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. Sequence similarities to known integrases include the highly conserved tetrad R-H-R-Y. 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 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 Nab. 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. Binding experiments employing distinct domains of gp341 and gp3452 indicated the C-terminus to be responsible for binding to the receptor on the cell surface of Nab. magadii L13. This 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 Nab. 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 Nab. magadii and the transformation /shuttle vector system developed by the group. In addition the method is used to construct different mutants