Aggregatibacter actinomycetemcomitans mediates protection of Porphyromonas gingivalis from Streptococcus sanguinis hydrogen peroxide production in multi-species biofilms

Bin Zhu,Eric Newsome,Jinlin Liu,Ping Xu,Lorna C. Macleod

doi:10.1038/s41598-019-41467-9

Abstract

Mixed species biofilms are shaped and influenced by interactions between species. In the oral cavity, dysbiosis of the microbiome leads to diseases such as periodontitis. Porphyromonas gingivalis is a keystone pathogen of periodontitis. In this study, we showed that polymicrobial biofilm formation promoted the tolerance of Porphyromonas gingivalis to oxidative stress under micro-aerobic conditions. The presence of Streptococcus sanguinis, an oral commensal bacterium, inhibited the survival of P. gingivalis in dual-species biofilms via the secretion of hydrogen peroxide (H2O2). Interestingly, this repression could be attenuated by the presence of Aggregatibacter actinomycetemcomitans in tri-species biofilms. It was also shown that the katA gene, encoding a cytoplasmic catalase in A. actinomycetemcomitans, was responsible for the reduction of H2O2 produced by S. sanguinis, which consequently increased the biomass of P. gingivalis in tri-species biofilms. Collectively, these findings reveal that polymicrobial interactions play important roles in shaping bacterial community in biofilm. The existence of catalase producers may support the colonization of pathogens vulnerable to H2O2, in the oral cavity. The catalase may be a potential drug target to aid in the prevention of periodontitis.

Highlights

According to the 2016 global burden of disease study, periodontal disease is estimated to affect 750,847 million people worldwide, making it the 11th most prevalent human disease[1]
The colony-forming units (CFUs) of P. gingivalis ATCC 33277 (Pg) grown under micro-aerobic conditions in 4-well chambers was lower than that of the initial inoculation, it was still greater than the CFU of Pg grown in the 14 mL test tube, suggesting that the biofilm formation increased the tolerance of Pg to oxidative stress from the presence of environmental oxygen (Fig. 1A)
It was shown that actinomycetemcomitans 652 (Aa) degraded H2O2 produced by sanguinis SK36 (Ss), which aided the survival of Pg in Pg-Aa-Ss tri-species biofilms under micro-aerobic conditions

Summary

Introduction

According to the 2016 global burden of disease study, periodontal disease is estimated to affect 750,847 million people worldwide, making it the 11th most prevalent human disease[1]. Oral microbiome studies by 16s rRNA sequencing suggest that the abundance of periodontitis-associated species, such as P. gingivalis, Treponema denticola and Tannerella forsythia, is significantly increased in disease sites of periodontitis patients[7,8]. Many of these pathogens are anaerobic species that survive in deep dental pockets where oxygen is limited. Streptococcus sanguinis is a Gram-positive, facultative anaerobe bacterium that is able to inhibit the growth of P. gingivalis[15] and produce a ROS, hydrogen peroxide (H2O2)[19,20] It is a pioneering colonizer in the oral cavity and a key player in oral biofilm development[21,22]. As A. actinomycetemcomitans can degrade H2O2, we proposed that A. actinomycetemcomitans might confer protection to P. gingivalis from the damage of H2O2 produced by S. sanguinis in mixed species biofilm

Methods

Results

Conclusion