Silo-Suh L A, Lethbridge B J, Raffel S J, He H, Clardy J, Handelsman J
Department of Bacteriology, University of Wisconsin, Madison 53706.
Appl Environ Microbiol. 1994 Jun;60(6):2023-30. doi: 10.1128/aem.60.6.2023-2030.1994.
Cultures and culture filtrates of Bacillus cereus UW85 suppress damping-off of alfalfa caused by Phytophthora medicaginis. We studied the role in disease suppression of two antibiotics from culture filtrates of UW85 that reversibly inhibited growth of P. medicaginis. We purified the two antibiotics by cation-exchange chromatography and high-voltage paper electrophoresis and showed that one of them, designated zwittermicin A, was an aminopolyol of 396 Da that was cationic at pH 7.0; the second, designated antibiotic B, appeared to be an aminoglycoside containing a disaccharide. Both antibiotics prevented disease of alfalfa seedlings caused by P. medicaginis. Purified zwittermicin A reversibly reduced elongation of germ tubes derived from cysts of P. medicaginis, and antibiotic B caused swelling of the germ tubes. Mutants generated with Tn917 or mitomycin C treatment were screened either for antibiotic accumulation in an agar plate diffusion assay or for the ability to suppress damping-off disease of alfalfa. Of 2,682 mutants screened for antibiotic accumulation, 5 mutants were substantially reduced in antibiotic accumulation and disease-suppressive activity. Of the 1,700 mutants screened for disease-suppressive activity, 3 mutants had reduced activity and they accumulated less of both antibiotics than did the parent strain. The amount of antibiotic accumulated by the mutants was significantly correlated with the level of disease suppression. Addition of either zwittermicin A or antibiotic B to alfalfa plants inoculated with a culture of a nonsuppressive mutant resulted in disease suppression. These results demonstrate that B. cereus UW85 produces two fungistatic antibiotics that contribute to suppression of damping-off disease of alfalfa.
蜡样芽孢杆菌UW85的培养物及其培养滤液可抑制由苜蓿疫霉引起的苜蓿猝倒病。我们研究了UW85培养滤液中的两种抗生素在病害抑制中的作用，这两种抗生素可可逆地抑制苜蓿疫霉的生长。我们通过阳离子交换色谱法和高压纸电泳法对这两种抗生素进行了纯化，结果表明其中一种被命名为两性霉素A的抗生素是一种396 Da的氨基多元醇，在pH 7.0时呈阳离子性；第二种被命名为抗生素B，似乎是一种含有二糖的氨基糖苷。这两种抗生素都能预防由苜蓿疫霉引起的苜蓿幼苗病害。纯化的两性霉素A可可逆地降低苜蓿疫霉囊肿衍生的芽管伸长，而抗生素B则导致芽管肿胀。用Tn917或丝裂霉素C处理产生的突变体，通过琼脂平板扩散试验筛选抗生素积累情况，或筛选抑制苜蓿猝倒病的能力。在筛选抗生素积累的2682个突变体中，有5个突变体的抗生素积累和病害抑制活性大幅降低。在筛选病害抑制活性的1700个突变体中，有3个突变体的活性降低，且它们积累的两种抗生素均比亲本菌株少。突变体积累的抗生素量与病害抑制水平显著相关。向接种了非抑制性突变体培养物的苜蓿植株中添加两性霉素A或抗生素B均可导致病害抑制。这些结果表明，蜡样芽孢杆菌UW85产生两种抑菌抗生素，有助于抑制苜蓿猝倒病。
