Topic 5 -Microbial Growth

Question 1

List the requirements for microbial growth

Answer 1

Physical:
Temperature, pH, osmotic pressure

Chemical:
NCHOPS totally organic
Nitrogen, Carbon, Hydrogen, Oxygen, Phosphorous, Sulphur
Trace elements (e.g. vitamins)
Organic growth factors (e.g. Fe, Mg, Cu, Zn, Co)

Question 2

A little bit about pH and microbes?

Answer 2

bacteria grow b/w pH 6.5-7.5
Moulds & yeast grow b/w 5 - 6
pH controlled by buffers
Acidophiles
Alkaliphiles

Question 3

Explain the importance of osmotic pressure to growth

Answer 3

Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
Hypertonic enviro’s cause plasmolysis (inside of cell shrinks)

Question 4

Use of Nitrogen (N) in growth?

Answer 4

amino acids, proteins, DNA, RNA

Question 5

Use of Carbon (C) in growth?

Answer 5

carbohydrates, lipids, aa, DNA, RNA. Carbon for cata/anabolism.

Question 6

Use of Hydrogen (H) in growth?

Answer 6

counter ion e.g. -OH & -COOH. Used as proton source for chemiosmotic formation of ATP

Question 7

Use of Oxygen (O) in growth?

Answer 7

found in most organic molecules e.g. glucose.

electron acceptor

Question 8

Use of Phosphorous/phosphate (P/Pi) in growth?

Answer 8

found as phosphate

ATP, NADP, DNA & RNA

Question 9

Use of Sulfur (S) in growth?

Answer 9

needed for aa cysteine and methionine & co factors

Question 10

What is the role of trace element Fe?

Answer 10

Iron.

needed for cytochromes in electron transport

Question 11

What is the role of Trace element Mg?

Answer 11

Magnesium

Counter iron for nucleotides and ATP

Question 12

What is the role of trace element Zn, Co, Cu & Mo?

Answer 12

Zinc, Cobalt, Copper, Molybdenum.

Enzyme cofactors

Question 13

How do aerobes avoid damage from O2?

Answer 13

Enzymes.
singlet oxygen=> boosts O2 to higher energy state
then to superoxide free radicals
Then to peroxide anion
then to hydroxyl radical

Question 14

Describe the visual growth of an obilgate aerobe?

Answer 14

all near top of tube where high [] of O2.

See diagram. pg 4

Question 15

Describe visual growth of facultative anaerobes?

Answer 15

more [] near top of tube but spread throughout tube.

Question 16

describe visual growth of obligate anaerobes?

Answer 16

all at bottom of tube where very low to no O2

Question 17

describe visual growth of aerotolerant anaerobes?

Answer 17

spread throughout tube

Question 18

describe visual growth of microaerophiles?

Answer 18

very sensitive, need exact right conditions. Found in strip through middle of tube or to particular needs.

Question 19

Explain the purpose of organic growth factors

Answer 19

organic compounds obtained from the enviro.
e.g. vitamins, aa, purines, pyrimidines
many bacteria do not require these
some microorganisms absolutely require a particular GF

Question 20

What is a culture medium?

Answer 20

nutrients prepared for microbial growth

Question 21

what does sterile mean?

Answer 21

contains no living organisms

Question 22

what is inoculum?

Answer 22

microbes introduced into medium

Question 23

what is a culture?

Answer 23

microbes growing in/on a culture medium

Question 24

what is a pure culture?

Answer 24

contains only one species or strain

Question 25

what is a colony?

Answer 25

population of cells arising from a single cell or spore or group of attached cells

Question 26

what is a colony forming unit (CFU)?

Answer 26

number of living cells in a sample that will grow, divide & form colonies on solid media

Question 27

what is a chemically defined media for bacterial growth?

Answer 27

exact chemical composition known. Microbes make all nutrients themselves, uses a lot of energy, takes longer to grow

Question 28

what is a complex media for bacterial growth?

Answer 28

e.g. beef extract and peptone (no defined chemical composition) Nutrients provided, faster growth

Question 29

How can single colonies be isolated?

Answer 29

streak plate method

Question 30

List the different kinds of bacterial growth (repro)

Answer 30

binary fission budding fragmentation of filaments conidiospores (asexual)

Question 31

Name & describe the 4 different bacterial growth phases

Answer 31

1. lag phase -little cell division occuring 2. exponential (log) phase -growth phase 3. stationary phase -bacterial death=bacterial division 4. death phase -cell lysis occurs

Question 32

List 4 ways of measuring cell growth

Answer 32

Plate count membrane filtration direct count under microscope turbidity

Question 33

List the 5 main groups of microbes classified according to their temp. range of growth, and what temp they grow at.

Answer 33

``` Psychrophiles -10 - 20C Psychotrophs 0-30C Mesophiles 10-50C Thermophiles 40-70C Hyperthermophiles 65-110C ```