摘要
定量分析了粪肠球菌(Enterococcus faecalis)在虾夷扇贝(Pactinopecten yessoensis)中的累积及其组织分布,以及扇贝血淋巴中2种免疫相关酶的活性变化。采用接触染毒法,将扇贝浸泡于含105个细菌细胞/mL的海水中处理2周,采用平板计数法测定了在不同暴露时间和不同扇贝组织中细菌累积数量的变化,并抽取扇贝血淋巴测定了超氧化物歧化酶(SOD)和酸性磷酸酶(ACP)活性。发现处理第7天时,扇贝中含菌量达到最高,为5.20 lg(CFU/g),第14天时又降低到与第3天相当的水平。而累积速率(RA)在第1天时最高,此后均逐渐降低。结果表明,随着在细菌中暴露时间的延长,扇贝累积的细菌数量增长明显减缓。消化道以及外套膜和鳃中细菌含量最高,比软组织平均值高1个数量级以上;而在血淋巴中含量极低,比软组织平均值低2个数量级以上。血淋巴中SOD和ACP酶活性均有先升高后降低的趋势,第7天时2种酶活性均达到最大。实验期间,扇贝血淋巴中免疫酶活性与体内累积的细菌数量变化趋势一致。血清中的可溶性免疫因子对细菌侵染更敏感,2种酶活性与扇贝组织中累积的细菌数量具有明显相关性,但在血细胞中则不明显,由此推测血清可能是扇贝杀灭和消化入侵细菌的首要场所。
Enterococcus faecalis is a common bacterium found in aquatic environment and intestines of warm-blooded animals and human.In summer,it can reach high level in sewage-polluted seawater and be accumulated by scallops.Large numbers of bacteria may constitute significant health risk to cultured animals at high temperature or in other specific conditions.However,the retention of E.faecalis in scallop remains unclear,and information about hosts＇ growth performance,innate immunity and disease outbreak after a long-term exposure to non-pathogenic fecal bacteria is limited.The present study aims to investigate the relationship between retention of an opportunistic bacterium and variation in immune enzyme activity in the scallop,Pactinopecten yessoensis.The findings of this study will be useful for developing aquaculture probiotics and will provide scientific basis for sustainable aquaculture of bivalves. By bath exposure,the accumulation and distribution of E.faecalis in scallop tissues were analyzed,and the variation in activities of two immunity-related enzymes in haemolymph were also detected.After exposure to seawater inoculum of 5 lg（CFU/mL） E.faecalis for two weeks,the uptake of bacteria at day 1,3,5,7 and 14 and their distribution in scallop tissues were detected by plate counting method respectively.The activity of acid phosphatase（ACP） and superoxide dismutase（SOD） were also determined both in haemocytes and in serum of P.yessoensis.The uptake results showed that at 7 d top level of E.faecalis[5.20 lg（CFU/g）]were tested in scallop tissues,but at 14 d it decreased to the level of 3 d after treatment.However,the rate of bacterial accumulation（RA） was the highest at 1 d,and then significantly decreased（P〈0.05）.It indicated that the bacterial accumulation rate in scallops decreased with exposure time.The top level of E.faecalis,over ten times higher than the average density of total tissues,was observed in digestive tract,mantle lobes and gills,but the lowest was detected in haemolymph,over 100 times lower than the average.SOD and ACP activities in cell-free haemolymph significantly increased to the maximum at 7 d,and then decreased.It can be deduced that there was a positive correlation between enzyme activities in serum and the bacterial accumulation in scallop（P〈0.05）.Soluble factors in serum were more sensitive to bacterial accumulation than those in haemocytes,therefore,the serum may be a chief part of innate immune system of bivalves to digest and kill invading bacteria.Bivalves have an open circulatory and innate immune system.Haemocytes and soluble factors operate in a coordinated way to provide protection from invading microorganisms,and different types of haemocytes play various roles in innate immunity.Understanding the immune response in bivalves to invasive infections at cellular and molecular levels offers a theoretical base for exploring molluscan probiotics.Further study on variations in activities and gene expression in haemocytes and the roles of different scallop tissues in immune system is required.
出处
《中国水产科学》
CAS
CSCD
北大核心
2011年第1期89-95,共7页
Journal of Fishery Sciences of China
基金
国家973计划项目(2006CB400608)
农业部农业公益性行业科研专项(nyhyzx07-047)
关键词
粪肠球菌
虾夷扇贝
累积
组织分布
超氧化物歧化酶
酸性磷酸酶
Enterococcus faecalis
Pactinopecten yessoensis
accumulation
distribution
superoxide dismutase
acid phosphatase
