Context: Recently, researchers at the Centre for DNA Fingerprinting and Diagnostics (CDFD) Hyderabad have got new insight into the molecular mechanism of the Tuberculosis (TB) bacterium.
Key Points

TB is caused by a bacterium called Mycobacterium tuberculosis (M.tb), which can travel through the air.

• M.tb is equipped with several proteins like PPE2 which help it to avoid and weaken the host immune-responses.
• Identification of important virulent proteins of M.tb is important for TB care and management programmes. 
• PPE2 protein works by blocking the production of compounds called reactive nitrogen species (RNS) and reactive oxygen species (ROS), which are some of the key elements of the human immune system.

According to new studies, PPE2 could also be playing an important role in regulating the synthesis of Vitamin B12 in the bacterium.

• Vitamin B12 plays a fundamental role in bacterial metabolism and gene regulation.
• The human body cannot synthesise Vitamin B12 and depends upon gut microbiota or external food supplements to meet its daily requirement.
• M.tb has genes for B12 synthesis but the true nature of its pathway in the bacterium is still a mystery and the new study might give some insight into this.

In M.tb physiology, there is a presence of a regulatory RNA element or riboswitch in a cluster of genes known as an operon in a functioning unit of its DNA.

• The cluster has three genes: PPE2, cobq, and cobu.
• While cobq and cobu genes are already known to be part of the Vitamin B12 biosynthesis process, not much is known about PPE2’s role.
• The study observed that PPE2 could bind to DNA located before operon ppe2-cobq1-cobu and might be playing a role in its regulation.

Vitamin B12 has a fundamental role in bacterial metabolism and gene regulation and if carefully investigated, ppe2-cobq1-cobu cluster and riboswitch together, may present opportunities to translate the basic knowledge of microbial metabolism into effective therapeutic methods.