Establishment of mass spectrometric profiling in Vibrio Population analyses Coastal areas of the North and Baltic Sea are threatened by potential pathogenic Vibrio species. So far, outbreaks were generally reported to occur in regions with elevated water temperature. But due to Global Warming, an infiltration of Northern European temperate waters by perilous vibrios can be assumed. Major human pathogenic species are V. cholerae, V. vulnificus and V. parahaemolyticus. These bacteria can be transmitted by contaminated water or seafood. Infections lead to fatal diarrheas, septicemias or gastroenteritides, and cases of death caused by V. vulnificus strains have recently been reported from Baltic Sea countries. This implies the significance and urgency of Vibrio population analyses. In this study, we aim to establish a mass spectrometric method to distinguish Vibrio strains on the species level. In contrast to DNA-based methods, species identification by this matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) method can be performed cost and time effective. First of all, identification results have to be confirmed by ribosomal protein fingerprinting. Additionally, MALDI-TOF cluster analyses allow the detection of possible interspecific groups with pathogenic properties. Another aim is to get information on the geographical distribution of specific Vibrio populations. For this reason potentially pathogenic vibrios are mapped according to their sampling site and environmental conditions like salinity or temperature at the sampling time. The outcome will be a detailed report about the composition of Vibrio populations in the North and Baltic Sea. Hence, it will be possible to answer the question whether pathogenic vibrios are to be perceived as a serious threat for German coasts. So far, over 600 potential pathogenic Vibrio isolates were collected from environmental samples of the North and Baltic Sea. Sampling took place all along the German Coast, from the Dutch border to the isle of Usedom near Poland. Reference mass spectra are acquired from all these strains. Hence, the MALDI-TOF database will be expanded by environmental vibrios, which in turn leads to more specific classification results of further Vibrio strains. In order to detect interspecific cluster, comparative analyses of MALDI-TOF and ribosomal protein fingerprinting are performed. Such a comparison has been already accomplished with V. alginolyticus strains isolated from the German Bight and it has been proven that MALDI-TOF can distinguish two interspecific V. alginolyticus groups which were identified by RNA polymerase beta unit sequence analyses. In context with this result, similar cluster should be expected in the case of potential pathogenic Vibrio species. Hence, mass spectrometric profiling by MALDI-TOF can be a huge improvement in Vibrio population analyses.