Introduction:
A microorganism or microbe is a living thing (organism) that is too small to be visible to the human eye (microscopic). Microorganisms can be bacteria, fungi, archaea or protists. Some microbiologists also include viruses, but others consider these as non-living.
Most micro-organisms are single-celled, or unicellular organisms, but there are unicellular protists that are visible to the human eye, and some multicellular species are microscopic.
Microorganisms live almost everywhere on earth where there is liquid water, including hot springs on the ocean floor and deep inside rocks within the earth's crust. Such habitats are lived in by extremophiles.
Microorganisms are critical to nutrient recycling in ecosystems, because they act as decomposers. Because some microorganisms can also take nitrogen out of the air, they are an important part of the nitrogen cycle. Pathogenic, or harmful, microbes can invade other organisms and cause disease.
There are many types of microorganisms, but there are good ones and bad ones. The good ones feed on things that were once living, such as fallen leaves and dead animals, causing them to breakdown or decay. The decayed materials mix with soil, providing essential nutrients for plants to use. Without this process, the nutrients in the soil would run out. These types of organisms are called decomposers. They are the natural recyclers of living things on our planet. Microbes also help us make some of our foods, such as bread, cheese, yogurt, beer, and wine. They feed on the sugar in grain, fruit, or milk, giving these foods a special texture and taste.
Some microbes, often called germs, can cause illness or disease. Chickenpox, mumps, and measles are caused by the bad microbes. They are infectious diseases. Some microbes can cause food to decay. Moldy bread or fruit, sour milk, and rotten meat are examples of decayed food. If eaten, this rotten food and drink can cause stomach upsets. Other microbes cause tooth decay. You can protect yourself from harmful microbes by storing and preparing food properly, cleaning your teeth, washing your hands, and by avoiding close contact with ill people.
· To provide the experience of preparing the culture medium agar
· To determine the microorganisms in the air in a healthy human body
· To determine the morphology of microorganisms in the culture medium agar
Result:
| Ways | Contamination |
| Air | 18 CFU |
| Hands | 5CFU/mL |
| Ear | Present |
| Normal breathing | 1 CFU |
| Violent coughing | 4 CFU |
 |
| Lab 4 results |
 |
| Air |
 |
| Ear |
 |
| Hand |
 |
| Normal Breathing |
 |
| Violent Coughing |
Discussion
Each distinct circular colony should represent an individual bacterial cell or group that has divided repeatedly. Being kept in one place, the resulting cells have accumulated to form a visible patch. Most bacterial colonies appear white, cream, or yellow in color, and fairly circular in shape.
Bacteria are usually classified on the basis of their shapes. Broadly, they can be divided into three types which are rod-shaped bacteria (Bacilli), sphere-shaped bacteria (Cocci), spiral-shaped bacteria (Spirilla).
They are millions of bacteria on our hands, also fungi and viruses. Staphylococcus aureus is the most common bacteria found on human hands. Staphylococcus aureus forms a fairly large yellow colony on rich medium. S. aureus can grow at a temperature range of 15 to 45 degrees and at NaCl concentrations as high as 15 percent. Staphylococci are perfectly spherical cells about 1 micrometer in diameter. The staphylococci grow in clusters because the cells divide successively in three perpendicular planes with the sister cells remaining attached to one another following each successive division. Since the exact point of attachment of sister cells may not be within the divisional plane and the cells may change position slightly while remaining attached, the result is formation of an irregular cluster of cells.
Group A Streptococcus (GAS) is a bacteria that is often found in the throat and on the skin of people. GAS is most often associated with “strep throat” and impetigo (blisters on the skin). On rare occasions, GAS can cause severe, life-threatening illness like toxic shock syndrome and necrotizing fasciitis (flesh eating disease). Strep throat is caused by a type of bacteria called group A streptococci. The tonsils may become infected (tonsillitis). Left untreated, strep throat may develop into rheumatic fever or other serious conditions.
Haemophilus influenzae are another common type of bacteria that can sometimes cause infections. Harmful types can cause diseases that include respiratory infections, ear infections or a type of meningitis. Children are now immunized against one disease-causing type called haemophilus influenzae type b (Hib).Before the experiment starts, spray some Lysol solution on the table and rub it with a sponge. The experiment must be done near the Bunsen burner to avoid contamination. The Petri dishes containing culture medium agar and the washed water from the hands should be rotated in the shape of 8 to make sure that the contains mixed together. The Petri dishes are inverted for incubation is to minimize the evaporation of water and also to minimize the contamination from extraneous bacteria. In either case the water or the contaminant has to diffuse up and around the inverted Petri dishes and covers. This diffusion is a slow process in the absence of strong convection of air.
References:
http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_Interpreting_Plates.shtml
