What do you call it when a bacterium dies? Cellular death is apoptosis, necrosis, and bacterial is ...? I don't simply want to write in a paper that it - well dies!
Death is appropriate. Using this word to describe both unicellular and multicellular organisms places them in the same hierarchy. This hierarchy is the domain of life.
Both prokaryotes and eukaryotes have unicellular and multicellular species.
If you choose another word for death I would suggest not using it exclusively for bacteria. If a reader finds the idea of bacterial death esoteric, they may be inspired to dig deeper into the subject. Encouraging an informed reader would seem to be an effective device in a paper for communicating scientific information.
You could qualify the word 'death' to be more precise. Senescence is the natural process of deterioration of life with age.
Google has a great tool for tracking word popularity. Here's a Google graph for 'senescence'.
Apoptosis and necrosis are only two ways by which eukaryote death is achieved. Certainly there are other ways. Say, if a tissue or organism burns, death is achieved before any nuclear changes, cell swelling or shrinking.
Same thing goes with bacteria. Death is the generic term. If you have more details, you can be more specific. In laboratories, cells die by lysis induced by the human experimenters, either by fancy P1 buffer or by the less sophisticated bleach. Sporulating bacteria autolyse the mother cells in the process of spore release. Overcrowded bacteria may decide to relieve some the pressure by having some individuals commit controlled suicide, called autolysis. For example, lytA is an autolysin stimulated by crowding in the pneumococci. The couple ccdA-ccdB sitting on the E coli plasmid F help ensure that daughter cells that did not inherit any plasmid copies commit programmed suicide. Details about these and some other described mechanisms of death in bacteria are to be found in http://www.ncbi.nlm.nih.gov/pmc/articles/PMC99002/
But if you are looking at some bacteria dying, and you have no evidence about the molecular mechanisms, death is good enough.