Comparative Study of Sargassum fusiforme Polysaccharides in Regulating Cecal and Fecal Microbiota of High-Fat Diet-Fed Mice

Seaweed polysaccharides represent a kind of novel gut microbiota regulator. The advantages and disadvantages of using cecal and fecal microbiota to represent gut microbiota have been discussed, but the regulatory effects of seaweed polysaccharides on cecal and fecal microbiota, which would benefit the study of seaweed polysaccharide-based gut microbiota regulator, have not been compared. Here, the effects of two Sargassum fusiforme polysaccharides prepared by water extraction (SfW) and acid extraction (SfA) on the cecal and fecal microbiota of high-fat diet (HFD) fed mice were investigated by 16S rRNA gene sequencing. The results indicated that 16 weeks of HFD dramatically impaired the homeostasis of both the cecal and fecal microbiota, including the dominant phyla Bacteroidetes and Actinobacteria, and genera Coriobacteriaceae, S24-7, and Ruminococcus, but did not affect the relative abundance of Firmicutes, Clostridiales, Oscillospira, and Ruminococcaceae in cecal microbiota and the Simpson’s index of fecal microbiota. Co-treatments with SfW and SfA exacerbated body weight gain and partially reversed HFD-induced alterations of Clostridiales and Ruminococcaceae. Moreover, the administration of SfW and SfA also altered the abundance of genes encoding monosaccharide-transporting ATPase, α-galactosidase, β-fructofuranosidase, and β-glucosidase with the latter showing more significant potency. Our findings revealed the difference of cecal and fecal microbiota in HFD-fed mice and demonstrated that SfW and SfA could more significantly regulate the cecal microbiota and lay important foundations for the study of seaweed polysaccharide-based gut microbiota regulators.     

匍枝马尾藻有性繁殖和人工育苗的初步研究

为研究匍枝马尾藻有性繁育过程的特点和人工育苗的可行性,通过野外观察和室内培养观察的方法,对匍枝马尾藻雌雄生殖托特点、受精卵分化等有性繁育过程、以及假根的形成、幼苗发育进行了研究,此外还对匍枝马尾藻的人工育苗进行了初步探索。试验结果表明,匍枝马尾藻的繁殖季节集中在每年的5—6月份;水温达到28℃时,生殖托出现排精排卵现象;从受精卵发育到形成具有假根的幼苗约需要48h;幼苗发育缓慢,35d后出现原生叶。人工育苗结果显示,幼苗栽培35d,幼苗株高为2.5~3mm,密度为6~10株/cm2;海区栽培60d后,匍枝马尾藻幼苗株高可达到7cm,幼苗密度为2株/cm2。本试验结果为匍枝马尾藻的人工规模环境育苗提供了技术指导。     

铜藻的受精卵发生与幼孢子体发育

通过室内培养, 观察了铜藻受精卵的发生与幼孢子体发育, 研究了幼孢子体的适宜培养条件, 为全人工育苗奠定理论基础。结果表明, 铜藻雌性生殖托的基部和中部首先集中排卵, 卵子粘附于生殖托表面完成受精和早期发生。刚释放的卵子具有8个核, 受精后, 8个核迅速融合成1个大核, 开始细胞分裂。前二次的细胞分裂均为横裂, 在萌发体的一端产生一个很小的“假根原细胞”, 后者最终发育成假根, 萌发体的其它细胞发育成苗体。受精后约48 h, 受精卵发育成具有假根芽的幼孢子体, 开始脱落附着; 培养15 d, 发育成具有2个叶片、体长超过3 mm的幼孢子体。在幼苗的早期培育阶段, 较高的温度和长光照时有利于幼苗的生长和叶片增加, 适宜培养条件为温度21~24 ℃, 光密度40 μmol photons/(m2?s), 光周期14 L∶10 D。     

马尾藻种群生活史性状时空变化的研究进展

马尾藻属(Sargassum),属褐藻门、无孢子纲、墨角藻目、马尾藻科,由瑞典藻类学家Agardh建立。目前,全世界已报道的马尾藻有400余种,广泛地分布于世界范围内的热带和温带地区,在我国据记载有100余种。马尾藻种类是潮间带和潮下带海藻区系的重要组成部分[2-3],作为主要支     

花生秧部分替代马尾藻对仿刺参生长、消化的影响

利用花生秧粉替代配合饲料中的马尾藻粉,研究不同比例花生秧替代马尾藻的配合饲料对仿刺参幼参的生长和消化的影响。试验设6组,替代比例分别为0％（对照组）、8％、16％、24％、32％和40％,每组3个重复,试验进行60 d。试验结果表明,各组仿刺参存活率均超过95％,且组间差异不显著（P ＞0．05）;24％替代组仿刺参特定生长率最大（0．58％／d）,高于对照组28．9％,8％替代组和16％替代组生长稍慢于对照组,但差异不显著（ P ＞0．05）,而32％替代组和40％替代组仿刺参生长明显慢于对照组（P ＜0．05）;各替代组水体化学需氧量、氨氮和亚硝酸盐氮含量与对照组差异不显著（P ＞0．05）;各替代组幼参对饲料消化率随替代比例变大而降低;试验前30 d肠道内蛋白酶和淀粉酶活性均高于后30 d ,淀粉酶活性对照组表现最大,并有随花生秧粉替代比例变大含量下降的趋势;5个替代组仿刺参体腔超氧化物歧化酶和碱性磷酸酶活力与对照组差异不显著（P ＞0．05）。     

Potential of Cellulase From Bacillus megaterium for Hydrolysis of Sargassum

Bacterial cellulase can be a promising biotechnological approach in seaweed degradation to facilitate extraction of bioactive molecules. In the present study, bacterial cultures were isolated from marine and terrestrial samples and screened for cellulase production. The selected cultures were grouped by random amplification of polymorphic DNA (RAPD) profiling, and the cultures showing a distinct banding pattern were identified by 16S rDNA sequence analysis. Cellulase from Bacillus megaterium (CB-sw1-I), a native isolate, was purified by ion-exchange chromatography with a purification fold of 6.91 and specific activity of 1.66 U. The purified enzyme with molecular weight of 43 kDa was optimally active at pH 6.0 and temperature of 60°C. The potentiality of enzyme in degradation of Sargassum thallus was evident with an increase in reducing sugar. Morphology of the thallus after 10 days digestion observed by scanning electron microscope also provided additional evidence for degrading ability of the enzyme. This enzyme could subsequently be used in hydrolysis of seaweed for extraction of bioactive molecules.     

海水环境中Hg~(2+)、Cd~(2+)、Pb~(2+)对张氏马尾藻幼孢子体的生物毒性研究

研究了含不同浓度汞离子(Hg~(2+))、镉离子(Cd~(2+))、铅离子(Pb~(2+))的自然海水对张氏马尾藻(Sargassum zhangii Tseng et Lu)幼孢子体的生物毒性。单因子实验结果表明,当海水中Hg~(2+)、Cd~(2+)、Pb~(2+)的浓度范围分别为0.04~1μmol·L-1、0.04~25μmol·L-1和0.04~25μmol·L-1时,Hg~(2+)、Cd~(2+)、Pb~(2+)对幼孢子体的生物毒性均随离子浓度的升高而显著增强,且随胁迫时间延长而累积;3种重金属离子对幼孢子体的生物毒性大小顺序为Hg~(2+)Cd~(2+)Pb~(2+)。正交实验结果表明,当Hg~(2+)、Cd~(2+)、Pb~(2+)分别以浓度0.08μmol·L-1、2.8μmol·L-1、3μmol·L-1共存时,对幼孢子体的毒性最强;当Hg~(2+)、Cd~(2+)、Pb~(2+)同时处于低浓度水平时,Pb~(2+)对幼孢子体的生长产生主导抑制效应,Cd~(2+)其次;相反,当各重金属离子同时处于高浓度水平时,Hg~(2+)对幼孢子体的生长产生主导抑制效应,Cd~(2+)其次;当Hg~(2+)、Cd~(2+)、Pb~(2+)联合作用时,Hg~(2+)、Cd~(2+)呈现协同效应,Hg~(2+)、Cd~(2+)对Pb~(2+)产生拮抗效应。建议在张氏马尾藻育苗过程中将海水中的Hg~(2+)、Cd~(2+)、Pb~(2+)浓度严格控制在0.04μmol·L-1以下,尤其要避免3种重金属离子的联合毒害。     

铜藻膳食纤维的提取及其理化特性研究

铜藻经复合酶解、化学处理、脱色、过滤等工艺流程,提取水溶性和水不溶性膳食纤维,研究蛋白酶种类、蛋白酶用量、复合酶比、料液比等因素对产率的影响,确立最佳工艺条件,并分析了提取的水不溶性膳食纤维的理化特性。结果表明,铜藻膳食纤维最佳提取条件为：蛋白酶加酶量2%,中性蛋白酶与纤维素酶比例30∶1,料液比1∶20（g/mL）,提取温度50 ℃,酶解时间2 h;最佳脱色条件为：料液比1∶20（g/mL）,过氧化氢浓度6%,脱色温度80 ℃,脱色时间1 h。水不溶性膳食纤维产率为32.14%,呈浅绿色;水溶性膳食纤维产率为2.26%,呈淡黄色。按照上述条件制备的水不溶性膳食纤维的膨胀力为(14.99±0.23) mL/g,持水力为1 255.50%±0.15%,吸附不饱和脂肪量为170.84%±0.18%,吸附饱和脂肪量为238.87%±0.37%。研究表明,铜藻的水不溶性膳食纤维具有较好的水合能力、吸附油脂等功能特性,可以作为原料开发多元化产品。     

岩相潮间带大型底栖生物多样性对铜藻藻场的响应

2011年4月至2012年1月间,在南麂列岛火焜岙铜藻藻场和藻场外沿岸潮间带各设1条断面,对大型底栖生物的种类和数量组成、物种多样性和群落结构特点进行调查。共鉴定出底栖生物108种,其中,底栖动物93种,底栖藻类15种;藻场与藻场外沿岸高潮区和中潮区的软体动物、节肢动物、环节动物、其他动物和藻类的年均生物量和丰度均无显著差异;低潮区藻场沿岸藻类生物量大于藻场外沿岸,其他类群的年均生物量和丰度无显著差异。每个季节各潮区除春季低潮区藻场沿岸的藻类生物量大于藻场外沿岸外,其他均无显著差异。藻场沿岸潮间带的优势种为条纹隔贻贝,藻场外沿岸为条纹隔贻贝和棘刺牡蛎。藻场沿岸和藻场外沿岸潮间带大型底栖生物的Shannon-Wiener指数(H'),Pielou均匀度指数(J)和Margalef丰富度指数(d)无显著差异(P0.05)。非度量多维标度(MDS)和聚类分析表明,群落结构主要与季节有关,但在铜藻藻场生长旺盛期与藻场有关,说明铜藻生长旺盛期对其群落结构有一定的影响。