Isolation of inhibitory factor in raw milk whey active against propionibacteria

Red-Brown Pigmentation of Acidipropionibacterium jensenii Is Tied to Haemolytic Activity and cyl-Like Gene Cluster

The novel Acidipropionibacterium genus encompasses species of industrial importance but also those associated with food spoilage. In particular, Acidipropionibacterium acidipropionici, Acidipropionibacterium thoenii, and Acidipropionibacterium jensenii play an important role in food fermentation, as biopreservatives, or as potential probiotics. Notably, A. jensenii and A. thoenii can cause brown spot defects in Swiss-type cheeses, which have been tied to the rhamnolipid pigment granadaene. In the pathogenic bacterium Streptococcus agalactiae, production of granadaene depends on the presence of a cyl gene cluster, an important virulence factor linked with haemolytic activity. Here, we show that the production of granadaene in pigmented Acidipropionibacterium, including A. jensenii, A. thoenii, and Acidipropionibacterium virtanenii, is tied to haemolytic activity and the presence of a cyl-like gene cluster. Furthermore, we propose a PCR-based test, which allows pinpointing acidipropionibacteria with the cyl-like gene cluster. Finally, we present the first two whole genome sequence analyses of the A. jensenii 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 Acidipropionibacterium 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 Acidipropionibacterium strains with haemolytic activity on food quality.

Group B streptococcal haemolysin and pigment, a tale of twins

Group B streptococcus [(GBS or Streptococcus agalactiae)] is a leading cause of neonatal meningitis and septicaemia. Most clinical isolates express simultaneously a β-haemolysin/cytolysin and a red polyenic pigment, two phenotypic traits important for GBS identification in medical microbiology. The genetic determinants encoding the GBS haemolysin and pigment have been elucidated and the molecular structure of the pigment has been determined. The cyl operon involved in haemolysin and pigment production is regulated by the major two-component system CovS/R, which coordinates the expression of multiple virulence factors of GBS. Genetic analyses indicated strongly that the haemolysin activity was due to a cytolytic toxin encoded by cylE. However, the biochemical nature of the GBS haemolysin has remained elusive for almost a century because of its instability during purification procedures. Recently, it has been suggested that the haemolytic and cytolytic activity of GBS is due to the ornithine rhamnopolyenic pigment and not to the CylE protein. Here we review and summarize our current knowledge of the genetics, regulation and biochemistry of these twin GBS phenotypic traits, including their functions as GBS virulence factors.

Propionibacterium jensenii produces the polyene pigment granadaene and has hemolytic properties similar to those of Streptococcus agalactiae

The red polyene pigment granadaene was purified and identified from Propionibacterium jensenii. Granadaene has previously been identified only in Streptococcus agalactiae, where the pigment correlates with the hemolytic activity of the bacterium. A connection between hemolytic activity and the production of the red pigment has also been observed in P. jensenii, as nonpigmented strains are nonhemolytic. The pigment and hemolytic activity from S. agalactiae can be extracted from the bacterium with a starch extraction solution, and this solution also extracts the pigment and hemolytic activity from P. jensenii. A partial purification of the hemolytic activity was achieved, but the requirement for starch to preserve its activity made the purification unsuccessful. Partially purified hemolytic fractions were pigmented, and the color intensity of the fractions coincided with the hemolytic titer. The pigment was produced in a soluble form when associated with starch, and the UV-visual spectrum of the extract gave absorption peaks of 463 nm, 492 nm, and 524 nm. The pigment could also be extracted from the cells by a low-salt buffer, but it was then aggregated. The purification of the pigment from P. jensenii was performed, and mass spectrometry and nuclear magnetic resonance analysis revealed that P. jensenii indeed produces granadaene as seen in S. agalactiae.