title: Influence of tetracycline exposure on the growth of wheat seedlings and the rhizosphere microbial community structure in hydroponic culture.
abstract: In this study, the effects of tetracycline exposure on wheat growth and the microbial community structure in the rhizosphere were investigated under hydroponic culture conditions. Exposure to various concentrations of tetracycline resulted in significant suppression of the growth of wheat roots and shoots, with minimum doses of 0.8 mg L(-1) and 4 mg L(-1) resulting in inhibition rates of 32% and 15.4%, respectively. Complete inhibition of the growth of these two parts of wheat plants was observed in response to treatment with tetracycline at 20 mg L(-1) and 100 mg L(-1), respectively. However, the germination of wheat seeds was not sensitive to exposure to tetracycline. The effects of tetracycline exposure on the microbial community in the wheat rhizosphere were evaluated through traditional cultivation and molecular biological analyses. The cultivation results indicated that bacteria were the dominant population, being present in concentrations of 1x 10(8)-2.45x 10(9)CFUs mL(-1), although 39% to 87% inhibition occurred in response to tetracycline. The concentration of fungi increased in all tetracycline treated samples to 2.5 to 15.8 times that of the control. The highest concentration of fungi (4.27x 10(8) CFU mL(-1)) was observed in response to 60 mg L(-1) tetracycline after 15 days of cultivation. In this stage, a large amount of fungal colonies was observed on the surface of the culture solution, the wheat roots became rotted and the plants became atrophic or even died. Molecular biological analysis indicated that the bacterial community structure was significantly different in samples that were exposed to high levels of tetracycline (over 20 mg L(-1)) than in samples that were exposed to lower concentrations. As the concentration of tetracycline increased, the diversity of the bacteria decreased. Additionally, several dominant sensitive species such as Sphingobacterium multivorum were suppressed by tetracycline, while some resistant species such as Acinetobacter sp. appeared or were conserved. The bacteria population tended to stabilize when the drug concentration exceeded 40 mg L(-1).
authors.affiliation: College of Life Sciences, Henan Normal University, Xinxiang, China.
authors.forename: Qingxiang
authors.initials: Q
authors.lastname: Yang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Wenyu
authors.initials: W
authors.lastname: Zhang
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Xie
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000900:Anti-Bacterial Agents / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D017753:Ecosystem; D004591:Electrophoresis, Polyacrylamide Gel; D018527:Hydroponics; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology; D012988:Soil Microbiology; D013752:Tetracycline / Q000633:toxicity*; D014908:Triticum / Q000254:growth & development* / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D013752:Tetracycline