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)
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???
viral common properties smallest，simple
structure DNA/RNA病毒的基本特性
parasite in living cell
widespread existence 分布广泛
high host –specific parasitism严格的宿主
特异性
Main contents
1 COMPOSITION AND STRUCTURE OF BACTERIOPHAGE
2 PHAGE MULTIPLICATION CYCLE
3 APPLICATION OF BACTERIOPHAGE
Requirement
Master the interrelation between phage and
bacteria
Master the following concepts :
1. lysogenic state 2. lysogenic phage
(temperate phage)
3.lysogenec bacteria 4.prophage
Understand the.size, shape and structure of
phage.
[Class hour: 1 hours ]
Composition of Bacteriophage
nucleic acid: either DNA or RNA but not
both
– ds DNA, ss RNA, ss DNA
– unusual or modified bases
– encode 3-5 gene products
Protein: function in infection and protect
the nucleic acid
Biological properties
生物学性状
Shape and structure
Seen by
EM :icosahedral 二十面体
–
–
–
–
Tadpol蝌蚪形
microsphere微球形
slim rod丝形
head core DNA/RNA
tail pipe-like
capsid protein coat
base plate
Antigenicity 抗原性
Resistive 抵抗力
– >Bacteria 75°C 30′
– sensitive to rays
filamentous
Composition and Structure
Composition
– Nucleic acid
Head/Capsid
Genome size
Modified bases
– Protein
Protection
Infection
Structure (T4)
– Size
– Head or
capsid
Contractile
Sheath
Tail
Tail Fibers
Base Plate
Types of Bacteriophage
Lytic or Virulent Phages毒性噬菌体
Lytic or virulent phages are phages which
can only multiply in bacteria and kill the
cell by lysis at the end of the life cycle.
噬菌体的种类
毒性噬菌体（virulent phage）
– 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
温和噬菌体（temperate phage）/
溶原性噬菌体（lysogenic phage）
– 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DNA能随细菌DNA复制，并
随细菌的分裂而传代
Life Cycle毒性噬菌体复制周期
Adsorption吸附
Penetration穿入
Biological Synthesis生物合成
Maturation and Release成熟和释放
Lysogenic or Temperate Phage
溶原性噬菌体或温和噬菌体
Lysogenic or temperate phages are those that
can either multiply via the lytic cycle or enter a
quiescent state in the cell. In this quiescent state
most of the phage genes are not transcribed; the
phage genome exists in a repressed state. The
phage DNA in this repressed state is called a
prophage because it is not a phage but it has the
potential to produce phage. In most cases the
phage DNA actually integrates into the host
chromosome and is replicated along with the host
chromosome and passed on to the daughter cells.
The cell harboring a prophage is termed a
lysogenic bacterium.
Lytic phage are enumerated by a plaque
assay. A plaque is a clear area which
results from the lysis of bacteria. Each
plaque arises from a single infectious
phage. The infectious particle that gives
rise to a plaque is called a pfu (plaque
forming unit).
Lytic or Virulent Phages毒性噬菌体
Lytic or virulent phages are phages which
can only multiply in bacteria and kill the
cell by lysis at the end of the life cycle.
噬菌现象
液体培养基 混浊
澄清
固体培养基中，出现噬斑（plaque）
一定体积内的噬斑形成单位数目（pfu）
温和噬菌体
前噬菌体（prophage）
溶原性细菌（lysogenic bacterium）
溶原性（lysogeny）
溶原状态
溶原性周期和溶菌性周期
溶原性转换
Animation summarizing the
lysogenic life cycle of a
temperate bacteriophage.
Lysogenic bacterium
PHAGE MULTIPLICATION
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
Application of Bacteriophage
噬菌体的应用
Used in treatment of bacterial infections细
菌感染的诊断与治疗
Used for the identification of pathogenic
bacteria细菌的鉴定与分型 (phage typing噬
菌体型分型)
Used in molecular biology分子生物学研究
的重要工具
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.
Assay for Lytic Phage
Plaque assay噬斑测定
整合在细菌染色体上的噬菌体基因
组称____________。
a.prophage
b.virulent phage
c.lysogenic bacterium
d.lysogeny
e.temperate phage