Bacteria exchange food via nanotubes

Date: Feb-24-2015A new study shows that some bacteria can form nanotubes between single cells

that allow the cells to exchange essential nutrients or metabolites with each

other.

Bacteria exchange amino acids via nanotubes.
Image credit: Martin Westermann, Friedrich Schiller University

Bacteria typically thrive in communities where colonies of many different species

collaborate and support each other's growth and exchange nutrients.

However, it has

not been clear whether they do this only by releasing the metabolites into the cell

environment for their neighbors to pick up, or whether they use other mechanisms of

nutrient exchange.

Now, writing in the journal Nature Communications, a team of scientists

from several German research centers - including the Max Planck Institute for

Chemical Ecology in Jena - reveals that bacteria exchange nutrients directly with

each other through nanotubes strung between single cells.

Their study investigates two species of bacteria: the gut microbe Escherichia

coli, and the soil bacterium Acinetobacter baylyi.

Bacterial cells partnered with neighbors and fed each other via nanotubes

The first thing the team did was delete different genes in each species so they

could no longer produce certain amino acids but could produce increased amounts of

others.

The scientists found that when cultured together, the bacteria were able to cross-feed each other - supplying to the other the amino acids that the other could not

produce for itself.

Then, they grew the two species of bacteria very close together but separated them with

a filter so amino acids could not pass between them via the culture medium and there

was no direct contact between the cells of the two species.

In the second experiment, the bacteria died. The team concludes it showed that

direct contact between cells is necessary for nutrient exchange and for both strains

to thrive.

When they looked at the culture containing the two species mixed together under

an electron microscope, the researchers saw tiny filamentous nanotubes connecting

individual cells. These were enabling the cells to exchange metabolites with each

other.

And they were surprised to discover that only E. coli was capable of

making the nanotubes, both among its own cells and between its cells and those of

A. baylyi, while the latter was not.

Perhaps only swimmers can form nanotubes

Christian Kost, who heads the Volkswagen funded Experimental Ecology and

Evolution Research Group at the Max Planck Institute, speculates that perhaps only

bacteria that can swim are able to find partners to connect to via nanotubes;

E. coli can swim while A. baylyi cannot.

He notes that that a lack of amino acids causes the cells that can swim to seek

partners and link up via nanotubes. When he and his colleagues deleted a gene so

they could not produce an amino acid, it triggered this behavior - the bacteria

sought to compensate by getting the nutrient from its neighbors.

When the missing amino acid was introduced to the culture, the bacteria

did not form nanotubes, suggesting that they only do so when they are "hungry" for

the required nutrient, explains Kost.

It can be an advantage for bacterial species living in communities to specialize

in certain processes and divide their labor to serve them - they save energy and

grow more efficiently.

The team is curious to find out if the bacteria also use other means to obtain

nutrients from each other - for instance, do they behave like parasites on each

other?

Another question they want to answer is whether the bacterial cells actively

choose the cells they attach to with nanotubes - this seems plausible in that it

would avoid accidentally attaching to unfriendly cells that send toxins down the

tubes. Kost adds:

"To me, the most exciting question that remains to be answered is

whether bacteria are in fact unicellular and relatively simply structured organisms

or whether we are actually looking at some other type of multicellularity, in which

bacteria increase their complexity by attaching to each other and combining their

biochemical abilities."

Meanwhile, Medical News Today recently reported on another study where

researchers discovered that  jumping between host

species may be easier for bacteria than previously thought. The study shows

that just one simple genetic mutation is all that separates a strain of bacteria

responsible for widespread epidemics in the global rabbit farming industry from one

that also infects humans.

Written by Catharine Paddock PhD

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.