Abstract
Tiny Earth (TE) is a popular international citizen science program aimed at improving public awareness on the growing antimicrobial resistance problem of which MicroMundo Albacete is a Spanish node. With a protocol that is focused on the isolation of antibiotics-producing actinomycetes from soil, 70% of the high school students in MicroMundo Albacete 2020 isolated colonies with antagonistic activity against Gram-positive tester bacteria. However, no activity was found against Gram-negative bacteria. Here, we further adapted the protocol toward a more targeted screening that also enables isolation of antagonistic bacteria against Gram negatives using two different reverse-antibiosis approaches involving a spraying technique or flipping soil sample disks upside down. Exploiting the soil samples from MicroMundo Albacete 2020, the new approaches yielded isolation of actinomycete bacteria with antagonistic activity against Gram-negative as well as Gram-positive tester bacteria. We propose that (educational) science programs which aim to search for antibiotic-producing bacteria may implement these approaches in their protocol to promote a successful and stimulating outcome of the experiment for the participating students.
Highlights
Continued emergence of multidrug-resistant bacteria is considered a growing and global human health threat
In the MicroMundo Albacete 2020 project, 200 selected bacterial isolates were tested for antagonistic activity against ESKAPE-like tester bacteria by high school students
In the studentsourcing program, these pathogenic bacteria are replaced by harmless “relatives.” Guided by results of the previous year (De Groot et al, 2019), we tested antagonistic activity against the Gram-positive ESKAPErelatives B. subtilis and S. epidermidis, and against Gram-negative E. coli
Summary
Continued emergence of multidrug-resistant bacteria is considered a growing and global human health threat. A higher percentage of the isolated bacteria with antagonistic activity against tester bacteria was obtained, making the project more alluring for the participating students (De Groot et al, 2019). To implement a more targeted screening that will make the protocol more amenable to pick up activity against Gram-negative bacteria, we, here, designed a further modification to the protocol, functionality of which is demonstrated with soil samples from the MicroMundo 2020 project. The bottom side facing up was inoculated with a tester bacterium by painting the entire surface of the plate using a sterile cotton swab (Deltalab) In both methods, appearance of halos is monitored after 1–3 days of incubation at 30°C. Taxonomic and phylogenetic DNA sequence analysis was performed using NCBI-Blast and MEGA X (Kumar et al, 2018) software
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