bacterioid

As adjectives the difference between bacterioid and bacteroid

is that bacterioid is (rare) resembling a bacterium while bacteroid is (biology) resembling bacteria.

As a noun bacteroid is

(dated) a micro-organism such as a bacterium or yeast.

As a noun bacterium

is (microbiology) a single celled organism with no nucleus.

As an adjective bacterioid is

(rare) resembling a bacterium.