Corncob formation between Fusobacterium nucleatum and Streptococcus sanguis.

Area of Science:

• Microbiology
• Dental Plaque Formation
• Bacterial Interactions

Background:

• Corncob formation in dental plaque was previously attributed solely to Bacterionema matruchotii and Streptococcus sanguis.
• Fusobacterium nucleatum has recently been observed to interact with S. sanguis, forming corncobs.

Purpose of the Study:

• To quantitatively characterize the in vitro kinetics of corncob formation involving Fusobacterium species.
• To elucidate the mechanisms and factors influencing the interaction between F. nucleatum and S. sanguis.

Main Methods:

• In vitro quantitative studies of corncob formation kinetics.
• Electron microscopy to visualize bacterial attachment.
• Treatment of bacteria with varying pH, ionic strength, cations, detergents, trypsin, and heat.

Main Results:

• Fewer S. sanguis were needed to saturate F. nucleatum strain 364 compared to strain 10953.
• Corncob formation was optimal at pH 8, with autoaggregation occurring at higher pH.
• Attachment appeared mediated by fimbriae on F. nucleatum, with differential sensitivity to treatments compared to Bacterionema species.

Conclusions:

• Fusobacterium nucleatum's interaction with Streptococcus sanguis contributes to dental plaque corncob formation.
• These interactions may bridge the transition from supragingival to subgingival plaque.
• Multiple receptor types likely mediate cocci attachment to fusiform bacteria.