Phi X 174 - 2.pptx

PG AND RESEARCH DEPARTMENT OF MICROBIOLOGY - SRI PARAMAKALYANI COLLEGE - ALWARKURICHI

1. SRI PARAMAKALYANI COLLEGE REACCREDITED WITH B GRADE WITH A CGPA OF 2.71 IN THE SECOND CYCLE OF NAAC AFFILIATED TO MANOMANIUM SUNDARANAR UNIVERSITY, TIRUNELVELI. ALWARKURICHI 627 412, TAMIL NADU, INDIA POST GRADUATE & RESEARCH CENTRE DEPARTMENT OF MICROBIOLOGY (Government Aided) ACADEMIC YEAR 2021-2022 II sem core: VIROLOGY (zmbm23) Unit- 2 BACTERIAL VIRUS : Phi X 174 PHAGE Submitted by, Indhumathi S Reg no: 20211232516110 I M.Sc., Microbiology Sri Paramakalyani College, Alwarkurichi. Submitted to, Dr.C.Mariappan Ph.D. Assistant professor, Department of microbiology, Sri paramakalyani college, Alwarkurichi.

2. synopsis

3. Introduction Bacteriophage (phages) Bacteriophages were first discovered in 1915 by  William Twort. In 1917 by Felix d'Herelle realized that they had the potential to kill bacteria . Viruses that attacks and infects the bacteria . Bacteriophage is specific to one form of bacteria Bacteriophage also infect archaea.

4. Taxonomial arrangement

5. History It is a bacteriophage infects the bacterium E.coli In 1962 ,  Walter fiers  and Robert Sinsheimer – demonstrated the physical, covalently closed circularity of ΦX174 DNA. The first DNA-based genome to be sequenced.This work was completed by Frederick sanger in 1977 . Studies of phage replication led to discovery of Rolling circle replication. Family : Microviridae provided the first evidence of overlapping genes.

6. Morphology The genome consists of circular ssDNA. Genome size ranges from 4.6 to 6.1 kb. The capsid is icosahedral (i.e.spherical). Diameter is 25-27nm Tailess icosahedral bacteriophage

7. Phi x 174 under electron microscope

8. Genome organization Genome: circular ssDNA. Consists of 5386 nucleotides. 10 genes codes for 11 proteins. Proteins are A , A* , B , C , D , E , F , G , H , J , K encoded. The 11 protein together contain a total of 1986 aminoacids 10 genes encoded for 11 proteins , because of overlapping genes.

9. Overlapping of genes The gene is organized in a such a way if one gene ends in a particular position, the succeeding gene starts with few nucleotide overlapping the terminal region of the first gene. This is called overlapping genes , where reading of genes are overlapped in their sequence

10. Arrangement of genes Gene A contains an internal translation initiation site to encode protein A* Gene B is encoded within A in different reading frame. Gene K is at the end of gene A and extend into gene C Gene E is totally within gene D. The termination codon of D overlaps intiation codon for gene J .

11. Genome encoded proteins

12. Life cycle of x174

13. Attachment of phage Infection begins when G protein binds to  lipopolysaccharides  on the bacterial host cell surface. Phage recognizes the lipopolysaccharide receptor in the outer membrane of E.coli by the minor spike protein H.

14. Entry of phage genome H protein (or the DNA Pilot Protein) pilots the viral genome through the bacterial membrane of  E.coli  bacteria The outer part recognizes the LPS receptor.The inner part of the H protein is responsible for the injection of genome into the host cell. Atleat one H protein enters into the host cell with the viral DNA.

15. Replication of Phi x174

16. Assembly of mature virions

17. Release of mature virions Cell lysis Requires E protein, which inhibits the Mra Y translocase , which is involved in the Synthesis of lipid I for the biosynthesis of peptidoglycan.

18. Reference https://www.slideshare.net/qamrunnisashaikh1997/phi-x-174-phage https://en.wikipedia.org/wiki/Bullavirinae https://www.ncbi.nlm.nih.gov/pmc/articles/PMC326969/ THANK YOU