A whole new world

Courtesy of Mark Welch et al, PNAS, 2016.
Courtesy of Mark Welch et al, PNAS, 2016.

To bacteria the human mouth is a whole world; the tongue and gums their own continents and each tooth a different nation. While small parts of these bacterial cities have been looked at before, researchers Jessica Mark Welch and Gary Borisy, from Marine Biological Laboratory and the Forsyth Institute in Massachusetts, respectively, have now mapped out their entire planet—in technicolour.

The researchers collected dental plaque from 22 healthy mouths for microscopic consideration. The scrapings were coated with probe molecules in a range of colours, each set of probes able to single out a group of bacteria. In total they were able to colour 96 per cent of the present bacteria.

Though others have worked in this space, Welch and Borisy have gone beyond previous endeavours to identify this bacteria, using a total of 15 probes in comparison to the usual one or two. Once able to perfect their technique, by equalising the intensity at which the probes glowed the bacteria shone from their map, the team could view a rainbow community of bacteria like no one has before.

The team were pleased to discover that the bacteria were not randomly dispersed, but organised. The mapped bacteria formed what the team have called ‘hedgehog’-like shapes—central magenta strands of Corynebacterium surrounded by a crown of Streptococcus.

“When we got our first images, we saw these fantastic structures and we were delighted,” said Borisy.

The results have astounded the plaque research community, who often considered plaque as a disorganised mass.

“These results show the very best of what can happen when you look at something well known–[in this case] plaque–in a new way,” said the study’s reviewer, Michael Fischbach from University of California, San Francisco. “The degree of organisation in the community is beyond my wildest dreams. This makes me think plaque is less like a random mixture of bacteria and more like a tissue; organized into sub-structures that probably have specific functions.”

Borisy and Welch are now looking to extend their research into other bacterial areas.

“We’ve begun looking at other sites,” said Borisy. “Plaque was a test bed; the technology is completely general. We could look at other microbiomes in the mouth, elsewhere in the body, in the natural environment, and in the built environment.”

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