Structure of HF-PS repetition units isolated from B. cereus strains ATCC and 14579. Two unrelated polysaccharides, Ne HF-PS and Ch HF-PS, were identified from B. cereus 14579. Ne HF-PS is synthesized irrespective of the growing conditions, whereas Ch HF-PS synthesis is regulated along the biofilm formation and according to culture medium, HCT (poor medium) or BHI (rich medium). a, and d, planktonic phase; b, early biofilm formation (28–48 h); c, late biofilm formation (72–96 h).