Date of Graduation

Spring 2015

Document Type

Honors Research Project

Degree Name

Bachelor of Science

Major

Natural Sciences - Divisional

Research Sponsor

Dr. Hazel Barton

First Reader

Dr. Sara Carlson

Second Reader

Dr. Donald Ott

Abstract

Caves are geologic systems, shaped by inorganic chemical processes (speleogenesis). Nonetheless, there is increasing evidence that biological processes also play a role in the origin and development of caves (biospeleogenesis). In order to examine the role that microorganisms may play in secondary passage enlargement we collected samples from Lechuguilla Cave, a deep cave system that is largely shielded from human impact. Samples were collected from areas where rock corrosion was obvious. In order to determine if microorganisms were involved with the observed corrosion, we used scanning electron microscopy (SEM) to identify apparent microbial pitting of the rock surface. To establish the identity of the organisms responsible for this pitting, pure cultures of 15 bacterial isolates were obtained. PCR amplification was then utilized in order to obtain the 16S small ribosomal RNA gene sequence of each. These DNA sequences were then assembled using Geneious, followed by alignment of the DNA sequences using the SILVA sequence aligner and ARB program. Aligned sequences were used to create a phylogenetic tree using the RAxML Blackbox software, and the robustness was tested with bootstrapping. This tree allowed us to identify the isolates as Brevibacterium, Citricoccus, Kocuria, Micrococcus, and Rothia. To determine if microorganisms within these genera were responsible for the calcite dissolution observed in the environment, they were each incubated for 36 days with a calcite crystal. These crystals were then visually inspected to look for evidence of calcite dissolution. Our results suggest that microorganisms isolated from the cave environment are capable of calcite dissolution, suggesting that such species may play a role in secondary speleogenetic processes.

Included in

Microbiology Commons

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