Bacteria are known to be the cause of some of the most repugnant smells on Earth. But, now marine microbiologists have discovered that this lowest of life forms has a sense of smell of its own.

A team at Newcastle University has found that bacteria have a molecular “nose” that’s able to detect airborne, smell-producing chemicals such as ammonia, the latest issue of the ’Biotechnology Journal’ reported.

This latest discovery shows that bacteria are capable of at least four of the five senses; a responsiveness to light -- sight – contact-dependent gene expression -- touch -- and a response to chemicals and toxins in their environment either through direct contact -- taste -- or through air -- smell.

The research, led by Dr Reindert Nijland, shows how bacteria are capable of olfaction -- sensing volatile chemicals in the air such as ammonia produced by rival bacteria present in the environment.

The microbiologists have also found that bacteria respond to this smell by producing a biofilm -- or ‘slime’ -- the individual bacteria joining together to colonise an area in a bid to push out any potential competitor.

Biofilm is a cause of infection on medical implants like heart valves, artificial hips and even breast implants.

Dr Nijland said: “This is the first evidence of a bacterial ‘nose’ capable of detecting potential competitors.

“Slime is important in medical and industrial settings and the fact that the cells formed slime on exposure to ammonia has important implications for understanding how biofilms are formed and how we might be able to use this to our advantage. The next step will be to identify the nose or sensor that actually does the smelling.”

Ammonia is one of the simplest sources of nitrogen -- a key nutrient for bacterial growth. Using rival bacteria Bacillus subtilis and B.licheniformus, both commonly found in the soil, the team found that each produced a biofilm in response to airborne ammonia and that the response decreased as the distance between the two bacterial colonies increased.

Team member Prof Grant Burgess said: “The sense of smell has been observed in many creatures, even yeasts and slime moulds, but our work shows for the first time that a sense of smell even exists in lowly bacteria.

“From an evolutionary perspective, we believe this may be the first example of how living creatures first learned to smell other living creatures.

“Bacterial infections kill millions of people every year and discovering how your bacterial enemies communicate with each other is an important step in winning this war. This research provides clues to so far unknown ways of bacterial communication.”

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