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91.
Jing Tu Fengying Lu Shuang Miao Xintao Ni Pan Jiang Hui Yu Linlin Xing Shengqing Yu Chan Ding Qinghai Hu 《Veterinary microbiology》2014,168(2-4):395-402
Riemerella anatipestifer causes epizootic infectious disease in poultry and serious economic losses especially to the duck industry. However, little is known regarding the molecular basis of its pathogenesis. The ability to acquire iron under low-iron conditions is related to the virulence of a variety of bacterial pathogens. In this study, a sip (Riean_1281) deletion mutant CH3Δsip was constructed and characterized for iron-limited growth, biofilm formation, and pathogenicity to ducklings. Results showed that siderophore-interacting protein (SIP) was involved in iron utilization and the sip deletion significantly reduced biofilm formation and adherence to and invasion of Vero cells. In addition, the sip gene was absent in 1 of 24 (4.17%) virulent strains and 2 of 3 (66.7%) avirulent strains of R. anatipestifer, and the sip gene from six R. anatipestifer strains, which belong to serotypes 1, 2, and 10, respectively, shared 100% amino acid identities to those of R. anatipestifer strains DSM15868 and RA-GD. These results suggested that siderophore-mediated iron acquisition may be an important iron-uptake pathway in R. anatipestifer. Animal experiments indicated that the median lethal dose of the CH3Δsip mutant in ducklings was about 35-fold higher than that of the wild-type CH3 strain. Thus, our results demonstrated that R. anatipestifer SIP was involved in iron acquisition and necessary for its optimal virulence. 相似文献
92.
93.
舟山渔场银鲳和灰鲳繁殖特性的比较 总被引:16,自引:3,他引:16
用常规的生物学调查方法对舟山渔场银鲳和灰鲳进行了周年的取样调查分析,并对其性腺做石蜡切片,观察性腺发育情况,对银鲳和灰鲳的繁殖特性进行比较研究。结果表明:银鲳和灰鲳在繁殖季节性比为1∶1;两者的性腺发育和卵母细胞发育没有显著差异(P>0.05),Ⅴ时相的卵母细胞卵径都为700~870 μm,油球1个,油球径260~400 μm,初级卵膜厚度12~19 μm;都为一个繁殖期内多次产卵类型的鱼类;繁殖期内银鲳、灰鲳雌性生殖群体的平均叉长分别为22.5 cm、29.0 cm,银鲳雄性生殖群体叉长主要集中在14.0~17.0 cm,灰鲳雄性生殖群体叉长为23.0~25.5 cm;银鲳的繁殖季节在每年的4月初至6月初,繁殖高峰在4月中旬到5月中旬,银鲳卵巢成熟系数最高可达25%;而灰鲳的繁殖期在每年的6月初至8月中旬,繁殖高峰在6月下旬到7月下旬,灰鲳的卵巢成熟系数最高只有12.6%。银鲳繁殖期的水温为18~24 ℃,灰鲳为24~28 ℃;其他环境条件差异不大。另外还对银鲳和灰鲳卵母细胞发育的特征、繁殖期内卵巢成熟系数的变动以及繁殖期内环境因子的变动对产卵群体的数量影响进行了讨论。 相似文献
94.
95.
ABSTRACT: The effect of pH on thermal gelation and transglutaminase (TGase; EC2.3.2.13)-induced suwari (setting) of surimi and actomyosin pastes was investigated. A strong and elastic gel was produced from walleye pollack surimi paste at pH 7.0 in the presence of Ca2+ using a two-step heating method. In contrast, walleye pollack actomyosin paste formed a weak gel under the same conditions as a result of the low concentration of endogenous TGase. In the presence of EGTA [ethyleneglycol bis(2-aminoethylether) tetraacetic acid], weak gels were formed at pH values of 7.0 and 6.0. Non-proteolytic modori (gel weakening) occurred extensively in the course of actomyosin gelation, but not in surimi gelation. Maximum TGase-induced myosin heavy chain cross-linking was observed at a slightly higher pH of 7.5 than at the optimal pH of endogenous TGase activity; the difference being derived from different substrates. Gelation of carp actomyosin paste at pH values of 5.5, 6.0, 6.5 and 7.0 was monitored by measuring storage modulus (G') and loss modulus (G"). A weak gel was formed at all pH values, but a slightly rigid and less elastic gel was obtained at lower pH values. The addition of microbial TGase (MTGase) formed strong elastic gels at pH 7.0 and 6.5. MTGase cross-linked myosin heavy chains even at pH 5.5, but contributed neither to suwari response nor strong gel formation. Overall, results suggest that the optimal pH for the gelation of surimi paste from easy-setting fish species is a compromise between the pH-optima of TGase activity and of preferable actomyosin conformation for myosin cross-linking. 相似文献
96.
通过对围网渔船起网过程中所受外力的实测和分析,表明在绞收括纲阶段临近结束时,即底环集中串挂在船舷括纲吊柱处时的外力,最大可达7,140公斤。起网时外力对船作用最终表现为外力矩,其数值与网具的纲索或网衣相对于船的出水点位置以及各种捕捞、起吊设备的安装位置有关,也即与力的作用线方向和作用点有关。作者认为在围网渔船稳性核核中,仅校核起吊底环和绞收网衣时的倾侧力矩是不够的,应选取整个起网过程中最大起网力矩(绞纲阶段末尾的倾侧力矩)用于渔船稳性校核和摇摆计算。 相似文献
97.
饲料中添加激素类等药剂促进僵鳗生长及复壮的研究 总被引:2,自引:0,他引:2
在工厂化、高密度、全人工控制的养鳗条件下,使用雌二醇、牛肝糜维生素、甲基睾丸素、强的松等药剂,可以显著地促进僵鳗的生长和复壮,在生产中可以取得较好的经济效益。同时,本试验对于露天止水式和水库网箱养鳗也有普遍的意义。 相似文献
98.
采用灰色系统理论与国际先进的人工神经网络模拟相结合的先进技术,进行了太湖、濑湖和金鸡湖的渔业资源开发的系统动力学模型研究。认为控制捕涝强度是调空太湖针银鱼,梅鲚,白虾3个主要经济种群的关键因素,专家鉴定认为,本研究填补国内空白,居国内领先水平。 相似文献
99.
100.
Ni Lar Shein M. Takushima M. Nagae H. Chuda K. Soyano 《Fish physiology and biochemistry》2003,28(1-4):107-108
The cDNA for glycoprotein hormone (GPH) α-subunit, β-subunits of the FSH (GtH I) and LH (GtH II) were isolated, cloned, and sequenced from sevenband grouper pituitary using RACE PCR. These results show that sevenband grouper has two different types of gonadotropins FSH (GtH I) and LH (GtH II), as other teleosts. 相似文献