PCB 3063 Chapter 6

prototroph

-a microorganism that does not require any organic growth factors

-can synthesize all needed compounds

-can grow on minimal medium

auxotroph

-a mutant organism that has lost the ability to synthesize one or more organic compounds

-need supplemental medium

F factor

A fertility factor in bacteria; a DNA segment that confers the ability to form pili for conjugation and associated functions required for the transfer of DNA from donor to recipient. It may exist as a plasmid or be integrated into the bacterial chromosome.

Plasmid

small, circular piece of DNA located in the cytoplasm of many bacteria

Conjugation

In bacteria, the direct transfer of DNA between two cells through direct contact.

Transformation

process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria

-extracellular DNA bind to competent cell at receptor site

Transduction in bacteria

DNA is transferred from a donor cell to a recipient via a bacteriophage

Gene mapping

In transformation and transduction, only genes close together are like to combine with new host

vertical gene transfer

between bacteria of same species

horizontal gene transfer

between bacteria of different species

Gene exchange in bacteria

Bacteriophage

viruses that infect bacteria

The head of a bacteriophage

protein-coated; contains DNA

Tale of bacteriophage

tube with a collar to inject DNA

Tail fibers on phages

recognize and bind to specific bacteria host

Life cycle of phage

-Binds to host

-Injects DNA

-Stops bacterial functions and degrades bacterial DNA

- Uses bacterial ribosomes and proteins to replicate phage DNA and make phage proteins

- Assembles new phages

-Lyses host cell and infects new cells

- Temperate phages may integrate into host genome and stay dormant

plaque assay

method used to measure the number of viral particles present in a sample

1. phage infected bacterial culture serially diluted

2. small sample mixed with fresh bacteria and melted agar

3. poured onto normal agar plate and incubated

4. lysis by phages will show up as a clear area (plaque)

5. count plaques to get phage density