Hydrocarbon biodegradation and transcriptome responses of cellulase, peroxidase, and laccase encoding genes inhabiting rhizospheric fungal isolates

Abstract

By using the indigenous micro-organisms of the polluted environment to be treated, bioremediation can be a successful strategy. PCR and RT-PCR molecular techniques were applied to examine the evolution of fungal isolates through putative genes f ligninolytic enzymes like lignin peroxidase (LiP), laccase (LaC), manganese peroxidase (MnP), and cellulase (Cx) as a response to polluting of the environment by hydrocarbons. In this study, isolation of rhizospheric fungal isolates, molecular identification, crude oil tolerance, and enzyme excretions were demonstrated. From the date palm rhizosphere, 3 fungal isolates were isolated and characterized morphologically and molecularly by ITS ribosomal RNA (rRNA) sequencing. The isolates were identified as Aspergillus flavus AF15, Trichoderma harzianum TH07, and Fusarium solani FS12 through using the BLAST tool in NCBI. All fungal isolates showed high tolerance to crude oil and survived with various responses at the highest concentration (20%). Aspergillus flavus AF15 and Trichoderma harzianum TH07 demonstrated promising oil-degrading tolerance ability based on the dose inhibition response percentage (DIRP) of the fungal isolates. A. flavus had a powerful capacity to production Cx, LaC, LiP and MnP with a range from 83.7 to 96.3 mL. Molecularly, nine genes of the ligninolytic enzymes, cbh (cbhI.1, cbhI.1, cbhII) lcc, lig (1, 2, 4 and 6) and mnp were tested for presence and expression (by PCR and RT-PCR, respectively). PCR showed that all isolates contained all the nine genes examined, regardless of capacity to enzymes production profiles, so the presence responses of nine genes did not correlate with enzymes-production ability. Gene expression analysis shows a more diverse pattern for tested isolates for example, Aspergillus flavus AF15 had over-expression of lig and mnp genes, Fusarium solani FS12 have a weak signal with lcc gene while, Trichoderma harzianum TH07 showed moderate expression of mnp and lcc genes. The power of the transcription of the gene leads to increased enzyme secretion by fungal isolates. Fungi are important microorganisms in the clean-up of petroleum pollution. They have bioremediation highly potency that is related to their diverse production of these catalytic enzymes.

Keywords

• Crude oil
• Soil borne-fungi
• Enzymes
• Genes