Bacterial Transformation: Definition, Steps & Analysis

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  • 0:02 A Clone: To Be or Not To Be
  • 0:42 Bacterial Transformation
  • 1:47 Transformation in Nature
  • 2:23 Transformation in the Lab
  • 3:51 Finding Transformed Cells
  • 5:13 Lesson Summary
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Lesson Transcript
Instructor: Angela Hartsock

Angela has taught college Microbiology and has a doctoral degree in Microbiology.

Bacteria can pick up genes or pieces of DNA from their environment in a process called transformation. In this lesson, we'll explore how this natural process can be exploited in the lab for genetic engineering of bacteria.

A Clone: To Be or Not To Be

'But I don't want to be a clone!' Wailed Daughter Bacterial Cell.

'For most of us, that is the way of our world, my young one.' Sighed Mother Bacterial Cell. 'For generations I have been passing my genes on to you and your sisters. I am proud that you are all clones of me.'

Daughter Bacterial Cell silently fumed. She wanted to be different.

'There is one way. . .' Said Mother Bacterial Cell. 'Although not all bacteria can do it.'

Daughter Bacterial Cell felt her hopes rise.

'You could pick up some new genes from the environment.' Said Mother Bacterial Cell. 'It would devastate me to see you using someone else's genes, but I would understand.'

Bacterial Transformation

In the bacterial world, cloning is usually the rule. One bacterial cell divides to give rise to two new cells called daughter cells. These cells are exact copies, or clones, of the mother cell. This is also called vertical gene transfer because the genes are being passed down from one cell to the next. But, bacteria do have a few tricks up their sleeves to add a little variety to their gene pool.

Horizontal gene transfer is the transfer or acquisition of genes from other (non-mother) cells, from viruses, or from the environment. Transformation is a specific kind of horizontal gene transfer where bacterial cells take up free DNA found in the environment. Not all bacterial cells can do transformation, those that can are called competent cells. Even competent cells typically don't do transformation all the time; it is turned on and off based on growth and environmental conditions. Transformation is used in nature and in the lab as a tool for genetic engineering of bacteria.

Transformation in Nature

When bacterial cells die naturally, their cells break apart and the cell material, including pieces of the chromosome, gets spilled out into the environment. If there is another bacterial cell in the vicinity that is competent for transformation, it can take up that free DNA and either incorporate it into their genome or degrade it.

Picking up that new DNA from the environment can give a bacterial cell a new ability or feature that might make it better adapted to its environment. Scientists aren't really sure how often this happens in nature; it seems to be rare, but there is evidence that it happens.

Transformation in the Lab

Scientists like to use nature as inspiration. In this case, scientists realized they could use transformation to add genes to bacteria for genetic engineering. Say there is a special protein that can be used for industrial or medical purposes, but you need to produce large amounts. Scientists can transform the gene for the protein into a bacterial cell, commonly E. coli, and the bacterial cells can mass produce the protein. But remember, not many bacteria can naturally do transformation. So scientists came up with several tricks to coax them. Here we'll look at one method.

These are the common steps in artificial transformation:

  1. Cells and DNA are added to a tube.
  2. Salt is added to help the DNA get close to the bacterial cell.
  3. The cells are first chilled then heated rapidly to get the cell membrane to loosen up enough for the DNA to get through.
  4. After that, the temperature is reduced, the salt is removed, some nutrients are added, and the cells recover.

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