Lecture 3 - microbial growth

Question 1

What are the physical factors which influence microbial growth?

Answer 1

Physical factors which influence microbial growth are intrinsic: Biochemical/nutritional factors i.e. O2 or carbohydrates and extrinsic factors: Environment, Temperature, pH, radiation etc.

Question 2

What are obligate aerobe, anaerobe, aerotolerant anaerobes and facultative anaerobes?

Answer 2

Obligate aerobes: require O2
Obligate anaerobes: Die in the presence of O2
Aerotolerant anaerobes: Cannot use O2 to grow but are O2 tolerant
Facultative anaerobe: Carry out aerobic metabolism in presence of O2 and anaerobic metabolism when O2 is absent. Hence, they grow better in O2 however can survive when absent.

Question 3

Explain the difference between aerobic and anaerobic respiration

Answer 3

Aerobic respiration is respiration that requires oxygen in the process. It is a redox reaction that processes energy in a form usable by organism. It uses electron transport chain with O2 as final exogenous electron acceptor.

Anaerobic respiration is oxidative phosphorylation without O2. It uses electron transport chain with inorganic molecule such as Sulphur. I.e. Sulfur reducing bacteria

Question 4

Explain the stages of growth curve

Answer 4

Lag phase is the phase in which the organism is metabolically active - growing in size, producing enzymes and energy in the form of ATP.
Exponential/log - this phase is where there is rapid cell division.
stationary - this is when cell division decreases and the number of new cells equal to the number of dying cells.
Death - the number of dying cells increase at an exponential rate/

Question 5

What are the three basic requirements for growth?

Answer 5

Electrons for cellular respiration, Carbon source as a source of matter for building blocks and ATP as a source of energy

Question 6

Explain the different energies microorganisms use

Answer 6

Different organisms utilise varying sources of energy. The two main types include phototrophs and chemotrophs. Phototrophs harness energy from light using photosystems I and II. Chemotrophs oxidise chemical compounds; inorganic (heterotrophs) or organic (autotrophic) to obtain energy . It primarily includes the transfer of energy through series of redox reactions and movement of electrons

Question 7

What microbial types will you expect to find at the top of the winogradsky column compared to the bottom?

Answer 7

At the top of the column, you would expect organisms which uses light energy so any photolithotrophic autotrophs and heterotrophs are expected at the top of the winogradsky column. Chemolithotrophic heterotrophs will be mainly found at the bottom.

Question 8

Consider the construction of a Winogradsky column. What is the importance of the inclusion of the mud

Answer 8

The mud contains the microorganisms which we want to grow in the column. It also provides nutrients and carbon for the microbes to grow.