Fungal-bacterial network in PAH-contaminated coastal marine sediment.

Fungal microbiome interacts with the other biotic components in coastal sediment playing a key role in the overall coordination of the whole microbial community. These interactions are affected by human activities, such as the constant affluence of polycyclic aromatic hydrocarbons (PAHs). Although fungi and bacteria interactions have been found to play a key role in PAH bioremediation in soil, the effect of PAHs on fungal diversity and their specific interactions with bacteria in coastal sediments are yet to be investigated. The understanding of fungal bacterial interactions under PAH contamination is critical for further bioremediation regarding the important fungal diversity observed in coastal sediment. Here, we investigated the fungal bacterial co-occurrence in PAH-contaminated sediments. The co-occurrence network, constructed with sequencing data (bacterial 16S and fungal 18S rRNA genes barcoding) from 51 PAH-contaminated samples, revealed modules dominated by either fungi or bacteria, reflecting probably the different types of interaction possible between fungi and bacteria. Then, a network constructed from non-contaminated sample data was compared with a network built from the corresponding PAH-contaminated samples issued from a mesocosm experiment. The comparison revealed the effect of PAHs in fungi and bacteria interactions, characterized by a PAH-contaminated network exhibiting less abundant and diverse fungal and bacterial ASVs than the non-contaminated network. However, the links between the remaining ASVs in the PAH-contaminated network showed stronger correlations. Noteworthy, an ASV affiliated to Chrytridiomycota phylum was identified as a keystone fungal ASV forming a module in association with facultative anaerobic and anaerobic bacteria affiliated to the families Prolixibacteraceae, Fusobacteriaceae, and Desulfobulbaceae. These results suggest that fungi promote bacterial anaerobic metabolisms, which are important to cope with the presence of PAHs in sediments. Our study reveals the importance of fungal bacterial interactions in coastal sediments paving the way for future studies to fully understand fungal role in coastal sediment.