# DBT JRF 2022 — Question 147

Exam: DBT JRF 2022 · Section: B · Topic: Marine Biotechnology › Metagenomics & VBNC Organisms · Difficulty: Medium

## Question

Due to the difficulty of isolating and culturing, many marine microorganisms are regarded as "viable but non-culturable" (VBNC). Which one of the following is a suitable method to hunt for useful genes in these organisms?

## Options

- **A.** in situ cultivation
- **B.** growing them in a large bioreactor
- **C.** barcode sequencing
- **D.** metagenomic analysis

## Answer

Option D

## Explanation

Metagenomics for studying unculturable marine microorganisms (VBNC): The VBNC (Viable But Non-Culturable) problem: estimated >99% of marine microorganisms cannot be grown in laboratory culture conditions — they have specific nutrient requirements, syntrophic partnerships, or pressure/temperature dependencies. Metagenomics solves this: 1. Collect environmental seawater sample. 2. Extract total community DNA directly (without culturing). 3. Fragment and sequence using NGS (shotgun metagenomics) or 16S rRNA amplicon sequencing. 4. Assemble sequences bioinformatically into contigs and MAGs (Metagenome-Assembled Genomes). 5. Annotate genes from assembled contigs → discover novel genes and biosynthetic pathways. Alternatives and why they fail: • In situ cultivation: still requires growing cells; VBNC by definition won't grow. • Large bioreactor: also requires cultivation. • Barcode sequencing: identifies species but doesn't discover novel genes. Answer: Metagenomics — direct environmental DNA sequencing without culturing — is the only culture-independent method to discover genes from VBNC marine microorganisms.

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