The two types of receptors that bind acetylcholine are and receptors.

"griffith's experiment discovering the "transforming principle" in pneumococcus bacteria. griffith's experiment, reported in 1928 by frederick griffith, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation." - griffith's experiment.

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom