Chapter 4. Bacteriophage Chapter 4. Bacteriophage 噬菌体噬菌体

•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

Biological propertiesBiological properties生物学性状生物学性状

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.

噬菌体的种类噬菌体的种类毒性噬菌体（毒性噬菌体（ virulent phagevirulent phage ））– 能在宿主菌细胞内复制增殖，产生许多子代噬能在宿主菌细胞内复制增殖，产生许多子代噬

菌体，并最终裂解细菌，称为毒性噬菌体菌体，并最终裂解细菌，称为毒性噬菌体温和噬菌体（温和噬菌体（ temperate phagetemperate phage ）） //

溶原性噬菌体（溶原性噬菌体（ lysogenic phagelysogenic phage ））– 噬菌体基因与宿主菌染色体整合，不产生子代噬菌体基因与宿主菌染色体整合，不产生子代

噬菌体，但噬菌体噬菌体，但噬菌体 DNADNA 能随细菌能随细菌 DNADNA 复制，复制，并随细菌的分裂而传代并随细菌的分裂而传代

Life CycleLife Cycle 毒性噬菌体复制周期毒性噬菌体复制周期

AdsorptionAdsorption 吸附吸附 PenetrationPenetration 穿穿入入

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.

噬菌现象噬菌现象

液体培养基 混浊 澄清液体培养基 混浊 澄清固体培养基中，出现噬斑（固体培养基中，出现噬斑（ plaqueplaque ））一定体积内的噬斑形成单位数目（一定体积内的噬斑形成单位数目（ pfupfu ））

温和噬菌体温和噬菌体前噬菌体（前噬菌体（ prophageprophage ））溶原性细菌（溶原性细菌（ lysogenic bacteriumlysogenic bacterium ））溶原性（溶原性（ lysogenylysogeny ））溶原状态溶原状态溶原性周期和溶菌性周期溶原性周期和溶菌性周期溶原性转换溶原性转换

Animation summarizing the lysogenic

life cycle of a temperate bacteriophage.

Lysogenic bacterium

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.

Assay for Lytic PhageAssay for Lytic Phage

Plaque assayPlaque assay 噬斑测定 噬斑测定

整合在细菌染色体上的噬菌体基因整合在细菌染色体上的噬菌体基因组称组称 ________________________ 。。

a.prophagea.prophage

b.virulent phageb.virulent phage

c.lysogenic bacteriumc.lysogenic bacterium

d.lysogenyd.lysogeny

e.temperate phagee.temperate phage