This laboratory study tested whether adding manganese and heme to growth medium changes biofilm formation by Bacillus cereus strains isolated from Korean soybean paste. Manganese, alone or with heme, strongly increased biofilm in some strains but not others, and manganese had a larger effect than heme. Induced biofilms carried more spores, resisted a quaternary ammonium sanitizer better and showed higher expression of motility and matrix genes.
Key numbers
- Supplement levels: manganese sulfate at a final concentration of 0.005% and heme at 10 µg/mL in brain heart infusion broth (Methods, p. 4).
- Manganese addition markedly promoted biofilm in three strains (one reference strain and two food isolates) under almost all conditions; the response was strain dependent (Results, p. 5; Fig. 1).
This paper reports no numerical findings relevant to manganese exposure in food or people.
Methods (brief)
Static biofilms were grown on stainless steel coupons at 30 degrees C for 48 h and quantified by crystal violet staining, cell counts, electron and confocal microscopy, and real-time PCR of selected genes.
Evidence fitness
The study supports an in vitro statement that manganese can promote biofilm formation by some foodborne Bacillus cereus strains on processing-type surfaces. It says nothing about the human gut microbiome or dietary manganese exposure.
Limitations
Laboratory medium and one supplement level only. The abstract and methods describe the strain set differently (six food isolates plus two reference strains versus six strains including two reference strains).
Related evidence
Update history
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