Adaptive responses of marine-derived Aspergillus terreus to salinity and chromium stress analysed by peptide mass fingerprinting

Fungi inhabiting marine environments often exhibit physiological and biochemical traits that enable survival in saline conditions, distinguishing them from many terrestrial counterparts. The presence of soluble osmolytes, affinity for sodium ions, and streamlined genomes aid marine biota to survive hypertonic environments. With the rise in anthropogenic activities, marine biota face multiple stresses that demand immediate acclimation and adaptation. This study evaluated the cellular responses of a marine-derived fungal isolate to variable salinities and Cr+6 concentrations using peptide mass fingerprinting on an LC-MS-MS QToF. The whole-cell proteins were extracted and digested with trypsin. A total of 659 proteins across nine variable conditions, including salinity (0, 35, 100 PSU) and Cr+6 (0, 100, 500 mg/L), were detected. Fifty-three housekeeping proteins were expressed across all conditions, categorised into carbohydrate metabolism, nucleotide metabolism, genetic information processing, and cellular processes using KEGG pathways. Variation in salinity led to the expression of proteins associated with DNA damage control and Reactive Oxygen Species (ROS) scavenging mechanisms, whereas an increase in Cr+6 concentration triggered the expression of proteins involved in enzymatic reduction and in transport/metal efflux. Thioredoxin expression was upregulated with fold change values of 5.011 and 5.032 at 100, and 500 mg/L Cr+6 at 35 PSU, and 2.358 and 1.839 at the same Cr+6 concentrations at 100 PSU. This indicated that upregulation of ROS-scavenging proteins was the predominant mechanism used by A. terreus under elevated Cr+6 and salt concentrations. This study observed the expression of multiple stress tolerance mechanisms to combat the synergistic effects of salt and Cr+6.