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Updated: Jul 22, 2025
Kinetic Visualization of Single-Cell Interspecies Bacterial Interactions
Published on: August 5, 2020
Interspecies interactions in mixed-species biofilms formed by Enterococcus faecalis and gram-negative bacteria
Florencia Mariani1,2, Guillermo E Juarez1,2, Claudia Barberis3,4
1Laboratorio de Patogénesis Bacteriana, Departamento de Investigaciones Bioquímicas y Farmacéuticas, Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y Diagnóstico (CEBBAD), Universidad Maimónides, Ciudad Autónoma de Buenos Aires, Argentina.
Abstract:
Diabetic foot ulcers (DFU) are exacerbated by bacterial colonisation. Here, a high prevalence of Enterococcus faecalis was observed in DFU patients from an Argentinean hospital. E. faecalis was frequently co-isolated with Escherichia coli, Morganella morganii, and Pseudomonas aeruginosa. The effect of interspecies interactions on bacterial growth was investigated in mixed-species macrocolony biofilms developed in Lubbock-Glc-agar. Similar cell counts were found for E. faecalis and M. morganii growing in mixed and single-species biofilms. An E. faecalis strain showed 1 Log higher cell counts in mixed biofilms with E. coli. Remarkably, E. faecalis strains showed 2 to 4 Log higher cell counts in mixed biofilms with P. aeruginosa. This effect was not observed in planktonic growth or biofilms developed in tryptic soy agar. The present findings reveal bacterial interactions that benefit E. faecalis in mixed-species biofilms, mainly with P. aeruginosa, in a medium that partially mimics the nutrients found in DFU.
Insights
Bacterial infections in diabetic foot ulcers (DFU) are common. This study found that Enterococcus faecalis grows significantly better in mixed biofilms with Pseudomonas aeruginosa, suggesting beneficial interactions in DFU environments.
Area of Science:
- Microbiology
- Infectious Diseases
- Biofilms
Background:
- Diabetic foot ulcers (DFU) are prone to bacterial colonization, complicating healing.
- Enterococcus faecalis is frequently found in DFU, often alongside other bacteria like Escherichia coli, Morganella morganii, and Pseudomonas aeruginosa.
Purpose of the Study:
- To investigate the impact of interspecies bacterial interactions on Enterococcus faecalis growth within biofilms relevant to the DFU environment.
Main Methods:
- Mixed-species macrocolony biofilms of E. faecalis with E. coli, M. morganii, and P. aeruginosa were cultured in Lubbock-Glc-agar.
- Bacterial cell counts were compared between single-species and mixed-species biofilms.
- Experiments were also conducted in planktonic cultures and on tryptic soy agar to assess medium-specific effects.
Main Results:
- E. faecalis showed similar growth in mixed biofilms with M. morganii compared to single-species biofilms.
- E. faecalis exhibited a 1-log increase in cell count when co-cultured with E. coli in mixed biofilms.
- A significant 2- to 4-log increase in E. faecalis cell counts was observed in mixed biofilms with P. aeruginosa.
- These enhanced growth effects were specific to biofilm formation in Lubbock-Glc-agar and not observed in planktonic cultures or on tryptic soy agar.
Conclusions:
- Interspecies interactions within biofilms can significantly benefit E. faecalis growth in a DFU-like environment.
- Pseudomonas aeruginosa demonstrates a particularly strong synergistic effect on E. faecalis proliferation in mixed-species biofilms.
- These findings highlight the complex microbial dynamics in DFU and suggest P. aeruginosa as a key interacting species influencing E. faecalis populations.
