Nuclear magnetic resonance is proving a useful tool to study live and intact bacteria, says a researcher in the US. Wei Li at the University of Tennessee has used nuclear magnetic resonance (NMR) spectroscopy to examine complex systems such as bacterial cell walls without damaging them.

Multidimensional high resolution magic angle spinning NMR (HRMAS NMR) spectroscopy is a technique somewhere between solid- and solution-state NMR spectroscopy. It effectively removes the broadening of the spectral lines that can confuse very complex samples (such as live bacterial cells), improving understanding of the data. Li has demonstrated how HRMAS NMR spectroscopy can be used to analyse the different components in intact cell walls.

The cell wall plays a 'critical role in bacterial survival and pathology,' said Li. It is a protective honeycomb of sugars and peptides that envelops the cell and an important target for new antibacterial drugs. It also plays a key role in the appearance of drug resistance. But classical analysis of cell walls is destructive - the structure must be separated into its individual components, which are then purified and examined individually. This is time-consuming and needs large amounts of material which is often impossible for slow-growing species of bacteria, explained Li. 

It is by no means certain that isolated cell walls faithfully reflect the native structures, said Li. Until now in vivo analysis of whole cell bacteria, especially the structures of their cell walls, has remained 'an unconquered frontier.' It may reflect the true biological conditions better than in vitro methods, Li explained.

The HRMAS NMR technique has found several applications. For example, the absence of a peak for a particular sugar can indicate that the synthetic path to that sugar is blocked, possibly by the action of an anti-microbial drug. The approach could provide important information about living cells and be an invaluable tool in drug development, genetics and the study of bacterial diseases, said Li.

Michael Spencelayh