Ecology Of Protists Research Articles

Marine toxin domoic acid alters protistan community structure and assembly process in sediments

Domoic acid (DA)-producing algal blooms have been the issue of worldwide concerns in recent decades, but there has never been any attempt to investigate the effects of DA on microbial ecology in marine environments. Protists are considered to be key regulators of microbial activity, community structure and evolution, we therefore explore the effect of DA on the ecology of protists via metagenome in this work. The results indicate that trace amounts of DA can act as a stressor to alter alpha and beta diversity of protistan community. Among trophic functional groups, consumers and phototrophs are negative responders of DA, implying DA is potentially capable of functional-level effects in the ocean. Moreover, microecological theory reveals that induction of DA increases the role of deterministic processes in microbial community assembly, thus altering the biotic relationships and successional processes in symbiotic patterns. Finally, we demonstrate that the mechanism by which DA shapes protistan ecological network is by acting on phototrophs, which triggers cascading effects in networks and eventually leading to shifts in ecological succession of protists. Overall, our results present the first perspective regarding the effects of DA on marine microbial ecology, which will supplement timely information on the ecological impacts of DA in the ocean.

Endogenous giant viruses contribute to intraspecies genomic variability in the model green alga Chlamydomonas reinhardtii.

Chlamydomonas reinhardtii is a unicellular eukaryotic alga that has been studied as a model organism for decades. Despite an extensive history as a model system, phylogenetic and genetic characteristics of viruses infecting this alga have remained elusive. We analyzed high-throughput genome sequence data of C. reinhardtii field isolates, and in six we discovered sequences belonging to endogenous giant viruses that reach up to several 100kb in length. In addition, we have also discovered the entire genome of a closely related giant virus that is endogenized within the genome of Chlamydomonas incerta, the closest sequenced relative of C. reinhardtii. Endogenous giant viruses add hundreds of new gene families to the host strains, highlighting their contribution to the pangenome dynamics and interstrain genomic variability of C. reinhardtii. Our findings suggest that the endogenization of giant viruses may have important implications for structuring the population dynamics and ecology of protists in the environment.

Insights into protist diversity and biogeography in intertidal sediments sampled across a range of spatial scales

AbstractThe relative importance of different ecological processes that shape community structure is a central but poorly understood topic in protist ecology. This study used an 18S rRNA gene sequencing approach to examine the relative contributions of environmental selective (environmental filtering) and neutral processes (dispersal and ecological drift) in the community assembly of three diverse protist groups (Bacillariophyta, Cercozoa, and Ciliophora) from intertidal sediment samples spanning a geographical distance up to 12,000 km. All three protist communities exhibited similar and distinct biogeographical patterns, and followed strong distance–decay relationships at continental scale (ca. 12,000 km), regional scale (ca. 1500 km), and local scale (ca. 50 km). Network analysis showed that temperature, salinity, nitrite and nitrate nitrogen, total nitrogen, and 0.1–0.25 mm grain size together associated with 60.8%, 55.5%, and 50.0% of the OTUs, which represented 68.1%, 58.5%, and 59.2% of sequence abundances for Bacillariophyta, Cercozoa, and Ciliophora co‐occurrence networks, respectively, indicating that these environmental variables played the central roles in influencing community composition. On the other hand, a neutral community model explained 73.6%, 64.2%, and 70.2% of community variation for Bacillariophyta, Cercozoa, and Ciliophora, respectively. More importantly, variation partitioning and partial Mantel tests showed that environmental selection exhibited a slightly greater influence on Ciliophora compared to spatial factors, but both components were roughly equivalent in Bacillariophyta and Cercozoa communities. Taken together, these results demonstrate that both environmental selection and neutral processes play important roles in creating the biogeographical patterns of protist communities in intertidal sandy beach ecosystems.

Abundant and diverse Tetrahymena species living in the bladder traps of aquatic carnivorous Utricularia plants

Ciliates are unicellular eukaryotes known for their cellular complexity and wide range of natural habitats. How they adapt to their niches and what roles they play in ecology remain largely unknown. The genus Tetrahymena is among the best-studied groups of ciliates and one particular species, Tetrahymena thermophila, is a well-known laboratory model organism in cell and molecular biology, making it an excellent candidate for study in protist ecology. Here, based on cytochrome c oxidase subunit I (COX1) gene barcoding, we identify a total of 19 different putative Tetrahymena species and two closely related Glaucoma lineages isolated from distinct natural habitats, of which 13 are new species. These latter include 11 Tetrahymena species found in the bladder traps of Utricularia plants, the most species-rich and widely distributed aquatic carnivorous plant, thus revealing a previously unknown but significant symbiosis of Tetrahymena species living among the microbial community of Utricularia bladder traps. Additional species were collected using an artificial trap method we have developed. We show that diverse Tetrahymena species may live even within the same habitat and that their populations are highly dynamic, suggesting that the diversity and biomass of species worldwide is far greater than currently appreciated.