Deep-sea Metagenomics
Illumina paired-end sequencing libraries were prepared for all deep-sea sediment samples using the NEBNext Ultra DNA Library Prep Kit, following the manufacturers instructions. The libraries were sequenced on the Illumina HiSeq 2500 platform with a 2  151 bp paired-end read configuration. Initial quality assessment of raw sequencing data included evaluation of read length distribution, Phred quality scores, base composition, and GC content. Quality filtering was carried out using Fastp (v0.1.3.2) with default parameters and the following key criteria: reads were retained only if they had a minimum average Phred score 30 (--qualified_quality_phred 30) and a post-trimming length 75 bp (--length_required 75). Adapter sequences were automatically detected and removed using Fastp's built-in adapter trimming module. Reads failing to meet these quality thresholds or falling below the minimum length were discarded. The high retention rate of quality-filtered reads across all samples demonstrated the effectiveness of the sequencing protocol and ensured the reliability of the dataset for subsequent metagenomic assembly and downstream analysis.