Bacterial Senses
Bacterial Senses
Bacteria have, despite their incredibly tiny size, a wide array of senses available to them – they can sense light, chemicals, water ‘purity’, magnetic fields, electric currents, temperature and oxygen though no bacteria is known that uses all of these senses.
Chemicals are the thing that almost all bacteria sense – some may serve as food and thus be useful to the bacteria while others may be harmful and so avoided. In between are those that are neutral.
Sensing light is a fairly common ability – it is important to any bacterium that uses photosynthesis as this allows these bacteria to hunt out the light that is their energy source. It is also important to other bacteria, however as strong light can destroy some of the enzymes within bacteria and this could result in injury or death.
Water ‘purity’ is an odd concept to many – scientists call this characteristic osmotic pressure. Put simply the water inside the bacteria should be about as ‘pure’ as the water outside. If the water outside is purer, then water will rush into the bacteria potentially causing it to burst, if the reverse is true then the water inside the bacteria will be effectively sucked out. Neither of these is desirable for the bacteria, so this type of sense is very useful!
Temperature is also important – E. coli for example will seek out a temperature of 34C. All bacteria are more efficient at one temperature than others and many have a mechanism to measure temperature.
Oxygen is like a chemical in that some bacteria have an absolute need for it and to others, it is poisonous. Some can do without it but given the choice they will use it. This means that many bacteria can sense oxygen and even though it is strictly a chemical element, it appears to be detected by a different mechanism to the one that identifies other chemicals.
Remarkably, some bacteria can sense magnetic and electric fields – it is not known what purpose (if any) these senses serve and some microbiologists believe that they are ‘accidents’ resulting from other features of the design of the bacteria.