I think apoptosis and autophagy play a role in fighting "invaders" (esp. viruses, don't know about bacteria), and the mitochondria play a role there.
Prusty found that HHV6 released a substance that inhibits mitochondria. David Attenborough always says the bugs will outsurvive us because they are more adaptable. More evidence that more research at cellular level is required.
Yes, viruses like EBV, HIV, and some HHV (I forgot which one) produce proteins that can open endoplasmic reticulum (ER) receptors that release Calcium; if those stores are emptied the cell opens calcium channels in the plasma membrane (through which, I guess, the virus can send its DNA/RNA). The released calcium from the ER can be taken up by the mitochondrion which, in turn, can produce autophagy signals. I can't remember exactly (if increased or decreased), but ATP plays a role here. (If it was decreased ATP, that would mean inhibited kinases, amongst others, I guess.) There are certainly other pathways that a virus can use. May depend on the virus. I don't know how it is with bacteria though. When I read this my sponatenous thought was viruses know exactly how the signaling pathways work - we don't (yet).
This should not be in "unrelated to ME/CFS". This may just be the crux of the issue. Mitochondria evolved from microbes, so it makes sense that they would perform a function like this. Since the mitochondria are the main site of energy production it's plausible that chronic infection could reduce their energy production since they're spending their resources fighting infections.
Hi @MaximilianKohler. Welcome to the forum. We have this subforum for research and information on science that may well have relevance to ME, but that is not directly ME research. So this thread is in the right place!
Here is something about Chlamydia that use the calcium pathway, too: https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1006911