Barbara Kalbacher

Bio: Barbara Kalbacher is an academic researcher from Laboratory of Molecular Biology. The author has contributed to research in topics: Thin-layer chromatography & Stringent response. The author has an hindex of 2, co-authored 2 publications receiving 677 citations.

The Multiple Signaling Systems Regulating Virulence in Pseudomonas aeruginosa

Abstract: Cell-to-cell communication is a major process that allows bacteria to sense and coordinately react to the fluctuating conditions of the surrounding environment. In several pathogens, this process triggers the production of virulence factors and/or a switch in bacterial lifestyle that is a major determining factor in the outcome and severity of the infection. Understanding how bacteria control these signaling systems is crucial to the development of novel antimicrobial agents capable of reducing virulence while allowing the immune system of the host to clear bacterial infection, an approach likely to reduce the selective pressures for development of resistance. We provide here an up-to-date overview of the molecular basis and physiological implications of cell-to-cell signaling systems in Gram-negative bacteria, focusing on the well-studied bacterium Pseudomonas aeruginosa. All of the known cell-to-cell signaling systems in this bacterium are described, from the most-studied systems, i.e., N-acyl homoserine lactones (AHLs), the 4-quinolones, the global activator of antibiotic and cyanide synthesis (GAC), the cyclic di-GMP (c-di-GMP) and cyclic AMP (cAMP) systems, and the alarmones guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), to less-well-studied signaling molecules, including diketopiperazines, fatty acids (diffusible signal factor [DSF]-like factors), pyoverdine, and pyocyanin. This overview clearly illustrates that bacterial communication is far more complex than initially thought and delivers a clear distinction between signals that are quorum sensing dependent and those relying on alternative factors for their production.

Ro small cytoplasmic ribonucleoproteins are a subclass of La ribonucleoproteins: further characterization of the Ro and La small ribonucleoproteins from uninfected mammalian cells.

Abstract: Small ribonucleic acid (RNA)-protein complexes precipitated by anti-Ro and anti-La antibodies from lupus patients have been examined with emphasis on their RNA components. In both ribonucleoprotein (RNP) classes, the numbers of different RNA molecules and their sequences vary between mouse and human cells. The complex mixtures of La RNAs include two previously sequenced 4.5S RNAs from mouse cells and 5S ribosomal RNA-like molecules from both mouse and human cells. All Ro and La RNAs possess 5-triphosphates. Some La RNAs have internal modifications typical of transfer RNAs. The Ro RNPs are quite stable and are localized by immunofluorescence in the cell cytoplasm, whereas the majority of the La RNPs turn over rapidly and reside in the nucleus. Despite these differences, reconstitution experiments show that the Ro particles carry the La as well as the Ro determinant. Studies using a nuclear transcription system demonstrate that most of the La RNAs are synthesized by RNA polymerase III. The possibility that the La protein(s) functions in the transcription or maturation of all RNA polymerase III transcripts is discussed.

Stringent control in e. coli

Abstract: INTRODUCfION .... ... ... .. . .. ... .. ... . ........ ... .... . .. . . . .. . .. . ..... ... ...... ... . ..... .. . ... ... 393 THE STRINGENT RESPONSE .. . . . . . . . .. . . ... ..... .. . .. . . . .... .... .... .... . . ... .... ....... 394 EFFECfS OF ppGpp IN VITRO .... ... .. .. ..... ... .... 396 MS NUCLEOTIDE SYNTHESIS AND METABOLISM . .... . .. . . . ...... .... .. . 399 ROLE OF STRINGENT CONTROL IN THE MAINTENANCE OF TRANSLATIONAL ACCURACy 401 CONCLUSIONS .. .. . .... .. . ... .. . ... .. ...... .. ... .. ... .. . .. . . . . . . .. . . . . . . . .. ... .. .. ... 408