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["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

http://www.bbc.co.uk/news/science-environment-10985313
16 August 2010 Last updated at 06:42 ET

Bacteria can 'smell' their environment, research shows
By Jason Palmer Science and technology reporter, BBC News
Vials of bacterial culture (Newcastle Uni) Vials nearest "well-fed" 
bacteria responded to ammonia in the air

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.
Sniff test

However, there is a distinction between an organism reacting to a 
chemical that it encounters directly (in analogy to the sense of taste) 
and a reaction to a chemical that is floating around in the air, says 
Reindert Nijland, lead author of the study.

"The difference is both in the mechanism that does the sensing, as well 
as in the compounds that are sensed," Dr Nijland, now at University 
Medical Centre Utrecht in the Netherlands, told BBC News.

"The compounds detected by olfactory organs are generally much more 
volatile than things you can taste like 'sweet' or 'salt', and therefore 
can provide information about things that can be much further away; you 
can smell a barbecue from a few blocks away whereas you have to 
physically touch and eat the steak to be able to actually taste it."
Continue reading the main story
“Start Quote

    If very simple organisms such as bacteria are capable of this that 
would imply that this ability evolved much earlier than expected”

End Quote Reindert Nijland University Medical Centre Utrecht

Bacteria are known to use their "senses" to detect chemicals that 
indicate the presence of other bacteria or competitors for food.

In some cases, they can produce a slimy material that causes them to 
stick together in what is known as a biofilm. Such biofilms can cause 
complications in cases ranging from implants to oil pipelines, but a 
familiar example is the plaque that forms on teeth.

Dr Nijland and Grant Burgess put a number of separate cultures of a 
bacterium called B. licheniformis in cylinders containing different 
"growth media" to cause them to multiply. Some were in a rich broth of 
food that allowed the bacteria to multiply quickly, releasing ammonia 
gas in the process, while others were in a medium that allowed the 
growth of biofilms - which can be initiated if the bacteria are in 
contact with ammonia.

They were surprised to find that some of the isolated bacteria cultures 
began to form biofilms spontaneously, with those physically closest to 
the "well-fed" bacteria showing the highest biofilm production.

The only explanation is that the bacteria sensed the presence of ammonia 
directly from the air above the cultures.
Film rights

Dr Nijland explained that the biofilm provides both a barrier and a 
means of transportation for the bacteria that have "smelled" nearby ammonia.

"It's tempting to speculate that [ammonia] provides the bacteria with 
information of a nearby nutrient source, since ammonia generally is a 
waste product of bacteria growing on a rich nutrient source," he said.

"The bacteria sense this, organise themselves in a biofilm which will 
prepare them for both competition with other species already feeding on 
the nutrient source, and enables swarming - migration via the matrix 
they have secreted to form the biofilm."

The surprise find has implications in our understanding of the 
difference between prokaryotes like bacteria, which have no neatly 
packaged parts within their cells, and the more advanced eukaryotes that 
include everything from yeast to humans.

"If very simple organisms such as bacteria are capable of this that 
would imply that this ability evolved much earlier than expected," said 
Dr Nijland.

"Understanding this phenomenon... will help us to develop methods to 
potentially interfere with this process and potentially develop new ways 
of preventing biofilm-related bacterial infections."

Related:

Arsenic-munching bacteria found 14 AUGUST 2008, SCI/TECH
http://www.bbc.co.uk/2/hi/science/nature/7558448.stm