Physiology LAB Investigation:


Read some recent articles on bacterial infections. From an area that interests you, choose an area to investigate bacteria growth in order to practise healthier hygiene, food preparation or food storage choices.

The term bacterial growth generally refers to the growth of a group of bacteria rather than a single cell. Single cells generally do not get larger in size, so the term growth refers to the reproduction of cells and can be seen as a colony or a continuous growth, depending on the type of inoculation. The type of count and, therefore, plate inoculation should be clear before beginning an investigation.
Bacteria most commonly reproduce by fission, the process by which a single cell divides to produce two new cells. The process of fission may take anywhere from 15 minutes to 16 hours, depending on the type of bacterium.
A number of factors influence the rate at which bacterial growth occurs, the most important of which are moisture, temperature, and pH. These factors should be kept constant.
Most forms of food preservation, such as freezing and drying, are designed to kill or inactivate bacteria that would otherwise damage food or cause disease. One of the most common methods of destroying bacteria in foods is pasteurization. Pasteurization is the process of heating a food product to a particular temperature for some given period of time. The temperature and time are selected to be sure that all bacteria in the food are killed by the process. The pasteurization of milk has made it possible to insure safe supplies of one of the most popular of all human foods.



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Plan a lab that allows you to investigate your interest. Poured nutrient agar plates will be provided. You can use a source (citation and reference needed) for basic bacteria inoculation techniques. Some good sourcses can be found in GCSE Biology, MacKean p 290; Biology, Roberts. p 25; You can use more than one source to outline proper inoculating techniques, which should be incorporated into your specific lab.

Antimicrobial vs. antibiotic drugs



Agdex#:
400/08
Publication Date:
11/04
Order#:
04-081
Last Reviewed:
11/04
Title: Antimicrobial Resistance in Agriculture

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Antimicrobial drugs have played a vital role in health management of both humans and animals for more than 50 years. In agriculture, antimicrobials are used to treat, control or prevent disease caused by micro-organisms, and to improve production or growth.
The use of antimicrobials in animals that are ready for market has always been closely monitored. Until recently, the focus has been on antimicrobial residues in food intended for human consumption. Some residues can lead to allergic reactions in a small percentage of the population. Other antimicrobial residues may increase the risk of other adverse health outcomes, such as cancer, and are banned by Health Canada for use in food-producing animals. There is increasing concern that the use of antimicrobials in agricultural production systems may contribute to antimicrobial resistance, primarily in zoonotic bacteria. Zoonotic bacteria can cause disease in both animals and humans, and are usually transferred from animals to humans by direct contact or through food.
The other areas of concern are transference of resistance, and multi-drug resistance. Resistance genes can transfer from bacteria of agricultural origin to disease-causing bacteria of human origin. Disease caused by bacteria that are multi-drug resistant can result in compromised treatment options, prolonged recovery, or in the worst case, treatment failure.
Q. What is an antimicrobial?
A. Antimicrobials are natural, semi-synthetic or synthetic substances, including antibiotics, which inhibit or kill micro-organisms (microscopic life forms such as bacteria, fungi, mycoplasmas, rickettsias, chlamydiae and protozoa).
Q. What is an antibiotic?
A. Antibiotics are natural substances produced by micro-organisms that, at low concentrations, are able to inhibit or kill other micro-organisms.
Poured petri dishes with agar.
The appearance of plates after they are made. The minimal medium is colorless (left), while the nutrient agar is tan (right).
Examine them for contamination. If any colonies are present, do not use that plate.


A picture of plates prepared plates
A picture of plates prepared plates

A picture of plates prepared plates


Some colony shapes
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external image bacterial%20colonies.gif


Petri dish showing bacteria colony count after spot-innoculation using a flat transfering surface such as a leaf or your finger tips
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Petri dish showing bacteria growth across the agar, with areas of no growth around several antibiotic discs. A very thin bacterial solution can be used to just cover the surface of the agar and the discs then inserted.

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Petri dishes can be streak-inoculated to show growth

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Further bacterial growth showing growth of aerobes (Ea, Pf and Af) and anaerobes (Lp, Se and Cb)

Figure 5-5 Growth of microbes on BHI plates

Growth of microbes on BHI plates
Growth of microbes on BHI plates

Growth of microbes on BHI plates

The left side plates were incubated anaerobically, while those on the right were incubated aerobically. Strict aerobes cannot grow in the absence of oxygen, while strict anaerobes cannot grow in the presence of oxygen. Note that Pf, Ea and Af grew slightly under anaerobic conditions due to residual oxygen from storage tube..

Some different ways to graph your results

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Bar chart showing effects of different media on bacteria growth


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Population "S" curve
The following can happen to the bacteria population if it is left too long - food and space run out!
The dotted line would happen if the space, resources and the population maintained a balance - called the carrying capacity.

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NOTES on Defense and Immunity (Chpt 24 in Campbell)



http://www.pbs.org/wgbh/nova/sciencenow/3318/02.html