Well, I don't know any experiment done in microorganisms in gravity stronger then Earth's, probably because such environment (a rocky planet/moon, with more gravity then Earth so we can land a probe and do experiments) don't exist in your solar system.
What we have is the data about the experiments with microorganisms in micro gravity done in the ISS. The current understanding tells that micro gravity alters two primary functions in bacteria, mass transfer and motility. See, in microorganisms the molecular transfer between cells are done by convection and diffusion, the first one is driven by gravity. In a micro gravity environment convection stops, which limits the bacteria to diffusion to maintain mass transfer.
In the case of mobility, bacteria have show to increase mobility in micro gravity environment, which leads to more capability to reach nutrients in the environment, at least in liquid cultures. Gravity has show to cause a severe nutrient depletion in comparison to the cultures in micro gravity.
So I think is sure to think that in a environment with higher gravity that Earth's, the effect will be more to "Oh god' we can't find food" then "Jesus we are been squeezed to death by your own weight", at least in the microscopic world.