Most computers are designed around silicon circuits powered by electricity, but there is more than one way to skin a cat, as they say. You can build a quantum computer , for example, based on things being in two places at once. Or, if you find yourself in a world without electricity, you can build a computer out of gears, and rotors. Photonic (optical) computers are also cool. (And chemical computers deserve a shout-out.)
Bacteria can also be employed for computing purposes, as some scientists have recently explored. Using a modified bacteria with a "Hin/hixC recombination system previously adapted from Salmonella typhimurium for use in Escherichia coli" a 19 person research team were able to make a working circuit-analogue that is based around DNA.
The engineered bacteria were tasked with figuring out a "Hamiltonian Path Problem" -- a difficult test to find a path through a three dimensional nodular space visiting each node at least once.
The test was a success.
The bacteria being bacteria naturally reproduced itself. The bacteria that was able to find the correct path the Hamiltonian puzzle had the genetic code to turn yellow, while the bacteria that wandered off maintained either red or blue colorings.
Programming bacterial computers is not an easy task - generally, much different tasks require a measure of genetic engineering. But perhaps in some circumstances, where a reoccurring problem needs solving, bacteria-powered computers might come in handy. And besides, how many computers can reproduce themselves?