Tag Archives: bacteria

Motility in Bacteria (Prokaryotes)

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flagella on bacteria

Flagella on bacteria by Mike Jones

Many types of bacteria have the ability to move. Movement in microorganisms allows them to locate food and to remove themselves from toxic micro-environments and less than desirable temperature conditions. Bacteria expend a large amount of energy during this process.

Bacteria use appendages called flagella to move. Flagella are composed of protein subunits called flagellin. Flagella can be located at one or both ends of a bacteria (polar flagellation) or spaced over the entire surface of the cell (peritrichous flagellation).

The appendages are not straight, but helical shaped (like a wave). The flagella for each species of bacteria have a constant wavelength (the distance between each wave in the flagella).

Unlike the human hair, a flagellum grows from the tip, not the base. Flagellin protein is made in the cell and transported through a hollow center to the tip of the flagellum. Therefore, if a tip is broke off, a new one is regenerated. The flagella are stiff structures and move only at the base, like a propeller.

The average speed of a bacteria is 50 micrometers per second. If the bacteria were the size of a cheetah, it would move at about 30 miles an hour.

How to Grow Bacteria on Nutrient Agar Plates

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Most bacteria is heterotrophic and gets energy from organic chemical compounds such as:

  • sugars
  • starch
  • protiens
  • fats

On this page we’ll be refering to heterotrophic bacteria and not autotrophic bacteria.

What Tools You’ll Need

To grow bacteria, you’ll need:

  • Nutrient Agar Plate: sterile petri dish with nutrient agar, a general purpose prepared media that grows many types of bacteria and fungi
  • Bacteria Culture: can be purchased online or collected
  • Sterile Swabs: to transfer the bacteria to the petri dish
  • Manifying Glass: to help identify the bacteria once it’s grown.

The Unseen World bacteria growing kit The Unseen World: Bacteria Culturing Kit contains all you need to grow your own bacteria.

How to Put the Bacteria on the Nutrient Agar Plate

Keep the lid over your plate to prevent contamination.

Keep the lid over your plate to prevent contamination.

Aseptic technique is the process of growing and transferring bacteria without contaminating the culture by touching or breathing on the sample.

If you have a specific bacteria culture, you can spread the bacteria on the plate using a sterile swab or innoculating loop. If you would like to collect bacteria growing on a sink, chair, table, or other areas, rub a sterile swab across the area you would like to test. Then transfer the bacteria to the nutrient agar plate by swiping the swab across the surface of the agar plate.

By holding the lid over the plate as you apply the bacteria, as in the picture here, you help prevent contamination. Avoid breathing on the swab or allowing it to make contact with other surfaces as you transfer it to the petri dish.

Where to Grow The Bacteria

Keep the bacteria out of sunlight: the UV rays may kill off the bacteria. Most bacteria grow best at normal human body temperature (98-99 degrees F). When growing bacteria, incubate at a temperature as close to this as possible. Bacteria grows slower at lower temperatures.

Some recommended places to incubate the bacteria are:

  • On top of a water heater
  • Under a warm light (but not sun light)

What to Expect

After 24-48 hrs, you may find many different-looking colonies growing on the nutrient agar plate. Each type of bacteria look a little different (color, shape, size) when they grow.

Where you can get supplies

Here are links to the various supplies you might need for growing bacteria:

Where you can get more information

If you have any questions, leave a comment down below or check out these links:

Gram Staining Bacteria

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grain staining bacteriaBacteria can be differentiated based on how they react to a a procedure of dying cells called Gram stain. Bacteria are divided into a group that turns purple (gram positive) and a group that turns red (gram negative). Bacteria that are gram (+) include Staphylococcs, Streptococcus, Bacillus and Micrococcus. Gram (-) bacteria include E.coli and Salmonella. The Gram staining procedure is as follows:

Gram Staining Bacteria Procedure

1.Place a drop of distilled water on a slide and, using a swab or inoculating loop, mix the bacteria with the water an smear the mixture on the slide. The mixture will appear cloudy. Using a flame, heat fix the bacteria to the slide (pass the slide through the flame a few times to “dry” the bacteria and affix it to the slide).

2. Using a dropper, add crystal violet to the slide. Let stand for 1 minute.

3. Add iodine to the slide. Let stand for 3 minutes.

4. Decolorize the sample with alcohol. Let stand for 30 seconds.

5. Counter stain the sample with safranin. Let stand 1-2 minutes. Using a dropper, rinse with distilled water.

Gram Staining Results

Gram positive bacteria will appear purple under the microscope. They have a single, thick cell wall. The crystal violet and iodine combine to attach to this wall. The decolorizer (alcohol) dehydrates the cell wall, causing the pores to close, trapping the stain inside. the safranin added in the final step, does not penetrate the wall.

Gram negative bacteria will appear red. The have a cell wall and additional thin layers of fatty sugars. The decolorizer easily penetrates these thin sugar layers, washing away the crystal violet – iodine chemical (purple color). The safranin in the last step attaches to these layers and appears red.