Distribution and potential roles of microbial protoporphyrin IX in marine sediments

Protoporphyrin IX (PPIX) serves as a pivotal precursor in the biosynthesis of porphyrins, playing a crucial role in both biological metabolism and biogeochemical cycling. This study investigates the spatial dynamics and co-occurrence patterns of PPIX within the microbial community of marine sediment. The concentrations of PPIX ranged from 7.38 - 91.33 ng/g. Clear patterns in spatiotemporal dynamics in the PPIX were observed, with a more pronounced spatial rather than seasonal variation. Notably, the PPIX and its derivatives in brackish sediment samples exhibited distinct characteristics from those found in saltwater samples. The Spearman test found that PPIX has a positive relationship with chlorophyll-a and pheophytin-a but not with chlorophyll-b or pheophytin-b. Significant positive correlations were identified between PPIX and nitrogen nutrients. Network and variation partitioning analyses highlighted the potential interactions between PPIX and microbial lineages. These findings indicate that PPIX is necessary for microorganisms and widely distributed in sedimentary environments. Additionally, this study underscores the influence of organic matter on microbial community composition and its responsiveness to environmental variations. These insights contribute to a comprehensive understanding of the potential ecological roles of PPIX within natural ecosystems. Protoporphyrin IX is necessary for microorganisms and widely distributed in sedimentary environments.PPIX showed a more pronounced spatial rather than seasonal variation.Porphyrins found in brackish sediment samples exhibited distinct characteristics compared with those present in saltwater samples.Environmental factors can further influence the distribution of porphyrins by affecting microorganisms and their interactions.