The effect of antibiotics on the bacterial community composition and the related biogeochemical cycle

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K22904
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 63:Environmental analyses and evaluation and related fields
• Research Institution: University of Tsukuba
• Principal Investigator: HAMA Takeo 筑波大学, 生命環境系, 名誉教授 (30156385)
• Co-Investigator(Kenkyū-buntansha): 大森 裕子 筑波大学, 生命環境系, 助教 (80613497)
• Project Period (FY): 2019-06-28 – 2021-03-31
• Keywords: 抗生物質 / 細菌群集 / 物質循環

Outline of Final Research Achievements

The effect of the antibiotics on the community composition of coastal bacteria and the related biogeochemical cycle was assessed by the culture experiments spiked by two antibiotics; erythromycin and oxytetracycline. The diversity of bacteria community showed the drastic decrease under high concentration of antibiotics; higher than 20 mg/L for erythromycin and 200 mg/L for oxytetracycline. Most of bacteria which showed the decrease under high antibiotics concentration belonged to Alphaproteobacteria, whereas Gammaproteobacteria exhibited the compositional increase.
Epifluorescence microscopy observation clearly showed that bacteria surviving under the high concentration was mainly composed by the particulate attached bacteria living in the aggregates. A little free living bacteria under the high concentration of antibiotics strongly suggests that the sensitivity against the antibiotics largely depends on the difference in their life-style.

Free Research Field

生物地球化学

Academic Significance and Societal Importance of the Research Achievements

抗生物質は人への使用に加えて、畜産動物や水産魚類にも使用されており、我が国の動物への使用量は、人への使用量の2倍に相当する。魚類の養殖においては、飼料に抗生物質を混ぜて与えており、海水中の抗生物質濃度を増加させる要因となる。
本研究は、水中の抗生物質濃度が増加は、細菌数を減少させ、さらに細菌群集の多様性を減少をもたらす可能性をもつことを明らかにした。抗生物質の環境中への排出に関しては、現在のところ法的規制は行われていない。抗生物質の「意図しない」効果を防止するため、環境中における抗生物質の挙動と生態系への影響に関する研究の強化の必要性が、強く示唆された。