The Mechanism of Al_2O_3 Nanoparticle Influence on RP4-mediated Conjugation:a Preliminary Research in Bacterium Morphology / 环境与健康杂志

ABSTRACT

Objective To explore the influence of Al2O3 nanoparticle (20nm in average) on RP4-mediated conjugation and its mechanism was explored further. Methods Mating was conducted between E.coli HB101(RP4) and Salmonella aberdeen Kauffmann 50312(strR) in saline at 25 ℃ without stirring for 8 h,the concentrations of Al2O3 nanoparticle were 0.005,0.05,0.5,5,50 mmol/L respectively. The initial concentration of donor and recipient were both about 109 cfu/ml(donor per recipient ratio was 1∶3).Later transmission electron microscope(TEM) and laser scan confocal microscope (LSCM) were exploited to investigate cell morphology and structure. Results 5 mmol/L and 50 mmol/L Al2O3 nanoparticle could increase the conjugal transfer frequency by 150-fold and 40-fold respectively. TEM observation on thin section indicated several bacterial were prone to form conjugational junction together in 5 mmol/L and 50 mmol/L Al2O3 nanoparticle treated group,which was rarely seen in control group. Meanwhile the cell envelope of bacterial was significantly damaged upon the treatment by 50 mmol/L Al2O3,which might be the reason why transfer frequency of 50 mmol/L Al2O3 group was less than 5 mmol/L Al2O3 group. LSCM result indicated that Al2O3 nanoparticle might damage cell envelope and the damage was positively related to the accumulation of Al2O3 in bacterial. Conclusion Al2O3 nanoparticle can stimulate RP4 conjugal transfer. Conjugative gene is highly regulated. Al2O3 nanoparticle might modulate conjugative gene expression directly or influence cell membrane permeability and thus modulate the process of conjugation indirectly .