Emergence of Antibiotic-Producing Microorganisms in Residential Versus Recreational Microenvironments

Aims: To identify novel antibiotic-producing microbial strains with unprecedented
pertinence. We hypothesize that site-specific soil samples will contain a variety of antibioticproducing
species (APS) with diverse specificity of molecular elements.
Place and Duration of Study: Laboratory of Microbiology, Division of Biological and Health
Sciences, University of Pittsburgh, Bradford, PA-16701, USA, between August 2010 and
May 2011.
Methodology: The environmental soil samples were collected from residential and
recreational sites in Southern, PA, USA at longitude: -76 42 21.7116, latitude: 39 56
35.7252; approximately 201 meters above sea level. Over 70 natural antibiotic-producing
soil bacteria were screened against 19 pathogenic microorganisms. Agar-plug assay was
established to identify the antibiotics’ potency and pathogenic inhibitory index calculations
were employed to measure the inhibitory potential of each isolate; 16S rRNA sequencing
was used for microbial classification.
Results: A total of 71 microorganisms from residential soil demonstrated zones of inhibition
(ZOI), followed by 9 organisms from recreational soil sample. A total of 15 bioactive strains
demonstrated convincing growth inhibitory properties against 16 clinically relevant
pathogens; 40% revealed pDNA presence, of which 67% exhibited stringent potencies against S. aureus. We observed a highly bioactive residential soil microbiota compared to
recreational soil.
Conclusion: 16S rRNA sequence analysis corroborated several of the species belonging
to Enterobacteriaceae, Xanthomonadaceae, and Bacillaceae. These findings may indicate
a co-evolutionary biosynthesis of novel antibiotics driven by the increase of bioactive
microbiota in residential environments.