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

1.从实验室长期饲养的豌豆蚜(Acyrthosiphon Pisum)分泌的蜜露中分离到革兰氏阴性菌。将菌种接种于液体培养罐中，经20倍浓缩后进行冷冻干燥，测定其抗菌活性。结果表明，该培养基对大肠杆菌和枯草芽孢杆菌均无抗菌活性，而蜜露本身即使在没有浓度的情况下也能非常有效地抑制大肠杆菌的生长。将蚜虫肠杆菌的培养基配以马铃薯葡萄糖培养基作真菌，用菌丝生长抑制法测定其抗真菌活性。结果表明，蚜虫肠道细菌分泌出一种对几种真菌的生长有抑制作用的物质。在某些有机溶剂中的分布实验表明，该有效物质是一种相对分子质量约为1,000.4的寡肽。没有生化证据表明这些肠道细菌与一些蚜虫物种所含的次生内共生菌有关。

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.