Mixed continuous culture experiments with an antibiotic-producing streptomycete andEscherichia coli

Abstract

Four strains ofStreptomyces aureofaciens capable of producing different amounts of tetracycline have been grown in continuous culture with either of two strains ofEscherichia coli orBacillus pumillus. Each of the bacteria had faster specific growth rates than any of the streptomycetes.E. coli NTCT 5993 had a higher affinity for sucrose than didS. aureofaciens SR 11. In mixed culture experiments, the bacteria displaced the streptomycete under the following conditions: (a) when the streptomycete produced no tetracycline; (b) in tetracycline-producing cultures after a fraction of the bacteria had died-the bacterial population that subsequently developed was resistant to the drug; and (c) when using tetracycline-resistant bacteria. Under nutrient conditions leading to high antibiotic levels, it was possible to kill all the bacteria, and the streptomycete survived after a transient fall in mycelium and tetracycline levels. No stable mixed population was ever seen. Once tetracycline-resistant bacteria had displaced the streptomycete, and tetracycline concentrations had fallen, a sensitive bacterial population reappeared. Competition between sensitive and resistantE. coli NCTC 5993 in the chemostat confirmed the selective advantage of the sensitive strain. Results were discussed in terms of the role of antibiotics in nature.

Why antibiotics: A comparative evaluation of different hypotheses for the natural role of antibiotics and an evolutionary synthesis

“…Attempts to test whether antibiotic producers have an advantage in experimental competition are few and have yielded mixed results [29][30][31] that have possible alternative interpretations. Other products such as microcins that have been clearly demonstrated to give a competitive advantage are produced during the exponential phase [32].…”

“…Nevertheless some fragmentary evidence for or against some of them can be found in literature. Evidence for competition is contradictory [29][30][31] and much of the positive evidence claimed to support competition hypothesis has other possible interpretations. Predation can account for the most of the observations interpreted as competition.…”

Streptomyces coelicolor increases the production of undecylprodigiosin when interacted with Bacillus subtilis

“…The growth of S. coelicolor in pure and interacted cultures was measured as the dry weight of cell material according to the method described before which separates the two species (Rasool and Wimpenny 1982). An Analox glucose analysis machine was used to determine the glucose concentration.…”

The Effect of Co-Culture on Production of Blue Pigment by Streptomyces coelicolor M145 with Bacillus subtilis as Auxiliary

“…The supernatant, containing extracellular blue pigment, was diluted with moderate distilled water and detected at 580 nm by a spectrophotometer [17][18][19]. Then a certain amount of deposition was immersed in 70 % of alcohol solution that is 10 times as heavy as the deposition at 60°C for 1 h to extract the intracellular blue pigment, and the testing method was same with that of extracellular pigment.…”