Question

How does the metagenomics approach helps to identify novel genes present in an environment? Explain the process.

Hint:

Metagenomics has revolutionized industrial biotechnology by helping scientists discover novel, highly stable enzymes (extremophilic lipases, cellulases, polymerases) in environments like deep-sea vents and hot springs.

Answer 1

Step 1: Concept
In environmental microbiology, over $99%$ of microbial species cannot be grown in laboratory cultures ("the great plate count anomaly"). Classical biology misses this vast genetic diversity. Metagenomics bypasses this by extracting and studying genomic DNA directly from environmental samples (soil, water, hot springs).

Step 2: The Metagenomics Process
The systematic identification of novel genes involves several steps:
1. Sample Collection: Environmental samples (soil, seawater, gut microbiome) are collected.
2. Extraction of environmental DNA (eDNA): Total genomic DNA from all microorganisms present in the sample is extracted.
3. Library Construction: The extracted DNA is fragmented and cloned into suitable vectors (plasmids, cosmids, or BACs) and transformed into host bacteria like E. coli to create a metagenomic library.
4. High-Throughput Screening:
- Sequence-based screening: The clones are sequenced directly. Bioinformatics tools assemble the reads and scan for open reading frames (ORFs) that match or differ from known gene families.
- Function-based screening: The library clones are grown on selective media to screen for novel enzymatic activities (such as cellulase, lipase, amylase, or antibiotic resistance) expressed by the foreign DNA in E. coli.
5. Characterization: Newly discovered genes are isolated, optimized, and utilized for industrial or pharmaceutical applications.
Final Answer: Metagenomics extracts total DNA directly from environmental samples without culturing the microbes. This DNA is cloned into a library and screened using sequence analysis or activity assays to discover novel genes for industrial and medical use.