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Biosorption of Heavy Metals onto the Surface of Bacteriophage T4
閱讀：278 發(fā)布時(shí)間：2015-5-25| 提 供 商 | 美國布魯克海文儀器公司 | 資料大小 | 3.4MB |
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Biosorption of heavy metals by bacterial and eukaryotic cell surfaces and the
subsequent transport in aqueous environments is well recognized. However, very little is
known about the roles viruses play in biosorption. Viruses outnumber prokaryotes and
eukaryotes in environmental systems. These organisms represent abundant
nanoparticulate organic colloids with reactive surfaces. Here we conducted a series of
experiments to assess the biosorption potential of Escherichia coli bacteriophage T4.
Adsorption of a heavy metal, Zn2+, to the surface of phage T4 was tested in a series of
purified phage/metal solutions (0 μM – 1000 μM at 23°C). The Langmuir isotherm
reasonably describes the sorption data, with an R-square of 0.8116. The Langmuir
constant was determined to be 0.01265 which demonstrates that the adsorption of zinc
onto the surface of phage T4 does occur, but not at a rapid rate. Studies have shown that
the phage T4 capsid proteins possess negatively charged binding sites, which are the Cterminus
for Soc and the N-terminus for Hoc. These two sites were proven to be
biologically active and are able to bind certain proteins and antibodies. Thus, it is likely
that these sites adsorb cations. Zeta potential analysis demonstrated phage T4 (1010 VLPs
mL-1) not exposed to zinc at pH 7.0 to be approximay -11.48 ± 1.16 mV. These results
demonstrate the surface of phage T4 is naturally electronegative, which supports the
capability of the surface of phage T4 to adsorb metal cations. This was subsequently
demonstrated when the zeta potential shifted to -2.96 ± 1.60mV at pH 7.0 and exposure
of 1010 VLPs mL-1 to 150μM Zn2+, which suggests that adsorption of Zn2+ ions onto the
phage resulted in the neutralization of negative charges on the phage surface. The effects
of pH have been determined to have an effect on the adsorption of Zn2+ onto the surface
of phage T4. Zn2+ adsorption is at a minimum when exposed to acidic pH and the amount
of Zn2+ adsorbed increases with the rise of pH until a pH of 7.5, where precipitation of
zinc hydroxide begins to occur and interferes with the adsorption process. Phage decay
can alter the available surface area for metal adsorption. Interestingly, the presence of
150 μM Zn2+ significantly increased infectivity relative to unamended controls (ANOVA
p<0.05), which indicates that Zn2+ enhances phage T4 infectivity. Together, the results
suggest that the sorption of metals to the surface of viruses could not only contribute to
nanoparticulate metal transport but also enhance infectivity that contributes to cell lysis in
environmental systems.