Award Date


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Biological Science

Number of Pages



The potential for the bioremediation of contaminated subsurface environments has led to investigations of the microbial ecology of various subsurface environments throughout the United States, including arid western regions. Initial research was conducted in uncontaminated sites and findings were to be compared with those from contaminated areas. Tunnel systems within the deep subsurface of Rainier Mesa, Nevada Test Site, afforded a unique opportunity to study microbial ecology because large amounts of material could be aseptically sampled with relative ease cmpared to drilling operations; Characterization of the microbiota within and between tunnel systems in Rainier Mesa demonstrated that bacterial communities were present in strata ranging from 50 to 450 m depth. These microbiota were heterogeneously distributed as were those from 19 samples taken within a 21 m{dollar}\sp3{dollar} section of rock from 400 m depth. Analysis of microbial communities along an elevational gradient included characterization of surface soil, a paleosol, volcanic rock (from an outcrop), zeolitized subsurface rock, fracture flow water, and outflow spring water. The unique microbial communities recovered from these various sites provided evidence that endolithic bacterial communities within the deep subsurface of Rainier Mesa have been in place for long periods of time; An analysis of subsurface samples before and after storage indicated that the recoverable microbial communities increased in abundance and decreased in diversity with prolonged storage. Some of the change in microbial communities with storage could be attributed to the proliferation of a few "weed" bacterial types. However, the recovery of new bacterial types throughout storage suggests that dormant bacterial types may be "awakened" due to some aspect of sampling or sample handling. These experiments demonstrated the need to minimize sample perturbation and storage time before analysis; The heterogeneous distribution of microbiota in zeolitized rock with negligible water flux, and the recovery of new bacterial types as a result of storage-related phenomena, provide mounting evidence that the bacteria extant within the subsurface of Rainier Mesa were dormant bacterial types. These bacteria may have survived for extended periods of time, but because they may be isolated in microhabitats as dormant forms, they may not be influenced by or be influencing their current surroundings.


Characterization; Mesa; Microbiota; Nevada; Rainier; Recovery; Site; Test

Controlled Subject

Microbiology; Ecology

File Format


File Size

9789.44 KB

Degree Grantor

University of Nevada, Las Vegas




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