Microbial Communities in Human

Human body is the reservoir of numerous groups of microbial species. It is estimated that over ten times more microbial cells than human cells. Apparently, this figure is alarming, but good thing is that, not all microbes are harmful for human body. Most of the microbes are beneficial for mankind. Only a few species are considered as pathogenic (disease causing organisms).Microbes that in habitat in human body without causing any harm moreover help the host in various ways are called Normal flora = “Indigenous microbiota”. Microbes consistently associate with body surfaces of animals.

•  Bacteria, Archaea

•  Fungi

•  Protozoa

•  Viruses

There are very few known about associations between humans and their symbionts. Symbionts means, when both parties take advantages by helping each other. For example Escherichia coli bacteria that live in the intestine of human body produce vitamin K and B which is helpful component for human body because human cannot able to produce those vitamins. On the other hand, E.coli takes nutrients from intestine of host where it lives and multiplies. Microorganisms form mutualistic interactions with host rather than commensalistic.

Both host and microbes benefit each other. E. coli is the best known bacterium that lives in human body. It is considered as an invariable component of the human intestinal tract.

•  Exact location and sequence of its 4,288 genes are known

•  However, we do not fully understand its ecological relationship with humans!

Microbes obtain from host

•  Nutrients

•  A stable environment: Suitable oxygen, pH, and temperature for growth

•  Protection and transport

The host obtains from microbes

•  Nutrients

•  Digestive benefits (gut microbes)

•  Stimulation of immune system

•  Protection against pathogenic microbes!

 Most abundant communities in the gut:

•  Bacteria

•  ~1000 species

•  > 7000 strains

Four major phyla are dominants:

• Bacteroidetes

•  Firmicutes

•  Actinobacteria

•  Proteobacteria

The Human Micro-biome Project

The best study between human and microbes relation was carried out in 2012. The name of the research was ‘Human Micro-biome Project (HMP)’. By using genome sequencing techniques have researchers been made a map of normal micro-biota that make-up of healthy humans. A references database has been created with normal microbial variation in human by Human Micro-biome Project researchers. In this research more than 5,000 samples were collected from various body sites of 15 men and 18 women. They have been used sites such as skin, nose, mouth, stool and vagina and 242 healthy U.S. volunteers were involved in that program. The samples (DNA, microbial and human) were analyzed with DNA sequencing machines. Ribosomal RNA, 16S rRNA were the identifying tools of bacterial species and extracting microbial genome data. Eventually more than 10.000 microbial species and 81% to 91% genera were identified that inhabit in the human ecosystems.

Written By: Md. Rayhan Mahmud
Admin of Microbial World