Reviewing personal bacteria - the human microbiome project.

Abstract

3Over the past 200 years scientists have been exploring the amazing world of genetics regarding clinical outcome; have they been overlooking something very important? the permanent inhabitant of our systems the microbes. We need to further understand the importance of these residents regarding our personal health, identity, and social interaction, since they have been estimated to outnumber human cells by a factor of ten to one.1 It is well established that most of these are harmless, whereas, some are beneficial especially the ones living in our gut, but generally this subject remained unstudied. Can we imagine that these gut microbes can influence brain function? Twenty years ago, people would have been amused at the idea. But recently, scientists have come to appreciate these communities and their influences upon human development, physiology, immunity, and nutrition. We now call the collection of microbes living in or on our bodies, the human microbiome.2 Taking advantage of recent technological advances, The “Human Microbiome Project (HMP)” was launched in 2008 by the National Institutes of Health, USA with the mission of generating resources enabling comprehensive characterization of the human microbiota and analysis of its role in human health and disease. The human microbiome comprises all the microorganisms (bacteria, fungi, viruses and other microbes) that live in or on the body. It is a five-year project, best characterized as a feasibility study, and has a total budget of $115 million.3 The study has been focusing on microbiology of five body sites: oropharynx, skin, vaginal, gut, and nasal/lung. The research has shown enormous diversity in identities and abundances of different bacteria.4-6 The first task is to find out the involvement of these microbes in health and disease and the challenge is to tame our microbial and metagenomic diversity and use the information to improve the overall human well being. By characterizing the genetic diversity of microbes that live in specific areas of the body, scientists have found astonishing results. Noah Fierer of the University of Colorado, Boulder, studied the bacteria that live on the skin. The work of Fierer et al.7 leads us to a trail of Microbial 'CSI'. All individuals harbour bacterial communities unique to them, which they leave behind on every touched object or surface and this could be used to identify them. This opens up an interesting new pathway in forensics and biology. The fingerprints may now have a whole new meaning and it may be used as another proof of identity. Pettersson's team revealed another area of extreme interest, the brain. They found that gut microbes regulated the activity of a gene important to the production of serotonin, the key brain chemical. The team studied the activity and anxiety levels in two types of mice, germ-free (GF) mice and specific pathogen free (SPF) mice with a normal gut microbiota by measuring gene activity in regions of the brain in both. Two genes associated with anxiety were found less active in the germ-free mice. Germ-free mice were more adventurous, social, daring and less anxious because they broke down brain chemicals associated with anxiety, such as noradrenaline and dopamine, faster than the other mice. Heijtz and his colleagues8 also showed a role for the microbiome in shaping behavior of the unborn by exposing germ-free mice to gut microbes during pregnancy. They found that the resulting offspring were less active and more anxious. They observed that the chemicals released by these gut microbes, during pregnancy, may affect fetal brain development and concluded that the microbial colonization process initiates signaling mechanisms that affect neuronal circuits involved in motor control and anxiety behaviour. The other major objective of the Human Microbiome Project is with regard to the study of the changes in the microbiome leading to human health and disease. Elizabeth et al.9, while studying delayed wound healing in diabetics have found altered bacterial community organization through modification at mRNA level in the wounds of the diabetics. The modified transcriptional profile explains mobilized defense and immune responses and thus clarifies to some extent the widely appreciated clinical observation that microbial colonization of diabetic wounds contributes to impaired wound healing. Moreover, this molecular discovery could be used to identify clinical populations at risk for chronic wounds, leading to improved preventive and therapeutic measures by using them as biomarkers.