蚕用益生芽孢杆菌SWL-19的筛选鉴定及其对肠道菌群多样性的影响

【目的】筛选对家蚕（Bombyx mori）具有益生作用的芽孢杆菌,改善家蚕肠道微环境,促进蚕业生产的发展。【方法】采用高温选育法对家蚕肠道内的芽孢杆菌进行初筛;以产胞外消化酶（蛋白酶、脂肪酶、纤维素酶和淀粉酶）及能在肠道定殖为基础,结合溶血试验、抗生素药敏试验和产消化酶能力大小等对芽孢杆菌进行复筛。通过形态、生理生化特征和16S rDNA序列分析鉴定菌种,再利用变性梯度凝胶电泳（DGGE）技术检测其在家蚕肠道内定殖情况及其对肠道内微生物菌群多样性的影响。【结果】共从57株细菌中筛选出两株能同时产蛋白酶、脂肪酶、纤维素酶和淀粉酶且不产生溶血现象的芽孢杆菌SWL-17和SWL-19。14种抗生素药敏纸片检测结果表明,二者对绝大多数抗生素敏感,且敏感程度基本相同。除SWL-19不能利用蔗糖发酵外,两个株菌的革兰氏染色、芽孢染色、产酸产气、柠檬酸利用、葡萄糖发酵、硝酸盐还原和V-P等生理生化特性均相同。二者生长速度相同,但菌落形态特征差异较大。SWL-17的菌落形态为淡黄色,圆形隆起,表面光滑湿润,边缘整齐,而SWL-19的菌落形态为乳白色不透明,表面扁平干燥,边缘不整齐。SWL-17产蛋白酶、脂肪酶、纤维素酶和淀粉酶的能力分别为（1.62±0.04）、（2.12±0.11）、（1.87±0.03）和（1.43±0.03）,SWL-19的产酶能力分别为（2.91±0.05）、（2.43±0.04）、（3.24±0.12）和（3.48±0.10）。因此SWL-19具有较高的产消化酶能力,且除脂肪酶外,其产蛋白酶、纤维素酶和淀粉酶的能力均显著性高于SWL-17（P＜0.05）。细菌16S rDNA序列比对和系统发育分析表明SWL-17和SWL-19分别为芽孢杆菌（Bacillus sp.）和枯草芽孢杆菌(B.subtilis),且SWL-19具有更清楚的遗传背景,适于进行后续试验。进一步DGGE试验结果表明,自然条件下家蚕肠道内的优势菌群为肠球菌属(Enterococcus)细菌,而外源性添加菌株SWL-19后能使家蚕肠道内的芽孢杆菌属和肠杆菌属细菌成为优势菌群,说明芽孢杆菌SWL-19能在家蚕肠道内定殖,并且能改变家蚕肠道内微生物菌群的结构和多样性。【结论】家蚕益生芽孢杆菌的筛选为研发蚕用复合微生态制剂提供菌株资源,在蚕业生产上具有重要的应用价值。     

Seeded breadfruit naturalized in the Caribbean is not a seeded variety of Artocarpus altilis

In the past, phenotypic resemblances between three species and natural hybrids belonging to the genus Artocarpus were a source of confusion between individuals belonging to these taxons. Now, results of amplified fragment length polymorphism analysis and morphological data concerning a great diversity of breadfruit are being published. We have considered historical data about the naturalization of breadfruit in the Caribbean, the number of seed per fruit in the seeded breadfruit cultivated in the Caribbean, and scientific knowledge about breadfruit published today. We have established that the seeded breadfruit grown in the Caribbean is in fact Artocarpus camansi Blanco (1837), recognized as a seeded wild ancestor of the domesticated breadfruit, and not a seeded variety of Artocarpus altilis [synonym Artocarpus incisa] as established by Duss (1897), still often referred to by modern authors.     

Identification and Characterization of Bacillus cereus SW7-1 in Bombyx mori (Lepidoptera: Bombycidae)

The bacterial diseases of silkworms cause significant reductions in sericulture and result in huge economic loss. This study aimed to identify and characterize a pathogen from diseased silkworm. SW7-1, a pathogenic bacterial strain, was isolated from the diseased silkworm. The strain was identified on the basis of its bacteriological properties and 16S rRNA gene sequence. The colony was round, slightly convex, opaque, dry, and milky on a nutrient agar medium, the colony also exhibited jagged edges. SW7-1 was Gram-positive, without parasporal crystal, and 0.8–1.2 by 2.6–3.4 µm in length, resembling long rods with rounded ends. The strain was positive to most of the physiological biochemical tests used in this study. The strain could utilize glucose, sucrose, and maltose. The results of its 16S rRNA gene sequence analysis revealed that SW7-1 shared the highest sequence identity (>99%) with Bacillus cereus strain 14. The bacterial strain was highly susceptible to gentamycin, streptomycin, erythromycin, norfloxacin, and ofloxacin and moderately susceptible to tetracycline and rifampicin. It exhibited resistance to other antibiotics. SW7-1 had hemolytic activity and could produce extracellular casease, lipase, and amylase. SW7-1 could reproduce septicemia-like symptoms with high mortality rate when re-fed to healthy silkworm. .The median lethal concentration (LC₅₀) was 5.45 × 10⁴ cfu/ml. Thus, SW7-1 was identified as B. cereus, which is a pathogen for silkworm and human infections are possible.     

蚕卵新型产附材料的筛选试验

目前，生产上使用的蚕卵产附材料大多是蚕种纸和散卵布。蚕种纸因用木材制造，要消耗大量树木不利于环境保护，而且制造工艺复杂，成本较高。且由于蚕种纸面积较小，增加了蚕种生产用工成本。散卵布虽然在一定程度上提高了制种功效，但是因为必须上浆且在蚕种保护时易发霉而对蚕种质量有一定影响。探索一种既不消耗木材有利于环境保护，又能提高制种功效和降低蚕种制造成本的化学材料，代替现行的蚕种纸和散卵布是摆在蚕种工作者面前的一项迫切任务。本试验为新型散卵布的筛选做了基础性的研究。