Comparison of nine extraction methods for bacterial identification using the ONT MinION sequencer

Area of Science:

• Microbial Forensics
• Molecular Biology
• Bioinformatics

Background:

• The 2001 Anthrax attacks highlighted the need for rapid microbial forensic analysis of unknown biological evidence.
• Traditional bacterial identification methods like culturing are time-consuming.
• Current molecular techniques, such as 16S rRNA gene sequencing, are often laboratory-bound and lengthy.

Purpose of the Study:

• To identify a "universal" bacterial DNA extraction method for rapid on-site microbial forensic analysis.
• To evaluate the suitability of Oxford Nanopore Technologies (ONT) MinION sequencing for forensic applications.
• To assess the cloud-based EPI2ME software for data analysis in forensic contexts.

Main Methods:

• Tested nine different bacterial DNA extraction methods.
• Utilized ONT MinION sequencing with the 16S Barcoding Kit and 16S FASTQ workflow.
• Evaluated species-level identification accuracy across various extraction methods and organisms.

Main Results:

• No single "universal" DNA extraction method was found to be optimal for all bacterial groups with ONT MinION sequencing.
• The DNeasy PowerSoil Kit and Noda et al. Chelex-100 method yielded comparable results and can be used as rapid extraction techniques.
• Accurate species-level identification was achieved in only 63% of cases, with most alignments around 89% accuracy, suggesting limitations for forensic use.

Conclusions:

• Current DNA extraction methods are not universally optimal for rapid forensic microbial identification using ONT MinION sequencing.
• The DNeasy PowerSoil Kit and Chelex-100 method offer potential for rapid DNA extraction in field settings.
• Further optimization of extraction and sequencing workflows is needed to improve accuracy for forensic microbial identification.