A bacterial-like mechanosensitive channel controls osmoregulation and infectivity in Trypanosoma cruzi

Trypanosoma cruzi, the causative agent of Chagas disease undergoes drastic cellular morphological and biochemical changes as it passes from extracellular epimastigote and trypomastigote forms, to intracellular/tissue non-motile stage. Here we describe and characterize a mechanosensitive channel in T. cruzi (TcMscS), which is homologous to bacterial MscS. TcMscS is present in the contractile vacuole of extracellular stages but redistributes to the plasma membrane in intracellular amastigotes. The heterologously expressed TcMscS is activated by membrane tension (12 mN/m) forming a large 0.4 nS pore permeable to both anions and cations and possibly small osmolytes. The TcMscS knockdown and knockout T. cruzi strains, generated by CRISPR-Cas9 gene targeting, show slower growth in intracellular and extracellular stages, inability to robustly regulate volume and a dramatically decreased infectivity. Our study shows that the tension-driven mechanosensitive channel fulfills multiple roles in different stages of T. cruzi life cycle and is essential for infectivity.

Expanding known dinoflagellate distributions: investigations of slurry cultures from Caspian Sea sediment

To investigate the disparity between plankton and cyst records, sediment slurry cultures were used to isolate the motile stage of dinoflagellates from Caspian Sea sediment. This has resulted in new records for this area ofKryptoperidinium foliaceum,Gymnodinium aureolumandWoloszynskiasp. and for the cyst record,Scrippsiella acuminata. TwoGonyaulaxspecies were isolated, one was identified asGonyaulax balticaand the other an unknown species. Cultures ofLingulodinium polyedrawere also isolated. The approach of using slurries was useful to provide cultures from sediments that were relatively poor in dinoflagellate cysts with contents.