2.6 Environmental Control of Micro-Organisms Flashcards
what is a micro-organism?
a very small, microscopic organism that is usually unicellular
why are micro-organisms used in industry and research?
as they are easy to keep, cheap and grow fast in culture
micro-organisms are found in all 3 domains of life: archaea, bacteria and eukaryota
describe ‘the 3 domains of life with a named example’
Archaea
e.g. halophiles
- a group of single-cell prokaryotes containing many of the extremophiles species, as well as some of the most ancient species of organism
Bacteria
e.g. e.coli
- a group of single-cell prokaryotes contains many pathogenic and useful species
Eukaryota
e.g. algae
- a group of eukaryotic cells including fungi, plants and animals
describe ‘fermenters’
Industrially, microbes are grown in large, vat fermenters which provide optimum living conditions which are controlled by a computer.
Filters are put on both the ‘air in’ and ‘air out’ tubes to prevent contamination from the outside getting in and the growing microbe from getting out.
how might micro-organisms be grown in a laboratory or classroom setting?
- petri dish
- agar slopes
- culture bottles
describe ‘the chemical conditions required for the growth of micro-organisms’
Energy Source
- some micro-organisms are able to use sunlight and the process of photosynthesis to produce their own food (e.g. unicellular algae)
- most, however, rely on a chemical substrate as a food source (e.g. bacteria and fungi)
Simple Chemical Compounds
- these are the basic nutrients that the micro-organism requires for growth
- they are generally contained within the growth medium for the organism (e.g. salts)
Complex Chemical Compounds
- some micro-organisms can synthesise all complex molecules from simple chemicals
- others, however, need some complex molecules provided in their growth medium as they are unable to create them (e.g. fatty acids and vitamins)
describe ‘the environmental conditions required for the growth of micro-organisms’
Sterile culture
- aseptic technique is necessary when growing micro-organisms
- contaminants may compete with the microbe for resources, limiting its growth
Temperature
- for every micro-organism, there is an optimum temperature range for its enzymes
- in industry, this is called a computer
Oxygen
- each microbe has its own optimum oxygen level
- some microbes can survive with little or no oxygen
- some microbes require constant aeration (bubbling)
pH
- microbes also have their own optimum pH levels
- can survive in a wide range of acid and alkali environments
give an everyday example of the environmental control of bacterial growth
-putting food in the fridge
describe ‘the erm growth’
the irreversible increase in the size or mass of an organism
why do we use dry biomass as a measure of growth in most unicellular organisms?
fresh biomass varies depending on water supply, dry biomass doesn’t
micro-organisms in culture conditions undergo a series of four distinct growth phases: lag, log/exponential, stationery, death
describe ‘the four distinct growth phases’
Lag
- cells adjust to new conditions
- time is taken to induce the enzymes needed for this new substrate and for DNA replication to occur
Log/Exponential
- cells are growing at their fastest rate
- there are no limiting factors
Stationery
- the number of new cells is equal to the number of cells that die (there is no net growth in numbers)
- metabolites accumulates and resource decreases
- secondary metabolites are produced
Death
- lack of substrate and the build up of toxic metabolites kills cells
- culture size decreases
why do we use a log scale to graph microbial growth?
when measuring microbial growth, the numbers involved are so massive that a normal scale would be meaningless
describe ‘primary metabolism and secondary metabolism’
Primary Metabolism
- occurs during the period of active growth (lag and log/exponential phases)
- it breaks substrates down to obtain energy and produces primary metabolites (such as amino acids)
- often useful to humans and industrial processes are used to collect them
Secondary Metabolism
- occurs at the very end of the exponential phase and during the stationary phase
- it describes the production of secondary metabolites (these are not used by the organism for growth or producing new cells, but may confer a selective advantage upon the organism)
- very useful to humans and so are cultivated on an enormous scale in order to be mass-produced
how does producing penicillin confer an ecological advantage onto the fungi, penicillium chrysgenum?
it kills bacteria in the medium, reducing competition for the fungus and increasing its chance of survival
