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人们越来越意识到使用化学农药的弊端,并开始积极寻求其他防治手段来替代或减少化学农药的使用。生物防治因其高效,对环境、生态及人类健康安全,无毒等优点得到了广泛重视和关注,并成为了目前植物病害防治的热点。目前,很多有益微生物及其代谢产物被成功应用于植物病害的生物防治中,包括真菌、细菌、放线菌、酵母等。在这些生防微生物中,芽孢杆菌属Bacillus是近年来生物防治研究的一个重点方向[1]。芽孢杆菌广泛分布于自然界各种不同环境中,包括土壤、水体、植物体表面及体内等。其生长速度快、营养需求简单、抗逆性强、易于在植物体表面定殖与繁殖、抑菌谱广、对人畜无害、不污染环境,且制剂生产的工艺简单、制剂稳定、储存时间长、施用方便,不仅符合人们对环境和健康的需求,而且为农林业的可持续发展提供了保障[1-2]。大量的研究表明:芽孢杆菌防治植物病害的作用方式多种多样,主要有拮抗作用、竞争作用、溶菌作用、诱导抗性和促进植物生长等[1]。拮抗作用是芽孢杆菌通过产生抑菌活性物质,抑制或杀死病原菌的现象,是芽孢杆菌最主要的作用方式,也是目前研究较为深入广泛的一种抑菌机制[3]。芽孢杆菌主要通过2种途径产生抑菌活性物质,分别是核糖体途径和非核糖体途径。核糖体合成的抑菌物质主要有活性蛋白类、酶类、细菌素等,如鞭毛蛋白、枯草菌素、葡聚糖酶、纤维素酶和几丁质酶等;非核糖体途径合成的抑菌物质主要有脂肽类、多肽类物质、挥发性抑菌物质等,如表面活性素(surfactins),伊枯草菌素(iturins),丰原素(fengycins),醇类,聚酮类,酚类,大环内酯类等[1-5]。菌株TJB-8是从杨树Populus根部土壤中分离得到的一株对杨树腐烂病菌Cytospora chrysosperma具有明显抑菌活性的拮抗细菌。本研究测定了菌株TJB-8无菌滤液的抑菌活性,鉴定了菌株,并初步分析了其抑菌活性物质。研究结果为该菌株的进一步工业开发和田间应用提供理论基础和科学依据。
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菌株TJB-8无菌滤液对杨树腐烂病菌具有明显的抑菌活性,培养12 h时,能有效地抑制杨树腐烂病菌菌丝生长;随着培养时间的延长,处理组的菌丝开始生长,至48 h后,处理组的菌丝停止生长。培养72 h后,抑制率达到97.42%(图 1A,图 1B,表 1)。无菌滤液对其他5种病原真菌也均有较好的抑菌活性。抑菌活性显示TJB-8无菌滤液对杨树腐烂病菌,细极链格孢菌Alternaria tenuissima,立枯丝核菌Rhizoctonia solani的抑菌活性最高,抑制率分别达到97.42%,96.65%和95.45%;对禾谷镰刀菌Fusarium graminearum的抑菌活性次之,抑菌率达到64.11%;对胶孢炭疽菌Colletotrichum gloeosporioides和尖孢镰刀菌Fusarium oxysporum的抑菌活性最低,但抑制率也分别达到58.40%和57.73%(表 2)。此外,通过观察杨树腐烂病菌对照组和处理组菌落边缘的菌丝发现,杨树腐烂病菌菌丝经过TJB-8无菌滤液作用后会产生局部膨大的畸形(图 1D),而对照组的菌丝生长正常、形态均匀(图 1C)。
图 1 拮抗菌株TJB-8无菌滤液对杨树腐烂病菌菌丝生长及形态的影响
Figure 1. Effect of sterile culture filtrate of strain TJB-8 on the growth and morphology of fungal hyphae
表 1 拮抗菌株TJB-8无菌滤液对杨树腐烂病菌的抑菌活性
Table 1. ntifungal activity of sterile culture filtrate of strain TJB-8 against Cytospora chrysosperma
培养时间/h 菌落扩展直径/mm 抑制率/% 处理组 对照组 12 0 ± 0 14.83 ± 0.29 100 ± 0 a 24 1.00 ± 0 33.67 ± 0.58 97.03 ± 0 b 36 1.60 ± 0.36 53.33 ± 1.15 97.00 ± 0.68 b 48 2.17 ± 0.76 72.17 ± 0.76 97.00 ± 1.06 b 60 2.17 ± 0.76 84.00 ± 0 97.42 ± 0.91 b 72 2.17 ± 0.76 84.00 ± 0 97.42 ± 0.91 b 说明:表中数据为平均数±标准差。同列数据后无相同小写字母的表示差异显著(P<0.05)。 表 2 拮抗菌株TJB-8无菌滤液的抑菌谱
Table 2. Antifungal spectrum of sterile culture filtrate of strain TJB-8
病原真菌 抑制率/% 杨树腐烂病菌Cytospora chrysosperma 97.42 ± 0.91 a 胶抱炭痕菌Colletotrichum gloeosporioides 58.40 ± 1.26 c 细极链格抱菌Alternaria tenuissima 96.65 ± 0.83 a 尖抱镰刀菌Fusarium oxysporum 57.73 ± 236 c 禾谷镰刀菌Fusarium graminearum 64.11 ± 2.87 b 立枯丝核菌Rhizoctonia solani 95.45 ± 1.10 a -
菌株TJB-8为革兰氏阳性菌,杆状,菌体大小为(0.8~1.1) μm × (2.1~3.0) μm,有鞭毛,产芽孢,兼性厌氧型。在LB培养基平板上菌落呈灰白色,不透明,表面光滑干燥,形状不规则近圆形,中部隆起,不产色素。依据菌株的生理生化特征(表 3),并利用统计学方法将拮抗菌株TJB-8和芽孢杆菌属内各个种的形态和生理生化特征进行聚类分析,鉴定菌株TJB-8与蜡样芽孢杆菌Bacillus cereus最为相近。
表 3 菌株TJB-8生理生化特性
Table 3. Physiological and biochemical characteristics of strain TJB-8
测定指标 菌株特性 蜡样芽孢杆菌 TJB-8 接触酶 + + 厌氧生长 + + V-P测定 + + 氧化酶 + + 柠檬酸盐利用 + + 卵磷脂酶水解 + + 硝酸盐还原 + + 明胶液化 + + 吲哚产生 + - 苯丙氨酸脱氨酶 - - 淀粉水解 + + 葡萄糖产酸 + + D-木糖产酸 - - L-阿拉伯糖产酸 - - 甘露醇产酸 - - 生长pH 5.7 + + 说明: +表示阳性或生长; -表示阴性或不生长。蜡样芽孢杆菌生理生化特性参见参考文献[9]。 -
菌株TJB-8的16S rDNA PCR扩增得到一段大小约为1.3 kb的基因片段,回收测序后,测定的片段大小为1 258 bp,提交到GenBank,序列号为KX886805。用ClustalX和MEGA软件进行分析,Neibour-Joining法构建系统发育树(图 2)。该菌株与模式菌株Bacillus cereus ATCC 14579相似度达100%。综合菌株TJB-8的形态学特征、生理生化特性及16S rDNA序列分析的结果,最终将菌株TJB-8鉴定为蜡样芽孢杆菌。
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真菌细胞壁裂解酶特性的检测结果显示,只有β-1, 3-葡聚糖酶(图 3A)和蛋白酶(图 3B)的检测平板中菌体周围产生明显透明圈,而其他裂解酶检测平板中菌体周围未见透明圈或晕圈出现,表明TJB-8能产生β-1, 3-葡聚糖酶和蛋白酶,而不能产生几丁质酶、纤维素酶和脂酶。
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TJB-8蛋白类和脂肽类提取物的抑菌活性检测结果表明:TJB-8的蛋白类和脂肽类提取物均具有较强的抑菌活性(图 4)。蛋白类和脂肽类提取物都能完全抑制杨树腐烂病菌菌丝生长,且抑菌活性稳定,培养72 h后依然保持100%的抑制率(表 4)。
图 4 菌株TJB-8蛋白类和脂肽类提取物的抑菌活性
Figure 4. Antifungal activities of crude proteins and lipopeptides produced by strain TJB-8
表 4 菌株TJB-8不同抑菌物质的抑菌活性
Table 4. Antifungal activities of different antifungal substances produced by strain TJB-8 against Cytospora chrysosperma
t/h 抑制率/% 蛋白类提取物 脂肽类提取物 挥发性气体 12 100 ± 0 a 100 ± 0 a 100 ± 0 a 24 100 ± 0 a 100 ± 0 a 78.26 ± 1.88 b 36 100 ± 0 a 100 ± 0 a 77.02 ± 1.08 b 48 100 ± 0 a 100 ± 0 a 76.08 ± 0.83 b 60 100 ± 0 a 100 ± 0 a 72 100 ± 0 a 100 ± 0 a -
TJB-8挥发性气体的抑菌活性检测发现,TJB-8的挥发性气体对杨树腐烂病菌具有很好的抑菌活性,能有效地抑制杨树腐烂病菌菌丝的生长(图 5)。挥发性气体的抑菌活性随着培养时间的延长而逐渐降低,但依然保持较高的抑菌率,培养48 h后其抑制率仍然达到76.08%(表 4)。
Antagonistic strain of TJB-8 and its antifungal substances
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摘要: 菌株TJB-8是从杨树Populus根部土壤中分离获得的一株对杨树腐烂病菌Cytospora chysosperma具有明显抑菌效果的细菌。基于形态学特征、生理生化特性和16S rDNA序列分析鉴定了TJB-8的分类地位,并分别采用菌丝生长速率法和二分皿法分析了其抑菌活性物质,为菌株TJB-8的实际开发利用提供理论基础。研究结果显示:菌株TJB-8的无菌滤液有效抑制了杨树腐烂病菌菌丝生长,抑制率达到97.42%(72 h),并使生长的菌丝产生畸形膨大;TJB-8的无菌滤液还能明显抑制胶孢炭疽菌Colletotrichum gloeosporioides,细极链格孢菌Alternaria tenuissima,尖孢镰刀菌Fusarium oxysporum,禾谷镰刀菌F.graminearum和立枯丝核菌Rhizoctonia solani的生长;菌株TJB-8经鉴定为蜡样芽孢杆菌Bacillus cereus,并发现其能产生β-1,3-葡聚糖酶和蛋白酶;此外,其产生的蛋白类物质、脂肽类物质及挥发性气体均表现出较强的抑菌活性,对杨树腐烂病菌的抑制率分别达到100%(72 h),100%(72 h)和76.08%(48 h)。蜡样芽孢杆菌TJB-8是一株抑菌活性强、抑菌谱广且能产生多种抑菌活性物质的拮抗细菌,作为一种生物杀菌剂具有较高的工业开发和田间应用的前景。Abstract: Strain TJB-8 has been isolated from the root soil of poplar and has exhibited a strong inhibitory effect against Cytospora chrysosperma, a predominant fungus causing poplar canker. In order to provide technical guidance for further exploitation and utilization of TJB-8, the species of TJB-8 and its antifungal substances were investigated in this study. The strain TJB-8 was identified based on morphological and physiological characteristics, as well as a phylogenetic analysis of partial 16S rDNA sequence; the antifungal substances of TJB-8 were analyzed by colony diameter assay and two-compartment plate method. Results revealed that sterile culture filtrates of TJB-8 had a strong antifungal activity against C. chrysosperma with an inhibitory rate of 97.42% (over 72 h). The hyphae of C. chrysosperma at the edge of the colony exhibited swelling after being treated with a sterile culture filtrate. Also, this sterile culture filtrate effectively inhibited the hyphae growth of Colletotrichum gloeosporioides, Alternaria tenuissima, Fusarium oxysporum, Fusarium graminearum, and Rhizoctonia solani. Strain TJB-8 was identified as Bacillus cereus and produced β-1, 3-glucanase and protease. Moreover, TJB-8 produced high antifungal activities against C. chrysosperma with crude proteins (100% in 72 h), lipopeptides (100% in 72 h), and volatiles (76.08% in 48 h). Thus, B. cereus TJB-8 was an antagonistic bacterium with strong antifungal activity, a wide inhibitory spectrum, and varied antifungal substances, having a broad prospect of industrial development and field application as a biological fungicide.
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Key words:
- forest protection /
- Bacillus cereus /
- antifungal activity /
- antifungal proteins /
- lipopeptides /
- volatiles
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表 1 拮抗菌株TJB-8无菌滤液对杨树腐烂病菌的抑菌活性
Table 1. ntifungal activity of sterile culture filtrate of strain TJB-8 against Cytospora chrysosperma
培养时间/h 菌落扩展直径/mm 抑制率/% 处理组 对照组 12 0 ± 0 14.83 ± 0.29 100 ± 0 a 24 1.00 ± 0 33.67 ± 0.58 97.03 ± 0 b 36 1.60 ± 0.36 53.33 ± 1.15 97.00 ± 0.68 b 48 2.17 ± 0.76 72.17 ± 0.76 97.00 ± 1.06 b 60 2.17 ± 0.76 84.00 ± 0 97.42 ± 0.91 b 72 2.17 ± 0.76 84.00 ± 0 97.42 ± 0.91 b 说明:表中数据为平均数±标准差。同列数据后无相同小写字母的表示差异显著(P<0.05)。 表 2 拮抗菌株TJB-8无菌滤液的抑菌谱
Table 2. Antifungal spectrum of sterile culture filtrate of strain TJB-8
病原真菌 抑制率/% 杨树腐烂病菌Cytospora chrysosperma 97.42 ± 0.91 a 胶抱炭痕菌Colletotrichum gloeosporioides 58.40 ± 1.26 c 细极链格抱菌Alternaria tenuissima 96.65 ± 0.83 a 尖抱镰刀菌Fusarium oxysporum 57.73 ± 236 c 禾谷镰刀菌Fusarium graminearum 64.11 ± 2.87 b 立枯丝核菌Rhizoctonia solani 95.45 ± 1.10 a 表 3 菌株TJB-8生理生化特性
Table 3. Physiological and biochemical characteristics of strain TJB-8
测定指标 菌株特性 蜡样芽孢杆菌 TJB-8 接触酶 + + 厌氧生长 + + V-P测定 + + 氧化酶 + + 柠檬酸盐利用 + + 卵磷脂酶水解 + + 硝酸盐还原 + + 明胶液化 + + 吲哚产生 + - 苯丙氨酸脱氨酶 - - 淀粉水解 + + 葡萄糖产酸 + + D-木糖产酸 - - L-阿拉伯糖产酸 - - 甘露醇产酸 - - 生长pH 5.7 + + 说明: +表示阳性或生长; -表示阴性或不生长。蜡样芽孢杆菌生理生化特性参见参考文献[9]。 表 4 菌株TJB-8不同抑菌物质的抑菌活性
Table 4. Antifungal activities of different antifungal substances produced by strain TJB-8 against Cytospora chrysosperma
t/h 抑制率/% 蛋白类提取物 脂肽类提取物 挥发性气体 12 100 ± 0 a 100 ± 0 a 100 ± 0 a 24 100 ± 0 a 100 ± 0 a 78.26 ± 1.88 b 36 100 ± 0 a 100 ± 0 a 77.02 ± 1.08 b 48 100 ± 0 a 100 ± 0 a 76.08 ± 0.83 b 60 100 ± 0 a 100 ± 0 a 72 100 ± 0 a 100 ± 0 a -
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