Institute of Biological Sciences, Biochemistry, Albert-Einstein-Strasse 3, University of Rostock, 18059 Rostock, Germany.
J Exp Bot. 2022 Jan 13;73(2):596-614. doi: 10.1093/jxb/erab476.
Microorganisms in the rhizosphere are abundant and exist in very high taxonomic diversity. The major players are bacteria and fungi, and bacteria have evolved many strategies to prevail over fungi, among them harmful enzyme activities and noxious secondary metabolites. Interactions between plant growth promoting rhizobacteria and phytopathogenic fungi are potentially valuable since the plant would benefit from fungal growth repression. In this respect, the role of volatile bacterial metabolites in fungistasis has been demonstrated, but the mechanisms of action are less understood. We used three phytopathogenic fungal species (Sclerotinia sclerotiorum, Rhizoctonia solani, and Juxtiphoma eupyrena) as well as one non-phytopathogenic species (Neurospora crassa) and the plant growth promoting rhizobacterium Serratia plymuthica 4Rx13 in co-cultivation assays to investigate the influence of bacterial volatile metabolites on fungi on a cellular level. As a response to the treatment, we found elevated lipid peroxidation, which indirectly reflected the loss of fungal cell membrane integrity. An increase in superoxide dismutase, catalase, and laccase activities indicated oxidative stress. Acclimation to these adverse growth conditions completely restored fungal growth. One of the bioactive bacterial volatile compounds seemed to be ammonia, which was a component of the bacterial volatile mixture. Applied as a single compound in biogenic concentrations ammonia also caused an increase in lipid peroxidation and enzyme activities, but the extent and pattern did not fully match the effect of the entire bacterial volatile mixture.
根际中的微生物丰富多样，具有很高的分类多样性。主要参与者是细菌和真菌，细菌已经进化出许多策略来战胜真菌，包括有害的酶活性和有毒的次生代谢物。植物促生根际细菌和植物病原菌真菌之间的相互作用具有潜在的价值，因为植物将受益于真菌生长的抑制。在这方面，挥发性细菌代谢物在真菌抑制中的作用已经得到证实，但作用机制还不太清楚。我们使用了三种植物病原菌真菌（核盘菌、立枯丝核菌和旋孢腔菌）以及一种非植物病原菌真菌（粗糙脉孢菌）和植物促生根际细菌粘质沙雷氏菌 4Rx13 进行共培养实验，以研究细菌挥发性代谢物对真菌的影响。作为对处理的反应，我们发现脂质过氧化作用升高，这间接反映了真菌细胞膜完整性的丧失。超氧化物歧化酶、过氧化氢酶和漆酶活性的增加表明存在氧化应激。适应这些不利的生长条件完全恢复了真菌的生长。一种具有生物活性的细菌挥发性化合物似乎是氨，它是细菌挥发性混合物的一个组成部分。以生物源浓度单独作为一种化合物应用时，氨也会导致脂质过氧化和酶活性增加，但程度和模式与整个细菌挥发性混合物的效果不完全匹配。
