Reversible Binding of Metal Ions onto Bacterial Layers Revealed by Protonation-Induced ATR-FTIR Difference Spectroscopy

Abstract

The ability of microorganisms to adhere to abiotic surfaces and the potentialities of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy have been exploited to study protonation and heavy metal binding events onto bacterial surfaces. This work represents the first attempt to apply on bacteria the recently developed method known as perfusion-induced ATR-FTIR difference spectroscopy. Such a technique allows measurement of even slight changes in the infrared spectrum of the sample, deposited as a thin layer on an ATR crystal, while an aqueous solution is perfused over its surface. Solutions at different pH have been used for inducing protonation/deprotonation of functional groups lying on the surface of Rhodobacter sphaeroides cells, chosen as a model system. The interaction of Ni(2+) with surface protonable groups of this microorganism has been investigated with a double-difference approach exploiting competition between nickel cations and protons. Protonation-induced difference spectra of simple model compounds have been acquired to guide band assignment in bacterial spectra, thus allowing identification of major components involved in proton uptake and metal binding. The data collected reveal that carboxylate moieties on the bacterial surface of R. sphaeroides play a role in extracellular biosorption of Ni(2+), establishing with this ion relatively weak coordinative bonds.

Cu-resistant Kocuria sp. CRB15: a potential PGPR isolated from the dry tailing of Rakha copper mine

“…in copper-loaded biomass, the peak transmittance and degree of bond stretching became lower than the unloaded biomass. Numerous workers have also reported similar results (Tunali et al 2006;Giotta et al 2011). The FTIR spectra of Cu free and Cu loaded biomass revealed a complex and additive influence of chemical structure of bacterial cell surface comprising different functional responsible for regulating the possible cell-cation interactions (Anand et al 2006).…”

Photosensitivity responses ofSagittula stellataprobed by FTIR, fluorescence and Raman microspectroscopy

“…The signal at 1305 cm À1 is not assigned to a specic group but to generic functional groups in agreement with that observed in the FTIR spectra of EPS from bacterial layers. [23][24][25] The difference spectrum pH 4 minus pH 10 shows negative peaks at 1398 and 1585 cm À1 and a positive peak at 1720 cm À1 indicating the presence of antisymmetric and symmetric COO moieties at pH 10 and also protonated COOH groups at pH 4. Fig.…”

Synthesis, characterization, and fluorescence properties of aniline‐g‐poly(styrene‐co‐maleic anhydride) and its lanthanide complexes

“…The results were consistent with the composition determination about the δ value. Two strong absorption bands at 1412–1414 and 1597–1598 cm −1 , assigned to the symmetric vibration absorption [ν s(COO−) ] and asymmetric vibration absorption [ν as(COO−) ] of the carboxylic groups, were present for the Ln(III) complexes. In addition, the difference of symmetric vibration absorption and asymmetric vibration absorption Δν (Δν = ν as(COO−) − ν s(COO−) ) of the Ln–AP/SMA complexes (Table ) ranged from 183–186 cm −1 ; this was smaller than that of Na–AP/SMA (196 cm −1 ).…”