Bacteriophage Unlabeled Diagram – Blank Sheet to Print

All 9 parts on the diagram

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Start here: 5 main parts 5

Head (capsid) The icosahedral protein shell, also called the capsid, that holds the DNA.
DNA T4's genome, packed tight inside the head. Double-stranded DNA about 169,000 base pairs long, encoding 289 proteins.
Tail sheath The contractile outer tube of the tail. It surrounds the tail tube until infection.
Baseplate The plate on the tail's end. A signal from the long tail fibres reaches it, and it changes shape to start infection.
Long tail fibres They recognize receptors on the surface of the bacterium. So they decide which bacteria the phage can infect.

The phage: 6 1

Short tail fibres Folded under the baseplate until the phage lands. They then unfold and bind the cell for good.

Infecting a cell: 3 3

Contracted tail sheath After the phage lands, the sheath contracts. That drives the tail tube into the cell.
Tail tube (core) The inner tube of the tail. Its tip punctures the outer membrane, and the DNA passes down it into the cell.
Outer membrane of the bacterium The outer membrane of the E. coli cell that the phage infects. The tail tube punctures it.

How this list was compiled: Read 2026-09-26. Wikipedia, Escherichia virus T4, https://en.wikipedia.org/wiki/Escherichia_virus_T4 : about 90 nm wide and 200 nm long; a double-stranded DNA genome of about 169 kbp encoding 289 proteins, held in an icosahedral head, also called a capsid; a contractile tail; long tail fibres that recognise host receptors and decide the host range; a recognition signal sent to the baseplate, which unravels the short tail fibres that bind irreversibly; the baseplate changing shape and the tail sheath contracting, so that the end of the tail tube punctures the outer membrane of the cell; the DNA travelling from the head through the tail tube into E. coli; the head assembled empty around a scaffolding protein that is later degraded, and DNA packed through a tiny pore by a motor at up to 2000 base pairs per second. Wikipedia, Bacteriophage, https://en.wikipedia.org/wiki/Bacteriophage , read the same day for the general account. Licence: own work

The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work

How it works

This bacteriophage unlabeled diagram is two drawings. Above, a T4 phage on its own, tail at full length. Below, the same phage on a bacterium, its tail squashed short. Nine label lines want a name, six above and three below.

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The nine names, by drawing

On the free phage: head, DNA, tail sheath, baseplate, long tail fibers and short tail fibers. On the landed phage: contracted tail sheath, tail tube and outer membrane of the bacterium.

Which shape takes which name

Above, the many-sided shape is the head and the coiled strand inside it the DNA. The long ringed tube is the tail sheath and the flat plate under it the baseplate. The long bent legs are the long tail fibers, and the small hooks folded under the plate the short ones. Below, the short wide tube over the plate is the contracted tail sheath, the thin tube pushed down from the plate is the tail tube, and the band it passes through is the outer membrane.

On the lower drawing the head, the plate, the legs and the strand passing into the cell are drawn again and take no name.
The answer key prints fibres, the British spelling of fibers. A class may also say capsid for the head and core for the tail tube.

Questions and answers

What does bacteriophage mean?

Bacterium eater. The word joins bacteria to the Greek phagein, to devour. Phage is the short form.

Is a bacteriophage a virus or a bacterium?

A virus. It is built of proteins round a genome of DNA or RNA, and it replicates inside the bacteria it infects. T4, the phage on the sheet, infects the bacterium Escherichia coli.

Do all bacteriophages have a tail?

No. A phage may be simple or elaborate in build. The tailed ones are sorted by their tail: short, long and contractile, or long and not contractile. T4 has a long contractile tail. A filamentous phage is another type altogether.

Where are bacteriophages found?

Wherever bacteria exist. They are among the most common and most varied entities in the biosphere.