| 摘要: |
| 在威海泊于、崮山及荣成3家海带育苗场，采用回染实验方法对采集的海带藻体表面褐藻酸降解菌数量分布及特点进行了初步研究。结果表明，采自荣成的病烂海带幼苗上，其总异养细菌数量(1.22×108cfu/g)比威海两家育苗场的正常海带幼苗上总异养细菌数量(崮山：1.15×106cfu/g及泊于：1.1l×106cfu/g)高100多倍，其褐藻酸降解菌的数量(4.88×107cfu/g)比后两家(崮山：8.0×104cfu/g及泊于：4.3×105cfu/g)的高100—500倍。与正常海带幼苗相比。烂苗脱落后的总异养细菌数量较高(2.42×107 ：1.11×106 )，而褐藻酸降解菌的数量相对更高(1.50×107 ：4.3×105 )；其中，脱落烂苗上的褐藻酸降解菌数量约占其总异养细菌数量的61.98%。将分离、纯化的部分褐藻酸降解菌对海带孢子体组织块进行回染实验，能引起海带组织产生绿烂现象，证明褐藻酸降解菌是海带烂苗的条件致病菌。 |
| 关键词: 海带,藻体,褐藻酸降解菌,回染 |
| DOI： |
| 分类号: |
| 基金项目:国家重点基础研究发展规划项目，G1999012004号 |
附件 |
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| DISTRIBUTION AND REINFECTION OF ALGINIC ACID DECOMPOSING BACTERIA ON JUVENILE LAMINARIA JAPONICA |
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LIN Wei1, ZHANG Wei-Wei1,2, YAN Xiao-Jun1,3, DUAN De-Lin1
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1.Institute of Oceanology，Chinese Academy of Sciences;2.Graduate School，Chinese Academy of Sciences;3.Faculty of Life Sciences and Biotechnology，Ningbo University
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| Abstract: |
| Samples of juvenile sporophyte of Laminaria japonica were collected from breeding house near city of Rongcheng and Weihai, Shandong peninsula. Alginic acid decomposing bacteria were isolated from the seaweeds surface. Study on distribution and infection of the bacteria was then studied.
At 22℃, isolation and purification of the bacteria were performed. Verification and correlation analysis between the number of heterotrophic bacteria and the decayed juvenile sporophytes was carried out. Results showed that the total number of heterotrophic bacteria (1.22×108cfu/g) on infected juvenile sporophyte in seeding net was 100 times higher than that from normal cultivars: (1.11—1.15)×106cfu/g, and that the number of alginic acid decomposing bacteria (4.88×107cfu/g)was up to 100—500 times of that of the latter [(0.8—4.3)×105cfu/g]. Compared with normal Laminaria juvenile sporophyte, the total number of heterotrophic bacteria from infected and dead sporophyte was ten times higher, and the number of alginic acid decomposing bacteria was about 200 times higher. It is estimated that the alginic acid decomposing bacteria took about 61.98% of the total of heterotrophic bacteria.
Re-infection tests indicated that the alginic acid decomposing bacteria was insensitive to high temperature, even though the occurrence of decayed juvenile sporophytes was at 6℃. The optimal temperature for growth of the isolated alginic acid decomposing bacteria was about 20℃. It will be time consuming and laborious if on1v isolated at 6℃, and will hinder the normal growth of alginic acid decomposing bacteria.
Lab study on the heterotrophic bacteria behavior indicated that the decayed Laminaria tissues occurred at 15℃ but 6℃. Dense population of farming and complicated bacterial function could be the possible reasons.
Some alginic acid decomposing bacteria isolated form the healthy juvenile sporophyte showed a moderate ability for decomposing alginic acid sodium at 25℃ but exhibited a strong ability against the infection at 15℃. While those from the decayed juvenile sporophytes or strong decomposition of alginic acid sodium at 25℃ did not showed the strong ability for infected the algal tissue at 15℃, this may ascribed to the culture conditions under different temperatures and re-infected algal materials. Our re-infected tests proved that the alginic acid decomposing bacteria is opportunistic pathogen to the Laminaria sporophyte.
Close co-relation existed between the decay of Laminaria and the alginic acid decomposing bacteria, this indicated that the de-attached juvenile sporophyte will possibly resulted in the fluctuation of alginic acid decomposing bacteria. Therefore, it is necessary to remove the de-attached juvenile sporophyte immediately when it occurred in the breeding seawater system, otherwise, the breeding seawater contaminated with de-attached juvenile sporophyte would cause the huge increase of alginic acid decomposing bacteria, and eventually led to the decay or de-attachment of juvenile sporophyte. |
| Key words: Laminaria japonica, Sporophyte, Alginic acid decomposing bacteria, Re-infection |
