Optimizing Illumina next-generation sequencing library preparation for extremely AT-biased genomes

Area of Science:

• Genomics
• Molecular Biology
• Bioinformatics

Background:

• Next-Generation Sequencing (NGS) has advanced genomic research but struggles with genomes of extreme base composition (e.g., high AT or GC content).
• Standard PCR amplification in library preparation causes uneven read coverage in AT/GC-rich regions, hindering genome assembly and variation analysis.
• PCR-free methods require large DNA amounts, unsuitable for clinical isolates.

Purpose of the Study:

• To develop and optimize NGS library preparation procedures for low DNA quantities.
• To create methods tolerant to extremely high AT-rich sequences.
• To improve sequencing of challenging genomes, including those from clinical samples.

Main Methods:

• Developed and optimized library preparation procedures for low-quantity DNA.
• Incorporated a PCR additive (TMAC) into library amplification.
• Compared optimized conditions with standard methods using Illumina sequencing.

Main Results:

• Optimized conditions produced amplified libraries with improved coverage of AT-rich regions.
• Reduced bias toward GC-neutral templates was observed.
• Demonstrated effectiveness on both non-clinical and clinical isolates, including those with host contamination.

Conclusions:

• Developed a robust NGS library amplification method for extremely AT-rich genomes.
• New conditions significantly reduce bias and maintain complexity across base composition extremes.
• Method benefits sequencing clinical samples with limited DNA input.