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What are micro-organisms? Free essay! Download now

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What are micro-organisms?

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Downloads to date: N/A | Words: 2600 | Submitted: 14-May-2009
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The microorganism term is used instead of microbes; they are very small organisms size and not be seen by naked eye, belonging to various groups: Bacteria, Fungi, Protozoa, one can add Viruses, characterized by their noncellular structure.


The micro-organisms are probably the first alive beings appeared on ground, they would be thus the common ancestors of all the living being. Although microorganisms appeared 3.8 billion years ago, they are observed by Pasteur and koch through their microscope way after their apparition. Pasteur delivered the fatal blow to the doctrine of spontaneous generation thanks to his examination and Koch discovered revealed the existence of bacilla at the origin of tuberculosis. Those discoveries changed radically the perception of the human beings on the world.

I as technician have been given a task by my head techncian, the task is to to isolate and analyse microbial samples from immediate environment and I should include:

• Analysing effectiveness of commercially disinfectants and antiseptics on an individual bacterial species.
• Morphological properties
• Examining the bacterial colonies on nutrient agar plates as well as their cellular characteristics (microscopically) by the use of gram stain.

Section 1: Isolation of microorganisms from the environment


 Petri dish containing a layer of sterile nutrient agar.
 Inoculating loop
 Bunsen burner
 Marker pen
 Sealing tape
 Soil sample
 Sink basin (tank water)
 Air in the lab
 Glass rod


1. Prepare the three Petri dishes and agar (under aseptic conditions) for inoculation. With a marker, label the bottom of the plates with the date, the name of the sample to be inoculated.

2. Obtain a suspension of the soil sample by dissolving the soil in distilled water. Sterilise the inoculating loop. Dip the cooled sterilised loop into the soil suspension then use it to make zigzag streaks across the surface of the agar. Tilt the edge of the Petri dish to keep out unwanted bacteria and close the lid as quickly as possible to avoid contamination. Secure the lid with short piece of sealing tape. Do not seal all the edge.

3. Immerse a swap in sterile water and swap the inside of a sink. Rub the swap over about 3-6 cm2 of the agar taking care not to introduce microorganisms from the air. Secure the lid with short piece of sealing tape.

4. For sampling the air, remove the lid from a plate and allow to sit uncovered for about 45 minutes. Then close the lid. Secure the lid with short pieces of sealing tape.

5. Incubate all plates inverted at 370 C. leave the plates until the next session.


Sample name Number of colony in each sample
Air 21
Water 86
Soil 65

Conclusion of Isolation of microorganisms from the environment session

From this session, I can see microorganisms had grown in all three different environments. From the result above I see fish water had the highest amount of colonies, from my observation the fish water whilst I was doing this experiment I could see is quiet dirty.

Section 11: microscopic examination and separation of bacteria colonies.


• Agar plates from section 1
• Ruler


1. Examine your plates
2. Count, if possible, or estimate the total number of organisms on each plate
3. Determine the number of different organisms based on differences in colony type on plates (e.g. round, concentric, wrinkled, irregular etc)
4. Describe the morphology of a few well-isolated colonies on each plate

Colour- yellow, white, colourless, opaque, etc
Size- measure diameter in mm
Shape- round, concentric, wrinkled, irregular etc
Texture- shiny, dull, mucoid, hairy, etc.
Margin or edge- entire, wavy, labate, irregular, filamentous

Laboratory report of microscopic examination and separation of bacteria colonies session.

1. What environment was sampled? Soil sample
Number of colonies 74 Number of different colonies 5

Colony type I Colony type II Colony type III
Colour White White Colourless
Size (diameter in mm) 3 1 5
Shape Round Concentric Round
Texture Hairy Dull Dull
Margin or Edge Wavy Entire Entire
Elevation Umbonate Flat Raised

Soil sample

Colony type I: was White in colour, measured 3 mm in size, round shaped very hair Texture. The Margin was wavy, Elevation was Umbonate. Colony type I: was White in colour, measured 1 mm in size, concentric shaped Dull Texture. The Margin was Entire, Elevation was flat. Colony type III: was White in Colour, measured 5 mm in size, round shaped and Dull Texture. The Margin was Entire, Elevation was raised. All Colonies turned out to be different.

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