The parabasalid symbiont community of Heterotermes aureus: Molecular and morphological characterization of four new species and reestablishment of the genus Cononympha.

The subterranean termite Heterotermes aureus is endemic to arid regions of southwestern USA and northern Mexico. Like other termites in the family Rhinotermitidae, it harbors a community of protists (Phylum Parabasalia) in its hindgut that aid in cellulose digestion. We investigated the hindgut community of H. aureus using light microscopy, single cell isolation, and high throughput amplicon sequencing. Here we describe four new parabasalid species from the classes Trichonymphea and Spirotrichonymphea. Three of the new species include Pseudotrichonympha aurea (Trichonymphea), Holomastigotoides aureus, and Holomastigotoides oxyrhynchus (Spirotrichonymphea). The fourth new species is a Spirotrichonympha-like protist for which we reinstate the genus Cononympha and describe under the name Cononympha aurea (Spirotrichonymphea). We also used high throughput amplicon sequencing with custom primers on DNA from fresh and ethanol preserved termites collected across the southwest USA and Mexico to investigate population-level differences in hindgut community composition. We report that the community is highly similar across populations: no additional parabasalid species were identified in any of the H. aureus specimens, but several specimens appeared to lack either C. aurea or H. oxyrhynchus.

Chimeric origins of ochrophytes and haptophytes revealed through an ancient plastid proteome.

Plastids are supported by a wide range of proteins encoded within the nucleus and imported from the cytoplasm. These plastid-targeted proteins may originate from the endosymbiont, the host, or other sources entirely. Here, we identify and characterise 770 plastid-targeted proteins that are conserved across the ochrophytes, a major group of algae including diatoms, pelagophytes and kelps, that possess plastids derived from red algae. We show that the ancestral ochrophyte plastid proteome was an evolutionary chimera, with 25% of its phylogenetically tractable nucleus-encoded proteins deriving from green algae. We additionally show that functional mixing of host and plastid proteomes, such as through dual-targeting, is an ancestral feature of plastid evolution. Finally, we detect a clear phylogenetic signal from one ochrophyte subgroup, the lineage containing pelagophytes and dictyochophytes, in plastid-targeted proteins from another major algal lineage, the haptophytes. This may represent a possible serial endosymbiosis event deep in eukaryotic evolutionary history.