Ch.6 : Microbial Growth Flashcards Preview

Microbiology > Ch.6 : Microbial Growth > Flashcards

Flashcards in Ch.6 : Microbial Growth Deck (44):
1

Physical Requirements for Growth

Temperature
pH
Osmotic Pressure

2

Chemical Requirements for Growth

CARBON
NITROGEN
PHOSPHOROUS
Sulfur
Trace Elements
Oxygen
Organic Growth Factor

3

Microbes classified into 3 groups based on temperature

Psychrophiles
Mesophiles
Thermophiles

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Psychrophile

Cold-loving microbes. 0-20 Degrees Celsius

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Mesophile

Moderate-temperature loving microbes 20-45 Degrees Celsius

Most disease-causing bacteria prefer 35-40 Degrees Celsius

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Thermophiles

heat-loving microbes. 55-85 Degrees Celsius

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*Psychrotrophs

0-35 Degrees Celsius

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*Hyperthermophiles

85-113 Degrees Celsius

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Minimum Growth Temperature

Lowest temperature at which the species will grow

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Optimum Growth Temperature

Temperature which species grow best.

Microbes cannot regulate internal temperature

11

Maximum Growth Temperature

Highest temperature at which growth is possible.

High temperatures may inhibit enzyme functioning and be lethal.

12

Acidophiles

growth optimum between pH 0 and pH 5.5

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Neutrophiles

growth optimum between pH 5.5 and pH 7

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Alkaliphiles (alkalophiles)

growth optimum between pH 8.5 and pH 11.5

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Plasmolysis

Shrinkage of cell's cytoplasm

Microorganisms composition is 80-90% water

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Hypotonic

Increase osmotic pressure (cell fills up)

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Hypertonic

Decrease osmotic pressure (cell shrivels)

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Trace Elements

Iron, Copper, Molybdenum, Zinc

Essential for the functions of certain enzymes, usually as cofactors. Too much is toxic

19

Halotolerant microbe found on human skin

Staphylococcus aureus

Halo = Salt

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Obligate Aerobes

absolute requirement for oxygen

ex. Pseudomonas

21

Obligate Anaerobes

cannot tolerate any oxygen (toxic)

ex. Clostridium

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Facultative Anaerobes

grow better with oxygen, but can grow just fine without it also; facultative means flexible

ex. E. coli

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microaerophiles

require small amounts of oxygen (2-10%) but large amounts are toxic

ex. Helicobactern pylori

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aerotolerant anaerobes

indifferent to oxygen; can grow in the presence of oxygen, but never use it to produce energy; obligate fermenters

ex. Streptococcus pyogenes (strep throat), lactic acid bacteria

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Singlet Oxygen

O2- that has been boosted into a higher energy state and is extremely toxic

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Superoxide free radicals

A toxic anion (O2-) with an unpaired electron

Must produce superoxide dismutase (SOD) to neutralize

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Peroxide Anion

An oxygen anion consisting of two atoms of oxygen (O2^-2)

Must produce catalase to neutralize it

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Hydroxyl Radical

A toxic form of oxygen (OH) formed in cytoplasm by ionizing radiation and aerobic respiration

29

Fastidious Organisms

organisms that cannot synthesize everything they need and require supplemental growth factors

ex. Neisseria (need all 20 aa, 7 vitamins), Mycoplasma

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Non-Fastidious Organisms

versatile, do not require supplemental growth factors

ex. E. coli, P. aeruginosa

31

Biofilms

A microbial community that usually forms as a slimy layer on a surface

Can be formed on any conditioned surface; Hard to remove
Very complex communities

32

Quorum sensing

Cell-to-cell chemical communication allows bacteria to coordinate their activity and group together into communities.

33

Planktonic

Free swimming bacterium

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Sessile

Grow attached to surfaces

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Extracellular Polymeric substance (EPS)

a glycocalyx that permits bacteria to attach to various surfaces

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Binary Fission

Prokaryotic cell reproduction by division into two daughter cells

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Lag Phase

The time interval in a bacterial growth curve during which there in no growth

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Log phase

The period of bacterial growth or logarithmic increase in cell numbers; also called exponential growth phase

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Stationary Phase

The period in a bacterial growth curve when the number of cells dividing equals the number of dying

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Death Phase

The period of logarithmic decrease in a bacterial population; also called logarithmic decline phase

41

Direct Measurement (counting chamber)

counts both live and dead cells

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Indirect Measurement (Spectrophotometry)

measures absorption or transmittance of light at 600nm wavelength

both live and dead cells absorb light

43

Turbidity

the cloudiness of a suspension

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Direct Measurement (Viable Cell Count)

*also called Dilution plating

counts only live cells
each viable cell leads to a colony
count colony forming units (cfu)