Comparison of a modified phenol/chloroform and commercial-kit methods for extracting DNA from horse fecal material.

The study investigates and compares two different methods for extracting bacterial DNA from horse feces for Next Generation Sequencing (NGS). The researchers suggest that the method involving a modification of a phenol/chloroform extraction plus an inhibitor removal solution yields higher DNA with less shearing than a commercial kit, despite potential safety concerns.

Introduction

• The research aims to compare different DNA extraction methods used for analyzing bacterial content in horse feces.
• The chosen methods for comparison were a modified phenol/chloroform extraction with an inhibitor removal solution (referred to as Ph/Chl+C3) and the commercial PowerFecal® DNA Isolation Kit (abbreviated as MoBio-K).
• The comparison’s primary metrics included DNA quality, quantity, and the results garnered through Next Generation Sequencing (NGS).

Methodology and Findings

• Six replicate samples, taken from a single horse feces ball, were subjected to each extraction method for comparison.
• The Ph/Chl+C3 method resulted in 100× higher DNA yields and demonstrated less shearing compared to the MoBio-K method.
• Both sample sets were then sent for NGS, specifically targeting the bacterial V3-V4 region of the 16S rRNA gene.
• The MoBio-K samples revealed greater relative abundance and more unique species of Bacteroidetes, while the Ph/Chl+C3 samples showed a higher relative abundance and more unique species of Firmicutes.
• Other major bacterial phyla were equally abundant in samples from both extraction methods.
• The Ph/Chl+C3 samples showed greater evenness of bacterial distribution, but there was no difference in the richness of Operational Taxonomic Units (OTUs).
• Principle coordinate analysis (PCoA) indicated a distinct separation between the two methods and tighter clustering (less variability) in Ph/Chl+C3 than in MoBio-K.

Conclusion

• The study suggests that the Ph/Chl+C3 may be the preferred method for research aiming to identify specific Firmicutes taxa, such as Clostridium and Bacillus, but the MoBio-K might be better for projects focused on Bacteroidetes abundance.
• Despite producing superior results, the Ph/Chl+C3 method carries safety concerns due to potential exposure to phenol and chloroform and issues around safe disposal.
• The researchers conclude that the MoBio-K may be a more suitable choice for researchers with limited access to safety equipment like a fume hood.