| Summary: | The novel <i>Acidipropionibacterium</i> genus encompasses species of industrial importance but also those associated with food spoilage. In particular, <i>Acidipropionibacterium acidipropionici</i>, <i>Acidipropionibacterium thoenii</i>, and <i>Acidipropionibacterium jensenii</i> play an important role in food fermentation, as biopreservatives, or as potential probiotics. Notably, <i>A. jensenii</i> and <i>A. thoenii</i> can cause brown spot defects in Swiss-type cheeses, which have been tied to the rhamnolipid pigment granadaene. In the pathogenic bacterium <i>Streptococcus agalactiae,</i> production of granadaene depends on the presence of a <i>cyl</i> gene cluster, an important virulence factor linked with haemolytic activity. Here, we show that the production of granadaene in pigmented <i>Acidipropionibacterium,</i> including <i>A. jensenii, A. thoenii,</i> and <i>Acidipropionibacterium virtanenii</i>, is tied to haemolytic activity and the presence of a <i>cyl</i>-like gene cluster. Furthermore, we propose a PCR-based test, which allows pinpointing acidipropionibacteria with the <i>cyl</i>-like gene cluster. Finally, we present the first two whole genome sequence analyses of the <i>A. jensenii</i> strains as well as testing phenotypic characteristics important for industrial applications. In conclusion, the present study sheds light on potential risks associated with the presence of pigmented <i>Acidipropionibacterium</i> strains in food fermentation. In addition, the results presented here provide ground for development of a quick and simple diagnostic test instrumental in avoiding potential negative effects of <i>Acidipropionibacterium</i> strains with haemolytic activity on food quality.
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