Microbial interactions impact stress tolerance in a model oral community

Area of Science:

• Microbiology
• Microbial Ecology
• Bacterial Interactions

Background:

• Microbial communities are shaped by complex interactions.
• Understanding these interactions is key to predicting community behavior under stress.
• The impact of microbial interactions on resilience to environmental change and invasion is not fully understood.

Purpose of the Study:

• To investigate how synergistic and antagonistic interactions between Aggregatibacter actinomycetemcomitans and Streptococcus gordonii affect community resilience.
• To determine the role of S. gordonii-produced L-lactate and H2O2 in mediating these interactions.
• To assess the impact of these interactions on susceptibility to environmental stress and invasion by other microbes.

Main Methods:

• Utilized a two-species in vitro colony biofilm model.
• Focused on the extracellular molecules L-lactate and hydrogen peroxide (H2O2).
• Evaluated microbial fitness, resilience to environmental change (tetracycline), and invasion dynamics (Serratia marcescens) in vitro and in a murine abscess model.

Main Results:

• Cross-feeding on L-lactate enhanced A. actinomycetemcomitans fitness but did not improve co-culture resilience to environmental change and could be detrimental under tetracycline stress.
• Hydrogen peroxide (H2O2) production by S. gordonii negatively impacted both species but enhanced A. actinomycetemcomitans tolerance to tetracycline.
• S. gordonii's inhibition of S. marcescens invasion was lost during co-culture with A. actinomycetemcomitans, and S. gordonii even promoted invasion in a murine model.

Conclusions:

• Microbial interactions significantly influence bacterial community fitness and resilience.
• The effects of microbial interactions are highly context-dependent and vary with environmental conditions.
• Seemingly beneficial interactions can lead to vulnerabilities, while antimicrobials can have dual roles under specific pressures.