Or search: ameba, foram, amoeba, protozoan, protozoon, testacean, rhizopoda, foraminifer
3 Syllables: SUU
dominance, dominant, Donovan, fraudulent, Jonathan, occupant, Ottoman, prominence, prominent, Protestant, Providence, Solomon, Solomon's, tolerance, tolerant
4 Syllables: USUU
concomitants, diocesan, improvidence, intolerance, intolerant, predominance, predominant, reconnaissance
4 Syllables: UUSU
concomitant
5 Syllables: UUSUU
cosmopolitan, metropolitan, Neapolitan

Found 27 words across 4 groupings. Skipped 2 excess words of a similar stem.