Microbes: Friends or Foes?

like 861

Image source: CCMB magazine Jigyasa, Volume 15, Siva and Swaminathan.

As we begin to learn about bacteria, virus, fungi, etc. the term we always in use is ‘germs’ – which always means something hazardous to living beings and something we need to keep away/get rid of. Over times, however the concepts have changed and scientists through several years of research work have defined an ecosystem, where there exists a healthy co-existence of living beings and microbes (especially bacteria and fungi). This collection of microbes is termed as ‘Microbiota’ and their genes collectively are called as ‘Microbiome’. The beneficial role of microbes is now greatly appreciated (the diseases burden of microbes is known to all and thus is not being discussed here in details).

In this article, we would focus more on humans (only for easy understanding). In humans, the symbiotic relationship between the microbiome and the host being fundamental to 'human fitness' is now well accepted- especially with microbial dysbiosis (microbial imbalance) now been implicated in several diseases including rheumatoid arthritis, muscular dystrophy, multiple sclerosis, fibromyalgia, neonatal necrotizing enterocolitis, diabetes, obesity, neurodevelopmental disorders, cancers and many more.

Microbes have been a great source of antibiotics, which have helped us fight infections for ages now. Species of the bacterial genus Streptomyces alone produce more than 500 different antibiotics, including cycloheximide, cycloserine, erythromycin, kanamycin, lincomycin, neomycin, nystatin, streptomycin, and tetracycline. Not only this, microbes help the humans in several ways, for e.g. in synthesis of vitamins, in digestion, in generation of beneficial short chain fatty acids (antioxidants from fibre digestion), etc.

Additionally, can we even appreciate the fact that microbes actually help build up host’s immunity and even fight infections. Seems ironical, is it not?  But it is true. The gut bacteria in fact build our immunity by helping in the development of a kind of lymphocytes, called the T helper lymphocytes, which determines the pro-inflammatory or anti-inflammatory responses to any infection. Microbiome help maintain the intestinal epithelial barrier function, thus preventing the food, bacteria/bacterial products, etc. present in the intestines from entering into the blood stream and causing systemic inflammation- which further initiates disorders like obesity, diabetes, arthritis, etc.

The importance of our helpful microbiome in prevention of infections is now slowly gaining ground with the studies reporting its role in preventing/alleviating diseases like malaria, Hepatitis B infection, HIV infection, etc.

A few studies in past few years clearly demonstrate that the gut bacteria render the host “resistant” or “susceptible“  to pathology after malaria infection (mouse studies). Certain lactic acid bacteria from the breast milk of healthy women can substantially inhibit the growth and infectivity of human immunodeficiency virus type 1, or HIV-1 and gut microbes are also essential for clearing the Hepatitis B infections in mice. Additionally there are reports where disturbance in the organ microbiome results in the resident bacterium causing infections for e.g. changes in intestinal bacteria cause the Clostridium diifficle infection; the commensal Helicobacter pylori causes gastric ulcers and cancer on change in the stomach flora; Streptococcus pneumoniae (pneumococcus), cause pneumonia on serious changes in respiratory tract microbiota; change in vaginal PH causes bacterial vaginosis which may increase the incidence of Human Papilloma Virus infection, leading to increased sexually transmitted diseases and finally cervical cancer. Intestinal dysbiosis results in an inflammatory Bowel Disease (IBD).

It has to be appreciated that too less or too much of anything is to be avoided and the same holds good for our association with Microbes…..they are our co-travellers and we need to maintain just the right kind of relationship with them!

 

Article by:

Dr. Archana B Siva

Principal Scientist

CSIR-Centre for Cellular and Molecular Biology

Uppal Road, Hyderabad-500007.

Email: abs@ccmb.res.in

Posted By : ScienceIndia Administrator