Chlamydia found under the Arctic floor

[pinball1970]

TL;DR

The team found the group of species growing without the need for host cells obtaining nutrients from the extreme environment around them.

The paper published last week is here.

https://www.cell.com/current-biology/fulltext/S0960-9822(20)30189-5

My understanding was Chlamydia are intracellular parasites and are dependent on a host cell much like a virus so this is unexpected?

 

[BillTre]

from wikipedia:

the genus Chlamydia, a group of obligate intracellular parasites of eukaryotic cells.[3] Chlamydial cells cannot carry out energy metabolism and they lack biosynthetic pathways.[7]

C. trachomatis is thought to have diverged from other Chlamydia species around 6 million years ago. This genus contains a total of nine species: C. trachomatis, C. muridarum, C. pneumoniae, C. pecorum, C. suis, C. abortus, C. felis, C. caviae, C. psittaci. The closest relative to C. trachomatis is C. muridarum, which infects mice.[5] C. trachomatis along with C. pneumoniae have been found to infect humans to a greater extent. C. trachomatis exclusively infects human beings. C. pneumoniae is found to also infect horses, marsupials, and frogs. Some of the other species can have a considerable impact on human health due to their known zoonotic transmission.

So yes, obligate parasites.
They may be infecting some eukaryotic cell found down there so they could still fill the group's nitch of being an obligate parasite.

 

[pinball1970]

from wikipedia:
So yes, obligate parasites.
They may be infecting some eukaryotic cell found down there so they could still fill the group's nitch of being an obligate parasite.

They could but the summary says they found no evidence of hosts and suggested a possible 'alternative life style strategy' for them.

 

[BillTre]

That's possible. Cholera is an example of a pathogen which has non-pathogenic varient strains, as well as closely related species that free live in water and can opportunistically infect fish.

If the Chlamydia has an 'alternative life style strategy', that would be breaking with the either the obligate intracellular lifestyle of the genus.
It could be a descendant of the Chlamydia's non-intracellular living ancestor.
It seems less likely that it went from being a intracellular pathogen to not being an intracellular pathogen. The wikipedia article said it had a reduced genome (genes not needed for extracellular living having been jettisoned).

 

[Laroxe]

I notice they make the important point that "the vast majority of this chlamydial diversity has been underexplored, biasing our current understanding of their biology" this is an important point, its still the case that our knowledge of the microbial communities that surround us is still very limited. Until very recently all the scientific effort to classify organisms was focussed on pathogens, its only since the development of genetic techniques that we have become more aware of the diversity involved. They make the point that in their study of this one species they have expanded by over a third the known genomic diversity in this phylum.
The problem with these methods is that they give only limited information about the organisms lifestyle or the way in which they interact with other organisms. They say the identified genomic features that may be indicative of host-association but in areas in which the bacterial communities had a population in which 43% belonged to this species its difficult to imagine they must all exist in an intracellular state.