Role of Fusobacterium nucleatum and Coaggregation in Anaerobe Survival in Planktonic and Biofilm Oral Microbial Communities during Aeration

Abstract

ABSTRACT Coaggregation is a well-characterized phenomenon by which specific pairs of oral bacteria interact physically. The aim of this study was to examine the patterns of coaggregation between obligately anaerobic and oxygen-tolerant species that coexist in a model oral microbial community. Obligate anaerobes other than Fusobacterium nucleatum coaggregated only poorly with oxygen-tolerant species. In contrast, F. nucleatum was able to coaggregate not only with both oxygen-tolerant and other obligately anaerobic species but also with otherwise-noncoaggregating obligate anaerobe–oxygen-tolerant species pairs. The effects of the presence or absence of F. nucleatum on anaerobe survival in both the biofilm and planktonic phases of a complex community of oral bacteria grown in an aerated (gas phase, 200 ml of 5% CO 2 in air · min −1 ) chemostat system were then investigated. In the presence of F. nucleatum , anaerobes persisted in high numbers (>10 7 · ml −1 in the planktonic phase and >10 7 · cm −2 in 4-day biofilms). In an equivalent culture in the absence of F. nucleatum , the numbers of black-pigmented anaerobes ( Porphyromonas gingivalis and Prevotella nigrescens ) were significantly reduced ( P ≤ 0.001) in both the planktonic phase and in 4-day biofilms, while the numbers of facultatively anaerobic bacteria increased in these communities. Coaggregation-mediated interactions between F. nucleatum and other species facilitated the survival of obligate anaerobes in aerated environments.