Salivary mucins promote the coexistence of competing oral bacterial species

Abstract

Mucus forms a major ecological niche for microbiota in various locations throughout the human body such as the gastrointestinal tract, respiratory tract and oral cavity. The primary structural components of mucus are mucin glycoproteins, which crosslink to form a complex polymer network that surrounds microbes. Although the mucin matrix could create constraints that impact inhabiting microbes, little is understood about how this key environmental factor affects interspecies interactions. In this study, we develop an experimental model using gel-forming human salivary mucins to understand the influence of mucin on the viability of two competing species of oral bacteria. We use this dual-species model to show that mucins promote the coexistence of the two competing bacteria and that mucins shift cells from the mixed-species biofilm into the planktonic form. Taken together, these findings indicate that the mucus environment could influence bacterial viability by promoting a less competitive mode of growth.

Spatial determinants of quorum signaling in a Pseudomonas aeruginosa infection model

“…Mucin had the most significant impact on diffusion and viscosity ( Fig. 1 ), and it has previously been shown to reduce QS induction in vitro ( 13 , 30 – 32 ), thus the lack of interaggregate signaling observed in SCFM2 is likely due to the presence of this polymer.…”

Mucins and Their Role in Shaping the Functions of Mucus Barriers

“…This community includes S. mutans (Kroes et al 1999, Siqueira & Rôças 2017, Verma et al 2018, which is often considered to be antagonistic to other bacterial species in coculture because it generates large amounts of lactic acid. While S. mutans will generally outcompete the commensal bacteria Streptococcus sanguinis in standard growth media, it appears that solutions containing the native salivary mucin MUC5B can support the prolonged coexistence of these two bacteria (Frenkel & Ribbeck 2017). This result suggests that mucins may play a specific role in suppressing interspecific competition and promoting stable assembly of multispecies communities in the oral cavity and likely also in other mucosal environments.…”

Mucus and Mucins: do they have a role in the inhibition of the human immunodeficiency virus?

“…Mucus layers form an ecological niche for microbiota in the various major internal tracts of the body. Microbes in the mucus gel will be constrained, thus being unable to have interactions such as cell-to-cell communications and inter-species competition [ 56 ]. It is also becoming apparent that mucus in the gut is critical to the maintenance of a homeostatic relationship between the gut microbiota, commensal flora dominated by Fermicutes and Bacteriodetes [ 57 ], and their hosts.…”

“…It is conceivable that large disulphide-bonded mucin polymers which form non-covalent interactions through the inter-digitation of their densely packed oligosaccharide side-chains [ 27 ] result in the formation of a network that surrounds microbes thus restricting their movements. It is not known how these constraints influence microbial interactions, such as cell-to-cell interactions and competition among the vast number of organisms that live in mucus [ 56 ]. In the case of microbiota in the oral cavity, salivary MUC5B affects intra-species interaction by promoting dispersal of bacteria and fungi.…”

“…In the case of microbiota in the oral cavity, salivary MUC5B affects intra-species interaction by promoting dispersal of bacteria and fungi. In an experimental, dual-species model Frenkel and Ribbeck [ 56 ] very recently showed that mucins, in this case salivary MUC5B, promoted the coexistence of two competing bacteria, S. sanguinis and S. mutans , perhaps by promoting a less competitive mode of growth between them.…”