Some bacteria can antagonize and competitively exclude pathogens by producing antimicrobial substances in their immediate environment. These antimicrobial agents can be grouped into enzymes, protein such as polypeptides and non-protein compounds. Of the various crop pests and pathogens that devastate harvests, oomycetes and fungi are the most broadly distributed groups causing global issues in food security and environmental damage in natural ecosystems. In this study, three bacterial isolates, Bacillus amyloliquefaciens (UQ154), Bacillus velezensis (UQ156) and Acinetobacter sp. (UQ202), previously shown to promote plant growth and anti-oomycete properties against Phytophthora spp., were selected for further investigation. These isolates were subjected to extractions with dichloromethane. The crude extracts were fractionated by preparative silica gel thin-layer chromatography and tested for their anti-oomycete activities against Phytophthora capsici. The results show that nine out of 16 fractions exhibited high (> 50%) P. capsici growth inhibition, comparable to the application of the live bacterial isolates. Using GCMS analyses, the compounds identified from the bacterial fractions were pyrrolopyrazine and various phenolic compounds, including the previously identified diketopiperazine compounds (DKPs) from the crude bacterial extracts. The ability of these bacterial isolates and their bioactive compounds to inhibit plant pathogen growth deserves further investigations, offering a potential roadmap for the development of bio-pesticides.

一些细菌可以通过在它们的直接环境中产生抗菌物质来对抗和竞争性地排除病原体。这些抗微生物剂可分为酶类、蛋白质（如多肽）和非蛋白质化合物。在破坏收成的各种农作物病虫害和病原体中，卵菌和真菌是分布最广的群体，在自然生态系统中造成全球粮食安全和环境破坏问题。在这项研究中，三种细菌分离株， 解淀粉芽孢杆菌 (UQ154)、贝雷兹 芽孢杆菌 (UQ156) 和 不动杆菌 属。(UQ202)，先前已证明可促进植物生长和抗疫霉属的抗卵菌特性  spp., 被选中进行进一步调查。这些分离物用二氯甲烷进行萃取。粗提物通过制备型硅胶薄层色谱分离，并测试它们对辣椒疫霉的抗卵菌活性 。 结果表明，16 个馏分中有 9 个表现出高 (> 50%)  P. capsici 生长抑制，可与活细菌分离物的应用相媲美。使用 GCMS 分析，从细菌组分中鉴定出的化合物是吡咯并吡嗪和各种酚类化合物，包括先前从细菌粗提物中鉴定出的二酮哌嗪化合物 (DKP)。这些细菌分离物及其生物活性化合物抑制植物病原体生长的能力值得进一步研究，为生物农药的开发提供潜在的路线图。