mystical microscopic objects

Unknown fibers destroyable with Ultra Violet.
no scale bar, but this object as thick as 1 micrometer and about 40 micrometers long.
As soon as I make it exposed to UV light it starts to collapse.
Does anybody knows what is it?
This objects formed in mineral media for methanogenic archaea with no organic matter as a source of carbon, only gas mixture of H2 and CO2.