doi:10.1038/nindia.2012.135 Published online 17 September 2012
Indian scientists studying gut bacteria in lean and fat people report that the research may open up a "novel and natural way" of combating obesity1.
The scientists, who studied the differences between the dominant gut microbiota of lean and obese Indians, discovered that certain bacterial groups are prominent in the obese in comparison to the lean.
Since a large fraction of microbes inhabiting gut cannot be grown in the laboratory, they used methods based on the direct detection of their genetic material, DNA. These methods focus on a specific gene, called 16S rRNA gene present in all living organisms except viruses. They report, for the first time, an analysis and comparison of gut microbiota by sequencing 16S rRNA gene libraries.
The study revealed that methane producing 'archaea' — a group of single-celled microorganisms genetically distinct from bacteria and often living in extreme environmental conditions — was one of the predominant organisms in the gut of obese people. The other major organisms in the obese were 'bacteroides', a genus of gram-negative, anaerobic, rod-shaped bacteria. Both are known to produce small chain fatty acids (SCFA) — specifically propionate and acetate. Acetate is known to increase adipose (fat) tissue in experimental animals.
"The predominance of bacteroides and archea results in elevated glucose and SCFA supply resulting in obesity," Yogesh Shouche, the lead investigator at the National Centre for Cell Science in Pune told Nature India. "The phenomenon is reversed in lean individuals who have comparatively lower bacteroides and archaea."
The researchers have identified a representative microbial diversity in Indians and demonstrated the prominence of certain bacterial groups in obese people.
These studies are important in many ways, Shouche explains. "If one confirms the association of specific groups of microbes with leanness, then it opens up the possibility of having a novel, natural means of controlling obesity. Cultivating such microbes in the lab are especially important for this."
Shouche admits that in order to establish a direct role of any bacteria in the pathogenesis or treatment of obesity, a much more in-depth study is required. "However, our work is a stepping stone in appreciation of obesity associated gut microbiota among Indians."
A follow-up study2 threw a surprise when the researchers attempted the isolation of gut microflora. They noticed that more than 25% of the cultivated anaerobes — organisms that do not require oxygen for their growth — seemed to be new to science. This, Shouche said,"suggests that gut microflora in Indian population is under explored and is a good source for finding novel bacterial species."