Head (capsid)
Usually an icosahedron packed with DNA. T4's head is a textbook icon about 110 nm long.
Darker cells mean a higher score for this topic on that metric.
Familiarity42
Medical weight40
Benefit62
Risk15
Research78
Live debate45
LessMore
Last reviewed Sources & creditsMedia creditsMethodology
Quick answers
Where should I start with Bacteriophages?
Read Identity → How they live → Body & health, then use compare rails.
Is this page advice for Bacteriophages?
Public-health education — not a care plan, prescription, or outbreak briefing.
What does the local lens add?
It names everyday desks for Tree of microbes before English norms look universal.
Are the scores a ranking of Bacteriophages?
No — editorial 0–100 browsing aids inside this atlas only.
How do I compare Bacteriophages to neighbours?
Use related cards and best-of / quiz rails after the first three chapters.
Which chapter is densest?
How they live and Body & health carry mechanisms; skim Identity first.
A tailed phage binds a receptor, contracts, and injects nucleic acid. Minutes later in a rich broth, hundreds of new particles may assemble. In the ocean the same logic runs more slowly.
Lysogeny is a truce: the phage genome rides along as the bacterium divides. UV or starvation can flip the switch to lysis. Description, not a recipe.
Parts
Tail
A tube that can contract in myoviruses. Not every phage has a tail — filamentous phages are threads.
Tail fibres
The matching keys. Change the fibre and the host range can change — a research fact, not instructions.
Genome
Typically DNA, from a few kilobases to half a megabase in jumbo phages. RNA phages exist too (MS2, 1961).
Baseplate
A landing gear that signals 'we have docked' before DNA moves.
No 70S factory
Protein synthesis is entirely the bacterium's. Phages are instructions plus a syringe.
Life cycle
1Adsorb
Fibres find a receptor — LPS, a porin, a pilus. No match, no infection.
2Inject
Nucleic acid enters the cytoplasm. The empty capsid stays outside — Hershey–Chase used that fact.
3Take over or integrate
Lytic programmes copy phage DNA. Temperate programmes may insert as prophage.
4Burst or wait
Lysis releases a burst of tens to hundreds of particles. Lysogeny waits for a later cue.
When headlines say a phage 'evolved overnight', they mean huge numbers and tight host matching, not a cartoon villain.
Keep exploring
More in Tree of microbes
Bacteria
Single-celled prokaryotes with cell walls — the oldest widespread life form, and both partners and pathogens.
Familiarity 95Viruses
Packets of DNA or RNA that are not cells — they replicate only inside living hosts.
Familiarity 96Fungi
A eukaryotic kingdom of yeasts, moulds and mushrooms — chitin walls, external digestion, partners of plants.
Familiarity 80Archaea
A prokaryotic domain that is not bacteria — methanogens, extremophiles and no known human pathogens.
Familiarity 35Protozoa
Motile unicellular eukaryotes — a teaching grade that includes pond ciliates and a minority of serious parasites.
Familiarity 58