Variable protein expression in marine-derived filamentous fungus Penicillium chrysogenum in response to varying copper concentrations and salinity†
Copper is one of the essential trace dietary minerals for all living organisms, but is potentially toxic at higher concentrations, mainly due to the redox reactions in its transition state. Tolerance of microbes towards copper is primarily attributed to chelation and biosorption. In this study, marine-derived filamentous fungi were evaluated for their ability to remove Cu(II) from a culture medium. Further, the cellular response of a select isolate to salinity stress (0, 35 and 100 PSU) and Cu(II) stress (0, 100, and 500 ppm) was studied using the peptide mass fingerprinting technique, which revealed expression of 919 proteins, of which 55 proteins were commonly expressed across all conditions. Housekeeping proteins such as citrate synthase, pyruvate carboxylase, ribosomal proteins, ATP synthases, and more were expressed across all conditions. Reactive oxygen species scavenging proteins such as glutaredoxin, mitochondrial peroxiredoxins and thioredoxins were expressed under Cu(II) and salinity stresses individually as well as in combination. Up-regulation of glutaredoxin under Cu(II) stress with fold change values of 18.3 and 13.9 under 100 ppm and 500 ppm of Cu(II) indicated active scavenging of free radicals to combat oxidative damage. The common mechanisms reported were enzymatic scavenging of free radicals, activation of DNA damage and repair proteins and probable intracellular metal chelation. This indicated multiple stress mechanisms employed by the isolate to combat the singular and synergistic effects of Cu(II) and salinity stress.