Environmental control of metabolism Flashcards
Microorganisms
Organisms too small to be seen without magnification
Three domains of life and
One example of each
Eukaryotes, Bacteria and Archea
Eukaryotes: animals
Bacteria: antino bacteria
Archea: nanoarcheaota
Uses of microbes:
Used in research and industry
Why are microbes used in research and industry:
Are easy to culture, they grow and reproduce rapidly.
Their food substrate is often cheap
They produce many products: yoghurt, cheeses, alcohols.
Their metabolism can be controlled and manipulated fairly easily.
How is optimum yield of useful products produced by microbes ensured?
They control the environmental conditions during the culture of yeast/bacteria.
In industry large containers which are constantly monitored are used.
Small scare growth media for microbes
Agar jelly (solid) in petri dishes or broth (liquid) in flasks. Both contain all the nutrients needed for growth of the microbes
Large scale growth media for microbes
Broth in industrial fermenters.
Contains all nutrients needed for growth of the microbes.
Composition of growth media for microbes since they cannot photosynthesise
Energy source - carbohydrate
Building blocks to make new cells - amino acids and nucleotides
Sometimes specific compounds - fatty acids, vitamins etc.
Nutrient may also be provided - beef extract
When growing microbes what environmental conditions must be composed?
Aseptic techniques: creating of sterile conditions to avoid contamination
Computing monitoring and control of environmental conditions.
Key factors that affect growth
Temperature
Oxygen concentration
pH
Glucose concentration
Computer controlled fermenters
Produce huge quantities of products,
If key factors varie they will see this and adjust them so that optimum conditions are kept.
Growth;
When rate of synthesis of new organisms material exceeds the rate of breakdown of material.
Involves an irreversible increase in dry biomass.
Why is dry biomass used as an indicator of growth rather than fresh biomass?
It’s more reliable since fresh biomass varies depending in water availability.
Measuring growth for bacteria and yeast cells -
Increase in numbers of cell number over a period of time
Generation / doubling time
Time taken for a cell to divide
How is the extent of growth of a microbial culture determined?
By taking samples from the culture and knowing the initial number of cells present
Two different types of cell count -
Viable cell count and total cell count
Viable cell count
Counts only living microorganisms
Total cell count
Counts viable and dead cells
Growth curve graph -
log(number of cells) against time 4 parts Lag phase m=>0 Exponential phase m=>1 Stationary phase m=0 Death phase m=
Lag phase
Little to no increase in cell number,, microbes adjust to conditions of the culture and begin to metabolise substrate, may need to induce enzymes, cells will prepare for cell division
Exponential phase
Contains the most rapid growth of microbes, growth rate is at a maximum due to plentiful nutrients
Stationary phase
Cell production and death are equal to one another, nutrients in culture become depleted and toxic metabolites are produced.
Why is the stationary phase sometimes encouraged?
Secondary metabolites (molecules not required for cell growth) are produced, for example antibiotics.
Why do microbes produce a secondary metabolite?
They confer an ecological advantage, by allowing the microbes that produce them to outcompete other microorganisms.
Death phase
Where lack of substrate and the toxic accumulation of metabolites causes death of cells
Which phase shows only viable cell count
Death phase
How is pH controlled?
Via the use of a buffer solution
Why do cells not divide in lag phase?
Enzymes are induced
Why does secondary metabolites give an ecological advantage?
It will kill other bacteria reducing competition for the microorganism.
