Abstract
We hypothesized that environmental microbiomes contain a wide range of bacteria that produce yet uncharacterized antimicrobial compounds (AMCs) that can potentially be used to control pathogens. Over 600 bacterial strains were isolated from soil and food compost samples, and 68 biocontrol bacteria with antimicrobial activity were chosen for further studies based on inhibition assays against a wide range of food and plant pathogens. For further characterization of the bioactive compounds, a new method was established that used living pathogens in a liquid culture to stimulate bacteria to produce high amounts of AMCs in bacterial supernatants. A peptide gel electrophoresis microbial inhibition assay was used to concurrently achieve size separation of the antimicrobial peptides. Fifteen potential bioactive peptides were then further characterized by tandem MS, revealing cold-shock proteins and 50S ribosomal proteins. To identify non-peptidic AMCs, bacterial supernatants were analyzed by HPLC followed by GC/MS. Among the 14 identified bioactive compounds, 3-isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione and 2-acetyl-3-methyl-octahydropyrrolo[1,2-a]piperazine-1,4-dione were identified as new AMCs. Our work suggests that antimicrobial compound production in microbes is enhanced when faced with a threat from other microorganisms, and that this approach can rapidly lead to the development of new antimicrobials with the potential for upscaling.
Highlights
Increasing antimicrobial resistance (AMR) in human, food, and plant pathogens severely limits our ability to treat diseases, and new antibiotics must be developed [1,2,3,4].To face this challenge, new sources, approaches and strategies are essential for discovering new antimicrobial compounds
From more than 600 different single bacterial colonies that were isolated from a soil sample, 60 isolates were found to possess antimicrobial activity against phytopathogens (Gram-negative Pseudomonas syringae pv. tomato DC3000 and Gram-positive Clavibacter michiganensis subsp. michiganensis) and two food pathogens (Gram-negative Escherichia coli and Gram-positive Listeria monocytogenes)
This was likely due to the bacterial isolation conditions, which had 28 ◦ C as the basic temperature for the initial isolation of environmental samples rather than 37 ◦ C, which was the temperature required for the food pathogen inhibition assays
Summary
Increasing antimicrobial resistance (AMR) in human, food, and plant pathogens severely limits our ability to treat diseases, and new antibiotics must be developed [1,2,3,4] To face this challenge, new sources, approaches and strategies are essential for discovering new antimicrobial compounds. Looking for less traditional antimicrobial compounds (AMCs) that may have been overlooked in previous natural product searches, such as antimicrobial peptides (AMPs), could be a potential solution to overcome AMR threats. Based on their overwhelming biodiversity, microbial communities from different environmental sources, such as soils, are a promising source for identifying new AMCs [5,6]. They can be found in diverse environments, including the soil, water, food spoilage and animal guts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
