Biology ETDs

Publication Date



Worldwide, lava tubes host colorful microbial mats on their walls and ceilings. Little is known about the diversity and ecological roles of the bacteria communities in the subsurface ecosystem of lava tubes. White and yellow microbial mats were collected from four lava tubes from the Azorean island of Terceira and from four lava tubes on the Big Island of Hawaii, to compare and contrast the diversity of bacteria found in lava tubes. The 16S rRNA gene was sequenced in order to determine the diversity within these caves, and to begin to elucidate the environmental controls on microbial diversity in the subsurface by comparing community structure to environmental parameters. One hundred ninety two sequences from 16 samples were analyzed. Fifteen phyla were found across the samples. With more Actinobacteria clones retrieved from Hawaiian communities, while more Alphaproteobacteria clones were found in Azorean communities. The Actinobacteria exhibited considerable novel diversity, with several distinct novel clades that shared less than 94% sequence identity. Geographical location was the major contributor to differences in community structure. The diversity of ammonia oxidation (amoA) and nitrogen fixation (nifH) genes in bacterial mats from lava tube walls in the Azores was investigated using denaturing gradient gel electrophoresis (DGGE). The lava tubes were found under different land use categories, pasture, forested and sea/urban. Soil and water samples from each lava tube were analyzed for nutrient content. Nitrosospira-like sequences dominated the ammonia oxidizing bacteria (AOB) community, and the majority of the diversity was found in lava tubes under forested land. The nitrogen fixation community was dominated by Klebsiella pneumonia-like sequences, and diversity was evenly distributed between pasture and forested land. The results suggest that land use is impacting the AOB more than the nitrogen fixing bacteria. Furthermore, the results of these studies underscore the need for further investigation of these unique ecosystems.

Project Sponsors

Cave Conservancy of the Virginias, Graduate Research Allocation Committee at the University of New Mexico Biology, University of New Mexico Biology Grove Scholarship, Student Research Allocation Committee at the University of New Mexico, National Speleological Society, New Mexico Space Grant Consortium, Fundaç\xe3o Ci\xeancia e Tecnologia




Nitrogen cycling, Microorganisms, Species Diversity, Lava Tubes, Caves, Hawai'i, Azores, nifH, amoA

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Northup, Diana

Second Committee Member

Porras-Alfaro, Andrea