Microbial growth

Question 1

list the physical requirments for growth

Answer 1

Temperature, pH and osmotic pressure

Question 2

list the chemical requirments for microbial growth

Answer 2

Supply of NCHOPS, supply of trace elements and organic growth factors

Question 3

Classify microbes into five groups, based on preferred temperature range

Answer 3

-10 - 20 (Psychrophiles)
0 - 30 (Psychrotrophs)
10-50 (Mesophiles)
40 - 70 (Thermophiles)
70 - 110 (Hyperthermophiles)

Question 4

what is the prefered tempreture for Psychrophiles

Answer 4

-10 to 20

Question 5

what is the prefered tempreture for Psychrotrophs

Answer 5

0 - 30

Question 6

what is the prefered tempreture for Mesophiles

Answer 6

10 - 50

Question 7

what is the prefered tempreture for Thermophiles

Answer 7

40 - 70

Question 8

what is the prefered tempreture for Hyperthermophiles

Answer 8

70 - 110

Question 9

what organsims grows in -10 - 20 degrees

Answer 9

Psychrophiles

Question 10

what grows in tempretures 70 - 110 degrees

Answer 10

Hyperthermophiles

Question 11

Identify why the pH of culture media is controlled

Answer 11

Majority of acids grow 6.5 - 7.5, fungi and yeasts prefer 5 - 6, therefore controlling the pH can restrict some growth.

Question 12

Explain the importance of osmotic pressure to microbial growth

Answer 12

There are three type of osmotic pressure: isotonic, hypertonic and hypotonic environments, most microorganisms are inhibited by high sat and sugar environments.
there are some exceptions:
Halophiles - grow in high salt environments
Saccharoplies - grow in high sugar environments

Question 13

Describe a use for each of the six elements NCHOPS in microbial growth

Answer 13

Nitrogen: synthesis of amino acids, DNA, RNA and proteins
Carbon: key for organic matter (catabolism and anabolism)
Hydrogen: Counter ion examples - OH and -COOH
Oxygen: Terminal electron acceptor in respiration
Phosphorus: Needed for ATP, NADP, DNA and RNA
Sulphur: Needed for the animal acids M&C and cofactors

Question 14

list the six trace elements needed for microbial growth and what they do

Answer 14

Iron: Required for cytochromes in electron transport
Magnesium: Counter ion for nucleotides and ATP. Is also a cofactor to a number of enzymes.
Zinc: Controls hormonal regulation of cell division
Cobalt: Cofactor/part of vitamin B12
Copper: Cofactor in ATP production
Molybdenum: protein production and detoxification

Question 15

how do aerobes avoid damage from toxic O2 species

Answer 15

Enzymes are able to break down the toxic oxygen through superoxide dismutase which breaks it down to H2O2 and oxygen. Then catalase produces water and oxygen, finally peroxide produces water.

Question 16

list the three enzyme which break down toxic oxygen and their products

Answer 16

superoxide dismutase - H2O2
catalase - H2O + O2
peroxide - H2O

Question 17

list the three enzyme which break down toxic oxygen

Answer 17

superoxide dismutase
catalase
peroxide

Question 18

list the types of microbes classified by their oxygen requirments

Answer 18

Obligate Aerobes: grows with air
Facultative Anaerobes:Facilitates air to grow faster
Obligate Anaerobes: grows without air
Aerotolerant anaerobes: can tolerate air
Microaerophile: loves a small portion of air

Question 19

Explain the purpose of organic growth factors annd their significance.

Answer 19

These are requirements for microbial growth hence they cannot be used or studied without sufficient growth factors.

Question 20

list the six diffrent types of growth media (bacterial)

Answer 20

Agar - a compex polysaccharide made from not metabolised seeweed it liquifies at 100.
Chemically defined media - we know the exact chemial make up
Complex media -not all componenets are defined
Differential media - an indicatior in the media dectes certain traits
Selective media - supress unwanted grown and encourages others
Enrichment media - encourages growth of microbes

Question 21

define anaerobic technique

Answer 21

reactive chemicals are added that remove oxygen, this allow for anerobic microbes to grow

Question 22

describe candel jars

Answer 22

The candle inside the jar will extinguish when all of the oxygen has been depleted. These are crucial for studying canophiles (high carbon dioxide)

Question 23

descripe the anaerobic jar

Answer 23

A jar which has machine attached that remove all of the oxygen present.

Question 24

descride the Anaerobic chamber

Answer 24

atmosphere is stripped using chemicals and the are port are used for work.

Question 25

Define colony and colony forming unit

Answer 25

Colony - population of cells arising from a single cell or spore or from a group of attached cells.
Colony forming unit (CFU) - Measure of the number of living (viable) cells in a sample that will grow, divide and form colonies, the streak plate method is used to isolate pure cultures.

Question 26

Describe how single colonies can be isolated by using the streak plate method

Answer 26

The loop is sterilised to ensure pure culture is made, the streaking method is made to create a concentration gradient, the first streak is heavily concentrated and everytime the loop is sterilised and done the concentration lessens.

Question 27

Define bacterial growth, including binary fission

Answer 27

Bacteria growth: binary fission is how bacterial growth occurs.
Binary fission: how bacteria reproduce, the DNA replicates, then the plasma membrane begins to cleave and finally the cell is split with cross walls and the cells separate.

Question 28

describe the phases of microbial growth

Answer 28

Lag phase - is comparing the growth factors and feeding itself, (minimal growth occurs)
Exponential /log phase: rapid growth occurs
Stationary phase: bacterial growth is equal to bacterial deaths
Death phase: where cell lysis occurs (also in log phase)

Question 29

Describe four methods of measuring cell growth

Answer 29

Plate count: The growth is diluted a number of record times, when it is possible to count the number is multiplied by the amount of dilution done.
Membrane filtration: water sample is filtered then grown on an agar plate.
Direct microscope count: glass slides with groves, are counted each box and an average is calculated.
Turbidity: spectrophotometer is used and the light that was able to shown through is able to be reverse engineered into an average.