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2nd draft of Advantages and disadvantages of bacteria essay

In general, this essay is much better now. It could still do with a little more detail in some places, as indicated in red throughout the essay.

Note to marker:

Before you mark this. I tried to find examples of bacteria as you stated I should do in your first draft comments, but the source I got this information from did not state this. I have marked in blue where the examples are needed, please could you kindly suggest an example. Thankyou very much.

The advantages and disadvantages of bacteria

Bacteria can be useful in genetic engineering, other biotechnological applications, medical technology and the food industry etc) and can be harmful (food spoilage, tooth decay and disease etc). However bacteria can also be harmfull, as they can cause tooth decay, disease ( some being fatal) and food decay. This is repetetive.

The advantages of bacteria for genetic Engineering are firstly economic- they contain a valuable source of enyzmes Bacteria produce more enzyme molecules in relation to their mass than most other organisms. The product yield can be increased by means of strain selection, mutation and optimisation of growth conditions. They are easy to manipulate genetically and can be subjected to gene transfer techniques. Secondly there is an environmental/economic advantage of bacteria- they can occupy a great variety of habitats and extremes of conditions, so their enzymes function in an enourmous range of PH and temperature. ("A New Introduction to Biology") WHY is this an advantage?

Ethically the use of bacteria in the cloning of animals is controversial. At the Roslin Institute in Scotland, scientists successfully cloned an exact copy of a sheep, named 'Dolly'. This was the first successful cloning of an animal and most likely the first occurrence of two organisms being genetically identical. ecently the sheep's health however has deteriorated detrimentally. Many people especially on the grounds of religion think it is immoral to "play God" by the use of modified bacteria. Dolly the sheep did not have any bacterial involvement. This sort of animal cloning involves the extraction of a nucleus from a cell of an animal and implanting the nucleus into a fertilised egg of the same type of animal – bacteria are not used.

Environmentally the bacteria used in genetic engineering chosen do not produce toxins or offensive odours and are non-pathogenic. Bacteria e.g. Burkholderia cepacia be of great benefit to the environment, as they may be used in the future to break up oil slicks in a technique known as bioremediation. Bacteria can also be used for biological pest control - some bacterium are toxic to a particular pest species e.g. Bacillus thuringiensis will kill the caterpillars of some insect pests

In biotechnological applications, bacteria are cultured usually by batch-fermentation define this on a large scale to produce chemical products such as vitamins and enzymes in industrial quantities. (The Oxford Interactive Encyclopedia). The advantages of using bacteria in biotechnological processes are that large scale fermentation, using both aerobic and anaerobic bacteria can be carried out in large bioreactors/fermentors.
Enzymes are usually produced by batch fermentation and bacteria are used. Bacteria are used because they can reproduce themseolves very quickly. In fermentation the protease enzyme etc. This last sentence (which is not actually a full sentence) does not make sense.

The disadvantages of using bacteria in biotechnological processes, are that the bacteriophages define ‘bacteriophage’ are a serious problem if they infect the contents of an industrial fermentor. Bacteria are expensive to purify and often unstable in the purified state.

(The Oxford Interactive Encyclopedia)

The bacterium Streptococcus converts sugar to lactic acid and slowly etch away the enamel on teeth cause tooth decay However Bacteria can be genetically modified and bacteria may banish tooth decay. According to dental researcher Jeffrey Hillman at the University of Florida in Gainesville a mouthful of genetically modified bacteria could keep tooth decay away for life. The scheme involves replacing your mouth's natural cavity-causing bacteria with GM bacteria designed to prevent tooth decay. Do you know HOW these GM bacteria prevent tooth decay?


The technicalogical applications of bacteria are advantageous. The enzymes contained in different bacteria can be used in the dairy industry- extracellular lipase is used to ripen blue chesses from mould e.g Penicillum roguefortii.The production of cheese by separating milk into curd and whey may be achieved by the addition to the milk of the enzyme rennet or by the addition of a bacterial culture. Also In the ripening process, micro-organisms, most commonly lactic-acid-producing bacteria, act on the cheese to produce the desired body and flavour. (The Oxford Interactive Encyclopedia)

Bacteria have a high growth rate and so bacteria can be used to help farmers save crops as they are used for genetic engineering; for example, bacteria can be used to insert genes for disease or herbicide resistance into plants. You could outline the process involved These are also used in biological pest control and are also necessary for the breakdown of sewage.


There are many types of bacteria that cause spoilage and they can be divided into: spore-forming and nonspore-forming. This can lead to food poisoning - an illness that you may get after eating food contaminated by certain bacteria For instance Botulism is an often fatal disease that results from eating improperly canned foods( spoiled canned food) , improperly processed, low-acid foods such as green beans, mush-rooms, spinach, olives and beef or fish contaminated with toxins released by the bacteria Clostridium botulinum.


Diseases range from the trivial to the life threatening because they are caused by a range of pathogenic organisms and are transmitted from person to person in a wide variety of ways.

Bacteria such as Salmonella are well known disease-causing agents. They give rise to a range of diseases from common complaints such as tonsilitus to much rarer and frequently lethal conditions such as tetanus. Malaria is caused by Plasmodium and causes "Flu-like" symptoms followed by invasion of liver and red blood cells. It is spread by female anopheles mosquito is the vector transmitting Plasmodium betwen people.

The uses of bacteria in medical technology are advantageous. Bacteria can be used to make antibiotics to cure diseases. One example is the new anthrax killer described in the Aug. 22 issue of Nature. Fischetti and his colleagues took their cue from a type of virus called a bacteriophage that preys on bacteria, replicating inside them. When it needs to escape, the phage uses an enzyme called a lysin to burst the bacteria's cell membrane, popping it like a balloon stuck with a pin. Phages use their lysin to escape, but lysin will also burst bacterial membranes if applied from the outside. This was tested on mice and it killed the anthrax. This is the use of a virus rather than a bacterium, then.

The enzymes in the bacteria are highly sensitive to changes in the physical and chemical environment surrounding them- environmental disadvantage. They may be denatured by even a small temperature rise and change in pH. This seems to contradict what you said in your second paragraph. I know that then you were referring to bacteria in general and here you mean any one type, but this needs to be made clear.This means that the conditions in which they work must be stringently controlled. In particular the enzyme-substrate mixture must not be contaminated with other substances that might affect the reaction so the equipment used must be scrupulously clean- this is time consuming, so an economic disadvantage.

In conclusion it seems that most bacteria are harmful to humans. However some bacteria are beneficial to us and without them we would suffer tooth decay etc. It seems that we need bacteria in order to cure harmful diseases as well as to speed up industrial processes and improve our environment. There are ethical issues involved when we talk about using them in genetic engineering. However these are from a minority and social issues like curing humans from fatal diseases should take priority.

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The effect of ethanol on beetroot

This is a very good piece of work, though a bit over-long! One or two issues to look at. You never really make it clear that the actual effect of ethanol on the lipid part of the membrane is to dissolve it. I'm sure you know, and you do hint at it at various places, but make it obvious. A lot of the scientific information, while correct, is irrelevant to THIS EXPERIMENT. Things like osmosis, active transport, phagocytosis etc are not involved in this experiment. An understanding of the chemical structure of the pigments in beetroot is not necessary either for designing the experiment nor for analysing the results, etc. You won't LOSE marks for this, its just that this extra information might raise doubts as to whether you can distinguish between relevant and irrelevant information. Remember you are not writing an essay on cell membranes and beetroot! I don't really agree with your conclusion from your preliminary work. You say the effect happens between 0% and 25%, but the leakage of pignment seems to continue to increase at 50% ethanol.

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effect of carbon dioxide on rate of photosynthesis

There are a number of issues that need addressing here. Your 'predicitve' graph does not exactly show the effect of different levels of carbon dioxide on photosynthesis - it actually shows the interaction of the effects of light intensity and CO2 conc. It would be better to do a graph showing CO2 conc. on the x axis. In your scientific reasoning section, you say "Carbon dioxide combines with water and is photosynthesised into oxygen and sugar. " At A2 level, you should know that this is incorrect - CO2 does NOT combine with water, it enters the Calvin cycle and contributes to the production of carbohydrates in the light independent stage of photosynthesis. You explain this later, I know, but that does not excuse this incorrect statement. When you deal with the Calvin cycle, you say "This reaction takes place in the stroma (matrix) of the chloroplast, where the energy stored in the ATP and NADPH is used to reduce carbon dioxide to organic carbon." yet organic carbon is never formed in photosynthesis. I find the mention of a preiliminary experiment a bit strange. No detailed procedure is given, neither are any actual results. What you describe is not really a preliminary experiment to the one you're doing here, anyway - it is just a different experimentwhich is related to the one you're doing here merely because it is on the same topic! In the account of variables, note that litmus paper does NOT keep the pH constant. Actuaqlly it does not even monitor the pH, as it can only tell if the pH is acidic or alkaline, not what the actual pH value is. If you are intending to monitor the pH value, universal indicator paper would have to be used, and your method must mention its use. In your apparatus list, you say "Litmus paper – to measure the pH of the solution to keep the CO2 concentration constant" but it actually does neither of these two things. You use the term 'rubisco' but do not say what this means. In 'control' you say "Water will only be used for the control of this experiment instead of NAHCO3. However, there is still some CO2 dissolved in the water. This must be taken account of when taking each reading and should be deducted from the total volume of O2 at that concentration. " To deduct it, you must know its actual value, but how are you going to determine that?