MFPL - 2016 RESEARCH GROUPS
ANGELA WITTE
φCh1, a model system for gene regulation of haloalkali-
philic Archaea facing two extremes: high pH and salt The virus φCh1 was found by spontaneous lysis of a culture of the haloalkaliphilic, archaeon, Natrialba magadii, an isolate from the soda lake, Lake Magadii in Kenya.
This organism has an optimal growth at 3.5M NaCl and at a pH of 9.5. The virus itself is used as a model system to analyse gene expression in haloalkaliphilic organisms, facing with two extremes: a high pH and high concentrations of salt. The sequence of φCh1, infecting the haloalkaliphilic archaeon Natrialba magadii, contains an open reading frame (int1) in the central part of its genome that belongs to the λ integrase family of site-specific recombinases. The flanking sequences of int1 contain several direct repeats of 30 bp in length (IR-L and IR-R), which are orientated in an inverted direction. The invertible region encodes two structural proteins (gp34 and gp36, encoded by ORF34 and ORF36) expected to represent the viral tail fibre proteins.
Angela Witte
In vitro experiments using purified protein variants gp341 and gp3452 (containing the C-terminus of gp36) revealed exclusive binding of gp3452 but not of gp341 to cells of the cured strain N. magadii L13. This specific binding could be inhibited by the addition of α-D-galactose. α-D-galactose also significantly reduced the infectivity of φCh1. The C-terminus contains a domain with similarities to the super-family of “galactose-like binding” proteins. In summary, the experiments gave evidence that gp3452 represents the anti-receptor of φCh1 that binds to specific carbohydrate ligands located on the cell surface of N. magadii. Currently the work concentrates on the identification and function of repressor and activator molecules encoded by the virus, gene regulation due to a recombination event, identification of the receptor for the virus on the cell surface of N. magadii and the transformation/shuttle vector system developed by the group. In addition, the method is used to construct different mutants.
Electron micrograph of φCh1 particle negatively stained with uranyl acetate.
SELECTED PUBLICATIONS Klein R, Rössler N, Iro M, Scholz H, Witte, A. Haloarchaeal myovirus φCh1 harbours a phase variation system for the production of protein variants with distinct cell surface adhesion specificities. Mol Microbiol 2012;83:137-50. PMID: 22111759 Mayrhofer-Iro M, Ladurner A, Meissner C, Derntl C, Reiter M, Haider F, Dimmel K, Rössler N, Klein R, Baranyi U, Scholz H, Witte A. Utilization of virus φCh1 elements to establish a shuttle vector system for halo(alkali)philic Archaea via transformation of Natrialba magadii. Appl Environ Microbiol 2013;79:2741-2748. PMID: 23416999 Derntl C, Selb R, Klein R, Alte B, Witte A. Genomic manipulations in alkaliphilic haloarchaea demonstrated by a gene disruption in Natrialba magadii. FEMS Microbiol Lett 2015;362(21). PMID: 26424765
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TEAM Yan Gillen Martin Kaufmann Michael Tschurtschenthaler