Surface enhanced Raman spectroscopy-based evaluation of the membrane protein composition of the organohalide-respiring Sulfurospirillum multivorans

Bacteria often employ different respiratory chains that comprise membrane proteins equipped with various cofactors. Monitoring the protein inventory that is present in the cells under a given cultivation condition is often difficult and time-consuming. One example of a metabolically versatile bacterium is the microaerophilic organohalide-respiring Sulfurospirillum multivorans. Here, we used surface enhanced Raman spectroscopy (SERS) to quickly identify the cofactors involved in the respiration of S. multivorans. We cultured the organism with either tetrachloroethene (perchloroethylene, PCE), fumarate, nitrate, or oxygen as electron acceptors. Because the corresponding terminal reductases of the four different respiratory chains harbor different cofactors, specific fingerprint signals in SERS were expected. Silver nanostructures fabricated by means of electron beam lithography were coated with the membrane fractions extracted from the four S. multivorans cultivations, and SERS spectra were recorded. In the case of S. multivorans cultivated with PCE, the recorded SERS spectra were dominated by Raman peaks specific for Vitamin B-12. This is attributed to the high abundance of the PCE reductive dehalogenase (PceA), the key enzyme in PCE respiration. After cultivation with oxygen, fumarate, or nitrate, no Raman spectral features of B-12 were found.

Automated summary

The study focused on using surface enhanced Raman spectroscopy (SERS) to quickly identify the cofactors involved in the respiration process of S. multivorans. Through SERS analysis of membrane proteins from the bacterium under different cultivation conditions, it was found that S. multivorans cultivated with tetrachloroethene mainly contained Vitamin B-12, while those cultivated with other electron acceptors did not.