Microbial cell surface proteins and secreted metabolites involved in multispecies biofilms

Abstract

A considerable number of infectious diseases involve multiple microbial species coexisting and interacting in a host. Only recently however the impact of these polymicrobial diseases has been appreciated and investigated. Often, the causative microbial species are embedded in an extracellular matrix forming biofilms, a form of existence that offers protection against chemotherapeutic agents and host immune defenses. Therefore, recent efforts have focused on developing novel therapeutic strategies targeting biofilm-associated polymicrobial infections, a task that has proved to be challenging. One promising approach to inhibit the development of such complex infections is to impede the interactions between the microbial species via inhibition of adhesion. To that end, studies have focused on identifying specific cell wall adhesins and receptors involved in the interactions between the various bacterial species and the most pathogenic human fungal species Candida albicans. This review highlights the important findings from these studies and describes the available tools and techniques that have provided insights into the role of secreted molecules orchestrating microbial interactions in biofilms. Specifically, we focus on the interactions that take place in oral biofilms and the implications of these interactions on oral health and therapeutic strategies.

The Streptococcus gordonii Adhesin CshA Protein Binds Host Fibronectin via a Catch-Clamp Mechanism

“…The filamentous adhesins, comprising pili and fibrils, are among the largest and most complex of all bacterial surface proteins. They are found in both Gram-positive and Gram-negative bacteria, including many pathogenic species, and have attracted considerable attention due to their roles in colonization, infection, and as vaccine candidates (2,3). Characteristically, these proteins form sizable polymeric assemblies that project outwards from the bacterial cell surface, presenting an adhesive target-binding region at their tip.…”

Clinical Implications of Oral Candidiasis: Host Tissue Damage and Disseminated Bacterial Disease

“…In these infections, the presence of one microorganism predisposes the host to colonization by others and in additive polymicrobial infections two or more nonpathogenic microorganisms together can cause disease (1,3). Adherence of organisms to surfaces and to each other is a prerequisite for establishing concurrent infections, which often stem from the formation of polymicrobial biofilms that form on biotic or abiotic surfaces (2,(4)(5)(6). In the oral cavity, the oral mucosa serves as an important barrier to the myriad of microbial species present in this complex environment.…”

“…In the oral cavity, the oral mucosa serves as an important barrier to the myriad of microbial species present in this complex environment. However, the interactions between the various species can be synergistic in that the presence of one microorganism generates a niche for other microorganisms (1,5,(7)(8)(9)(10)(11).…”

“…In fact, the majority of C. albicans infections are associated with its ability to form biofilms where adhesion of yeast cells to the substrate is followed by proliferation and hypha formation resulting in a network of cells embedded in extracellular polymeric matrix (21)(22)(23). In the oral cavity, C. albicans coexists and forms tight associations with various commensal bacterial species forming complex mucosal biofilms, a phenomenon known to play an important factor in C. albicans colonization (2,5,10,11,(24)(25)(26). Thus, when Candida infections arise, they often occur in association with bacteria (27).…”

Contribution of Host Signaling and Virome to the Mycobiome

“…It is well established that fungi communicate with each other via quorum signaling chemical compounds [1]. It is also increasingly recognized that bacteria and fungi communicate with each other via quorum signaling as well as a variety of other mechanisms including the physical interactions that can occur within biofilms [2][3][4][5].…”