Bacteriophage vector

my preparation on bacteriophage vector for a brief 10-minute class presentation.

1. Bacteriophage vectors Ashes Karki Chhetri 201503015

2. What is a Bacteriophage? Any group of viruses that infect bacteria Also called phage or bacterial virus Discovered independently ; Frederick W. Twort (1915) , Great Britain Félixb hérelle (1917) , France Infect bacterial cell by injecting their genetic material

3. Characteristics of Bacteriophage Simple viruses that consist of a nucleic acid surrounded by protein capsid The nucleic acid may be DNA or RNA, and maybe ds or ss

4. Life cycle of Bacteriophage Lytic cycle Bacteriophages that replicate through lytic life cycles are called lytic bacteriophages Lytic phages are more suitable vectors used in RDT Also known as virulent cycle There is large scale production of phage particles, eventually leading to cell lysis Lytic phages take over machinery of the cell to make phage comp.

5. 2. Lysogenic cycle Bacteriophages capable of lysogenic cycle are termed temperate phages Lysogenic or temperate phages incorporate their nucleic acid into the chromosome of the host cell, and replicates with it as a unit without destroying the cell Phage DNA becomes integrated into bacterial genome Under certain conditions, lysogenic ohages can be induced to follow a lytic cycle Example; phage lambda of E.coli

6. Why Bacteriophages as vector? If the genome of phage particle is removed and instead a gene of interest to be transported to a test organism is out in the phage particle, it can act as useful vector Used for cloning large pieces of DNA, 5-25 kb Used for preparing genomic library Generally, only lysogenic phages, more specifically the lentiviruses are used for this purpose Bacteriophages make suitable cloning vectors as they can accept large pieces of DNA

7. Type of phage vectors LAMBDA PHAGE It has a icosahedron head (20 faces) The head is made of protein of several tyoes and contains 46,500 bp long genomic DNA Contains ds circular DNA of about 17 micrometres in length Consists of 48,514 bp of known sequence Phage lamba is a virus of e.coli k12 which does not kill the host inspite of being capable of destroying it

8. Both the ends of 5’ terminus consist of 12 bases which extend beyong the 3’ terminus This results in single strand complementary region - cohesive ends The cohesive ends form bp can can easily circularize The ds region formed after base pairing of complementary nucleotides is designated COS

9. 2. P1 PHAGE VECTOR Temperate bacteriophage that infects E.coli and some other bacteria When undergoing lysogenic cycle, the phage genome exists as a plasmid in the bacterium, unlike lamba phage (that integrate into host DNA) Has icosahedral head with six tail fibers The genome of P1 phage is moderately large, ~93kbp In the viral particle, it is in the form of linear ds DNA molecule In the host, it circularizes and replicates as a plasmid

10. 3. Phage M13 VECTOR M13 forms the basis of cloning system designed to easily introduce mutation into genes inserted into phage genome Also used in phage display methodologies and peptide libraries It is a filamentous bacteriophage Ss circular DNA 6400 bp length The genome codes for a total of 10 genes

11. Gene II, V and X code for phage DNA synthesis Gene VIII codes for major structural and protein of Bacteriophage particles Gene III codes for the minor coat protein Following infection, major coat protein is stripped off and minor coat protein remains attached

12. Importance of Bacteriophage in Biotechnology study of Bacteriophage sheds light in development of new biotechnology products Bacteriophage therapy - makes use of lytic phage particles as an alternative in the antimicrobial treatment of resistant bacterial infections Development of Bacteriophage based vaccines Important for ecology and evolution of bacteria Enormous impact on the global carbon cycle Detection of pathological bacterial strains