http://grdspublishing.org/index.php/life <p><strong>ISSN 2454-5872</strong></p> Global Research & Development Services Publishing en-US LIFE: International Journal of Health and Life-Sciences 2454-5872 <p><strong>Copyright of Published Articles</strong></p> <p>Author(s) retain the article copyright and publishing rights without any restrictions.</p> <p><a href="http://creativecommons.org/licenses/by-nc/4.0/"><img src="https://i.creativecommons.org/l/by-nc/4.0/88x31.png" alt="Creative Commons License" /></a><br />All published work is licensed under a <a href="http://creativecommons.org/licenses/by-nc/4.0/">Creative Commons Attribution-NonCommercial 4.0 International License</a>.</p> http://grdspublishing.org/index.php/life/article/view/3052 <p><strong><em>Research Objectives:</em></strong><em> This study investigated whether co-culturing environmental bacterial isolates against Enterococcus faecalis (NTUCC 687) in the presence of ampicillin or tetracycline could elicit antimicrobial production, and whether this response was temperature-dependent.</em></p> <p><strong><em>Methodology:</em></strong><em> A total of 96 environmental bacterial isolates (arrayed in a 96-well plate) collected from built and natural surfaces around NTU Clifton campus were co-cultured against an Enterococcus faecalis lawn using an in-house stamping assay on UTI ChromoSelect agar. Plates were incubated at 25°C, 30°C, 37°C, and 42°C for 24–72 hours. For elicitation, UTI agar was fortified separately with ampicillin (0.05 µg/mL) or tetracycline (0.05 µg/mL). These low (sub-inhibitory) concentrations were used as stressors to probe signalling-associated induction of antimicrobial activity rather than direct growth inhibition. Antimicrobial activity was recorded as categorical zones of inhibition, classified as small (+), medium (++), or large (+++).</em></p> <p><strong><em>Findings:</em></strong><em> Tetracycline elicited a higher frequency of large (+++) zones of inhibition than ampicillin, peaking at 30°C (12 isolates, 12.5%), followed by 42°C (9 isolates, 9.4%), 25°C (5 isolates, 5.2%), and 37°C (3 isolates, 3.1%). In contrast, ampicillin produced only two large zones (2.1%), both observed at 25°C. These patterns indicate that antimicrobial elicitation was modulated by both antibiotic stressor type and incubation temperature within the co-culture assay.</em></p> <p><strong><em>Research Outcomes and Future Scope:</em></strong><em> These findings support co-culture-based elicitation as a practical strategy for uncovering latent antimicrobial potential in environmental bacteria and highlight temperature as a key modulator of expression. Future work should identify the active producers and compounds involved, investigate underlying molecular mechanisms, and assess scalability for antimicrobial discovery.</em></p> Sunday Stephen Abi Copyright (c) 2026 https://creativecommons.org/licenses/by-nc/4.0 2026-01-20 2026-01-20 01 02 10.20319/icrlsh.2026.0102