| Project/Area Number |
16380131
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Kyoto University |
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Principal Investigator |
IMAI Ichiro Kyoto University, Graduate School of Agriculture, Associate Professor (80271013)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAHARA Hiroyuki Kyoto University, Graduate School of Agriculture, Professor (80026567)
YOSHINAGA IKuo Kyoto University, Graduate School of Agriculture, Assistant Professor (40230776)
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| Project Period (FY) |
2004 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥16,010,000 (Direct Cost: ¥15,200,000、Indirect Cost: ¥810,000)
Fiscal Year 2007: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
Fiscal Year 2006: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2005: ¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2004: ¥6,200,000 (Direct Cost: ¥6,200,000)
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| Keywords | red tides / algicidal bacteria / control / seaweed bed / Zostera bed / detrital particle / development of seaweed bed / Seto Inland Sea / 浮遊細菌 / 殺藻レンジ / 播磨灘 / 特異性 / デトライタス / 16S rDNA / α-プロテオバクテリア / γ-プロテオバクテリア / 褐藻細菌 |
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| Research Abstract |
Algicidal bacteria, that kill microalgae, play an important role in terminating red tides in the coastal sea, and are hoped to apply for the control of red tide occurrences in near future. We found the existence of huge number of algicidal bacteria attaching to the surface of seaweeds (max. several millions /g wet tissue) for the first time in the coast of the Seto Inland Sea, and showed a possibility as the important source for algicidal bacteria in coastal ecosystem.
Many algicidal bacteria were isolated from the seawater and seaweeds in the seaweed bed of the bank of the Kansai International Airport. Algicidal bacteria were mainly composed of Bacteroides group and γ-proteobacteria, and α-proteobacteria (first record) as minor group. Main genera were Cytophaga, Alteromonas and Pseudoalteromonas.
In Harima-Nada, main red tide area of the Seto Inland Sea, algicidal bacteria were isolated from the seawater samples of the fractions of "free-living" and "particle-associated" (>3μm) in the summer season. Frequency of algicidal bacteria was much higher in "particle-associated" fraction than "free-living" (5 times). Algicidal bacteria tend to live on the detrital particles.
Bacteria were isolated from the surface of Zostera and from seawater in a Zostera bed in Osaka Bay. The densities of algicidal bacteria were found to be 1 × 10^7〜 9 × 10^7 per g wet leaf on the surface of seagrass, which were about one order of higher than the case of seaweeds (first discovery). In seawater of the Zostera bed, algicidal bacteria were in the order of 10^3〜 10^4 cells per ml. Cell densities of phytoplankton were extremely few in seawater in the Zostera bed. It is considered that algicidal bacteria in Zostera beds vigorously kill microalgae and these bacteria would play an important role in prevention of red tide occurrence.
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