Biofilm Detection in Natural Unconsolidated Porous Media Using a Low-Field Magnetic Resonance System

• Published in: Environmental science & technology 2013-01, Vol.47 (2), p.987-992
• Main Authors: Sanderlin, Alexis B, Vogt, Sarah J, Grunewald, Elliot, Bergin, Bridget A, Codd, Sarah L
• Format: Article
• Language: English
• Subjects: Alginates - chemistry; Applied sciences; Bacillus - physiology; Bacteria; Bioassays; Biofilms; Biofilms - growth & development; Biofouling; Bioreactors - microbiology; Bioremediation; Decontamination. Miscellaneous; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Equipment Design; Exact sciences and technology; Geology; Glucuronic Acid - chemistry; Groundwaters; Hexuronic Acids - chemistry; Magnetic Resonance Spectroscopy - methods; Natural water pollution; NMR; Nuclear magnetic resonance; Pollution; Pollution, environment geology; Porosity; Sensors; Silicon Dioxide - chemistry; Soil and sediments pollution; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es3040686

The extent to which T 2 relaxation measurements can be used to determine biofouling in several natural geological sand media using a low-field (275 kHz, 6.5 mT) NMR system has been demonstrated. It has been previously shown that, at high laboratory strength fields (300 MHz, 7 T), T 2 techniques can be used as a bioassay to confirm the growth of biofilm inside opaque porous media with low magnetic susceptibilities such as borosilicate or soda lime glass beads. Additionally decreases in T 2 can be associated with intact biofilm as opposed to degraded biofilm material. However, in natural geological media, the strong susceptibility gradients generated at high fields dominated the T 2 relaxation time distributions and biofilm growth could not be reliably detected. Samples studied included Bacillus mojavensis biofilm in several sand types, as well as alginate solution and alginate gel in several sand types. One of the sand types was highly magnetic. Data was collected with a low-field (275 kHz, 6.5 mT) benchtop NMR system using a CPMG sequence with an echo time of 1.25 ms providing the ability to detect signals with T 2 greater than 1 ms. Data presented here clearly demonstrate that biofilm can be reliably detected and monitored in highly magnetically susceptible geological samples using a low-field NMR spectrometer indicating that low-field NMR could be viable as a biofilm sensor at bioremedation sites.