Metabolism and Survival Key Area 6a Micro-organisms and their growth

By the end of this topic you should be able to: State that microorganisms include bacteria, archaea (thermophiles) which are prokaryotes State that some species of eukaryotes are also classed as microorganisms e.g. photosynthetic algae State that microorganisms can use a wide range of substrates for metabolism and produce a wide range of products in their metabolic pathways State that all microorganisms require an energy source (chemical/light) Say why simple chemical compounds are necessary in the growth media of microorganisms Explain why some growth media require more complex compounds Explain why sterile techniques are important when culturing microorganisms State that microorganisms require a suitable temperature, suitable oxygen concentration and an optimum pH for growth

Microorganisms

Microorganisms - introduction Microbiology is a specialised area of biology that studies organisms that are too small to be seen without magnification. These are known as microorganisms or microbes. In today's world, microbiology makes up one of the largest and most complex biological sciences because it deals with microbe-human and microbe-environmental interactions. These interactions are relevant to disease (in both plants and animals), drug therapy, immunology, genetic engineering, industry, agriculture and ecology.

Microorganisms Microorganisms include archaea, bacteria and some species of eukaryote. They include species that use a wide variety of substrates for metabolism and produce a range of products from their metabolic pathways. Microorganisms are used because of their adaptability, ease of cultivation and speed of growth.

Micro-organism means .. very small, normally unicellular, micro-scopic Examples in the 3 domains of life: Bacteria e.g…. E.coli, Staphlococcus Aureus,.. Archae e.g. … methanogens, thermophiles… Eukarya slime molds, algae, yeast

Growth of microorganisms (cell culture) Microorganisms can be cultured relatively easily in a laboratory. They must be given an appropriate growth medium* and the environmental conditions must be carefully controlled to ensure successful growth. * Growth media – a solid (agar jelly) or liquid (broth) substance used to grow, transport or store microrganisms. The agar is usually found in petri dishes whilst the broth can be in flasks or bottles

Growth of microorganisms - media When culturing micro-organisms their growth media must contain raw materials for biosynthesis as well as an energy source. Growth media can be composed of specific substances or can contain complex ingredients such as beef extract. Many micro-organisms produce all the complex molecules required for biosynthesis (amino acids, vitamins, fatty acids). Other micro-organisms require these to be supplied in the growth media

Growth of microorganisms - media Two types of media are commonly used: complex media contains one or more crude sources of nutrients and their exact chemical composition and components are unknown - defined media (or synthetic media) is media in which the components of the medium are chemically known and are present in relatively pure form.

Growth of microorganisms Microorganisms require an energy source (which may be chemical or light) Energy from chemical substrates can be provided in the growth media. Photosynthetic micro-organisms derive their energy from light

Growth of microorganisms – environmental conditions In industrial processes, microorganisms are grown in large fermenters (or bioreactors) which are constantly monitored and controlled by sensors and computers. Any necessary change to the environment to maintain optimum conditions is brought about by the computer

Growth of microorganisms – environmental conditions In order to grow cells in culture they must be supplied with a growth media and the correct environmental conditions, including: Sterility: sterile conditions in fermenters reduce competition with desired micro-organisms for nutrients and reduce the risk of spoilage of the product

Growth of microorganisms – environmental conditions temperature (controlled using an incubator) – essential for maintaining optimum condition for enzymes pH (controlled by the use of buffers or addition of acid/alkali) Oxygen levels (controlled using oxygen sensor and sterile air supply) - some microorganisms are anaerobic and will not grow in the presence of oxygen, others will require a good oxygen supply for aerobic respiration

Production of the product can also be monitored and the whole process brought to a halt when the required concentration is reached The advantage of using fermenters is that: it can be done efficiently on a large scale it saves energy no raw materials are wasted

Energy source Chemical or light Simple chemical compounds Basic nutrients are required for growth e.g. salts Complex chemical compounds Some require things like fatty acids or vitamins that they cannot produce themselves Sterile culture Cuts down competition and so allows a much faster growth Temperature There will be an optimum temperature range for the particular micro-organisms enzymes Oxygen Some will require aeration (bubbling air through) of the culture. Others will only survive in low or no oxygen (again tolerance curve) pH The correct pH needs to be maintained – tolerance curve