Cell surface lectin-binding glycoconjugates on marine planktonic protists

Abstract

Carbohydrate-protein interactions appear to play an important role in the phagocytosis of microbial prey by free-living protozoa. The present study utilizes FITC-labelled plant lectins to investigate the presence and localization of cell surface glycoconjugates on live and fixed planktonic protists (Dunaliella primolecta, Oxyrrhis marina, Goniomonas amphinema, Paraphysomonas vestita and Euplotes vannus). With live flagellate preparations, lectins primarily bound to external cell surfaces, with minimal internal staining observed. In contrast, cell fixation permeabilized cell membranes, allowing lectins to bind to internal structures, such as nuclear membranes and food vacuoles, interfering with the characterization of cell surface glycoconjugates. The method developed to label cell surface sugar moieties of live planktonic protists successfully overcomes the problems associated with fixation, and thus provides a useful protocol for future studies on protistan cell surface carbohydrate characterization.

Trait changes induced by species interactions in two phenotypically distinct strains of a marine dinoflagellate

“…Genes that clustered into category D in Alex2 included those for lectins (C-type and Ricin-B-type), which were significantly enriched in the expression analysis after 48 and 96 h ( Figure 5). In addition to phagocytosis, lectins have an important role in cell-cell recognition as well as receptor-mediated and clathrin-dependent endocytosis (Roberts et al, 2006;Varki et al, 2009). In addition, Alex2 exhibited a significant enrichment for genes associated with other adhesive (MAM) receptors after 48 and 96 h ( Figure 5), and these loci may contribute to endocytotic processes.…”

Lectins and Tetrahymena – A review

“…This can help the engulfment and use as nourishment of the prey, bacteria for the predator [63], Tetrahymena. It was demonstrated earlier that amoebae are using galactose-binding lectins for attaching Legionella pneumophila [64,65] as well as Acanthamoeba castellanii, which uses mannose-binding lectin for phagocytizing yeast [66]. Marine planktonic dinoflagellates, Oxyrrhis marina and others, use also a mannose-binding lectin to recognize and attach phytoplanktonic preys [66].…”

Nitrogen-deficient microalgae are rich in cell-surface mannose: potential implications for prey biorecognition by phagotrophic protozoa

“…They postulate that O. marina might utilise feeding receptors to recognise mannose moieties on potential prey items (e.g. microalgae [5,19]) and highlight functional similarities between protistan feeding receptors and macrophage mannose receptors which recognise highly conserved carbohydrate motifs on pathogenic organisms (4). Interestingly, the obligate and highly specific relationship between symbiotic dinoflagellates and reef building corals is already understood to be mediated by lectinglycan interactions (31).…”

“…In experiments reported here, a flow cytometric protocol optimised for marine microalgae (19), was used to quantify the density of cell-surface mannose on Isochrysis galbana that had been precultured using low-or high-nitrate f/2 nutrient media (8). Pertinently, O. marina (the phagotrophic protozoan on which mannose-specific feeding receptors have been revealed) has been observed to select against I. galbana in mixed prey feeding experiments (7,10,16); the 'distaste' shown towards I. galbana is interesting, because it is typically associated with elevated C:N ratios in I. galbana.…”

“…Fluorescein isothiocyanate-labelled Con A (FITC-Con A) isolated from the jack bean, Canavalia ensiformis (Vector laboratories) was used to label cell surface mannose residues on all stationary phase I. galbana populations according to the methodology of Roberts et al (19). Briefly, 1mL volumes from each I.galbana population (≈1.0 × 10 6 cells mL -1 ) were centrifuged (30sec, 600g) and resuspended in filtered seawater (FSW).…”