2.6 environmental control of metabolism Flashcards
What are microorganisms?
- archaea
- bacteria
- some species of eukaryotes
Why are microorganisms used ?
- their adaptability
- ease of cultivation
- speed of growth
What do microorganisms use and produce?
a wide variety of substrates for metabolism and produce a range of products from their metabolic pathways
What do many microorganisms produce and some do not? What do the ones that don’t require?
- all the complex molecules required for biosynthesis (amino acids, vitamins, fatty acids)
- they require these to be supplied in the growth media
What is required in the growth media when culturing microorganisms?
- their growth media requires raw materials for biosynthesis
- an energy source
Where is an energy source derived from?
- chemical substrates
- or from light in photosynthetic microorganisms
What are 4 different culture conditions?
- sterility
- control of temperature
- oxygen levels
- pH
What do sterile conditions in fermenters do?
- reduce competition with desired microorganisms for nutrients
- and reduce risk of spoilage of the product
What are the 4 phases of growth and changes in culture conditions?
- lag phase
- log/exponential phase
- stationary phase
- death phase
What happens in the lag phase?
enzymes are induced to metabolise substrates
what happens in the log/exponential phase?
the most rapid growth of microorganisms due to plentiful nutrients
What happens in the stationary phase?
- the nutrients in the culture are becoming depleted
- production of toxic metabolites
- secondary metabolites such as antibiotics are also produces
- happens when the rate of production of new cells is equal to the death rate of older cells
What is the advantage of the secondary metabolites produced in the stationary phase?
in the wild these metabolites confer an ecological advantage by allowing the microorganisms which produce them to outcompete other microorganisms
What happens in the death phase?
occurs due to the toxic accumulation of metabolites or the lack of nutrients in the culture
-the death rate of cells is greater then the production rate of new cells
What is the difference between viable and total cell count?
- viable cell count includes counting only the living microorganisms
- total cell count involves counting viable and dead cells
What is the difference between the graphs of total and viable cell count?
only viable cell count shows a death phase where cell numbers are decreasing
What are industrial fermenters used for?
used to culture micro-organisms on a huge scale
-controlled by automatic computers
What shape does the graph of the exponential growth phase of a culture make when plotted on semi log graph paper?
straight line
what is biosynthesis?
a multi-step, enzyme catalysed process in living organisms in which substrates are converted into more complex products
What is a growth medium?
substance which provides microorganisms with an energy source and raw materials for biosynthesis
What is a secondary metabolite?
a substance not associated with growth that is produced during the stationary phase of growth of a culture of microorganisms. An example would be antibiotics
What does sterility mean?
not containing contaminated microorganisms
name a way to control temperature when culturing microorganisms?
water jackets and thermostat
name a way of controlling oxygen levels when culturing microorganisms
air inlets, paddles
name a way of controlling pH levels when culturing microorganisms
buffer, addition of acids or alkaline
what is a way of making things sterile?
aseptic techniques
