A long term goal of the Microbial Observatories Program is the discovery of new species. The influence of environmental gradients on microbial communities is also of interest. A powerful mechanism in the evolution of new species is geographic isolation; if species discovery is but a single goal, we might consider cultivating bacteria (Archaea and Bacteria) and describing their communities from the most isolated habitats. The fact is, however, that many of Earth’s most isolated places have already been visited and extensively studied by microbiologists, e.g., Antarctica. We have instead opted to explore a much closer area, and one noted for its biodiversity.
|Fig 1. There are only five natural lakes on Hawai‘i’s 132 islands. We sampled Lake Laysan on Laysan Atoll, Lake Kauhako on Moloka‘i, Lake Wai‘ele‘ele on Maui, Green Lake on Hawai‘i, and an unreported anchialine pond on the Pearl and Hermes Atoll. [ Honolulu]|
The Hawaiian Archipelago is widely recognized as a biodiversity ‘hotspot’, where some endemic Eucarya may be restricted to a single island, or even to a single location high on one volcano (Carr et al., 1989). On most Hawaiian islands one can find habitats as diverse as xerophytic deserts, grasslands, and lush rain forest, each of which may host native plant and animal species. Although plants, birds and insects present conspicuous examples of adaptive evolution in Hawai‘i (e.g., Amadon, 1947), investigations of bacterial species or consortia in the islands' terrestrial habitats have not been reported. The implications for microbial diversity of plant and animal speciation in isolated regions remain unexplored (e.g,. Staley, 1997; Myers et al., 2000). Isolating novel microorganisms is not necessarily a straightforward task, since their ranges or growth requirements cannot be predicted (Bull et al., 1992). Novel microorganisms may, however, offer phylogenetic insights or new bioproducts, so habitats considered likely to host species or consortia of interest should be protected (Colwell, 2000). Such habitats should also be explored. This is true for Hawai‘i, where endemic fauna and flora are considered to be at great risk of extinction, and because many islands have yet to be inventoried.
Distinct habitat types in Hawai‘i may lend themselves to studies of microbial diversity. Anchialine pools for example are accessible, but although they may host unique crustaceans their littoral locations might also ensure their bacterial flora is similar to that of the adjacent ocean. In contrast to the strictly coastal anchialine pools, a type of habitat that occurs in different locations and whose each example can be differentiated by physical, chemical or climatic factors might yield a broader range of microorganisms. Areas that have been little explored and/or unaffected by human activities would also merit investigation. Sites meeting each of these criteria do exist in Hawai‘i, in the form of natural lakes. Indeed, only five lakes have been described in Hawai‘i (Maciolek, 1982). These lakes in fact range over 3960 m (13000 ft) elevation and 1150 nautical miles of the archipelago (Fig 1 ). All but one occur in craters, but they otherwise have little in common. Chemically, the lakes vary from freshwater to hypersaline, oxic to anaerobic, and also differ in terms of inorganic nutrient concentrations, and surrounding vegetation and animal flora. Only one lake hosts vertebrates, and even these are introduced fish. Nutrient cycling in each lake is probably dominated by bacteria since invertebrates tend also to be poorly represented. We aim to employ both molecular and cultivation techniques to describe microbial diversity within each lake water or sediment sample. Neither technique alone is able to detect all species in a sample, so we hope that by combining the two methods we will detect microorganisms that might otherwise be missed by a single method approach. Through this approach, we also aim to discover and cultivate new bacterial species. Novel species may be detected by molecular methods only, but there can be no substitute for actually having a viable microorganism in vitro. We are also establishing a collection of microorganisms from Hawaiian lakes, archiving all pure strains under glycerol or by lyophilizing. This ensures the cultures are available to other parties, and also that they may be used in other studies. For example, several have already been screened in another laboratory for activities against MRSA and other clinically important pathogens.
We believe that Hawaiian lakes
present an ideal opportunity to study microbial diversity. Their different
locations, morphometries and chemistries also facilitate studies of microbial
communities across environmental gradients. Few habitats in Hawai‘i
have not been influenced by human activities, but the inaccessibility
of these lakes has ensured they remain largely pristine. Hawaiian lakes
have also been largely overlooked in the biological literature, with most
reports tending towards specific components of their biota, particularly
in Lake Waiau on the island of Hawai‘i (Laws & Woodcock, 1981;
Massey, 1981; Kinzie et al., 1998). The last and most thorough summary
of Hawaiian lakes dates back 20 years, and considered only bathymetry,
chemistry and the more prominent biota (Maciolek, 1982).
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