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The main interest of the group is the understanding of life under extreme conditions. Therefore, we study the virus φCh1 as a model system for gene regulation of haloalkaliphilic Archaea facing two extremes: high pH and salt.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 analyze 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.
In vitro as well as in vivo experiments using purified protein variants gp341 and gp3452 were used to identifiy the ant-receptor of virus φCh1 infecting 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.
Genomic manipulations in alkaliphilic haloarchaea demonstrated by a gene disruption in Natrialba magadii. The viral gene ORF79 encodes a repressor regulating induction of the lytic life cycle in the haloalkaliphilic virus φCh1. Complete genome sequence of the model halovirus PhiH1 (ΦH1). Halobacterium salinarum virus ChaoS9, a novel halovirus related to PhiH1 and PhiCh1.
Genome map of ChaoS9 compared to φCh1 and φH1. (a) Cumulative AT-skew of all three virus genomes. (b) Genome map of phiCh1; (c) Genome map of ChaoS9; (d) Genome map of phiH1. Scale bar at bottom shows length, in kb. Pink shading between genome maps indicates similarity of encoded proteins (tBLASTx) at ≥ 30% amino acid identity level. Colour coding of genes indicates those encoding proteins with predicted (or experimentally determined) functions. Some of these genes are labeled along the gene maps.
Haloarchaeal myovirus ?Ch1 harbours a phase variation system for the production of protein variants with distinct cell surface adhesion specificities.
Klein, R; Rössler, N; Iro, M; Scholz, H; Witte, A
Antimicrobial activity of a chimeric enzybiotic towards Staphylococcus aureus.
Manoharadas, Salim; Witte, Angela; Bläsi, Udo
Genetic diversity and phylogenetic relationships of bacteria belonging to the Ochrobactrum-Brucella group by recA and 16S rRNA gene-based comparative sequence analysis.
Scholz, Holger C; Al Dahouk, Sascha; Tomaso, Herbert; Neubauer, Heinrich; Witte, Angela; Schloter, Michael; Kämpfer, Peter; Falsen, Enevold; Pfeffer, Martin; Engel, Marion