title: Spatial variation in frequency and intensity of antibiotic interactions among Streptomycetes from prairie soil.
abstract: Antibiotic interactions are believed to be significant to microbial fitness in soil, yet little is known of the frequency, intensity, and diversity of antibiotic inhibition and resistance among indigenous microbes. To begin to address these issues, we studied the abilities of streptomycete isolates from prairie soil to inhibit growth and display resistance to antibiotics produced by a test collection of 10 streptomycete isolates. Wide variations in antibiotic inhibition and resistance for prairie isolates among three locations and four soil depths within a 1-m2 plot were revealed. Fewer than 10% of 153 prairie isolates inhibited all 10 test isolates, while more than 40% of the isolates did not inhibit any of the test isolates. No field isolate was resistant to all of the test isolates, nor was any isolate susceptible to all of the test isolates. No correlation between inhibition and resistance phenotypes was found, suggesting that inhibition and resistance are under independent selection. The significant spatial variation in the frequency and intensity of antibiotic inhibition implies that the fitness benefits of antibiotic production are not the same among locations in soil. In contrast, the consistency of resistance over space indicates that its significance to fitness across locations is stable or the costs of maintaining resistance in the absence of selection are small or nonexistent. The spatial clustering of antibiotic inhibitory activity suggests a variable matrix of selection pressures and microbial responses across the soil landscape.
authors.affiliation: Department of Plant Pathology. Plant Science Research Unit, Agricultural Research Service, U.S. Department of Agriculture, St. Paul, Minnesota 55108, USA. davel001@umn.edu
authors.forename: Anita L
authors.initials: AL
authors.lastname: Davelos
authors.forename: Linda L
authors.initials: LL
authors.lastname: Kinkel
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Samac
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology*; D003470:Culture Media; D024881:Drug Resistance, Bacterial; D017753:Ecosystem; D008826:Microbial Sensitivity Tests; D006109:Poaceae; D012987:Soil; D012988:Soil Microbiology; D013302:Streptomyces / Q000145:classification / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D012987:Soil