Chapter 4. Chapter 4. Bacteriophage Bacteriophage 噬噬体 噬噬体 • Bacteriophages Bacteriophages ( phages ) are ( phages ) are obligate obligate intracellular intracellular parasites that parasites that multiply inside multiply inside bacteria by making bacteria by making use of some or all use of some or all of the host of the host biosynthetic biosynthetic machinery . They machinery . They
Chapter 4. Bacteriophage 噬菌体. Bacteriophages ( phages ) are obligate intracellular parasites that multiply inside bacteria by making use of some or all of the host biosynthetic machinery . They are viruses that infect bacteria. Bacteriophage (Phage). - PowerPoint PPT Presentation
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•Bacteriophages Bacteriophages ( phages ) are obligate ( phages ) are obligate intracellular parasites intracellular parasites that multiply inside that multiply inside bacteria by making use bacteria by making use of some or all of the of some or all of the host biosynthetic host biosynthetic machinery . They are machinery . They are viruses that infect viruses that infect bacteria.bacteria.
Bacteriophage (Phage)Bacteriophage (Phage)
Definition - Obligate intracellular parasites that Definition - Obligate intracellular parasites that multiply inside bacteria by making use of some multiply inside bacteria by making use of some or all of the host biosynthetic machineryor all of the host biosynthetic machinery
SignificanceSignificance– Models for animal cell virusesModels for animal cell viruses– Gene transfer in bacteriaGene transfer in bacteria– Medical applicationsMedical applications
Identification of bacteria - phage typingIdentification of bacteria - phage typing
Treatment and prophylaxsis???Treatment and prophylaxsis???
viral common properties viral common properties smallestsmallest ,, simple structure DNA/RNAsimple structure DNA/RNA 病病毒的基本特性毒的基本特性parasite in living cellparasite in living cell
widespread existence widespread existence 分布广泛分布广泛high host –specific parasitismhigh host –specific parasitism 严格的宿主严格的宿主特异性特异性
3 APPLICATION OF BACTERIOPHAGE
2 PHAGE MULTIPLICATION CYCLE
1 COMPOSITION AND STRUCTURE OF BACTERIOPHAGE
Main contents
RequirementRequirement
Master the interrelation between phage and Master the interrelation between phage and bacteriabacteriaMaster the following concepts :Master the following concepts :1. lysogenic state 2. lysogenic phage 1. lysogenic state 2. lysogenic phage (temperate phage) (temperate phage) 3.lysogenec bacteria 4.prophage3.lysogenec bacteria 4.prophageUnderstand the.size, shape and structure of Understand the.size, shape and structure of phage.phage.[Class hour: 1 hours ][Class hour: 1 hours ]
Composition of Bacteriophage Composition of Bacteriophage
nucleic acid: nucleic acid: either DNA or RNA but not either DNA or RNA but not both both – ds DNA, ss RNA, ss DNA ds DNA, ss RNA, ss DNA – unusual or modified basesunusual or modified bases– encode 3-5 gene productsencode 3-5 gene products
Protein: Protein: function in infection and protect function in infection and protect the nucleic acidthe nucleic acid
Shape and structure Shape and structure Seen by EM :Seen by EM :icosahedral 二十面体 – TadpolTadpol 蝌蚪形蝌蚪形– microspheremicrosphere 微球形微球形– slim rodslim rod 丝形丝形– head core DNA/RNA head core DNA/RNA
tail pipe-like tail pipe-like
capsid protein coat capsid protein coat base plate base plate Antigenicity Antigenicity 抗原性抗原性Resistive Resistive 抵抗力抵抗力– >Bacteria 75°C 30′>Bacteria 75°C 30′– sensitive to rayssensitive to rays
filamentous
Composition and StructureComposition and Structure
CompositionComposition– Nucleic acidNucleic acid
Genome sizeGenome size
Modified basesModified bases
– ProteinProteinProtectionProtection
InfectionInfection
Structure (TStructure (T44))
– SizeSize– Head or capsidHead or capsid– TailTail
Tail
Tail Fibers
Base Plate
Head/Capsid
Contractile Sheath
Types of BacteriophageTypes of Bacteriophage
Lytic or Virulent PhagesLytic or Virulent Phages 毒性噬菌体毒性噬菌体 Lytic or virulent phagesLytic or virulent phages are phages which are phages which
can only multiply in bacteria and kill the can only multiply in bacteria and kill the cell by lysis at the end of the life cycle.cell by lysis at the end of the life cycle.
Biological SynthesisBiological Synthesis 生物合成生物合成 Maturation and ReleaseMaturation and Release 成熟和释放成熟和释放
Lysogenic or Temperate PhageLysogenic or Temperate Phage溶原性噬菌体或温和噬菌体溶原性噬菌体或温和噬菌体
Lysogenic or temperate phagesLysogenic or temperate phages are those that can are those that can either multiply via the lytic cycle or enter a quiescent either multiply via the lytic cycle or enter a quiescent state in the cell. In this quiescent state most of the phage state in the cell. In this quiescent state most of the phage genes are not transcribed; the phage genome exists in a genes are not transcribed; the phage genome exists in a repressed state. The phage DNA in this repressed state repressed state. The phage DNA in this repressed state is called a prophageis called a prophage because it is not a phage but it has because it is not a phage but it has the potential to produce phage. In most cases the phage the potential to produce phage. In most cases the phage DNA actually integrates into the host chromosome and is DNA actually integrates into the host chromosome and is replicated along with the host chromosome and passed replicated along with the host chromosome and passed on to the daughter cells. The cell harboring a prophage is on to the daughter cells. The cell harboring a prophage is termed a lysogenic bacteriumtermed a lysogenic bacterium..
Lytic phage are enumerated by a plaque Lytic phage are enumerated by a plaque assay. A plaque is a clear area which assay. A plaque is a clear area which results from the lysis of bacteria. Each results from the lysis of bacteria. Each plaque arises from a single infectious plaque arises from a single infectious phage. The infectious particle that gives phage. The infectious particle that gives rise to a plaque is called a pfu (plaque rise to a plaque is called a pfu (plaque forming unit). forming unit).
Lytic or Virulent PhagesLytic or Virulent Phages 毒性噬菌体毒性噬菌体
Lytic or virulent phages are phages which Lytic or virulent phages are phages which can only multiply in bacteria and kill the can only multiply in bacteria and kill the cell by lysis at the end of the life cycle.cell by lysis at the end of the life cycle.
PHAGE MULTIPLICATION PHAGE MULTIPLICATION CYCLE- Life Cycle:CYCLE- Life Cycle:
Lysogenic or Temperate Phage 溶原性噬菌体或温和噬菌体
溶原性细菌的溶原性周期和溶菌性周期溶原性细菌的溶原性周期和溶菌性周期
Application of BacteriophageApplication of Bacteriophage噬菌体的应用噬菌体的应用
Used in treatment of bacterial infectionsUsed in treatment of bacterial infections 细细菌感染的诊断与治疗菌感染的诊断与治疗Used for the identification of pathogenic Used for the identification of pathogenic bacteriabacteria 细菌的鉴定与分型 细菌的鉴定与分型 (phage typing(phage typing噬菌体型分型噬菌体型分型 ) )
Used in molecular biologyUsed in molecular biology 分子生物学研究分子生物学研究的重要工具的重要工具
Medical Applications of PhageMedical Applications of Phage
““I strongly believe phage could become an I strongly believe phage could become an effective antibacterial tool” - effective antibacterial tool” - Carl Merril, Chief of the Carl Merril, Chief of the Laboratory of Biochemical Genetics, National Institute of Mental Laboratory of Biochemical Genetics, National Institute of Mental Health, NIH.Health, NIH.
““It might be another string on the bow, such It might be another string on the bow, such that when (conventional antibiotics) fail, here’s that when (conventional antibiotics) fail, here’s something that has a chance of working. But something that has a chance of working. But it’s not going to be a panacea” - it’s not going to be a panacea” - Joshua Lederberg, Joshua Lederberg, Sackler Foundation Scholar at The Rockefeller UniversitySackler 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 PhageMedical Applications of PhageExponential Biotherapies (Rockville, MD)Exponential Biotherapies (Rockville, MD)– Vancomycin resistant Vancomycin resistant Enterococcus facium Enterococcus facium and and
Streptococcus pneumoniaeStreptococcus pneumoniae
Phage Therapeutics (Bothell, WA)Phage Therapeutics (Bothell, WA)– Staphylococcus aureusStaphylococcus aureus and and Staphylococcus epidermidisStaphylococcus epidermidis
Intralytix, Inc. (Baltimore, MD)Intralytix, Inc. (Baltimore, MD)– SalmonellaSalmonella in meat and poultry in meat and poultry
Biopharm Ltd. (Tblisi, Georgia)Biopharm Ltd. (Tblisi, Georgia)– Infections associated with burnsInfections associated with burns
University of IdahoUniversity of Idaho– Escherichia coliEscherichia coli O157:H7 in cattle 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.