In the presence of NEM, cells were treated with R9/GFP complexes in the presence of CytD, EIPA, or wortmannin (Wort), respectively, and analyzed by the MTT assay. Selleck CHIR 99021 Significant differences were determined at P < 0.01 (**). Data are presented
as mean ± SD from nine independent experiments. (B) The membrane leakage assay by a two-color fluorescence assay. The 6803 strain of cyanobacteria was treated with the same conditions in (A). SYTO 9 AZD8931 ic50 stains nucleic acids of live and dead cells in the GFP channel, while SYTOX blue stains nucleic acids of membrane-damaged cells in the BFP channel. Blue and green fluorescence were detected in BFP and GFP channels using a Leica confocal microscope at a magnification of 630×. Discussion In this study, Dinaciclib we demonstrate that both 6803 and 7942 strains of cyanobacteria use classical endocytosis for protein ingestion. Macropinocytosis is used by R9-mediated delivery system as an alternative route of cellular entry when classical
endocytosis is blocked (Figure 2b, 2c, and 3). Our finding of macropinocytosis-mediated entry of a CPP is consistent with studies of protein and DNA delivery in other eukaryotic cells [29, 30, 34]. We also demonstrate that cyanobacteria possess red autofluorescence. Identification and quantification of cyanobacteria in environmental samples or cultures can be time-consuming (such as plating, fluorescent staining, and imaging) and sometimes costly. Schulze et al. recently presented a new and fast viability assay for the model organism 6803 strain of cyanobacteria . This method used red autofluorescence of 6803 strain of cyanobacteria to differentiate viable cells from nonviable cells without tedious preparation [35–39]. A combination of this new assay with absorption spectra or chlorophyll concentration measurements was further proposed for more accurate quantification of the vitality of cyanobacteria PLEKHB2 . Most previous reports have focused on photosynthesis as the major route by which cyanobacteria obtain nutrition,
while only a handful of studies have evaluated endocytosis as a means of nutrition ingestion [1, 40, 41]. The first indication of macropinocytosis in cyanobacteria came from our initial screening of CPP-mediated noncovalent protein transduction among some representative organisms . We found that the mechanism of protein transduction in cyanobacteria may involve both classical endocytosis and macropinocytosis . While cyanobacteria contain cell walls and peptidoglycan layers , these structures did not hinder the penetration of CPPs in cyanobacteria (Figure 3), Gram-negative bacteria, Gram-positive bacteria and plants [26, 42, 43]. Our study is the first report that cyanobacteria use both endocytosis and macropinocytosis to internalize exogenous macromolecules (Figures 2 and 3).