Blepharismins, produced by the protozoan, Blepharisma japonicum, form ion-permeable channels in planar lipid bilayer membranes

Distinguishing Activities in the Photodynamic Arsenals of the Pigmented Ciliates Blepharisma sinuosum Sawaya, 1940 and Blepharisma japonicum Suzuki, 1954 (Ciliophora: Heterotrichea)

Blepharismins are photodynamic hypericin-like dianthrones produced as a variable pigment blend in Blepharisma ciliates and mostly studied in the Afro-Asiatic Blepharisma japonicum. The present work describes the bioactivity of pigments from the Brazilian Blepharisma sinuosum. Comparative analyses showed that the pigments from both species can trigger photo-induced modifications in phospholipids, but different redox properties and biological activities were assigned for each pigment blend. Stronger activities were detected for B. sinuosum pigments, with the lethal concentration LC₅₀ 10 × lower than B. japonicum pigments in light-irradiated tests against Bacillus cereus and less than half for treatments on the human HeLa tumor cells. HPLC showed B. sinuosum producing a simpler pigment blend, mostly with the blepharismin-C (~ 70%) and blepharismin-E (~ 30%) types. Each blepharismin engaged a specific dose-response profile on sensitive cells. The blepharismin-B and blepharismin-C were the most toxic pigments, showing LC₅₀  ~ 2.5-3.0 µm and ~ 100 µm on B. cereus and HeLa cells, respectively, after illumination. Similarity clustering analysis compiling the bioactivity data revealed two groups of blepharismins: the most active, B and C, and the less active, A, D and E. The B. sinuosum pigment blend includes one representative of each clade. Functional and medical implications are discussed.

Sodium ion internalized within phospholipid membranes

Seven phospholipids, modified with ester groups in their hydrophobic chains, were synthesized and examined for their ability to promote sodium ion flux across vesicular membranes. It was found by 23Na NMR that only the phospholipids having short chain segments beyond their terminal ester groups catalyze sodium ion transfer by up to 2 orders of magnitude relative to a conventional phospholipid, POPC. The rates increase with the concentration of the ester-phospholipid admixed with POPC in the bilayer. More surprisingly, the rates increase with the time allowed for the vesicles to age. This was attributed to ester-phospholipid migrating in the bilayers to form domains that solubilize the sodium ion within the hydrocarbon interior of the membrane. Such membrane domains explain why shift reagent-modified NMR spectra display three 23Na signals representing sodium outside the vesicles, sodium within the vesicular water pools, and sodium within the membranes themselves.

A multidisciplinary approach to describe protists: a morphological, ultrastructural, and molecular study on Peritromus kahli Villeneuve-Brachon, 1940 (Ciliophora, Heterotrichea)

This study represents the first extended report on a species of the ciliate genus Peritromus, widespread in marine biotopes, characterized by a dorso-ventral differentiation peculiar among Heterotrichea. Morphological observations (live, stained, scanning, and transmission electron microscope) were combined with behavioral and molecular data. On the basis of the whole body of observations, the species was recognized as Peritromus kahli. Scanning and transmission electron microscopy have revealed a number of features such as peculiar chalice-like structures external to the dorsal surface, two types of extrusomes, and differences between dorsal and ventral somatic ciliature. The almost complete SSrDNA gene sequence was also determined. A molecular phylogenetic analysis indicated that Peritromus diverged early from other members of the Class Heterotrichea. The dorso-ventral differentiation that certainly influences the behavior of P. kahli (e.g. preference for crawling and thigmotaxis) may have been selected as an adaptation to the constraints of the interstitial habitat.

Extrusomes in Ciliates: Diversification, Distribution, and Phylogenetic Implications

Exocytosis is, in all likelihood, an important communication method among microbes. Ciliates are highly differentiated and specialized micro-organisms for which versatile and/or sophisticated exocytotic organelles may represent important adaptive tools. Thus, in ciliates, we find a broad range of different extrusomes, i.e ejectable membrane-bound organelles. Structurally simple extrusomes, like mucocysts and cortical granules, are widespread in different taxa within the phylum. They play the roles in each case required for the ecological needs of the organisms. Then, we find a number of more elaborate extrusomes, whose distribution within the phylum is more limited, and in some way related to phylogenetic affinities. Herein we provide a survey of literature and our data on selected extrusomes in ciliates. Their morphology, distribution, and possible function are discussed. The possible phylogenetic implications of their diversity are considered.