Isolation, Identification and Remedial Result of An Antibiotic Substance produced by Aphid Enterobacteria

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1. Gram-negative bacteria were collected from the honeydew excreted by the pea aphids, Acyrthosiphon pisum which had been reared in the laboratory for a long period. The bacteria were culture in LB and the medium was determined for its antibiotic activity after 20fold concentration by lyophilization. The result showed that the medium did not have antibiotic activity against either E.coli or Bacillus subtilis while the honeydew itself, even without concentration, inhibited the growth of E.coli very effectively.2. The cultured medium of the aphid enterobacteria was mixed with the potato dextrose medium for fungi, and determined for its anti-fungal activity in terms of hyphal growth retardation. As a result, it was shown that the aphid enterobacteria excreted a substance that inhibited the growth of several fungi specifically and effectively.3. The distribution experiments with some organic solvents suggested that this effective substance was an oligopeptide with molecular weight of about 1,000.4. There was no biochemical evidence that these enterobacteria were related to secondary endosymbionts that some aphid species harbor.