Abstract
AimsTo identify novel antibiotic-producing microbial strains with unprecedented pertinence. We hypothesize that site-specific soil samples will contain a variety of antibiotic-producing species (APS) with diverse specificity of molecular elements.Place and Duration of StudyLaboratory of Microbiology, Division of Biological and Health Sciences, University of Pittsburgh, Bradford, PA-16701, USA, between August 2010 and May 2011.MethodologyThe 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.ResultsA 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.Conclusion16S 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.
Highlights
The microbial products of secondary metabolism carry an important role in human health, providing roadmaps for the biosynthesis of many synthetic and semi-synthetic drugs
We aimed to explore the natural antibiotic biosynthesis potentials of microorganisms isolated from soil collected at residential and recreational sites and hypothesized that site-specific soil samples will contain a diversity of antibioticproducing strains (APS) with a variety of molecular elements
To determine the molecular elements which may be involved in antibiotic production in sitespecific soil isolates, we looked for plasmid DNA existence and found it in several residential soil-derived antibiotic-producing species (APS), designated as Y14p, Y29p, Y40p, Y17p, Y63p, and Y67p (Fig. 2a)
Summary
The microbial products of secondary metabolism carry an important role in human health, providing roadmaps for the biosynthesis of many synthetic and semi-synthetic drugs. Natural soil harbors over 109 microorganisms/ gram and provides an ideal reservoir for bioactive microbiota, which springs virtually all clinical antibiotics used today [2,3]. Today nearly 500 antibiotics are found each year and over 80% of antibiotics in clinical use are obtained from soil isolates [1]. These bioactive microorganisms are most abundantly present at the top few inches of the soil, in soil containing straw and agricultural products [2,4]. In addition to the elevated use of therapeutic drugs in urban or residential environments, residential soils contain exceptionally high bioactivity and are abundant reservoirs of antibiotic-resistant microorganisms[5,6]
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