27 November 2018 Today’s Title: CW: Genetic engineering and bacteria Learning Question: how can bacteria take up genetic information from other organisms?

Aims from specification (l) describe the advantage to microorganisms of the capacity to take up plasmid DNA from the environment

Key words Genetic engineering Restriction enzymes Bacterial plasmids Antibiotic resistance Transformation Altered plasmids Transgenic

Why do we want to genetically engineer organisms? Improving a feature of the recipient organism Inserting a gene into a crop plant to give herbicide resistance – increase crop yield while controlling weeds Inserting growth-controlling gene into cattle e.g. myostatin to promote muscle growth Engineering organism that can synthesise useful products Inserting the gene for a human hormone e.g. insulin or somatotrophin into a bacteria and growing the bacteria produces large quantities of the hormone for human use Inserting gene for pharmaceutical chemical into female sheep so that it is produced in milk and easily collected Inserting gene for beta-carotene production into rice so that the molecule is present in the edible part of the rice plant. Beta-carotene can be converted into vitamin A in people who eat it.

Bacterial cells and plasmids are often used in genetic engineering Identified gene can be cut using restriction enzymes and then placed in a vector. Bacterial plasmids are often used as vectors – plasmids are small, circular pieces of DNA found in many bacteria types. Plasmids are separate from main chromosomes and often carry genes for antibiotic resistance. Plasmids cut with same restriction enzyme used to cut out gene, complementary sticky ends form. In the presence of the enzyme ligase, they will reseal to reform the original plasmid

Transformed and transgenic bacteria Large quantities of plasmids and bacterial cells are mixed with calcium salts and “heat shocked” to stimulate uptake of plasmid by bacterial host. Heat shocking – culture temperature is lowered to freezing then quickly increased to 40oC to increase their ate at which plasmids are taken up Inefficient process – about 0.25% of plasmids are taken up Bacteria that do take up altered plasmids are described as transformed Transformation results in bacteria containing new DNA – they are now transgenic bacteria

Bacterial conjugation and the advantages of taking up new DNA

Bacterial conjugation and the advantages of taking up new DNA Swapping copies of plasmid DNA between bacteria. Can occur between different species of bacteria Significant as plasmids carry genes for antibiotic resistance Serious health risks to humans (MRSA)

Bacterial transformation and pneumonia in mice

Questions Suggest how the DNA content from the S-strain differs from that in the R-strain Pneumococcus Apart from DNA take-up as described above, what other genetic process could give rise to genetic variation in bacterial cells?

Answers The S-strain bacteria and the R-strain bacteria both contain the bacterial chromosome; however, the S-strain bacteria also contain a plasmid. The gene for production of pneumococcal toxin is present on the plasmid Mutation