabolic rates and growth rates

21
Q

Competition used in the lab

A

E.coli have 25 reactions to produce the 12 necessary precursor metabolites needed for macromolecule building
Need atleast glycolysis, CAC and pentose phosphate pathway
S.equi cant make all 12 precursor metabolites so rely on the growth medium to provide some for them (THB provides, MSB doesnt)
Both grown in THB and MSB, then cultured on eosin methylene blue agar plates (EMB) for E.coli as allows only them to grow and blood agar plates + streptomycin allowing only S.equi to grow

22
Q

Antagonism and how this was tested in the lab and results

A

2 living things, one gains an advantage and the other is harmed
Bacteriocins are a waste product produced, inhibitory molecule which is ribosomally translated (therefore, info encoding primary structure is directly encoded in DNA of producer strain)- S.equi produce this, can kill other bacteria
Added S.pyogenes FF22 and 71-698 aswell as S.uberis and S.dysgalactiae
The S.pyogenes strains were found to be inhibited by S.equi= antagonism

23
Q

Commensalism and how this was tested in the lab

A

One organism benefits, the other is unaffected
Add antibiotic sensitive microbe with an antibiotic resistant one
E.coli XLI-Blue contains a plasmid which encodes for a B-lactamase enzyme, exported outside of cells and released into extracellular environment to degrade things with a B-lactam ring (including antibiotics such as ampicillin)
Sensitive microbe was M.luteus, was found to grow near the E.coli strip meaning that the E.coli provides resistance and allows it to grow= commensalism

24
Q

Types of microbes in response to salinity

A

Non-halophile= up to 0.3% NaCl
Mild halophile= 1-4% NaCl
Moderate halophile= 5-10% NaCl
Extreme halophile= 12-35% NaCl

25
Q

How was microbe response to salinity tested

A

Use TSB with 1%, 3%, 8% and 15% NaCl
Add E.coli in each and leave at 37degC
Add S.epidermidis in each and leave at 37degC
Add L.anguillarum in each and leave at 12degC

26
Q

Results for effect of salinity

A

E.coli grew best at 1% and decreased as salinity increased (is a non/ mild halophile due to normally living in gut)
S.epidermidis grew best at 8%, inhibited elsewhere (is an extreme halophile as grows on the skin)
L.anguillarum grew good in 1% and 3% (better than E.coli at higher salinity as it is a moderate halophile and is from marine environments)

27
Q

Types of microbes in response to temperature

A

Psychrophiles= 0-20degC eg L.monocytogenes, important for food preservation
Mesophiles= 20-45degC eg E.coli and S.aureus, most soil and all human microbes
Thermophiles= 45-80degC eg Thermus aquaticus, thermal pools and soils in summer
Hyper thermophiles= >80degC eg P.fumarii requires >90degC to grow, hot springs, marine hydrothermal vent

28
Q

How was effect of temperature tested in the lab

A

TSB with B.stearothermophilus
TSB with E.coli
TSB + 1.5% NaCl with L.anguillarum
Three with of each of the above, each in 12degC, 37degC and 60degC

29
Q

Results of effect of temperature in the lab

A

B.stearothermophilus grew best at 60degC due to being a thermophile
E.coli grew best at 37degC due to being a mesophile in the gut, little growth in 12degC
L.anguillarum grew best at 12degC, little bit at 37degC due to living in marine environments and being a psychrophile/mesophile. Less able to grow with increasing temp

30
Q

UV and microbes

A

Kills all kinds of microbes due to short wavelength and high energy
Most lethal at 260nm as it is most effectively absorbed by DNA here and forms thymine dimers
Microbes isolated from the environment often show increased signs of UV exposure tolerance

31
Q

How was effect of UV light tested in the lab

A

Plate TSA plates with E.coli and another with B.subtilis
Remove the lid of the plate, expose each quarter for either 0, 10, 20 or 40s

32
Q

Why were lids removed when testing effect of UV light

A

UV would struggle to penetrate through the lid and results wouldnt be as accurate

33
Q

Why were plates wrapped in foil after UV exposure

A

Prevents bacteria from doing photoreactivation where they use light and photolyase enzyme to repair the thymine dimers

34
Q

Results of effect of UV in the lab

A

E.coli died and didnt grow in all UV presence= no tolerance
B.subtilis has growth in all, decreased growth with increased UV light exposure= tolerant due to the ability to form endospores

35
Q

pH in the environment

A

Acidity is more common than alkalinity
Acidity develops in oxidising environments and the biosphere is predominantly aerobic
Sulfuric acid occurs from the oxidation of sulfides H2S and FeS2 (common in volcanic/ geothermal, bogs, swamps and acidic soil)
Humans have caused a higher number of acidic environments
Acid rain from combustion of sulfurous fossil fuels= lakes become acidic (ph of 4)
Acid mine drainage leads to leachates which have pH of 2-3

36
Q

How was effect of pH tested in the lab

A

Test organisms Escherichia, Listonella and Lactobacillus were all grown at various pH in optimal conditions
Absorbance was read at 600nm
The higher the absorbance, the more bacteria there were

37
Q

Results of effect of pH in the lab

A

Listonella prefer alkaline environments (higher absorbance at higher pH)
Escherichia prefer neutral pH (higher absorbance at neutral pH)
Lactobascillus prefer acidic environments (higher absorbance at low pH)

38
Q

How to get percentage of fungal and endospore growth relative to viable count

A

(CFU/mL (of fungi or endospores)/ viable count) x 100

39
Q

Features of cells from PCA in gram stain

A

Gram +ve rods

40
Q

Features of endospore formers in gram stain

A

Gram +ve rods

41
Q

Rhizobia results at lab 4

A

There were nodules (black dots) present on the roots of white clover in inoculated tube
There were no nodules on the white clover in the uninoculated tube

42
Q

How did winogradsky column look at week 4

A

Clear H2O 15mm from top
10mm below water, mud was brown and rusty orange
40mm below water, mud was brown and slightly rusty orange
Mud at the bottom was black or a very dark blue

43
Q

What makes the Todd Hewitt broth highly nutritious

A

Content of peptones, dextrose and salts

44
Q

Microbes grown in lab cultures and competition

A

When grown in lab cultures, organisms dont have pressures for competition and therefore, a pure culture achieves growth rate which is dependent on genetic abilities and the given growth conditions
When another organism is added then competition may occur

MICR222 (8 decks)

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