Mouth with probably over 240 species of bacteria inside |
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It’s been an interesting week in the stratosphere with a fireball in Wisconsin caught on video and a giant ash plume from the eruption of Iceland’s Eyjafjallajökull volcano.
But I’m feeling a bit introspective. Published in The ISME Journal, researchers (including a couple from the J. Craig Venter Institute in Rockville and the Institute For Genome Sciences at the University of Maryland School of Medicine) finally determined the bacterial diversity of our mouths or at least of 10 lucky individuals.
The researchers collected 26 separate samples from different parts of each healthy person’s mouth and pooled them, collecting and amplifying the RNA sequences present. RNA (or ribonucleic acid) contains the important coding information from DNA. RNA is necessary to every living organism, transcribed from DNA and translated into protein. Without RNA, there would just be pieces of DNA code, unable to be read or to be used as a template to construct protein. By isolating and amplifying a specific piece of RNA present only in bacteria, scientists are able to determine specific species through deciphering the sequences. In this study, around 1000 sequences per mouth were analyzed.
So what did they find? Contrary to past estimates that the mouth harbors 500-700 different bacterial species, this study found about 240 belonging to 9 different phyla or groups. As you may expect, not every mouth is the same. Subject 4 had the greatest number of bacteria (lucky duck), and only around 50 different species were expected to be shared between any two individuals with 11 shared between all 10 of the people studied. If you’re really into species (and who isn’t?), the magic 11 are: Haemophilus parainfluenzae, Streptococcus oralis, Streptococcus sanguinis, Granulicatella adiacens, Veillonella parvula, Veillonella dispar, Rothia aeria, Actinomyces naeslundii, Actinomyces odontolyticus, Prevotella melaninogenica and Capnocytophaga gingivalis. Interestingly, although every subject had sequences belonging to the group of bacteria known as Neisseria, no single specific Neisseria species was shared across all subjects. Our mouth bacterial flora also appears to be very distinct from that found in our colon, confirming that these are very different environments (as if we didn’t know that already).
It’s already known that bacterial flora can be passed from mother to child. I wonder if this study had been conducted with healthy couples who kiss frequently, if they would find a more similar bacterial diversity than 10 strangers. But that study probably isn’t a strong candidate for NIH funding.
