| According to this study or thesis,a strain of salt-tolerant bacterium was isolated from offshore sediment.It’s physiological and biochemical characteristics,growth and degradation conditions along with salt-tolerant metabolic pathways were studied.In addition,the effect of application of microbial fuel cells inoculated with this strain was tested.The main conclusions are as follows:(1)The salt-tolerant bacterium isolated from the marine sediment was named KB-3.16S rDNA showed that the KB-3 had 99%sequence similarity to Staphylococcus epidermidis,therefore,belonging to this genus.Physiological and biochemical analysis showed the great environmental adapibility of KB-3,which was able to utilize six kinds of 22 carbon sources and tolerate a variety of growth inhibitors.(2)KB-3 have strong salt tolerance and drug resistance.The growth conditions of KB-3 were analyzed and the results showed that KB-3 could grow at a pH range of 5-8,a temperature range of 20-42 ℃and a concentration range of NaCl from 0-150 g/L.As the optimum growth conditions KB-3 showed a salinity level of 0 g/L NaCl,pH level of 6.0 and temperature level of 37 ℃.(3)KB-3 has a variety of mechanisms to adapt to high salt environment.On the one hand,KB-3 can selectively release sodium ions from cell membrane and adsorb appropriate amount of potassium ions into the cells from the environment through ion channels.On the other hand,strain KB-3 is capable of secreting compatible substances such as pyrimidine and lysine to balance the internal and external osmotic pressure.KB-3 contains mnhA and other salt-tolerant genes.(4)KB-3 has a good ability to withstand and degrade antibiotics.Strain susceptibility results showed that KB-3 was resistant to antibiotics such as tetracycline and chloramphenicol.It can tolerate tetracycline up to a level of 16 ppm.The maximum degradation of tetracycline in 24 h reached up to 6 ppm.Therefore,KB-3 contains Par,Nor and other resistance genes.(5)MFCs inoculated with KB-3 have demonstrated ideal power generation under the condition of high salt antibiotic wastewater treatment.At a concentration range of NaCl from 0-50 g/L,KB-3 presented superior biological activity with a MFC current density up to 1 A/m2;However,the current density dropped to 0.5 A/m2 at NaCl concentration of 75 g/L.When treating with a range of tetracycline concentration from 0-8 ppm,MFCs power generation efficiency could maintained at 1 A/m2 until tetracycline reached to a level of 16 ppm where current density dropped to 0.5 A/m2. |
