Microbial life in the unsaturated subsurface under conditions of extremely low recharge: an extreme environment

Fred J. Brockman; Christopher J. Murray; Ellyn M. Murphy; Bruce Bjornstad; David Balkwill; David B. Ringelberg; Susan Pfiffner; Robert Griffiths

doi:10.1117/12.278793

11 July 1997 Microbial life in the unsaturated subsurface under conditions of extremely low recharge: an extreme environment

Fred J. Brockman, Christopher J. Murray, Ellyn M. Murphy, Bruce Bjornstad, David Balkwill, David B. Ringelberg, Susan Pfiffner, Robert Griffiths

Author Affiliations +

Proceedings Volume 3111, Instruments, Methods, and Missions for the Investigation of Extraterrestrial Microorganisms; (1997) https://doi.org/10.1117/12.278793
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

Abstract

Deep unsaturated sediments with very low levels of sediment- associated nutrients and extremely low levels of vertical movement of moisture (i.e., recharge) were studied as a model extreme environment to better understand microbial survival over geologic time periods and the resulting spatial distribution of viable microorganisms. Chloride mass balance measurements indicate that the study site has received an average annual recharge of 15 micrometers since the last Pleistocene flood approximately 13,000 years ago. Viable biomass as determined by measurement of phospholipid fatty acid in 75 g samples was approximately 10⁴ cells/g sediment. However, highly sensitive microbial activity assays failed to detect microbial activity in > 60% of 10 g samples. Microbial activity was not detected in 29% of replicate 10 g samples in the presence of nutrients for 244 days, indicating that viable microorganisms are spatially discontinuous. In separate experiments, microbial activity was not detected in 0.1 g or 1 g samples but was encountered in 37% of the 10 g samples and in 75% of the 100 g samples. These results indicate that viable microorganisms exist in `hotspots' separated by extensive regions of excluding conditions. In addition, the results suggest that if extremely low nutrient flux conditions exist at target extraterrestrial locations, successful recovery of viable microorganisms may require acquisition of many, or large, samples.

Citation Download Citation

Fred J. Brockman, Christopher J. Murray, Ellyn M. Murphy, Bruce Bjornstad, David Balkwill, David B. Ringelberg, Susan Pfiffner, and Robert Griffiths "Microbial life in the unsaturated subsurface under conditions of extremely low recharge: an extreme environment", Proc. SPIE 3111, Instruments, Methods, and Missions for the Investigation of Extraterrestrial Microorganisms, (11 July 1997); https://doi.org/10.1117/12.278793

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available