Amina Ali
Unit 15: Microbiological Techniques
Assignment 2: Classification of micro-organisms
Task 3
D4 Outline the potential usefulness of a variety of identification techniques in a specific application
Streak plate technique
Streak plate technique is used to identify and classify micro-organisms, it is useful for isolating
specific bacteria from a sample containing a mixture of microorganisms. The advantages of when
streak plating is used to grow bacteria on a growth media surface is, it produces individual bacterial
colonies which are isolated and sampled. These samples can be used to grow a microbiological
culture on a new plate so that the organism can be identified, studied or tested. Leading to the
identification of causative agent of the bacterial disease.
Another advantage is streak plating enables you to select and work with individual colonies and it is
the ideal method for doing general work with a specific type of microorganism. It is useful for
microscopic observation as the result is usually (individual identical) colonies therefore, it’s easier to
collect and transfer colonies for examination. Streak plate technique is reliable, convenient and isn’t
complicated as long as you have a good streaking skill, there should be visible results (individual
colonies) in a single agar plate.
Streak plating is a frequently used technique in the medical profession when identifying the
causative agent in bacterial diseases and finding an appropriate treatment. The principle of this
technique is not complicated for a microbiologist therefore, the speed of the results is dependent on
the growth of the sample. Generally, it is an efficient technique. However, if there is contamination
and other spores have grown, then each type of colony needs to be streaked again on a separate
plate to obtain a pure culture. Thus, accurate results are delayed.
Contamination is usually due to incorrect technique implementation. For instance, if the loop used
to streak the broth did not go deep enough into the agar, this is caused by human error. Therefore,
the bacteria may not settle and grow. Another error that can happen is if the quantity of inoculum is
not measured beforehand, this can cause a reflux with different amounts. If the loop is not sterilised
long enough (in the blue flame) it can cause contamination, introducing other bacteria on the plate.
In these circumstances the speed of the results is hindered and efficiency is reduced because the
results are not accurate therefore have to be disposed of and repeated.
Membrane filtration technique
Membrane filtration is high pressure water that is forced through a membrane (a thin material with
very small pores) to remove small particles (including bacteria). It is an alternative to flocculation,
sedimentation, adsorption, extraction or distillation. Advantages of this technique are flexibility;
systems can be specifically designed and are relatively simple to scale up. Also, it can be used for
separation, concentration and purification of a variety of materials across a wide range of industries.
It is useful for separating particles according to size as membranes can be manufactured in uniform
and highly precise manner. Other advantages are, the filtration can function effectively at low
temperatures, the energy requirements are generally low, it’s not harmful to the environment and
uses clean technology.
Membrane filtration technique is being used in many industrial processes. As this technology is
becoming more profitable than traditional methods, more industries such as food, pharmaceutical,
biotechnological, chemical sectors are implementing this filtration technique. It is already used to
filter and monitor drinking water. Water filtration is a continuous operation so it is difficult to say the
speed of the results because the process is a cycle, there is no beginning and end. However, in terms
