minimizing harm

[MicroBob]

When measuring temperatures it is always good to keep in mind that the wires deduct some heat from the temperature sensor.

IR thermometers depend to a high degree on the surface of the object. A chromed metal surface radiates nearly no heat. So it might be a good idea to put a thin lazer of paint (any colour) on the cover slip.

When using a long pass filter 400nm as a slide the UV would be blocked nicely. If only they were less expensive

[mnmyco]

UV is inherently deadly to life. Keep in mind that microbes in nature can seek the depths to avoid UV as well as seek what shade there is. Neither are a realistic options to microbes on a slide. UV will always cause damage to DNA and the ability to repair that damage depends on the species we are talking about, and the extent of the damage.

IR will dry out the slide and heat it up, but you could just add water and/or reduce the time you keep slides on the microscope.

MNMyco