The subphylum Wallemiomycetes contains three species distinguished by both genetic and morphological characteristics: W. ichthyophaga, W. sebi and W. muriae¹. These species have been isolated from environments with low water availability and are considered to be the most xerophilic and halophilic fungi isolated to date².  W. ichthyophaga requires at least 10% NaCl to grow and thrives in saturated salt media. We isolated a strain of W. ichthyophaga from salted sheep pelts, which were subsequently dewooled in water without any noticeable skin damage.  We hypothesised that enzyme(s) secreted by the fungus might be facilitating the dewooling process, and so began to investigate the secretome of the sheep pelt isolate.  We undertook a geLC-MSMS approach to identify the proteins secreted by the organism after two months growth in Wilson’s media containing 20% NaCl.  Clarified culture medium was concentrated and desalted by ultrafiltration.  Six separate samples were analysed; three technical replicates of two biological replicates, and positive identifications were made only when stringent criteria were met. This resulted in the identification of only 22 unique secreted proteins which was less than expected, as during the secretome analysis, the genome of Wallemia ichthyophaga EXF-994 was published and is predicted to encode 152 “highly likely secreted” proteins. We therefore repeated the experiment without pre-fractionation (i.e. using LC-MSMS on the trypsinised desalted concentrated secretome), and these results will be reported.  One of the identified glucosidases was further purified using IEC and SEC, and characterised. The enzyme was shown to be N-glycosylated, was most active at 10% NaCl, and interestingly, appeared to be able to hydrolyse both beta-(1,4) and alpha-(1,4) linkages.

References.
1. Zalar, P., de Hoog, G.S., Schroers, H., Frank, J.M., & Gunde-Cimerman N. (2005). Leeuwenhoek International Journal of General and Molecular Microbiology, 87, 311-328.
2. Zajc, J., Liu, Y., Dai, W., Yang, Z., Hu, J., Gostincar, C. & Gunde-Cimerman N. (2013).  BMC Genomics, 14, 1-21.