Chapter 4 bacteriophage
? 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,
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 to over 100 gene
products
? Protein,function in infection and protect
the nucleic acid
Structure of Bacteriophage
? different sizes and shapes
icosahedral
二十面体
filamentous
Tail
Tail Fibers
Base Plate
Head
Contractile
Sheath
Capsid
DNA
Types of Bacteriophage
? Lytic or Virulent Phages
毒性噬菌体
? Lysogenic or Temperate Phage
溶原性噬菌体或温和噬菌体
Lytic or Virulent Phages
? Definition,
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,
? Life Cycle
? Adsorption吸附
? Penetration穿入
? Biological Synthesis生物合成
? Maturation and Release成熟和释放
Adsorption吸附
Penetration穿入
Biological Synthesis生物合成
Maturation and Release成熟和释放
Bacteriophage
binding to and
injecting their
DNA into a
bacterial cell
normal
bacteriophage
bacteriophage
after contraction
of sheath
Assay for Lytic Phage
? Plaque assay噬斑测定
? 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),
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,
Lysogenic bacterium
Induction
Animation summarizing the
lysogenic life cycle of a
temperate bacteriophage,
溶原性细菌的溶原性周期和溶菌性周期
? When a cell becomes lysogenized,
occasionally extra genes carried by the
phage get expressed in the cell,These
genes can change the properties of the
bacterial cell,This process is called
lysogenic conversion,
lysogenic conversion
溶原性转换
Application of Bacteriophage
? Used in treatment of bacterial infections
? Used for the identification of pathogenic
bacteria (phage typing 噬菌体型分型 )
? Used in molecular biology
? 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,
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 to over 100 gene
products
? Protein,function in infection and protect
the nucleic acid
Structure of Bacteriophage
? different sizes and shapes
icosahedral
二十面体
filamentous
Tail
Tail Fibers
Base Plate
Head
Contractile
Sheath
Capsid
DNA
Types of Bacteriophage
? Lytic or Virulent Phages
毒性噬菌体
? Lysogenic or Temperate Phage
溶原性噬菌体或温和噬菌体
Lytic or Virulent Phages
? Definition,
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,
? Life Cycle
? Adsorption吸附
? Penetration穿入
? Biological Synthesis生物合成
? Maturation and Release成熟和释放
Adsorption吸附
Penetration穿入
Biological Synthesis生物合成
Maturation and Release成熟和释放
Bacteriophage
binding to and
injecting their
DNA into a
bacterial cell
normal
bacteriophage
bacteriophage
after contraction
of sheath
Assay for Lytic Phage
? Plaque assay噬斑测定
? 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),
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,
Lysogenic bacterium
Induction
Animation summarizing the
lysogenic life cycle of a
temperate bacteriophage,
溶原性细菌的溶原性周期和溶菌性周期
? When a cell becomes lysogenized,
occasionally extra genes carried by the
phage get expressed in the cell,These
genes can change the properties of the
bacterial cell,This process is called
lysogenic conversion,
lysogenic conversion
溶原性转换
Application of Bacteriophage
? Used in treatment of bacterial infections
? Used for the identification of pathogenic
bacteria (phage typing 噬菌体型分型 )
? Used in molecular biology
