20Enterococcus faecalis is a commensal bacterium of the human gut that requires the 21 ability to pass through the stomach and therefore cope with low pH. E. faecalis has also 22 been identified as one of the major tyramine producers in fermented food products, 23 where they also encounter acidic environments. In the present work, we have 24 constructed a non-tyramine producing mutant to study the role of the tyramine
In the search for strains producing antifungal compounds, a new tetraene macrolide CE-108 (3) has been isolated from culture broth of Streptomyces diastaticus 108. In addition, the strain also produces the previously described tetraene rimocidin (1) and also the aromatic polyketide oxytetracycline. Both tetraene compounds, structurally related, are produced in a ratio between 25 to 35% (CE-108 compared to rimocidin), although it can be inverted toward CE-108 production by changing the composition of the fermentation medium. This paper deals with the characterization of the producer strain, fermentation, purification, structure determination and biological properties of the new macrolide tetraene CE-108.
Enterococcus faecalis is one of the most controversial species of lactic acid bacteria. Some strains are used as probiotics, while others are associated with severe and life-threatening nosocomial infections. Their pathogenicity depends on the acquisition of multidrug resistance and virulence factors. Gelatinase, which is required in the first steps of biofilm formation, is an important virulence determinant involved in E. faecalis pathogenesis, including endocarditis and peritonitis. The gene that codes for gelatinase (gelE) is controlled by the Fsr quorum-sensing system, whose encoding genes (fsrA, fsrB, fsrC, and fsrD) are located immediately upstream of gelE. The integration of a DNA fragment into the fsr locus of a derived mutant of E. faecalis V583 suppressed the gelatinase activity and prevented biofilm formation. Sequence analysis indicated the presence of IS256 integrated into the fsrC gene at nucleotide position 321. Interestingly, IS256 is also associated with biofilm formation in Staphylococcus epidermidis and Staphylococcus aureus. This is the first description of an insertion sequence that prevents biofilm formation in E. faecalis.
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