The art style I am going for will have the bacteria sporting cyborg-esque appendages/modes of transport whilst the body's immune system will have a more 'ethereal meets conventional weaponry' theme. My rationale for this is that in theory the body works in a similar way to warfare. The B cell identifies the enemy bacteria and analyses it, it then gets reinforcements which make antibodies. The antibodies essentially act as a beacon, drawing the attention of a macrophage which then eats it. Very reminiscent of a small company of soldiers laser tagging enemy armoured machines for destruction by air strike or artillery. By making them appear ethereal it will set off a nice contrast between the visceral looking bacteria.
Influential works I'm looking at for the bacteria:
The organic, yet inorganic appearance is both fascinating and repulsive