सूक्ष्मजीव मस्तिष्क में क्या करते हैं? What microbes are doing in the Brain?

Author : Dr. P. D. GUPTA

Former Director Grade Scientist, Centre for Cellular and Molecular Biology, Hyderabad, India

www.daylife.page 

A community of bacteria, fungi, and viruses (microbes) are living in the human brain. It is strange but true. Traditionally, the brain was thought to be a sterile environment devoid of any microbial presence. Understanding the involvement of   brain microbes has profound implications for human health. There are still many unknowns about the brain microbes, including how microorganisms enter the brain, what controls which microbes live in the brain, and the complete map of which microbes reside in a healthy brain. However, recent scientific investigations have challenged this paradigm and shed light on the potential existence of diverse and dynamic microbes within the brain. The brain microbiome is a subset of the gut microbes, and it's likely to have fewer microbes. The spectrum of brain microbes varies between individuals and brain regions, with the highest microbial burden in the cingulate cortex. They live there but do not necessarily actively reproduce. These microbes are largely quiescent (just living quietly). In fact scientists’ considered that   the brain is presumably a “dead end” for any microbes that reside there. The statement that the brain is not sterile is strengthened by the several verification techniques performed in these experiments; however, these findings were later on challenged by papers that reflected on the experiments previously performed. It is important to note that the concept of the brain microbes is still in its early stages, and many aspects remain to be elucidated.An imbalance or alteration in the composition of the brain microbes has been associated with several neurological and neuropsychiatric disorders, such as Alzheimer's disease, multiple sclerosis, Parkinson’s disease, depression, and anxiety. Understanding the complex interactions between the brain and its resident microorganisms may provide novel insights into causes of the disease, progression, and potential therapeutic interventions for these conditions. etiology

This field faces challenges such as sample contamination, technical limitations, and methodological differences, which need to be addressed to ensure the reliability and validity of research findings. The brain can also exert control over the gut microbes through neural, endocrine, and immune mechanisms Alterations in the brain microbes could have implications for neurological disorders The brain microbes are different from the bacteria which cause “ brain diseases such as brain abscesses and encephalopathies”, The disease causing microbes are of different types, the only function of these to cause disease Nevertheless, the emerging evidence supporting the presence of a brain microbes represents a paradigm shift in our understanding of the brain and its intricate relationship with microorganisms.

Here are some things to know about the brain microbes: The concept of a brain microbiome was first suggested in 2013 by a study that observed non-human RNA sequences that aligned with over 170 bacteria and phages. The study also transplanted human brain tissue into immunocompromised mice, where the same bacterial sequences were detected. 

Health implications: Some studies suggest that a disturbance in the balance of microbes in the brain can lead to disease. For example, some bacteria and fungi have been found in the brains of patients with neurodegenerative diseases (NDs). Several studies have linked specific bacteria and fungi to the development of neurodegenerative diseases. Highlight the available studies which support the theory of the brain microbes and their role in neurodegenerative diseases.  

Table 1. A summary of the evidence supporting and disproving the brain microbiome theory in neurodegenerative disease.