The document discusses the lysogenic and lytic cycles of bacteriophages. It describes how the lysogenic cycle involves the integration of bacteriophage nucleic acid into the host bacterium's genome, allowing the genetic material to replicate with the host cell. The lytic cycle causes the virus to take over the host's DNA to produce viral proteins and particles, ultimately lysing the host cell. Both cycles can occur in bacteria and eukaryotes. The document also discusses prophages, lysogeny induction, and references several papers on bacteriophage therapy and resistance mechanisms.

1. MOLECULAR
MECHANISMS AND LYTIC
ACTION OF
BACTERIOPHAGE.
Dmitri Popov , PhD Radiobiology, MD (Russia).
Advanced MedicalTechnology and Systems Inc. Canada.

2. Bacteriophage
• Key words:
• Bacteriophage, lysogenic cycle, lytic cycle,
• Under work
• DOI: 10.13140/RG.2.1.4777.6240
•

3. Bacteriophage
• Bacteriophages are bacterial viruses that invade bacterial cells and, disrupt
bacterial metabolism and cause the bacterium to lyse.
• bacterial viruses (bacteriophage), could be separated in group with high lytic,
resulting in complete host cell lysis, however other group caused of
incomplete lysis.
• Lysogeny, or the lysogenic cycle, is one of two cycles of viral reproduction
(the lytic cycle is the other).
• Lysogeny is characterized by integration of the bacteriophage nucleic acid into
the host bacterium's genome or formations of a circular replicon in the
bacterium's cytoplasm.

4. Bacteriophage
• Lysogeny, or the lysogenic cycle, is one of two cycles of viral reproduction
(the lytic cycle is the other).
• Lysogeny is characterized by integration of the bacteriophage nucleic acid into
the host bacterium's genome or formations of a circular replicon in the
bacterium's cytoplasm.
• In this condition the bacterium continues to live and reproduce normally.
• The genetic material of the bacteriophage, called a prophage, can be
transmitted to daughter cells at each subsequent cell division, and a later
event (such as UV radiation or the presence of certain chemicals) can release it,
causing proliferation of new phages via the lytic cycle.
• Lysogenic cycles can also occur in eukaryotes, although the method of DNA
incorporation is not fully understood

5. Bacteriophage
• The lytic cycle involves the virus entering a host cell, taking control of the host
DNA to produce viral DNA and the viral proteins that provide the structural
component of the bacteriophage.
• After the cell has many new virus particles assembled, digesting the host cell
wall from within and releasing the new viruses.
• For example, the bacteriophage lambda, after infecting an E. coli host cell,
normally multiplies until several hundred progeny are produced, at which time
the bacterial cell is lysed and the progeny released (Alberts et al. 1989).

6. Bacteriophage
• The lysogenic cycle involves the virus entering the cell, and instead of creating new
virus particles, is characterized by integration of the bacteriophage nucleic acid into
the host bacterium's genome.
• The newly integrated genetic material acts as an additional set of genes that can be
replicated when the DNA of the host cell is replicated and the host cell divides.
• The virus is thus transmitted to daughter cells at each subsequent cell division,
although the phages remain inert, causing no harm to the host cells.
• Lysogenic cycles can also occur in eukaryotes, although the method of incorporation
of DNA is not fully understood.
• Canchaya,C., C. Proux, G. Fournous,A. Bruttin, and H. Brüssow. Prophage
genomics. Microbiol. Mol. Biol. Rev. 67(2): 238–76.PMID 12794192. Retrieved November 8,
2008.

7. Bacteriophage
• Prophage is the term for a phage DNA in its dormant state, typically
integrated into the host bacteria's chromosome, but also can include the rare
cases where the phage exists as a stable plasmid within the host cell.
• The lysogenic bacterium multiples normally until some environmental
induction, such as ionizing radiation or ultraviolet light threatens the bacterial
cell and induces the prophage to initiate the lytic cycle.
• The prophage expresses gene(s) that repress the phage's lytic action, and the
phage enters the lytic cycle when this suppression is disrupted.
• http://www.newworldencyclopedia.org/entry/Lysogenic_cycle

8. Conclusion:
• Lysogenic and lytic cycles can occur in bacteria.
• Lysogenic and lytic cycles can occur in eukaryotes.
• Lysogenic cycle can occur in cancer cells ( oncolytic action)
• Lysogenic cycle can be induced in the cancer cells with integrated phage’s DNA.
• Bacteriophage could be used for therapy bags resistant to major antibiotics.
• Bacteriophage could create resistance to bacteriophage.
• Bacteriophage could modify bacteria and bacteria can acquire new toxic features.
• Bacteriophage could be dangerous and used for creation biological weapon.
• Bacteriophage could be useful for creation new anticancer drugs.

9. Literature
• ANTIMICROBIALAGENTSAND CHEMOTHERAPY,
• 0066-4804/01/$04.0010 DOI: 10.1128/AAC.45.3.649–659.2001
• Mar. 2001, p. 649–659Vol. 45, No. 3
• Copyright © 2001,American Society for Microbiology.All Rights Reserved.
• BacteriophageTherapy
• ALEXANDER SULAKVELIDZE,1*ZEMPHIRAALAVIDZE,1,2AND J. GLENN MORRIS, JR.1
• Division of Molecular Epidemiology, Department of Epidemiology and Preventive Medicine,
University of Maryland
• School of Medicine, Baltimore, Maryland 21201,1 and Eliava Institute of Bacteriophage,
Microbiology,
• andVirology, Georgian Academy of Sciences,Tbilisi,Georgia 3800602

10. Literature
• Bacteriophage resistance mechanisms
• Simon J. Labrie*, Julie E. Samson and Sylvain Moineau
• *Department of Civil &Environmental Engineering,
• Massachusetts Institute ofTechnology, Cambridge, Massachusetts 02139, USA.
• Département de biochimie et de microbiologie, Faculté des
• sciences et de génie, Université Laval.

11. Literature
• Sulakvelidze, A., Alavidze, Z. & Morris, J. G. Jr.
• Bacteriophage therapy. Antimicrob. Agents Chemother. 45, 649–659 (2001).
• Akçelik, M. A phage DNA injection-blocking type resistance mechanism encoded
by chromosomal DNA in Lactococcus lactis subsp. lactis PLM-18.
• Milchwissenschaft 53, 619–622 (1998).

12. Literature
• Under analysis.