**Executive Summary**
This document details a new study published in PNAS by researchers from Bose Institute and Rutgers University that overturns a 50-year-old model of bacterial gene regulation. The study reveals that the sigma factor does not dissociate after initiation but remains bound to RNA polymerase throughout transcription in Bacillus subtilis and a variant of E. coli. This finding has significant implications for understanding bacterial physiology, evolution, and the development of new antibiotics.
**Key Points / Main Content**
* **Overturning Established Model:** A 50-year-old textbook model of bacterial gene regulation, known as the "sigma (σ) cycle," has been challenged. This model posited that sigma factors bind RNA polymerase to initiate transcription and then dissociate to allow elongation.
* **Universal Phenomenon Questioned:** Researchers have found that the sigma cycle is not a universal phenomenon across all bacteria.
* **New Findings in Bacillus subtilis and E. coli:** Contrary to previous beliefs, the principal transcription initiation factor in Bacillus subtilis (σA) and a modified version of the Escherichia coli σ70 factor remain bound to RNA polymerase throughout the transcription process, not just during initiation.
* **Methodology:** The study utilized modern techniques including biochemical assays, chromatin immunoprecipitation, and fluorescence-based imaging to observe sigma factor behavior in real-time.
* **Contrast with Full-Length E. coli σ70:** This finding contrasts with full-length E. coli σ70, which is released stochastically during elongation.
* **Implications:** The discovery opens new avenues for understanding bacterial gene regulation and evolution, and has broad implications for microbiology, potentially influencing research in bacterial physiology, stress response, and antibiotic development.
* **Publication:** The study was published in the Proceedings of the National Academy of Sciences (PNAS).
* **Authorship:** The study was authored by researchers from Bose Institute and Rutgers University.
**Impact Analysis**
**Researchers in Microbiology**
* **Impact:** Researchers will need to revise their understanding of bacterial gene regulation and transcription initiation, as the sigma cycle is no longer considered a universally applicable model. This will influence approaches to studying bacterial physiology and stress response.
* **Action Required:** Update scientific knowledge and research methodologies to incorporate the findings regarding the continuous binding of sigma factors to RNA polymerase in certain bacterial species.
**Antibiotic Developers**
* **Impact:** The new understanding of bacterial transcription offers potential new targets for the development of antibiotics. Inhibitors could be designed to disrupt this continuous binding process, thereby blocking infection mechanisms.
* **Action Required:** Explore the potential of targeting the interaction between sigma factors and RNA polymerase for the development of novel antimicrobial agents.
**Microorganisms (for biofuel, plastic, therapeutic compound production)**
* **Impact:** The research could lead to more efficient design of microorganisms for producing biofuels, biodegradable plastics, and therapeutic compounds by better understanding and manipulating their gene regulation mechanisms.
* **Action Required:** Utilize the insights from this study to engineer microorganisms for improved production of desired compounds.
Key Entities Referenced
Bose Institute: An autonomous institute of the Department of Science and Technology (DST) that conducted research.
Department of Science and Technology (DST): The parent department of the Bose Institute involved in the research.
Rutgers University: A university that collaborated on the research.
Proceedings of the National Academy of Sciences (PNAS): The journal where the research findings were published.
Dr. Jayanta Mukhopadhyay: Corresponding author of the study and researcher from the Bose Institute.
Ministry of Science & Technology
Indian scientists helped rewrite a 50-year-old
biological rule
Posted On: 02 MAR 2026 3:38PM by PIB Delhi
A new study overturns a central textbook model of bacterial gene regulation and unveils new paths for
understanding bacterial gene regulation and its evolution.
This could help designing better antibiotics or regulatory inhibitors that block infection mechanism and
design microorganisms that produce biofuels, biodegradable plastics, or therapeutic compounds
efficiently.
For nearly 50 years, biology has related the story of how bacteria turn their genes on with the help of the
so-called “σ (sigma) cycle” – factors that bind RNA polymerase to initiate transcription and then
dissociate to allow elongation. This concept was built largely on observations of bacterial strain E. coli
σ70.
However, Researchers from the Bose Institute, an autonomous institute of the Department of Science and
Technology (DST) and Rutgers University reveal that the cycle is not a universal phenomenon.
In a study published in the Proceedings of the National Academy of Sciences (PNAS) they have reported
that, contrary to decades of scientific belief, the principal transcription initiation factor in Bacillus subtilis
—σA—and a modified version of the Escherichia coli σ70 factor remain bound to RNA polymerase
throughout transcription, rather than being released after initiation.
“Our work shows that in Bacillus subtilis, the σA factor stays attached to RNA polymerase all the way
through the transcription process,” said Dr. Jayanta Mukhopadhyay, corresponding author from the Bose
Institute. “This fundamentally changes how we think about bacterial transcription and gene regulation.”Using a combination of modern techniques like biochemical assays, chromatin immunoprecipitation, and
fluorescence-based imaging — the researchers watched the sigma factor’s behaviour in real time. They
found that Bacillus subtilis σA and an E. coli σ70 variant lacking a part called 1.1 remain stably associated
with transcription complexes. This is in stark contrast to full-length E. coli σ70, which is released
stochastically during elongation.
“These findings provide compelling evidence that the long-accepted σ cycle does not apply to all
bacteria,” added co-author Aniruddha Tewari of Bose Institute. “It opens new avenues for understanding
bacterial gene regulation and its evolution.”
The discovery has broad implications for microbiology, potentially influencing how researchers approach
bacterial physiology, stress response, and the development of antibiotics targeting transcription.
The study, was authored by Aniruddha Tewary, Shreya Sengupta, Soumya Mukherjee, Nilanjana Hazra,
from Bose Institute and YWE and RHE and Yon W. Ebright, Richard H. Ebright, and Jayanta
Mukhopadhyay from Rutgers University, USA
Publication link: doi:10.1073/pnas. 2503801122
****
NKR/FK
(Release ID: 2234503) Visitor Counter : 384
Read this release in: Urdu , (cid:0)(cid:0)(cid:0)(cid:0)(cid:0)(cid:0) , Tamil