Creating a physical model of a biological concept -- especially microscopic organisms -- can make an abstract idea easier to understand, like balloons made to look like bacteria. Students can play with the bacteria, interact with them and use them for projects exploring where bacteria live, how they divide and what kills them.
Fill balloons with coloured water. This represents the cytoplasm. Before sealing the balloon, include two rubber bands twisted together to represent a DNA plasmid, a large cotton ball to represent the nucleoid and some glitter to represent the ribosomes. Don't completely fill the balloons; you don't want them taut.
Attach a ribbon to one end of the balloon to represent the flagellum of the bacteria.
Attach coloured tissue paper to the outside of the balloon with glue to represent Gram-positive bacteria.
Attach short strips of small ribbon to the outside of the balloon to represent the bacteria's pili.
Twist one of the elongated balloons in half to show a bacteria that's in the process of dividing.
Use graduated colours of balloons and arrange the colours in concentric circles to show generations of bacteria as it spreads out from the centre of the colony.
Attach the balloons to something like cardboard to represent the substrate on which they grow. This substrate can be decorated according to context. If the presentation will be held regarding bacterial contamination of meat, make the cardboard look like a piece of meat by colouring it red and giving it striations. The balloons should indent when pressed together.
Consider using the types of elongated balloons often used for balloon animals, especially when representing E. coli. To represent apoptosis, pop the balloons. To represent necrosis, deflate the balloons.