Episode Summary

Intricate networks of tunnels in garnet gemstones seem to have come from tunneling microorganisms!

Thanks to Magnus Ivarsson for his contribution!

Microbe of the episode: Streptomyces griseosporeus

News item

Tiny tunnels inside garnets appear to be the result of boring microorganisms

Journal Papers

Other interesting stories

Episode outline

Background: Caves actually nice place to live
  • Durable, well-conditioned, stylish
  • Not necessarily roomy or bright or easy to furnish
Some microbes like caves too—enough to make their own!
  • Endoliths – microbes living in substrate like rock, or shells, corals, or wood
  • Often chemolithotrophs, eating minerals, but sometimes heterotrophs or photoauto
Some excavate little cavities on surface, some make complex tunnels
  • Usually chemical, like acid or chelators; also some force involved, if filamentous
  • Harder substrates usually have less deep excavations
What’s new: But now, Magnus Ivarsson and colleagues, publishing in PLOS One, have discovered that tunnels found in a fairly hard mineral, garnets, seem to be created by microbes!

The press release says this is a finding about boring microorganisms, but I think they're actually quite interesting!

Methods: Here's Dr. Ivarsson describing the study: "Our study is on complex networks of microsized tunnels in garnets found all over Thailand. We find them in river sediments, soils, etc. We believe the tunnels were formed by microbial dissolution, most probably by fungi; they are the only type of microbe that can produce these sort of very complex mycelium-like networks."

Microscopic, mineral, and chemical analyses
  • Not conclusive evidence that tunnels caused by living thing, but suggestive
Tunnels start wider and get narrower going in
  • Some have red filamentous structures inside
  • And fatty acids of various compositions found inside
    • Could have come in from outside, but none found on outside
Authors have plans for future too: "We haven't found the responsible species yet, but in the future we will go back to Thailand and we will sample for DNA and RNA and hopefully also isolate the responsible fungi."

Next important questions: how could they bore through such hard mineral? And why?
  • Iron available in garnets could be useful
Applications and implications: Relevant to gem trade: "Garnets are a type of gem, and the gem is a big industry in Thailand. These tunnels decrease the value of garnets as a gem, so understanding why these tunnels form, and where we can look for gems and garnets without these deforms will be very important for this business."

Sometimes microbes chewing stuff makes it more valuable, like yeast and grapes
  • Other times, not so much!
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