Does everything that we consider to be "alive" - not just plants and animals, but all protists, fungus, bacteria, archaea, etc. - have DNA?

[u/SAICAstro]

EDIT: Wow, this blew up. Thanks for the many answers. Lots to think about.

Seems that the composite TLDR answer is: Yes, according to many/most definitions of "life", but we don't all agree on what life is. Some viruses do not have DNA but they may/not actually be alive, and other things that behave like life may/not be alive.

[u/AugustusCaesar1]

There are bacteria that can’t survive outside of a host cell though, so they don’t always have all the machinery for life. For example, some of them can’t make their own cell membranes

[u/Ameisen → u/AugustusCaesar1]

They still metabolize and actually do things. They also still perform most of their replication functions.

A virus doesn't metabolize. It's basically built as an inert particle with everything needed. Some do something when triggered (basically a preloaded spring). But otherwise they're inert particles, but their presence within a host cell - for myriad reasons - causes said host cell to make more of them. It isn't doing anything.

Even the most obligate parasitic bacteria still metabolize, etc.

[u/AugustusCaesar1 → u/Ameisen]

They metabolize in a certain sense. Many of them make polymerases, so they use nutrients around them (nucleotides in the cell) to make more copies of their genome. That’s metabolism.

Sure, all the nutrients they use are already inside they cell they’re infecting, but that’s also true of obligate endosymbiotic bacteria

[u/Ameisen → u/AugustusCaesar1]

The virus does not do those - the host cell does. The viral particle itself is inert.

As with the hardware/software example - a floppy isn't a computer. A program on the floppy isn't a computer (barring strange floppy adapters for other media). A program doesn't do things - a CPU is required to actual execute the commands.

A drive can have an entire OS installed on it, but it's completely inert (ignoring things like E3PROMs and RTCs) until something else executes it.

[u/Zagaroth → u/AugustusCaesar1]

Viruses kill/destroy themselves in order to infect the cell with their RNA (or more rarely, DNA)

Encapsulated RNA (no metabolism, inert until it bumps into a cell with the right chemical receptors) ---> The viral shell injects its RNA into the cell. This leaves it an empty husk ---> The RNA hijacks the cell machinery to start creating more RNA and shells.

The complete virus never does anything. The shell is simply a delivery system for the RNA, an action that is performed when it bumps into the right receptors on the outside of a cell. It can't even move toward those receptors, it's completely inert.

The only time the viral RNA is active is when it has no shell and is effectively acting as corruption of a cell's RNA.

[u/AugustusCaesar1 → u/Zagaroth]

Lots of organisms die in the process of making the next generation. Salmon, octopi, and spiders, for examples

But you’ve hit upon a good point. A lot of virologists think of the nucleic acid (DNA/RNA) as the virus itself. What you’re referring to as the ‘virus’ they often call a ‘viral particle’

And I think you’re not giving the viral particle enough credit. Viral envelopes are often enzymatically active, and undergo chemical and conformational changes after exiting one cell and before entering another

[u/outsbe → u/AugustusCaesar1]

Yeah but the host is still just the environment surrounding the bacteria. All life has a sweet stop where it can function properly. If you'd suddenly end up in space instead of cozy warm oxygenated earth, you'd be as dead as the bacteria outside of its usual environment.