Identification of V. parvula and S. gordonii adhesins mediating co-aggregation and its impact on physiology and mixed biofilm structure

The dental plaque is a polymicrobial community where biofilm formation and co-aggregation, the ability to bind to other bacteria, play a major role in the construction of an organized consortium. One of its prominent members is the anaerobic diderm Veillonella parvula, considered as a bridging species, which growth depends on lactate produced by oral Streptococci. Understanding how V. parvula co-aggregates and the impact of aggregation has long been hampered due to the lack of appropriate genetic tools. Here we studied co-aggregation of the naturally competent strain V. parvula SKV38 with various oral bacteria and its effect on cell physiology. We show that V. parvula requires different trimeric autotransporters of the type V secretion system to adhere to oral Streptococci and Actinomyces. In addition, we describe a novel adhesin of Streptococcus gordonii, VisA (SGO_2004), as the protein responsible for co-aggregation with V. parvula. Finally, we show that co-aggregation does not impact cell-cell communication, which is mainly driven by environmental sensing, but plays an important role in the architecture and species distribution within the biofilm.