Mapping Bacterial Responses to Reactive Nitrogen and Oxygen Species

A study in Microbiological Research explored the impact of varying ratios of Reactive Nitrogen Species (RNS) and Reactive Oxygen Species (ROS) on pathogenic bacteria, including Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa.

The Surrey-based researchers employed advanced imaging and transcriptional analysis to determine the differential responses of these bacteria to varying RNS and ROS balances.

The findings were analogized to weed control in a garden. RNS acts like complete weed removal (uprooting), preventing regeneration. Conversely, a ROS-dominant environment is akin to superficial cutting; the bacteria may initially appear weakened but can recover, develop biofilms (protective layers), and exhibit increased resistance.

This research is significant due to the escalating global threat of drug-resistant infections, which diminish the efficacy of many antibiotics. A molecular-level understanding of RNS and ROS interactions could facilitate the development of novel therapeutic strategies that augment the body's innate defenses and mitigate the progression of antimicrobial resistance (AMR).

We used to think both reactive oxygen and nitrogen hurt bacteria in the same way, but our research found it is more complicated. While nitrogen-heavy environments kill bacteria, an oxygen-rich environment can actually make bacteria stronger and harder to kill, especially by helping them form protective layers that resist antibiotics.”

Dr. Jorge Gutierrez, Senior Lecturer, Food Microbiology, University of Surrey

The team utilized a specialized plasma device, ReCAP (developed by Fourth State), to expose bacterial cultures to precisely controlled RNS and ROS mixtures. Bacteria were cultured in both liquid and solid (gel-like) media. High-resolution imaging, including scanning electron microscopy, was used to visualize detailed alterations in bacterial membranes.

Furthermore, transcriptional analysis (which identifies active and inactive genes under specific conditions) was conducted to track the response of key genes to different RNS/ROS ratios.

This integrated approach enabled the researchers to directly correlate specific molecular changes with bacterial survival mechanisms, providing concrete evidence of how the RNS/ROS balance determines bacterial fate.

The study underscores that treatments enhancing RNS may be beneficial in combating antibiotic-resistant bacteria, whereas treatments primarily boosting ROS could potentially exacerbate the problem. Further investigation is warranted to comprehensively elucidate the relationship between RONS and bacterial responses, potentially paving the way for more efficacious antibacterial approaches in the future.

The research highlights how treatments that boost reactive nitrogen species might be good for fighting antibiotic-resistant bacteria, while treatments that mainly boost reactive oxygen species could make things worse. More research needs to be done to fully understand the relation between RONS and bacterial responses, which could lead to more effective antibacterial strategies in the future.”

Dr. Jorge Gutierrez, Senior Lecturer, Food Microbiology, University of Surrey