Grazing of acidophilic bacteria by a flagellated protozoan

dNanoscale titanium dioxide (TiO 2 ) is increasingly used in consumer goods and is entering waste streams, thereby exposing and potentially affecting environmental microbes. Protozoans could either take up TiO 2 directly from water and sediments or acquire TiO 2 during bactivory (ingestion of bacteria) of TiO 2 -encrusted bacteria. Here, the route of exposure of the ciliated protozoan Tetrahymena thermophila to TiO 2 was varied and the growth of, and uptake and accumulation of TiO 2 by, T. thermophila were measured. While TiO 2 did not affect T. thermophila swimming or cellular morphology, direct TiO 2 exposure in rich growth medium resulted in a lower population yield. When TiO 2 exposure was by bactivory of Pseudomonas aeruginosa, the T. thermophila population yield and growth rate were lower than those that occurred during the bactivory of non-TiO 2 -encrusted bacteria. Regardless of the feeding mode, T. thermophila cells internalized TiO 2 into their food vacuoles. Biomagnification of TiO 2 was not observed; this was attributed to the observation that TiO 2 appeared to be unable to cross the food vacuole membrane and enter the cytoplasm. Nevertheless, our findings imply that TiO 2 could be transferred into higher trophic levels within food webs and that the food web could be affected by the decreased growth rate and yield of organisms near the base of the web.

Section: Discussionmentioning

confidence: 99%

Differential Growth of and Nanoscale TiO ₂ Accumulation in Tetrahymena thermophila by Direct Feeding versus Trophic Transfer from Pseudomonas aeruginosa

Mielke

Priester

Werlin

et al. 2013

“…Alphaproteobacterial endosymbionts have been discovered in some protists (7). Protists isolated from AMD graze on acidophilic bacteria (18,22), suggesting that they likely play a predatory role and influence the abundances of various community members. Perhaps more importantly, eukaryotes likely play a large role in the cycling of carbon within AMD communities.…”

mentioning

confidence: 99%

Insights into the Diversity of Eukaryotes in Acid Mine Drainage Biofilm Communities

Baker¹,

Tyson²,

Goosherst

et al. 2009

108

Microscopic eukaryotes are known to have important ecosystem functions, but their diversity in most environments remains vastly unexplored. Here we analyzed an 18S rRNA gene library from a subsurface ironand sulfur-oxidizing microbial community growing in highly acidic (pH < 0.9) runoff within the Richmond Mine at Iron Mountain (northern California). Phylogenetic analysis revealed that the majority (68%) of the sequences belonged to fungi. Protists falling into the deeply branching lineage named the acidophilic protist clade (APC) and the class Heterolobosea were also present. The APC group represents kingdom-level novelty, with <76% sequence similarity to 18S rRNA gene sequences of organisms from other environments. Fluorescently labeled oligonucleotide rRNA probes were designed to target each of these groups in biofilm samples, enabling abundance and morphological characterization. Results revealed that the populations vary significantly with the habitat and no group is ubiquitous. Surprisingly, many of the eukaryotic lineages (with the exception of the APC) are closely related to neutrophiles, suggesting that they recently adapted to this extreme environment. Molecular analyses presented here confirm that the number of eukaryotic species associated with the acid mine drainage (AMD) communities is low. This finding is consistent with previous results showing a limited diversity of archaea, bacteria, and viruses in AMD environments and suggests that the environmental pressures and interplay between the members of these communities limit species diversity at all trophic levels.

“…3C in reference 4). In addition, they keep organic carbon levels low and produce dissolved carbonate ions, which are likely important for the growth of chemolithoautotrophic acidophilic prokaryotes.There have been few prior reports of eukaryotes in AMD (14,18,25,34,36,38). Two extremely acidophilic (pH, Ͻ1) and metal-tolerant mitosporic fungi, Scytalidium acidophilium and Acontium velatum, were isolated by Starkey and Waksman (38).…”

mentioning

confidence: 99%

“…The taxonomic characterization of these isolates was based on their morphology. McGinness and Johnson (34) and Johnson and Rang (25) cultured unidentified protists from an AMD site and showed that they were able to graze on acidophilic bacteria in culture.…”

mentioning

confidence: 99%

Metabolically Active Eukaryotic Communities in Extremely Acidic Mine Drainage

Baker¹,

Lutz

Dawson³

et al. 2004

162

127

Acid mine drainage (AMD) microbial communities contain microbial eukaryotes (both fungi and protists) that confer a biofilm structure and impact the abundance of bacteria and archaea and the community composition via grazing and other mechanisms. Since prokaryotes impact iron oxidation rates and thus regulate AMD generation rates, it is important to analyze the fungal and protistan populations. We utilized 18S rRNA and beta-tubulin gene phylogenies and fluorescent rRNA-specific probes to characterize the eukaryotic diversity and distribution in extremely acidic (pHs 0.8 to 1.38), warm (30 to 50°C), metal-rich (up to 269 mM Fe 2؉ , 16.8 mM Zn, 8.5 mM As, and 4.1 mM Cu) AMD solutions from the Richmond Mine at Iron Mountain, Calif. A Rhodophyta (red algae) lineage and organisms from the Vahlkampfiidae family were identified. The fungal 18S rRNA and tubulin gene sequences formed two distinct phylogenetic groups associated with the classes Dothideomycetes and Eurotiomycetes. Three fungal isolates that were closely related to the Dothideomycetes clones were obtained. We suggest the name "Acidomyces richmondensis" for these isolates. Since these ascomycete fungi were morphologically indistinguishable, rRNA-specific oligonucleotide probes were designed to target the Dothideomycetes and Eurotiomycetes via fluorescent in situ hybridization (FISH). FISH analyses indicated that Eurotiomycetes are generally more abundant than Dothideomycetes in all of the seven locations studied within the Richmond Mine system. This is the first study to combine the culture-independent detection of fungi with in situ detection and a demonstration of activity in an acidic environment. The results expand our understanding of the subsurface AMD microbial community structure.The Richmond Mine at Iron Mountain, which is near the city of Redding in northern California, is a subsurface mine that contains chemolithotrophic microbial communities that are sustained by energy derived from pyrite (FeS 2 ) oxidation (4). The dissolution of pyrite from the Richmond Mine ore body yields warm (35 to 57°C), extremely acidic (typically pHs 0.5 to 0.9), metal-rich (for a review, see reference 4) fluids referred to as acid mine drainage (AMD). At the Richmond Mine it is possible to access, via mining tunnels, several environments that harbor these extremely acidophilic communities.Microbial eukaryotes likely play critical, but as yet only partially determined, roles in AMD communities. Fungal hyphae comprise a significant but variable portion of the total biomass in many biofilm communities in the Richmond Mine, particularly in those growing in flowing solutions. The hyphae may contribute to the anchoring of biofilms to pyrite sediments and may confer structure, especially to "slime streamers" (4). Relatively large fungal filaments also provide surfaces for the attachment of prokaryotes (see Fig. 3C in reference 4). In addition, they keep organic carbon levels low and produce dissolved carbonate ions, which are likely important for the growth of chemolithoautot...