Enterobacteria phage λ (lambda phage, coliphage λ) is a bacterial
virus, or bacteriophage, that infects the bacterial species
Escherichia coli (E. coli). It was discovered by
Esther Lederberg in
1950 when she noticed that streaks of mixtures of two E. coli strains,
one of which treated with ultraviolet light, was "nibbled and
plaqued". The wild type of this virus has a temperate lifecycle
that allows it to either reside within the genome of its host through
lysogeny or enter into a lytic phase (during which it kills and lyses
the cell to produce offspring); mutant strains are unable to
lysogenize cells – instead, they grow and enter the lytic cycle
after superinfecting an already lysogenized cell.
The phage particle consists of a head (also known as a capsid), a
tail, and tail fibers (see image of virus below). The head contains
the phage's double-strand linear
DNA genome. During infection, the
phage particle recognizes and binds to its host, E. coli, causing DNA
in the head of the phage to be ejected through the tail into the
cytoplasm of the bacterial cell. Usually, a "lytic cycle" ensues,
where the lambda
DNA is replicated and new phage particles are
produced within the cell. This is followed by cell lysis, releasing
the cell contents, including virions that have been assembled, into
the environment. However, under certain conditions, the phage
integrate itself into the host cell chromosome in the lysogenic
pathway. In this state, the λ
DNA is called a prophage and stays
resident within the host's genome without apparent harm to the host.
The host is termed a lysogen when a prophage is present. This prophage
may enter the lytic cycle when the lysogen enters a stressed
2 Life cycle
2.1.1 N antitermination
Lytic life cycle
2.2.1 Rightward transcription
22.214.171.124 Q antitermination
2.2.2 Leftward transcription
126.96.36.199 xis and int regulation of insertion and excision
Lysogenic (or lysenogenic) life cycle
2.3.2 Maintenance of lysogeny
188.8.131.52 Control of phage genome excision in induction
3 Multiplicity reactivation and prophage reactivation
5 Protein function overview
Lytic or lysogenic?
Lambda as a genetic tool
8 See also
10 Further reading
11 External links
Bacteriophage lambda virion (schematic). Protein names and their copy
numbers in the virion particle are shown. The presence of the L and M
proteins in the virion is still unclear.
The virus particle consists of a head and a tail that can have tail
fibers. The whole particle consists of 12–14 different proteins with
more than 1000 protein molecules total and one
DNA molecule located in
the phage head. However, it is still not entirely clear whether the L
and M proteins are part of the virion.
Linear layout of lambda phage genome with major operons, promoter
regions and capsid coding genes.
The genome contains 48,490 base pairs of double-stranded, linear DNA,
with 12-base single-strand segments at both 5' ends. These two
single-stranded segments are the "sticky ends" of what is called the
cos site. The cos site circularizes the
DNA in the host cytoplasm. In
its circular form, the phage genome, therefore, is 48,502 base pairs
in length. The lambda genome can be inserted into the E. coli
chromosome and is then called a prophage. See section below for
Lambda phage J protein interaction with the LamB porin
Lambda phage is a non-contractile tailed phage, meaning during an
infection event it cannot 'force' its
DNA through a bacterial cell
membrane. It must instead use an existing pathway to invade the host
cell, having evolved the tip of its tail to interact with a specific
pore to allow entry of its
DNA to the hosts.
Lambda binds to an E. coli cell by means of its J
protein in the tail tip. The J protein interacts with the maltose
outer membrane porin (the product of the lamB gene) of E. coli, a
porin molecule, which is part of the maltose operon.
The linear phage genome is injected through the outer membrane.
DNA passes through the mannose permease complex in the inner
membrane  (encoded by the manXYZ genes) and immediately
circularises using the cos sites, 12-base G-C-rich cohesive "sticky
ends". The single-strand viral
DNA ends are ligated by host DNA
DNA injection into the cell membrane using Mannose PTS
permease a sugar transporting system as a mechanism of entry into the
DNA gyrase puts negative supercoils in the circular chromosome,
causing A-T-rich regions to unwind and drive transcription.
Transcription starts from the constitutive PL, PR and PR' promoters
producing the 'immediate early' transcripts. At first, these express
the N and cro genes, producing N, Cro and a short inactive protein.
Early activation events involving N protein
Cro binds to OR3, preventing access to the PRM promoter, preventing
expression of the cI gene. N binds to the two Nut (N utilisation)
sites, one in the N gene in the PL reading frame, and one in the cro
gene in the PR reading frame.
The N protein is an antiterminator, and functions to extend the
reading frames to which it is bound. When
RNA polymerase transcribes
these regions, it recruits the N and forms a complex with several host
Nus proteins. This complex skips through most termination sequences.
The extended transcripts (the 'late early' transcripts) include the N
and cro genes along with cII and cIII genes, and xis, int, O, P and Q
genes discussed later.
The cIII protein acts to protect the cII protein from proteolysis by
FtsH (a membrane-bound essential E. coli protease) by acting as a
competitive inhibitor. This inhibition can induce a bacteriostatic
state, which favours lysogeny. cIII also directly stabilises the cII
On initial infection, the stability of cII determines the lifestyle of
the phage; stable cII will lead to the lysogenic pathway, whereas if
cII is degraded the phage will go into the lytic pathway. Low
temperature, starvation of the cells and high multiplicity of
infection (MOI) are known to favor lysogeny (see later discussion).
N Antitermination requires the assembly of a large ribonucleoprotein
complex to effectively prolong the anti-termination process, without
the full complex the
RNA polymerase is able to bypass only a single
This occurs without the N protein interacting with the DNA; the
protein instead binds to the freshly transcribed mRNA. Nut sites
contain 3 conserved "boxes," of which only BoxB is essential.
RNA sequences are located close to the 5' end of the pL and
pR transcripts. When transcribed, each sequence forms a hairpin loop
structure that the N protein can bind to.
N protein binds to boxB in each transcript, and contacts the
RNA polymerase via
RNA looping. The N-RNAP complex is
stabilized by subsequent binding of several host Nus (N utilisation
substance) proteins (which include transcription
termination/antitermination factors and, bizarrely, a ribosome
The entire complex (including the bound Nut site on the mRNA)
continues transcription, and can skip through termination sequences.
Lytic life cycle
This is the lifecycle that the phage follows following most
infections, where the cII protein does not reach a high enough
concentration due to degradation, so does not activate its promoters.
The 'late early' transcripts continue being written, including xis,
int, Q and genes for replication of the lambda genome (OP). Cro
dominates the repressor site (see "Repressor" section), repressing
synthesis from the PRM promoter (which is a promoter of the lysogenic
The O and P proteins initiate replication of the phage chromosome (see
Q, another antiterminator, binds to Qut sites.
Transcription from the PR' promoter can now extend to produce m
the lysis and the head and tail proteins.
Structural proteins and phage genomes self-assemble into new phage
Products of the lysis genes S,R, Rz and Rz1 cause cell lysis. S is a
holin, a small membrane protein that, at a time determined by the
sequence of the protein, suddenly makes holes in the membrane. R is an
endolysin, an enzyme that escapes through the S holes and cleaves the
cell wall. Rz and Rz1 are membrane proteins that form a complex that
somehow destroys the outer membrane, after the endolysin has degraded
the cell wall. For wild-type lambda, lysis occurs at about 50 minutes
after the start of infection and releases around 100 virions.
Rightward transcription expresses the O, P and Q genes. O and P are
responsible for initiating replication, and Q is another
antiterminator that allows the expression of head, tail, and lysis
genes from PR’.
For the first few replication cycles, the lambda genome undergoes θ
This is initiated at the ori site located in the O gene. O protein
binds the ori site, and P protein binds the DnaB subunit of the host
replication machinery as well as binding O. This effectively
commandeers the host
Soon, the phage switches to a rolling circle replication similar to
that used by phage M13. The
DNA is nicked and the 3’ end serves as a
primer. Note that this does not release single copies of the phage
genome but rather one long molecule with many copies of the genome: a
These concatemers are cleaved at their cos sites as they are packaged.
Packaging cannot occur from circular phage DNA, only from concatomeric
The Q protein modifies the
RNA polymerase at the promoter region and
is recruited to
RNA polymerase. The Q protein turns into a RNA
polymerase subunit after it is recruitment to RNAP and modifies the
enzyme into a processive state. Note that NusA can stimulate the
activity of the Q protein.
Q is similar to N in its effect: Q binds to
RNA polymerase in Qut
sites and the resulting complex can ignore terminators, however the
mechanism is very different; the Q protein first associates with a DNA
sequence rather than an m
The Qut site is very close to the PR’ promoter, close enough that
the σ factor has not been released from the
holoenzyme. Part of the Qut site resembles the -10 Pribnow box,
causing the holoenzyme to pause.
Q protein then binds and displaces part of the σ factor and
The head and tail genes are transcribed and the corresponding proteins
Leftward transcription expresses the gam, red, xis, and int genes. Gam
and red proteins are involved in recombination. Gam is also important
in that it inhibits the host
RecBCD nuclease from degrading the 3’
ends in rolling circle replication. Int and xis are integration and
excision proteins vital to lysogeny.
xis and int regulation of insertion and excision
Diagram showing the retro-regulation process that yields a higher
concentration of xis compared to int. The m
RNA transcript is digested
by bacterial RNase starting from the cleaved hairpin loop at sib.
xis and int are found on the same piece of mRNA, so approximately
equal concentrations of xis and int proteins are produced. This
results (initially) in the excision of any inserted genomes from the
RNA from the PL promoter forms a stable secondary structure with
a stem-loop in the sib section of the mRNA. This targets the 3' (sib)
end of the m
RNA for RNAaseIII degradation, which results in a lower
effective concentration of int m
RNA than xis m
RNA (as the int cistron
is nearer to the sib sequence than the xis cistron is to the sib
sequence), so a higher concentrations of xis than int is observed.
Higher concentrations of xis than int result in no insertion or
excision of phage genomes, the evolutionarily favoured action -
leaving any pre-insterted phage genomes inserted (so reducing
competition) and preventing the insertion of the phage genome into the
genome of a doomed host.
Lysogenic (or lysenogenic) life cycle
The lysogenic lifecycle begins once the cI protein reaches a high
enough concentration to activate its promoters, after a small number
The 'late early' transcripts continue being written, including xis,
int, Q and genes for replication of the lambda genome.
The stabilized cII acts to promote transcription from the PRE, PI and
The Pantiq promoter produces antisense m
RNA to the Q gene message of
the PR promoter transcript, thereby switching off Q production. The
PRE promoter produces antisense m
RNA to the cro section of the PR
promoter transcript, turning down cro production, and has a transcript
of the cI gene. This is expressed, turning on cI repressor production.
The PI promoter expresses the int gene, resulting in high
concentrations of Int protein. This int protein integrates the phage
DNA into the host chromosome (see "
No Q results in no extension of the PR' promoter's reading frame, so
no lytic or structural proteins are made. Elevated levels of int (much
higher than that of xis) result in the insertion of the lambda genome
into the hosts genome (see diagram). Production of cI leads to the
binding of cI to the OR1 and OR2 sites in the PR promoter, turning off
cro and other early gene expression. cI also binds to the PL promoter,
turning off transcription there too.
Lack of cro leaves the OR3 site unbound, so transcription from the PRM
promoter may occur, maintaining levels of cI.
Lack of transcription from the PL and PR promoters leads to no further
production of cII and cIII.
As cII and cIII concentrations decrease, transcription from the
Pantiq, PRE and PI stop being promoted since they are no longer
Only the PRM and PR' promoters are left active, the former producing
cI protein and the latter a short inactive transcript. The genome
remains inserted into the host genome in a dormant state.
The prophage is duplicated with every subsequent cell division of the
host. The phage genes expressed in this dormant state code for
proteins that repress expression of other phage genes (such as the
structural and lysis genes) in order to prevent entry into the lytic
cycle. These repressive proteins are broken down when the host cell is
under stress, resulting in the expression of the repressed phage
genes. Stress can be from starvation, poisons (like antibiotics), or
other factors that can damage or destroy the host. In response to
stress, the activated prophage is excised from the
DNA of the host
cell by one of the newly expressed gene products and enters its lytic
The integration of phage λ takes place at a special attachment site
in the bacterial and phage genomes, called attλ. The sequence of the
bacterial att site is called attB, between the gal and bio operons,
and consists of the parts B-O-B', whereas the complementary sequence
in the circular phage genome is called attP and consists of the parts
P-O-P'. The integration itself is a sequential exchange (see genetic
recombination) via a
Holliday junction and requires both the phage
protein Int and the bacterial protein IHF (integration host factor).
Both Int and IHF bind to attP and form an intasome, a
DNA-protein-complex designed for site-specific recombination of the
phage and host DNA. The original B-O-B' sequence is changed by the
integration to B-O-P'-phage DNA-P-O-B'. The phage
DNA is now part of
the host's genome.
Maintenance of lysogeny
A simplified representation of the integration/excision paradigm and
the major genes involved.
Lysogeny is maintained solely by cI. cI represses transcription from
PL and PR while upregulating and controlling its own expression from
PRM. It is therefore the only protein expressed by lysogenic phage.
Lysogen repressors and polymerase bound to OR1 and recruits OR2, which
will activate PRM and shutdown PR.
This is coordinated by the PL and PR operators. Both operators have
three binding sites for cI: OL1, OL2, and OL3 for PL, and OR1, OR2 and
OR3 for PR.
cI binds most favorably to OR1; binding here inhibits transcription
from PR. As cI easily dimerises, the binding of cI to OR1 greatly
increases the affinity of the binding of cI to OR2, and this happens
almost immediately after OR1 binding. This activates transcription in
the other direction from PRM, as the N terminal domain of cI on OR2
tightens the binding of
RNA polymerase to PRM and hence cI stimulates
its own transcription. When it is present at a much higher
concentration, it also binds to OR3, inhibiting transcription from
PRM, thus regulating its own levels in a negative feedback loop.
cI binding to the PL operator is very similar, except that it has no
direct effect on cI transcription. As an additional repression of its
own expression, however, cI dimers bound to OR3 and OL3 bend the DNA
between them to tetramerise.
The presence of cI causes immunity to superinfection by other lambda
phages, as it will inhibit their PL and PR promoters.
Transcriptional state of the PRM and PR promoter regions during a
lysogenic state vs induced, early lytic state.
The classic induction of a lysogen involved irradiating the infected
cells with UV light. Any situation where a lysogen undergoes DNA
damage or the
SOS response of the host is otherwise stimulated leads
The host cell, containing a dormant phage genome, experiences DNA
damage due to a high stress environment, and starts to undergo the SOS
RecA (a cellular protein) detects
DNA damage and becomes activated. It
is now RecA*, a highly specific co-protease.
Normally RecA* binds LexA (a transcription repressor), activating LexA
auto-protease activity, which destroys LexA repressor, allowing
DNA repair proteins. In lysogenic cells, this response
is hijacked, and RecA* stimulates cI autocleavage. This is because cI
mimics the structure of LexA at the autocleavage site.
Cleaved cI can no longer dimerise, and loses its affinity for DNA
The PR and PL promoters are no longer repressed and switch on, and the
cell returns to the lytic sequence of expression events (note that cII
is not stable in cells undergoing the SOS response). There is however
one notable difference.
The function of LexA in the SOS response. LexA expression leads to
inhibition of various genes including LexA.
Control of phage genome excision in induction
The phage genome is still inserted in the host genome and needs
DNA replication to occur. The sib section beyond the
normal PL promoter transcript is, however, no longer included in this
reading frame (see diagram).
No sib domain on the PL promoter m
RNA results in no hairpin loop on
the 3' end, and the transcript is no longer targeted for RNAaseIII
The new intact transcript has one copy of both xis and int, so
approximately equal concentrations of xis and int proteins are
Equal concentrations of xis and int result in the excision of the
inserted genome from the host genome for replication and later phage
Multiplicity reactivation and prophage reactivation
Multiplicity reactivation (MR) is the process by which multiple viral
genomes, each containing inactivating genome damage, interact within
an infected cell to form a viable viral genome. MR was originally
discovered with phage T4, but was subsequently found in phage λ (as
well as in numerous other bacterial and mammalian viruses). MR of
phage λ inactivated by UV light depends on the recombination function
of either the host or of the infecting phage. Absence of both
recombination systems leads to a loss of MR.
Survival of UV-irradiated phage λ is increased when the E. coli host
is lysogenic for an homologous prophage, a phenomenon termed prophage
Prophage reactivation in phage λ appears to occur
by a recombinational repair process similar to that of MR.
Protein interactions that lead to either
Lysogenic cycles for
The repressor found in the phage lambda is a notable example of the
level of control possible over gene expression by a very simple
system. It forms a 'binary switch' with two genes under mutually
exclusive expression, as discovered by Barbara J. Meyer.
Visual representation of repressor tetramer/octamer binding to phage
lambda L and R operator sites (stable lysogenic state)
The lambda repressor gene system consists of (from left to right on
The lambda repressor is a self assembling dimer also known as the cI
protein. It binds
DNA in the helix-turn-helix binding motif. It
regulates the transcription of the cI protein and the Cro protein.
The life cycle of lambda phages is controlled by cI and Cro proteins.
The lambda phage will remain in the lysogenic state if cI proteins
predominate, but will be transformed into the lytic cycle if cro
The cI dimer may bind to any of three operators, OR1, OR2, and OR3, in
the order OR1 = OR2 > OR3. Binding of a cI dimer to OR1 enhances
binding of a second cI dimer to OR2, an effect called cooperativity.
Thus, OR1 and OR2 are almost always simultaneously occupied by cI.
However, this does not increase the affinity between cI and OR3, which
will be occupied only when the cI concentration is high.
At high concentrations of cI, the dimers will also bind to operators
OL1 and OL2 (which are over 2 kb downstream from the R operators).
When cI dimers are bound to OL1, OL2, OR1, and OR2 a loop is induced
in the DNA, allowing these dimers to bind together to form an octamer.
This is a phenomenon called long-range cooperativity. Upon formation
of the octamer, cI dimers may cooperatively bind to OL3 and OR3,
repressing transcription of cI. This autonegative regulation ensures a
stable minimum concentration of the repressor molecule and, should SOS
signals arise, allows for more efficient prophage induction.
In the absence of cI proteins, the cro gene may be transcribed.
In the presence of cI proteins, only the cI gene may be transcribed.
At high concentration of cI, transcriptions of both genes are
Some base pairs with serve a dual function with promoter and operator
for either cl and cro proteins.
Protein cl turned ON, with repressor bound to OR2 polymerase binding
is increased and turn OFF OR1.
Lysogen repression all 3 sites bound is a low occurrence due to OR3
weak binding affinity. OR1 repression increases binding affinity to
OR2 due to repressor-repressor interaction. Increased concentrations
of repressor increase binding.
Protein function overview
Function in life cycle
Regulatory protein CIII. Lysogeny, cII Stability
(Clear 3) HflB (FtsH) binding protein, protects cII from degradation
Lysogeny, Transcription activator
(Clear 2) Activates transcription from the PAQ, PRE and PI promoters,
transcribing cI and int. Low stability due to susceptibility to
cellular HflB (FtsH) proteases (especially in healthy cells and cells
undergoing the SOS response). High levels of cII will push the phage
toward integration and lysogeny while low levels of cII will result in
Repressor, Maintenance of Lysogeny
(Clear 1) Transcription inhibitor, binds OR1, OR2 and OR3 (affinity
OR1 > OR2 = OR3, i.e. preferentially binds OR1). At low
concentrations blocks the PR promoter (preventing cro production). At
high concentrations downregulates its own production through OR3
Repressor also inhibits transcription from the PL promoter.
Susceptible to cleavage by RecA* in cells undergoing the SOS response.
Lysis, Control of Repressor's Operator
Transcription inhibitor, binds OR3, OR2 and OR1 (affinity OR3 > OR2
= OR1, i.e. preferentially binds OR3). At low concentrations blocks
the pRM promoter (preventing cI production). At high concentrations
downregulates its own production through OR2 and OR1 binding. No
cooperative binding (c.f. below for cI binding)
Replication protein O. Initiates
DNA replication by
binding at ori site.
DNA replication by binding to O and DnaB
subunit. These bindings provide control over the host
RecBCD nuclease from degrading 3' ends—allow rolling
circle replication to proceed.
Holin, a membrane protein that perforates the membrane during lysis.
Endolysin, Lysozyme, an enzyme that exits the cell through the holes
Holin and cleaves apart the cell wall.
Rz and Rz1
Forms a membrane protein complex that destroys the outer cell membrane
following the cell wall degradation by endolysin. Spanin, Rz1(outer
membrane subunit) and Rz(inner membrane subunit).
Phage capsid head proteins.
Head decoration protein.
Major head protein.
Minor capsid protein.
Portal protein B.
Large terminase protein.
Host specificity protein J.
M V U G L T Z
Minor tail protein M.
Tail tape measure protein H.
Tail assembly protein I.
DNA-packing protein FI.
Tail attachment protein.
Tail fiber assembly protein.
Genome Integration, Excision
Integrase, manages insertion of phage genome into the host's genome.
In Conditions of low int concentration there is no effect. If xis is
low in concentration and int high then this leads to the insertion of
the phage genome. If xis and int have high (and approximately equal)
concentrations this leads to the excision of phage genomes from the
Excisionase and int protein regulator, manages excision and insertion
of phage genome into the host's genome.
Antitermination for Transcription of Late Early Genes
Antiterminator, RNA-binding protein and
RNA polymerase cofactor, binds
RNA (at Nut sites) and transfers onto the nascent RNApol that just
transcribed the nut site. This RNApol modification prevents its
recognition of termination sites, so normal
RNA polymerase termination
signals are ignored and
RNA synthesis continues into distal phage
genes (cII, cIII, xis, int, O, P, Q)
Antitermination for Transcription of Late
DNA binding protein and RNApol cofactor, binds
Qut sites) and transfers onto the initiating RNApol. This RNApol
modification alters its recognition of termination sequences, so
normal ones are ignored; special Q termination sequences some 20,000
bp away are effective. Q-extended transcripts include phage structural
proteins (A-F, Z-J) and lysis genes (S, R, Rz and Rz1). Downregulated
by Pantiq antisense m
RNA during lysogeny.
DNA repair protein, functions as a co-protease during SOS response,
auto-cleaving LexA and cI and facilitating lysis.
Lytic or lysogenic?
Diagram of temperate phage life cycle, showing both lytic and
An important distinction here is that between the two decisions;
lysogeny and lysis on infection, and continuing lysogeny or lysis from
a prophage. The latter is determined solely by the activation of RecA
SOS response of the cell, as detailed in the section on
induction. The former will also be affected by this; a cell undergoing
SOS response will always be lysed, as no cI protein will be allowed
to build up. However, the initial lytic/lysogenic decision on
infection is also dependent on the cII and cIII proteins.
In cells with sufficient nutrients, protease activity is high, which
breaks down cII. This leads to the lytic lifestyle. In cells with
limited nutrients, protease activity is low, making cII stable. This
leads to the lysogenic lifestyle. cIII appears to stabilize cII, both
directly and by acting as a competitive inhibitor to the relevant
proteases. This means that a cell "in trouble", i.e. lacking in
nutrients and in a more dormant state, is more likely to lysogenise.
This would be selected for because the phage can now lie dormant in
the bacterium until it falls on better times, and so the phage can
create more copies of itself with the additional resources available
and with the more likely proximity of further infectable cells.
A full biophysical model for lambda's lysis-lysogeny decision remains
to be developed. Computer modeling and simulation suggest that random
processes during infection drive the selection of lysis or lysogeny
within individual cells. However, recent experiments suggest that
physical differences among cells, that exist prior to infection,
predetermine whether a cell will lyse or become a lysogen.
Lambda as a genetic tool
Lambda phage has been used heavily as a model organism, and has been a
rich source for useful tools in microbial genetics, and later in
molecular genetics. Uses include its application as a vector for the
cloning of recombinant DNA; the use of its site-specific recombinase
(int) for the shuffling of cloned DNAs by the gateway method; and the
application of its Red operon, including the proteins Red alpha (also
called 'exo'), beta and gamma in the
DNA engineering method called
recombineering. The 48 kb
DNA fragment of lambda phage is not
essential for productive infection and can be replaced by foreign DNA.
Lambda phage will enter bacteria more easily than plasmids making it a
useful vector that can destroy or can become part of the host's DNA.
Lambda phage can be manipulated and used as an anti-cancer vaccine,
nanoparticle, targeting human aspartyl (asparaginyl) β-hydroxylase
Lambda phage has also been of major importance in the
study of specialized transduction.
Lambda holin family
Molecular weight size marker
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Snyder, L. and Champness, W. "Molecular
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edition 2007 (Contains an informative and well illustrated overview of
Splasho, Online overview of lambda (illustrates genes active at all
stages in lifecycle)
Wikispecies has information related to Λ-like viruses
Life Cycle, Basic Animation of
Lambda Lifecyecle (illustrates
infection and lytic/lysogenic pathways with some protein and
Time-lapse microscopy video from MIT showing both lysis and lysogeny
by phage lambda
Phage Life cycle (basic visual demonstration of Lambda
bacteriophage life cycle)
Phage genome in GenBank
Phage Reference Proteome from UniProt
Phage Protein Structures in NCBI (3D display of protein
structures for bacteriophage Lambda)
Major model organisms in genetics
Types of nucleic acids
precursor, heterogenous nuclear
Small Cajal Body RNAs
Trans-acting small interfering