Discriminating pathogenic and non-pathogenic Francisella strains with three proteogenomic biomarkers

摘要

In conclusion, we proposed a set of three m/z values to be checked for a quick classification of a Francisella strain by whole-cell MALDI-TOF mass spectrometry. The histone-like protein HU form B, the 10 kDa chaperonin Cpn10 and the 50S ribosomal protein L24 are giving m/z values that allow distinguishing between the different Francisella species known to date, as well as the subspecies from Francisella tularensis. The approach requires a pure culture as mixed bacteria could lead to a high number of m/z peaks, suppression of some of the signals, and a strong increase of the noise. Moreover, due to the huge diversity of bacteria on Earth, many different bacteria could exhibit the three m/z values while not a Francisella strain. A preliminary analysis should be carried out to point at the presence of a Francisella strain, such as gram-staining and isolation on different nutritive broth. New analytical methods could also be carried out to search for the three biomarkers such as nanoLC-MS analysis of undigested protein extracts. In this case, determination of the masses with a high level of accuracy could be reached thus allowing identification even if the sample is not a pure culture. By extension of the dual profiling by MALDI-TOF and shotgun characterization by nanoLC-MS/MS concept carried out in the present study, the search of specific biomarkers for other relevant bacterial genus could be proposed in the future. Monitoring bacteria with relevant biomarkers, i.e. specific in terms of molecular mass, as well as abundant and thus easily detectable, is valuable to better characterize medical or environmental samples.