A biodiversity study of high temperature mud pool microbial communities: implications of regional/geographical isolation and endemism
Date
2006
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Publisher
University of Delaware
Abstract
In assessments of global biodiversity, extreme environments like terrestrial and deep-sea hydrothermal venting systems have been the focus of much scientific research. Created by the interactions of crustal plates and “hot spot” eruptive events, these unique ecological niches have led to a wealth of information on the diversity and evolution of life on earth. The organisms that thrive in high temperature ecosystems have challenged our understanding of the physical and biochemical constraints on the upper temperature limits for life and stimulated new theories on the origins of life on earth and the possible existence of life on other planets. One terrestrial extreme environment that has remained relatively uncharacterized in terms of microbial biodiversity is the high temperature mud pool. While molecular and geochemical technologies, independent of traditional isolation and cultivation methodologies, have contributed immensely to the study of life in other high temperature systems like submarine hydrothermal vents and terrestrial hot springs, high temperature terrestrial mud pools have yet to be explored using these sophisticated tools. ☐ The aim of this research was to perform an intensive survey of the microbial diversity of high temperature mud pools on a regional and geographical scale using a combination of molecular and geochemical analytical techniques. Mud pool samples were collected from the thermal fields of the Taupo Volcanic Zone (TVZ), New Zealand (regional survey); Rincon de la Vieja National Park, Costa Rica; Lassen Volcanic Park, USA; and Yellowstone National Park, USA. Bacterial community analysis was performed using a combination of DNA fingerprinting and sequencing analyses. Community level analysis of high temperature mud pools showed the majority of the pools were dominated by members of the gamma Proteobacteria, the Cytophaga- Flavobacteria, and the alpha Proteobacteria. These bacterial signatures persisted across a broad range of physiochemically distinct mud pools. Although the dominant groups were consistent across the majority of the pools, the bacterial diversity observed in the DGGE fingerprinting analysis suggested physical isolation might dictate bacterial community diversity of individual pools over both a regional and geographical range. ☐ The second objective of this study was to determine if the mud pool communities support a unique endemic community when compared to hot spring systems. Samples were collected from a mud pool and several closely associated hot springs within the Tokaanu Thermal Area, New Zealand. DNA fingerprinting analysis of the bacterial and archaeal communities showed a unique microbial assemblage unique to the Tokaanu mud compared to neighboring hot water features. The mud pool was found to harbor a diversity of bacteria relating to the Firmicutes, epsilon Proteobacteria, gamma Proteobacteria, Thermus sp., and others from high temperature and deep subsurface environments. Signatures of the archaeal community associated with this pool revealed a closely related group of Archaea forming a unique clade of the Crenarchaeota. The strong similarities between these archaeal signatures and their relative distance from other characterized Crenarchaeotes suggested these microbes are endemic to the Tokaanu mud pool system.