Bacteriophage

Bacteriophage (Phage) Definition - Obligate intracellular parasites that multiply inside bacteria by making use of some or all of the host biosynthetic machinery Significance Models for animal cell viruses Gene transfer in bacteria Medical applications Identification of bacteria - phage typing Treatment and prophylaxsis???

Medical Applications of Phage “I strongly believe phage could become an effective antibacterial tool” - Carl Merril, Chief of the Laboratory of Biochemical Genetics, National Institute of Mental Health, NIH. “It might be another string on the bow, such that when (conventional antibiotics) fail, here’s something that has a chance of working. But it’s not going to be a panacea” - Joshua Lederberg, Sackler Foundation Scholar at The Rockefeller University Reassessment of Medicinal Phage Spurs Companies to Study Therapeutic Uses American Society for Microbiology News 64:620-623, 1998

Medical Applications of Phage Exponential Biotherapies (Rockville, MD) Vancomycin resistant Enterococcus facium and Streptococcus pneumoniae Phage Therapeutics (Bothell, WA) Staphylococcus aureus and Staphylococcus epidermidis Intralytix, Inc. (Baltimore, MD) Salmonella in meat and poultry Biopharm Ltd. (Tblisi, Georgia) Infections associated with burns University of Idaho Escherichia coli O157:H7 in cattle Reassessment of Medicinal Phage Spurs Companies to Study Therapeutic Uses. American Society for Microbiology News 64:620-623, 1998. Phages eyed as agents to protect against harmful E. coli. American Society for Microbiology News 65:666-667, 1999.

Bacteriophage T4 Lambda ()

Composition and Structure Nucleic acid Genome size Modified bases Protein Protection Infection Tail Tail Fibers Base Plate Head/Capsid Contractile Sheath Structure (T4) Size Head or capsid Tail

Infection of Host Cells Adsorption LPS for T4 Irreversible attachment Sheath Contraction Nucleic acid injection

Types of Bacteriophage Lytic or virulent phage: Phage that can only multiply within bacteria and kill the cell by lysis. (e.g., T4)

Lytic Phage Multiplication Cycle Total Phage Extracellular Phage Eclipse Intracellular accumulation phase Time after Infection Number of Infectious Particles Lysis Eclipse Early genes Phage DNA synthesis Late genes Intracellular accumulation Lysis and Release

Assay for Lytic Phage Plaque assay Method Plaque forming unit (pfu) Measures infectious particles Bacteria Phage +

Types of Bacteriophage Lysogenic or temperate phage: Phage that can either multiply via the lytic cycle or enter a quiescent state in the bacterial cell. (e.g., ) Expression of most phage genes repressed Prophage Lysogen

Events Leading to Lysogeny Circularization of the phage chromosome Cohesive ends Lygase Closed Circle Cohesive Ends Linear Double Stranded Opened Circle

Events Leading to Lysogeny gal bio Site-specific recombination Phage coded enzyme Repression of the phage genome Repressor protein Specific Immunity to superinfection

Termination of Lysogeny Induction Adverse conditions Role of proteases recA protein Destruction of repressor gal bio Gene expression Excision Lytic growth

Lytic vs Lysogenic Cycle? Role of repressor Role of cro gene product Role of proteases

Significance of Lysogeny Model for animal virus transformation Lysogenic or phage conversion Definition: A change in the phenotype of a bacterial cell as a consequence of lysogeny Modification of Salmonella O antigen Toxin production by Corynebacterium diphtheriae