Effect of Zinc Oxide Nanocrystals in Media Containing E. coli and C. xerosis Bacteria

Abstract

The present investigation is centered on the study of the growth curves of E. coli and C. xerosis bacteria in the presence of nanosize particles of Zinc Oxide. Previous works demonstrated the sensitivity of the bacteria, when these were reproduced in media that contain nanoparticles of luminescent silicon and Cobalt Ferrite. Doped ZnO nanocrystals were synthesized by conventional precipitation in ethanol solutions as reported by Spanhel and Anderson for bare ZnO. In our case, the syntheses were carried out under room-temperature conditions.The experimental results of E. coli bacteria in contact with a stable suspension of nanoparticles of Zinc Oxide, shows a growth curve without adaptation period. Moreover a short and slowly logarithmic stage has been observed, reaching the stationary stage after approximately four hours compared with one in absence of the nanoparticles (standard curve). During the observations, a change in the lifetime of the bacteria (metabolism) with particulate was noticed,as well as the beginning of the mortality stage. However, different results were recorded for silicon and ferrite. For the case of the bacteria C. xerosis, the curve with particles is above its standard curve, for all times with none of the oscillations which occured in the nanometer silicon. For these bacteria the beginning of the mortality stage is observed when they have particles. For both bacteria with Zinc Oxide nanoparticles this occurs approximately after nine hours.

Current understandings of toxicity, risks and regulations of engineered nanoparticles with respect to environmental microorganisms

“…It has also been reported that electrons generated by nanoparticles may enhance enzymatic function of external membrane proteins, may speed up electron transport chain function, and facilitate cell metabolism. Some of the studies have also shown no noticeable influence of nanoparticles on bacteria [25,58].…”

Effect of Fe nanoparticle on growth and glycolipid biosurfactant production under solid state culture by marine Nocardiopsissp. MSA13A

“…Nanoparticles (NPs) have been hypothesized to be influence microbial production, growth and survival. Previous reports evidenced the effect of different NPs on the growth and secondary metabolite production in various microorganisms [ 8 , 9 ]. But reports revealed that NPs like Ag, Au and oxides of Al, Ti, Si and Zn have detrimental effect on the cells of microorganisms [ 10 ].…”