Freezing bacteria results in the same thing in anything frozen: the water in the bacteria expands when it turns to ice, breaking the cell walls. This can lead to texture problems in food, but in a single-cell organism, it’s fatal.
But it’s not a sure thing. There may not be enough water in the bacteria so that expansion is a problem, for instance. Frozen meat may have some bacteria dormant inside it and not cooking it thoroughly can lead to disease.