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There are mysterious groups of microbes in our mouths that have evaded Petri dishes for years, with scientists unable to coax them to grow them in the lab.

But Floyd Dewhirst and his team at the Forsyth Institute, a Cambridge, Mass.-based dental research center, have figured out the trick to making them thrive. And that could be very useful in future research.


Having the bacteria available in a culture allows scientists to inspect them closely and perform experiments to see if they can cause or prevent disease.

“What I really like about my research in studying these bacteria is that I get to be the first person to isolate a particular bug,” Dewhirst said. “It’s being able to be on the cutting edge of science, and sort of be the first person to see something that no one has ever seen or worked with before.”

It has not been an easy process. The Forsyth team started trying to cultivate the bugs, known as microbial dark matter, 10 years ago. And last year, the team was able to grow one notoriously elusive group of microbes called TM7s.


Dewhirst’s has cultured 10 strains of the bug, including ones shaped like a bowling pin and a snake-like one that seems to grow inside of its bacterial host.

“One of the things that we have found about these unusual organisms is that they are parasites on other bacteria,” said Dewhirst. “And so, one of the reasons that nobody was ever able to grow them is that they tried to grow them in pure culture.”

  • The original article of Vartoukian et al, in PLoS ONE 11(1): e0146926.
    doi:10.1371/journal.pone.0146926 stated that “On the basis that truly difficult-to-culture organisms may depend for growth on signal interaction and metabolic cooperation with other bacteria within the biofilm community that they inhabit, undiluted suspensions of plaque were placed in central wells in agar culture plates, to stimulate growth of previously-uncultivated
    oral bacteria in heavily-diluted subgingival plaque samples, inoculated onto the periphery of the plates.” There was nothing in that article that implied that they had isolated bacteria that “grow inside of its bacterial host”. I am wondering where this truly sensational information comes from?

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