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Amaral Zettler Laboratory
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Linda Amaral Zettler,
Associate Research Scientist
Linda Amaral Zettler's CV >>
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ASTROBIOLOGY: Microbial diversity and population structure studies in the Río Tinto
One of the goals of NASA's Astrobiology program is to explore the limits of life on Earth as analogues for environments on Mars, Europa and other planets that might support life. Our current research centers on such an analog: the Rio Tinto, a 100 km long river in southwestern Spain, that has a pH range of 1.7-2.5, high concentrations of heavy metals, and an iron content that is thought to resemble conditions that may exist on Mars. Our recent small-subunit rRNA-based studies reveal unexpectedly high eukaryotic phylogenetic diversity in the river. These studies tell us that protists can thrive and dominate in extreme environments. To date, molecular surveys of the Río Tinto have been restricted to domain-level investigations of prokaryotes OR eukaryotes but combined studies have not been undertaken. In this project we employ a new technique called SARST in combination with traditional full-length rRNA gene sequencing of novel taxa to explore the river's diversity at the three-domain level of life. Our sampling for molecular surveys takes into account spatial and temporal scales and concomitant physico-chemical measurements. By combining diversity information with physical and chemical data, we can explore how geochemical forces shape community structure in the Río Tinto. Using multivariate statistical methods, we hope to ultimately reveal potential physico-chemical correlations with distributions of prokaryotes and eukaryotes in the river.
This work is being carried out in collaboration with Ricardo Amils at the Autonomous University of Madrid in Spain.
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LEXEN: Adaptations of unicellular eukaryotes to extremely acidic environments
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Our diversity studies in the Rio Tinto identify organisms that live under acid/high metal extremes but tell us little about how these organisms have adapted to such environments. We are currently focusing on exploring the alterations in physiological mechanisms that might allow for growth of eukaryotic microbes at acid extremes. To this end we have isolated divergent protists from the Rio Tinto such as Chlamydomonas sp., Euglena cf. mutabilis (shown), Chlorella sp., and a lobose amoeba, assigned to the genus Vannella. We are currently isolating and characterizing ion-transporting ATPases in these cultures and comparing these genes with those from neutrophilic counterparts obtained from culture collections. We predict that special properties of these ion transporters allow protists to survive in the Rio Tinto's extreme conditions.
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This work is being carried out in collaboration with Peter Smith and Mark Messerli with the Biocurrents Center at the MBL.
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Microbial Observatories : A Tropical Microbial Observatory: Collaborative research on microbial diversity in caterpillars
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The goal of the Microbial Observatory of Caterpillars (MOCAT) is to explore prokaryotic and eukaryotic microbial diversity in relation to macro-organismal species diversity in a tropical forest system using the caterpillar and its environs as a focal point. MOCAT, established in 2001 at the Center for Research on the Dry Forest in the Area de Conservacíon Guanacaste (ACG) in northwestern Costa Rica, was the first concerted effort to study the diversity of the entire microbial community (bacterial, archaeal and eukaryal) associated with a subsection of this ecosystem: the caterpillars of the saturniid moth Rothschildia lebeau feeding on the leaves of the dry forest deciduous tree Spondias mombin (Anacardiaceae). Our work explores the protistan diversity component of the project using both culture-dependent and culture-independent methods.
Our studies reveal a much greater diversity of protistan taxa occurring on associated leaf food and in the caterpillar frass (fecal pellets) than in the caterpillar gut itself.
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This work is part of a NSF-funded Microbial Observatory headed by Anna-Louise Reysenbach at Portland State University.
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The Woods Hole Center for Oceans and Human Health: Human pathogens and coastal ocean processes
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Some human pathogens are natural members of the marine microbial community (e.g Vibrio species), but many others, such as the protist Giardia, are introduced into seawater from sewage input and terrestrial runoff. Despite the potential for their impact on human health, little is known about the occurrence, much less the prevalence and distribution, of traditionally non-marine human pathogens. The survival and persistence of various pathogens is most certainly influenced by environmental conditions, and the contamination of coastal and estuarine areas through freshwater runoff, sewage and thermal pollution have the potential to alter local environmental conditions. Studies that examine pathogen presence and persistence need to be coupled with predictive models in order to begin to determine where and when the risks of potential infection, or simply the presence of pathogens, are highest. This project aims to determine the distribution and abundances of particular human pathogens (Giardia, Cryptosporidium, Acanthamoeba, Naegleria, Vibrio and Legionella) in a significantly impacted estuarine environment, Mount Hope Bay, MA. Data will be collected over spatially and temporally relevant scales (multiple sites, multiple years). Observations of the physico-chemical environment will be combined with biological distribution and persistence information, to build and validate a three-dimensional water quality/eutrophication model for the bay that could be used to predict where and when pathogens could be found.
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This work is being carried out in collaboration with Rebecca Gast at the Woods Hole Oceanographic Institution.
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