Interrelationships between Wolinella recta and Streptococcus sanguis in Mixed Continuous Cultures

Abstract

Mixed cultures of Wolinella recta, an asaccharolytic formate-oxidising bacterium, and Streptococcus sanguis, a saccharolytic formate-producing bacterium, were studied in chemostats with glucose as the limiting nutrient and fumarate and/or oxygen as an electron acceptor. Steady-state cultures were established at different levels of fumarate and air supply. Two different types of relationships between both species were recognised in such cultures. A commensal relationship, with W.recta growing at the expense of formate produced by S.sanguis, was observed in strictly anaerobic cultures with fumarate as the sole electron acceptor. A distinctly mutualistic relationship was established in aerated cultures. In these cultures W.recta scavenged oxygen (or possibly H₂O₂ produced by S.sanguis) whereas S.sanguis provided W.recta with formate through the fermentation of glucose. The ecological consequences for the role of W.recta in the changeover from a healthy to a diseased subgingival microflora is discussed.

Key Words:

• Wolinella recta
• Streptococcus sanguis
• Periodontal disease
• Commensalism
• Mutualism