ATR–FTIR spectroscopic evidence for biomolecular phosphorus and carboxyl groups facilitating bacterial adhesion to iron oxides

Attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy has been used to probe the binding of bacteria to hematite (α-Fe(2)O(3)) and goethite (α-FeOOH). In situ ATR-FTIR experiments with bacteria (Pseudomonas putida, P. aeruginosa, Escherichia coli), mixed amino acids, polypeptide extracts, deoxyribonucleic acid (DNA), and a suite of model compounds were conducted. These compounds represent carboxyl, catecholate, amide, and phosphate groups present in siderophores, amino acids, polysaccharides, phospholipids, and DNA. Due in part to the ubiquitous presence of carboxyl groups in biomolecules, numerous IR peaks corresponding to outer-sphere or unbound (1400 cm(−1)) and inner-sphere (1310-1320 cm(−1)) coordinated carboxyl groups are noted following reaction of bacteria and biomolecules with α-Fe(2)O(3) and α-FeOOH. However, the data also reveal that the presence of low-level amounts (i.e., 0.45-0.79%) of biomolecular phosphorous groups result in strong IR bands at ~1043 cm(−1)(,) corresponding to inner-sphere Fe-O-P bonds, underscoring the importance of bacteria associated P-containing groups in biomolecule and cell adhesion. Spectral comparisons also reveal slightly greater P-O-Fe contributions for bacteria (Pseudomonad, E. coli) deposited on α-FeOOH, as compared to α-Fe(2)O(3). This data demonstrates that slight differences in bacterial adhesion to Fe oxides can be attributed to bacterial species and Fe-oxide minerals. However, more importantly, the strong binding affinity of phosphate in all bacteria samples to both Fe-oxides results in the formation of inner-sphere Fe-O-P bonds, signifying the critical role of biomolecular P in the initiation of bacterial adhesion

Soil Chemical Insights Provided through Vibrational Spectroscopy

Vibrational spectroscopy techniques provide a powerful approach to the study of environmental materials and processes. These multifunctional analytical tools can be used to probe molecular vibrations of solid, liquid, and gaseous samples for characterizing materials, elucidating reaction mechanisms, and examining kinetic processes. Although Fourier transform infrared (FTIR) spectroscopy is the most prominent type of vibrational spectroscopy used in the field of soil science, applications of Raman spectroscopy to study environmental samples continue to increase. The ability of FTIR and Raman spectroscopies to provide complementary information for organic and inorganic materials makes them ideal approaches for soil science research. In addition, the ability to conduct in situ, real time, vibrational spectroscopy experiments to probe biogeochemical processes at mineral interfaces offers unique and versatile methodologies for revealing a myriad of soil chemical phenomena. This review provides a comprehensive overview of vibrational spectroscopy techniques and highlights many of the applications of their use in soil chemistry research