Microbial diversity in The Cedars, an ultrabasic, ultrareducing, and low salinity serpentinizing ecosystem

Our plain-English summary of Microbial diversity in The Cedars, an ultrabasic, ultrareducing, and low salinity serpentinizing ecosystem, by S. Suzuki, S. Ishii, A. Wu, et al (Proceedings of the National Academy of Sciences of the United States of America, 2013).

The study

• Authors: S. Suzuki, S. Ishii, A. Wu, A. Cheung, A. Tenney, G. Wanger, J.G. Kuenen, K.H. Nealson
• Journal: Proceedings of the National Academy of Sciences of the United States of America
• Published: 2013;110(38):15336-41
• Cited by: 79 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The Cedars, in coastal northern California, is an active site of peridotite serpentinization. The spring waters that emerge from this system feature very high pH, low redox potential, and low ionic concentrations, making it an exceptionally challenging environment for life. We report a multiyear, culture-independent geomicrobiological study of three springs at The Cedars that differ with respect to the nature of the groundwater feeding them. Within each spring, both geochemical properties and microbial diversity in all three domains of life remained stable over a 3-y period, with multiple samples each year. Between the three springs, however, the microbial communities showed considerable differences that were strongly correlated with the source of the serpentinizing groundwater. In the spring fed solely by deep groundwater, phylum Chloroflexi, class Clostridia, and candidate division OD1 were the major taxa with one phylotype in Euryarchaeota. Less-abundant phylotypes include several minor members from other candidate divisions and one phylotype that was an outlier of candidate division OP3. In the springs fed by the mixture of deep and shallow groundwater, organisms close to the Hydrogenophaga within Betaproteobacteria dominated and coexisted with the deep groundwater community members. The shallow groundwater community thus appears to be similar to those described in other terrestrial serpentinizing sites, whereas the deep community is distinctly different from any other previously described terrestrial serpentinizing community. These unique communities have the potential to yield important insights into the development and survival of life in these early-earth analog environments.

In plain English

This study did not examine asbestos, asbestos fibers or human health. The authors studied microbes in three springs at The Cedars in coastal northern California, where water reacts with ultramafic rock (serpentinization). The spring water has very high pH, very low redox potential and low ionic concentrations. From 2009 to 2011 they sampled springs GPS1, NS1 and BS5 and a nearby creek. They identified microbes from their DNA without growing them in culture. Each spring's dry-season chemistry was stable over the 3 years; rainwater floods the springs in the rainy season. Bacterial diversity in the springs was low compared with the creek. GPS1, fed only by deep groundwater, had the lowest richness, dominated by Chloroflexi, Firmicutes, candidate division OD1 and two undefined phyla. NS1 and BS5, fed by a mix of deep and shallow groundwater, were dominated by Betaproteobacteria close to the genus Hydrogenophaga, and BS5 also by Gammaproteobacteria. Only one archaeal type was found. The authors proposed, as a hypothesis based on correlation analyses, that the source groundwater mainly drives which microbes are present. They said more springs should be analyzed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Multiyear, multiple-season, culture-independent field study of spring microbial communities using small subunit (16S and 18S) rRNA gene clone libraries
• Who was studied: Microbial communities in three ultrabasic springs (GPS1, NS1, BS5) and the adjacent creek at The Cedars, coastal northern California. Samples were taken in 2009 (May and September) and October 2011, among other dates.
• Main results:
  • The chemical and physical properties of each spring in the dry season were stable over the 3-year study period. All three springs are inundated with meteoric water during the rainy season (November to April).
  • Diversity of bacterial operational taxonomic units in the ultrabasic springs was low compared with the adjacent creek water
  • The springs NS1 and BS5 are fed by a mixture of deep and shallow groundwater; GPS1 is fed only by deep groundwater
  • GPS1 had the lowest species richness, dominated by phyla Chloroflexi and Firmicutes, candidate division OD1, and two undefined phyla
  • NS1 was dominated by Betaproteobacteria; BS5 was dominated by Beta- and Gammaproteobacteria
  • Two abundant phylotypes at BS5 and NS1 were closely related to the genus Hydrogenophaga
  • Only one archaeal phylotype was detected, present in all ultrabasic springs in every year and season
  • 8 of 10 abundant phylotypes in GPS1 were also detected at BS5 and NS1
  • In the BS5 pool, most deep-groundwater phylotypes decreased in relative abundance at the surface compared with the bottom
• The authors' conclusion: The authors proposed the hypothesis that the main driver of microbial diversity in the three springs is the inoculum provided by the source groundwaters, strongly affected by exposure to the oxic interface
• Limitations the authors state:
  • The authors stated that more springs should be analyzed to test and refine their hypothesis
  • The hypothesis rests on correlation analyses and sequence comparisons
  • Some groups' distributions may depend on factors the authors did not measure

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Peridotite, Serpentinization.

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