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Published on: July 7, 2011
Freeze-Thaw Pretreatment Can Improve Efficiency of Bacterial DNA Extraction From Meconium
Yuntian Xin1, Jingxian Xie2, Bingru Nan1,3,4
1Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China.
Abstract:
Although the presence of live microbes in utero remains under debate, newborn gastrointestinal bacteria are undoubtedly important to infant health. Measuring bacteria in meconium is an ideal strategy to understand this issue; however, the low efficiency of bacterial DNA extraction from meconium has limited its utilization. This study aims to improve the efficiency of bacterial DNA extraction from meconium, which generally has low levels of microflora but high levels of PCR inhibitors in the viscous matrix. The research was approved by the ethical committee of the Xiamen Maternity and Child Health Care Hospital, Xiamen, China. All the mothers delivered naturally, and their newborns were healthy. Meconium samples passed by the newborns within 24 h were collected. Each sample was scraped off of a sterile diaper, transferred to a 5-ml sterile tube, and stored at -80°C. For the assay, a freeze-thawing sample preparation protocol was designed, in which a meconium-InhibitEX buffer mixture was intentionally frozen 1-3 times at -20°C, -80°C, and (or) in liquid nitrogen. Then, DNA was extracted using a commercial kit and sequenced by 16S rDNA to verify the enhanced bacterial DNA extraction efficiency. Ultimately, we observed the following: (1) About 30 mg lyophilized meconium was the optimal amount for DNA extraction. (2) Freezing treatment for 6 h improved DNA extraction at -20°C. (3) DNA extraction efficiency was significantly higher with the immediate thaw strategy than with gradient thawing at -20°C, -80°C, and in liquid nitrogen. (4) Among the conditions of -20°C, -80°C, and liquid nitrogen, -20°C was the best freezing condition for both improving DNA extraction efficiency and preserving microbial species diversity in meconium, while liquid nitrogen was the worst condition. (5) Three freeze-thaw cycles could markedly enhance DNA extraction efficiency and preserve the species diversity of meconium microflora. We developed a feasible freeze-thaw pretreatment protocol to improve the extraction of microbial DNA from meconium, which may be beneficial for newborn bacterial colonization studies.
Insights
Improving bacterial DNA extraction from newborn meconium is crucial for infant health studies. A novel freeze-thaw protocol enhances DNA yield and preserves microbial diversity, overcoming challenges of low microflora and PCR inhibitors.
Area of Science:
- Microbiology
- Genomics
- Neonatal Health
Background:
- The neonatal gut microbiome is vital for infant health, but its study is hindered by difficulties in extracting bacterial DNA from meconium.
- Meconium presents challenges due to low microbial levels, high viscosity, and PCR inhibitors, limiting accurate analysis of the early-life gut microbiota.
Purpose of the Study:
- To develop and optimize a freeze-thaw pretreatment protocol for enhanced bacterial DNA extraction efficiency from meconium.
- To validate the protocol's effectiveness in improving DNA yield and preserving microbial species diversity for 16S rDNA sequencing.
Main Methods:
- Meconium samples from healthy newborns were collected and subjected to a novel freeze-thaw protocol involving controlled freezing cycles (-20°C, -80°C, liquid nitrogen) and thawing strategies.
- Optimized parameters included meconium amount (30 mg lyophilized), freezing duration (6 hours at -20°C), and number of freeze-thaw cycles (three).
- Bacterial DNA was extracted using a commercial kit, and efficiency was verified via 16S rDNA sequencing.
Main Results:
- A freeze-thaw protocol using three cycles at -20°C significantly enhanced bacterial DNA extraction efficiency compared to other conditions.
- The -20°C condition proved optimal for both DNA yield and preservation of microbial species diversity, outperforming -80°C and liquid nitrogen.
- Immediate thawing after freezing yielded higher DNA extraction efficiency than gradient thawing methods.
Conclusions:
- The developed freeze-thaw pretreatment protocol is a feasible and effective method for improving microbial DNA extraction from meconium.
- This optimized protocol facilitates more accurate studies of newborn bacterial colonization and the early-life gut microbiome's impact on infant health.
