[Show abstract][Hide abstract] ABSTRACT: As part of a Microbial Observatory of Caterpillars located in the Area de Conservacíon Guanacaste (ACG) in northwestern Costa Rica, we isolated a novel species of the genus Vannella associated with the food of the caterpillars of the saturniid moth Rothschildia lebeau, namely the leaves of the dry forest deciduous tree Spondias mombin (Anacardiaceae). The new species can be distinguished from other described species of the genus by the presence of a plasmalemma coated with a thickened, osmiophilic lamina containing glycostyles, and by its unusual habitat, the leaf surfaces or phylosphere of S. mombin. We further established the novelty of our isolate by sequencing its nuclear small-subunit (SSU) rRNA gene and inferring its phylogenetic position among all other currently sequenced members of the genera Vannella and Platyamoeba. Our results reveal that our isolate shares most recent common ancestry with three strains of Platyamoeba placida, the type species of the genus Platyamoeba. Despite this placement, the isolate clearly possesses glycostyles that are the hallmark of the genus Vannella. In addition to the cultured isolate, we also present a closely related sequence from a SSU rRNA gene clone library constructed from a DNA extract of leaf-wash of S. mombin with sterile water.
[Show abstract][Hide abstract] ABSTRACT: Spain's Rio Tinto, or Red River, an example of an extremely acidic (pH 1.7-2.5) environment with a high metal content, teems with prokaryotic and eukaryotic microbial life. Our recent studies based on small-subunit rRNA genes reveal an unexpectedly high eukaryotic phylogenetic diversity in the river when compared to the relatively low prokaryotic diversity. Protists can therefore thrive in and dominate extremely acidic, heavy-metal-laden environments. Further, because we have discovered protistan acidophiles closely related to neutrophiles, we can hypothesize that the transition from neutral to acidic environments occurs rapidly over geological time scales. How have these organisms adapted to such environments? We are currently exploring the alterations in physiological mechanisms that might allow for growth of eukaryotic microbes at acid extremes. To this end, we are isolating phylogenetically diverse protists in order to characterize and compare ion-transporting ATPases from cultured acidophiles with those from neutrophilic counterparts. We predict that special properties of these ion transporters allow protists to survive in the Rio Tinto.