1. Bacteriophages

2. Discovery of phages
In 1896, Ernest Hanbury Hankin discovered large differences in the concentration of cholera bacteria at different points of the Ganges river
Following filtration, the water was still capable of killing cholera bacteria
People bathing in the Ganges River at Calcutta

3. Discovery of phages
French-Canadian microbiologist Félix d'Hérelle was working in Paris during WWI
Discovered "an invisible, antagonistic microbe of the dysentery bacillus".
Filtered culture was able to kill dysentery-causing bacteria
He also recorded a dramatic account of a man suffering from dysentery that the bacteriophages cured.

4. History of phages
First complete genome sequence was fX174 genome (Sanger et al., Nature 1977)
First complete shotgun genome sequence was lambda phage (Sanger et al. J. Mol. Biol. 1982)
Courtesy of nlm.gov

5. Phages Bacteriophages are viruses of bacteria
Phages are specific to particular bacterial hosts
Estimated 1031 bacteriophages on Earth
Population is extremely dynamic: 1025 infections/sec
Phages are the largest reservoir of unexplored genetic information 5

6. Do phage cause human disease?
Only one good example:
Shiga toxin (Stx2) is a gene present in a phage which infects Escherichia coli O157:H7. The toxin leads to disease in humans.
More often they are beneficial:

7. What do phages do? 7

8. What about the phages we’re working with?
Infect M. smegmatis bacteria
a fast-growing (~3hr doubling time) bacteria
not a pathogen, but rather a soil bacterium
Phage can be isolated from soil, compost etc.
Look for plaque formers on lawns of M. smegmatis bacteria
Safety-
- must not be immunosuppressed, talk to me if you have concerns
No food in lab
Wash hands, clean spills

9. Mycobacteriophages ~250 of them have completely sequenced genomes
Average genome size: ~72kbp
Average number of genes: 88/genome
High genetic diversity
Most genes of unknown function

10. How can we learn more about phages?
Single nucleotide changes
Small insertions and deletions
Deletions of whole genes
Rearranging gene order
Combining different
phages together
Codon optimization
Maximal difference in
codons