Bacteria have a sense of smell.

From BBC News:

Research has shown that bacteria - among the simplest life forms on Earth - have a sense of smell.

Scientists from Newcastle University in the UK have demonstrated that a bacterium commonly found in soil can sniff and react to ammonia in the air.

It was previously thought that this "olfaction" was limited to more complex forms of life known as eukaryotes.

The finding, published in Biotechnology Journal, means that bacteria have four of the five senses that humans enjoy.

The discovery also has implications in the understanding and control of biofilms - the chemical coatings that bacteria can form on, for example, medical implants.

Bacteria have already demonstrated the ability to react to light, in analogy to sight, and to change the genes that they express when confronted with certain materials, in analogy to touch.