Environmental control of metabolism Flashcards
What are micro-organisms?
Micro-organisms are archaea, bacteria and some species of eukaryotes.
Explain the two types of growth media
complex media contain one or more crude sources of nutrients and their exact chemical composition and components are unknown;
defined media, or synthetic media, are media in which the components of the medium are chemically known and are present in relatively pure form.
What do you need to culture a microoragnism?
Microorganisms require an energy source (which may be chemical or light) and simple chemical compounds for biosynthesis
Other microorganisms require more complex compounds to be added to the growth media, including vitamins and fatty acids
Environmental Conditions needed to culture microorganisms
temperature (controlled using an incubator);
pH (controlled by the use of buffers or addition of acid/alkali);
gaseous environment (some microorganisms are anaerobic and will not grow in the presence of oxygen, others will require a good oxygen supply);
light (if it is a photosynthetic microorganism).
Why is the aseptic technique used?
to prevent contamination of cultures by unwanted organisms;
to prevent the organism that is being cultured from contaminating the environment (that is, the laboratory and the people in it);
to reduce competition with desired micro-organisms for nutrients and reduce the risk of spoilage of the product.
How to sterilise equipment?
heat sterilisation
Main stages of growth?
lag phase - where microorganisms adjust to the conditions of the culture by producing enzymes that metabolise the available substrates;
exponential (logarithmic) phase - during this phase the rate of growth is at its highest due to plentiful nutrients;
stationary phase - occurs due to the nutrients in the culture media becoming depleted and the production of toxic metabolites. Secondary metabolites are also produced, such as antibiotics. In the wild these metabolites confer an ecological advantage by allowing the micro-organisms which produce them to outcompete other micro-organisms;
death phase - occurs due to the toxic accumulation of metabolites or the lack of nutrients in the culture.
