ROLE OF FUSOBACTERIUM-NUCLEATUM AND COAGGREGATION IN ANAEROBE SURVIVAL IN PLANKTONIC AND BIOFILM ORAL MICROBIAL COMMUNITIES DURING AERATION

Coaggregation is a well-characterized phenomenon by which specific pai rs 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 commun ity, Obligate anaerobes other than Fusobacterium nucleatum coaggregate d only poorly with oxygen-tolerant species. In contrast, F. nucleatum was able to coaggregate not only with both oxygen-tolerant and other o bligately anaerobic species but also with otherwise-noncoaggregating o bligate anaerobe-oxygen-tolerant species pairs. The effects of the pre sence or absence of F, nucleatum on anaerobe survival in both the biof ilm and planktonic phases of a complex community of oral bacteria grow n in an aerated (gas phase, 200 mi of 5% CO2 in air.min(-1)) chemostat system were then investigated. In the presence of F. nucleatum, anaer obes 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 (Por phyromonas gingivalis and Prevotella nigrescens) were significantly re duced (P less than or equal to 0.001) in both the planktonic phase and in 4-day biofilms, while the numbers of facultatively anaerobic bacte ria increased in these communities. Coaggregation-mediated interaction s between F, nucleatum and other species facilitated the survival of o bligate anaerobes in aerated environments.