If bacteria, viruses, parasites were really as threatening as I interpret them to be on the basis of your statements, how could the many species have existed at all in the course of their existence on this earth? Why don't people die in immense numbers all the time? How can it be that people grow old?

From my point of view, the assumption that humans are capable of biological warfare is due to the belief in the total feasibility and specific targeting of what is intended.

But it is also said that each organism's biome is distinctly different from every other organism's, according to another theory. What some researchers seek to identify as "hostile", "parasitic", "killing", others want to find out as "beneficial", "interacting" and "making healthy".

Some years ago I read a scientific paper on the subject of tapeworms in the organism, which until then had always been considered enemies of the organism and which were now considered to have their benefits. Unfortunately, I don't remember where I found it. The organism is far more than its DNA, the so-called building blocks of life, if you take it as the ultimate realisation that all life is the same, is in strong conflict with what is happening at the higher levels of the organism.

Similar to physics, where there have been or are efforts to establish an all unifying theory, I see this in biology, where the all unifying theory is genetics.

Ultimately, this leads to the long-standing dispute between pure materialism, according to which all living things can be explained and manipulated on the basis of their individual parts, and what people call consciousness or spirituality, according to which there is an intelligence at work that opposes materialism.

The "truth" will have to be assumed somewhere in the middle, I think, without being able to pin it down.

Placebo research and how one's mind influences one's body and vice versa are the great unknowns that materialistically attuned minds are reluctant to engage with because it offers them too much fuzziness and uncertainty.
For example, it is still not really known why anaesthesia works the way it does and there has been research into this where patients have been operated on by surgeons in hospital using only hypnosis and felt no pain at all during the operation. This raises the interesting question of how much the body/mind does its own to become insensitive to pain and how much is externally supplied and ultimately you can't really tell the two apart.