Paramecium food vacuoles
This is a paramecium with food vacuoles stained by Congo Red stained yeast cells. Note the contractile vacuole with the characteristic "sun" shapeed radiating canals. This image is about 0.5 hours after the the stained feeding. Compare this image to the previous image in my photostream, where the vital stain Neutral Red was used. As a basic stain, Neutral Red stained the cytoplasm, whereas the acid stain Congo Red did not stain the cytoplasm. (Ball, G. (1927). Studies on Paramecium. III. The Effects of Vital Dyes on Paramecium caudatum. Biological Bulletin, 52(1), 68-78. )
A specimen of Northern Indiana Lake water was cultured to increase ciliate concentration. The ciliates were stained using Congo Red stained yeast. The 0.25 g. yeast was added to 20 ml water and then boiled to kill the yeast. A small amount of Congo Red dye was added to the cooled liquid to obtain a dark red colour. The stained yeast was added to an aliquot of the culture and placed on 3 microscope slides over a period of several hours. The Congo Red is an acid dye. Acid stains have been shown not to stain cytoplasm in paramecium. The paramecia and other ciliates eat the stained yeast such that the food vacuoles become evident. Over time as digestion occurs, some of the Congo Red turns blue as the acidity increases. However, paramecia were observed excreting red stained yeast, so this color change does not always occur.
This protocol is based largely on www.gtac.edu.au/wp-content/uploads/2016/01/EnergisingCell.... Most protocols had the Congo Red added to the live yeast prior to boiling. As a carcinogen, I did not want to deal with the vapours. I thought it might stain the dead cells and then I found the Georga Tech protocol which confirmed this.
Imaged on an Olympus BHS microscope using a Sony A7S.
Paramecium food vacuoles
This is a paramecium with food vacuoles stained by Congo Red stained yeast cells. Note the contractile vacuole with the characteristic "sun" shapeed radiating canals. This image is about 0.5 hours after the the stained feeding. Compare this image to the previous image in my photostream, where the vital stain Neutral Red was used. As a basic stain, Neutral Red stained the cytoplasm, whereas the acid stain Congo Red did not stain the cytoplasm. (Ball, G. (1927). Studies on Paramecium. III. The Effects of Vital Dyes on Paramecium caudatum. Biological Bulletin, 52(1), 68-78. )
A specimen of Northern Indiana Lake water was cultured to increase ciliate concentration. The ciliates were stained using Congo Red stained yeast. The 0.25 g. yeast was added to 20 ml water and then boiled to kill the yeast. A small amount of Congo Red dye was added to the cooled liquid to obtain a dark red colour. The stained yeast was added to an aliquot of the culture and placed on 3 microscope slides over a period of several hours. The Congo Red is an acid dye. Acid stains have been shown not to stain cytoplasm in paramecium. The paramecia and other ciliates eat the stained yeast such that the food vacuoles become evident. Over time as digestion occurs, some of the Congo Red turns blue as the acidity increases. However, paramecia were observed excreting red stained yeast, so this color change does not always occur.
This protocol is based largely on www.gtac.edu.au/wp-content/uploads/2016/01/EnergisingCell.... Most protocols had the Congo Red added to the live yeast prior to boiling. As a carcinogen, I did not want to deal with the vapours. I thought it might stain the dead cells and then I found the Georga Tech protocol which confirmed this.
Imaged on an Olympus BHS microscope using a Sony A7S.