Where are Bacteria Science Project and Science Experiment.
Science Project Experiment Idea - Where bacteria are found?
By the following experiments information may be obtained concerning the distribution of bacteria.
As in these experiments it is important to keep separate the descendants of different bacteria, a solid or semi-solid food material must be used.The food mixtures which we prepare to obtain a growth of bacteria, are called culture media.In the previous experiment the beef tea was a liquid culture medium.A solid culture medium is made by adding to beef tea some agar-agar, a vegetable gelatine obtained from certain kinds of sea weeds.(Details of preparation are given in the appendix.)Into Petri dishes (flat dishes especially designed for study of bacteria) which have been highly heated to kill any living organisms present, pour some of this melted agar medium.Cover the dishes immediately.In a short time the culture medium will become jellylike and ready for use.
Experiment.Expose open dishes in several of the following places for five minutes, then close and label : a classroom, a corridor before the passing of classes, a corridor during passing of classes, a window sill outside of room, street, subway, park, etc.
Experiment.By means of a needle, which has been heated (sterilized) to kill organisms upon it, put into dishes small amounts of material which you wish to test for the presence of microorganisms;
e. g. dust from floor, saliva, dirt from under finger nails, milk, soil, etc.
Experiment.Test various other substances, e.g. pupil's finger, breath, paper and silver money, drinking water, the edge of drinking
cup, blade of a knife, pencil point, etc. Take care in every case that you prevent the entrance of any other material.
Describe the results of these experiments.The spots which you see are colonies of bacteria or mold (Figure 77).Are there indications of the presence of more than one kind of microorganisms?Do you see any mold colonies?They are fluffy or hairy in appearance instead of waxy like the bacteria colonies.Does the agar culture med um in these d'shes was exposed to the air for about 5 minutes there seem to be any connection between the presence of dust and the abundance of microorganisms?
Problem 3.Size, shape, and method of multiplication of bacteria.Could you see the bacteria upon the agar plate when the plate was first exposed to the air?What does this indicate as to the size of the bacteria?You will find that they can be seen only with rather a high power of a compound microscope. FOUR TYPES OF BACTERIA: A, cocci; B, bacilli; C, spirilla; D, branched filamentous organism.
They are the smallest and simplest plant life known.The average rod-shaped bacterium measures about 50000 of an inch in diameter.Some are larger and many are much smaller, some being so small that they are invisible under the highest power lenses, but known to be present because of the effect which they produce in the substance in which they are living.A calculation of the number in a cubic inch of average sized bacteria will give you some idea of the extreme smallness of these plants.
If you are fortunate enough to have a compound microscope for the use of your class you may observe the shape of the bacteria.If no microscope is available, examine the drawings representing the different shapes.It will be noted that there are three principal forms of bacteria; spherical or ball-shaped (coccus), rod-shaped (bacillus), and spiral-shaped (spirillum). They multiply by dividing into two.These in turn, after growing to full size, will again divide.If conditions are favorable, bacteria may grow to full size and divide again in thirty minutes.It has been estimated that if bacterial multiplication went on unchecked and the division of each bacterium took place as often as once an hour, the descendants of each individual would in two days number 281,500,000,000.Actually, such unchecked multiplication never occurs except for a very short period, as conditions develop which interfere with further growth.
Not all microorganisms are bacteria.Yeasts and molds are rather closely related to the bacteria.There are also animals (protozoa) of approximately as simple structure as the bacteria.Some of these, because of the harm that they do, are of very great interest to us.
Since these extremely small living things cause our food to decay, it is important that we know the conditions which are favorable and conditions which are unfavorable for their growth, hence our next problem is : Science Project Idea: What conditions are favorable and what unfavorable for growth of bacteria and molds? This problem can best be solved by a number of experiments.
Bacterial Growth Experiment Take a number of test tubes, and into each pour about an inch of the beef tea culture medium to which has been added some material known to contain bacteria.
1. Stopper two tubes with cotton.Put one in a warm place, near a radiator or stove and the other in a cold place, as in the ice box.
2. Take two test tubes.Boil the contents of one.Stopper both tubes with cotton and keep both under the same conditions.
3. Into one of three test tubes put all the salt that will dissolve in the beef tea.Into the second put one half the quantity of salt placed in the first.Put nothing in the third.
4. Into one of three test tubes put an amount of sugar equal to the amount of beef tea.Into the second put one half this amount of sugar.Put nothing in the third.
After a few days, examine the various test tubes for bacteria.What is the apparent effect on bacteria of (1) warmth, (2) boiling, (3) salt, 4) sugar?
Science Project Bacterial Growth and Requirement for Air Expose to the air for ten minutes several Petri dishes containing agar culture medium.Paste over the covers black paper from which have been cut large letters for purposes of identification.Put the dishes where they will be exposed to sunlight.Examine after several weeks.Record the result.
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