Periodic Reporting for period 1 - BOB (The role of bacteriocins in shaping oral biofilms)
Reporting period: 2022-01-10 to 2024-01-09
Biofilms are the most common form of microbial life in nature, but also an important pathogenic mechanism. In humans, biofilms account for up to 80% of the total number of microbial infections including oral diseases such as periodontitis and dental caries. Understanding how bacterial biofilms are formed is thus key to controlling the infection process and understanding bacterial behaviour.
Within biofilms, microorganisms aggregate in close proximity enabling substrate exchange and distribution of metabolites. Among these metabolites, bacteriocins are ubiquitous antimicrobial peptides produced across the bacterial kingdom and primarily considered a bacterial defence system. They have been long studied as potential alternatives to antibiotics and as food preservatives, however, little is known about their social role in shaping biofilm communities. In this project, we explored the role of mutacins produced by Streptococcus mutans in oral biofilm formation.
The overall objectives were (1) to investigate the distribution of bacteriocin genes in oral streptococci; (2) to establish a biofilm model to study bacteriocin-biofilm interactions; (3) to evaluate the role of bacteriocins in shaping streptococcal biofilms, and; (4) to study the transcriptome stress response of S. mutans challenged with mouthwashes/antibiotics in biofilms.
Overall, this project contributed to understanding the role of bacteriocins from an ecological perspective.
Within biofilms, microorganisms aggregate in close proximity enabling substrate exchange and distribution of metabolites. Among these metabolites, bacteriocins are ubiquitous antimicrobial peptides produced across the bacterial kingdom and primarily considered a bacterial defence system. They have been long studied as potential alternatives to antibiotics and as food preservatives, however, little is known about their social role in shaping biofilm communities. In this project, we explored the role of mutacins produced by Streptococcus mutans in oral biofilm formation.
The overall objectives were (1) to investigate the distribution of bacteriocin genes in oral streptococci; (2) to establish a biofilm model to study bacteriocin-biofilm interactions; (3) to evaluate the role of bacteriocins in shaping streptococcal biofilms, and; (4) to study the transcriptome stress response of S. mutans challenged with mouthwashes/antibiotics in biofilms.
Overall, this project contributed to understanding the role of bacteriocins from an ecological perspective.
This project took an interdisciplinary approach to shed light on how bacteriocins can impact biofilm formation using models of S. mutans caries-associated biofilms.
First, an initial bioinformatic analysis of S. mutans genomes from public databases was performed to get an overview of bacteriocin gene distribution in this species. Next, biofilm-forming and bacteriocin-encoding S. mutans were used to optimise microtiter plate and hydroxyapatite discs-based biofilm models to study bacteriocin-related interactions. Competition experiments with wild-type strains and bacteriocin mutants were performed. These models were used to assess the relevance in mono- and multi-species biofilm formation of bacteriocin structural and putative unpaired immunity genes using mono-species S. mutans and dual-species S. mutans-Streptococcus gordonii and S. mutans- Streptococcus cristatus biofilm set-ups. Finally, to get a deeper overview of which genes were involved in biofilm formation in S. mutans, a transcriptomic analysis of wild type and a bacteriocin deletion mutant challenged with amoxicillin and chlorhexidine was performed. The results show that bacteriocin deletion strains have a competitive disadvantage and exhibit inferior performance in biofilm formation pointing to a potential role of bacteriocin genes in modulating the formation of oral biofilms. Thus, bacteriocin genes could represent potential therapeutic targets for biofilm control. Some experiments of this work are still ongoing.
The project results were presented at several national and international conferences. A review article on the multiple roles of bacteriocins has been published (doi: 10.1007/s00248-024-02357-4. Two research articles are expected to be published from this work. Additionally, the book Novel Approaches in Biopreservation for Food and Clinical Purposes on Food biopreservation was edited as part of external collaborations (ISBN 9781032213552).
As a fundamental research project, the obtained results will mainly appeal to the scientific community in the field of antimicrobials and biofilms. Given the ubiquity of bacteriocins, the implemented bacteriocin-biofilm interactions model can be applied to study other natural or problematic biofilms, in health, the food industry or other industrial processes. Likewise, this project’s results lay the ground to study other bacterial genes that might be involved in biofilm formation with the ultimate goal of better understanding biofilm biology.
First, an initial bioinformatic analysis of S. mutans genomes from public databases was performed to get an overview of bacteriocin gene distribution in this species. Next, biofilm-forming and bacteriocin-encoding S. mutans were used to optimise microtiter plate and hydroxyapatite discs-based biofilm models to study bacteriocin-related interactions. Competition experiments with wild-type strains and bacteriocin mutants were performed. These models were used to assess the relevance in mono- and multi-species biofilm formation of bacteriocin structural and putative unpaired immunity genes using mono-species S. mutans and dual-species S. mutans-Streptococcus gordonii and S. mutans- Streptococcus cristatus biofilm set-ups. Finally, to get a deeper overview of which genes were involved in biofilm formation in S. mutans, a transcriptomic analysis of wild type and a bacteriocin deletion mutant challenged with amoxicillin and chlorhexidine was performed. The results show that bacteriocin deletion strains have a competitive disadvantage and exhibit inferior performance in biofilm formation pointing to a potential role of bacteriocin genes in modulating the formation of oral biofilms. Thus, bacteriocin genes could represent potential therapeutic targets for biofilm control. Some experiments of this work are still ongoing.
The project results were presented at several national and international conferences. A review article on the multiple roles of bacteriocins has been published (doi: 10.1007/s00248-024-02357-4. Two research articles are expected to be published from this work. Additionally, the book Novel Approaches in Biopreservation for Food and Clinical Purposes on Food biopreservation was edited as part of external collaborations (ISBN 9781032213552).
As a fundamental research project, the obtained results will mainly appeal to the scientific community in the field of antimicrobials and biofilms. Given the ubiquity of bacteriocins, the implemented bacteriocin-biofilm interactions model can be applied to study other natural or problematic biofilms, in health, the food industry or other industrial processes. Likewise, this project’s results lay the ground to study other bacterial genes that might be involved in biofilm formation with the ultimate goal of better understanding biofilm biology.
This project contributed to understanding the non-antimicrobial function of bacteriocins specifically on streptococcal biofilms. From a biofilm perspective, bacteriocin gene deletion strains were less competitive in biofilm-forming capacity and can therefore be potential targets to debilitate biofilms. Importantly, a bacteriocin-biofilm workflow was established and can be transferred to other gene-targeted biofilm studies.
On the other hand, full characterization of substances such as bacteriocins intended to be used for health and food applications is necessary from a safe use perspective. In this sense, it would be interesting to evaluate biofilm-related food spoilage and the impact of bacteriocin-encoding biofilm-forming protective cultures on these biofilms.
On the other hand, full characterization of substances such as bacteriocins intended to be used for health and food applications is necessary from a safe use perspective. In this sense, it would be interesting to evaluate biofilm-related food spoilage and the impact of bacteriocin-encoding biofilm-forming protective cultures on these biofilms.