Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

From single cells to multicellular life

06.11.2014

Max Planck researchers capture the emergence of multicellular life in real-time experiments

All multicellular creatures are descended from single-celled organisms. The leap from unicellularity to multicellularity is possible only if the originally independent cells collaborate. So-called cheating cells that exploit the cooperation of others are considered a major obstacle.


Diversity among nascent multicellular collectives: In such dishes containing various strains of Pseudomonas fluorescens scientists have observed in real time the evolution of simple self-reproducing groups of cells from previously individual cells.

© Gayle Ferguson

Scientists at the Max Planck Institute for Evolutionary Biology in Plön, Germany, together with researchers from New Zealand and the USA, have observed in real time the evolution of simple self-reproducing groups of cells from previously individual cells.

The nascent organisms are comprised of a single tissue dedicated to acquiring oxygen, but this tissue also generates cells that are the seeds of future generations: a reproductive division of labour. Intriguingly, the cells that serve as a germ line were derived from cheating cells whose destructive effects were tamed by integration into a life cycle that allowed groups to reproduce.

The life cycle turned out to be a spectacular gift to evolution. Rather than working directly on cells, evolution was able to work on a developmental programme that eventually merged cells into a single organism. When this happened groups began to prosper with the once free-living cells coming to work for the good of the whole.

Single bacterial cells of Pseudomonas fluorescens usually live independently of each other. However, some mutations allow cells to produce adhesive glues that cause cells to remain stuck together after cell division. Under appropriate ecological conditions, the cellular assemblies can be favoured by natural selection, despite a cost to individual cells that produce the glues. When Pseudomonas fluorescens is grown in unshaken test tubes the cellular collectives prosper because they form mats at the surface of liquids where the cells gain access to oxygen that is otherwise – in the liquid – unavailable.

Given both costs associated with production of adhesive substances and benefits that accrue to the collective, natural selection is expected to favour types that no longer produce costly glues, but take advantage of the mat to support their own rapid growth. Such types are often referred to as cheats because they take advantage of the community effort while paying none of the costs. Cheats arise in the authors’ experimental populations and bring about collapse of the mats. The mats fail when cheats prosper: cheats obtain an abundance of oxygen, but contribute no glue to keep the mat from disintegrating – the mats eventually break and fall to the bottom where they are starved of oxygen.

Paul Rainey, who led the study at the New Zealand Institute for Advanced Study and the Max Planck Institute for Evolutionary Biology, explains: “Simple cooperating groups – like the mats that interest us – stand as one possible origin of multicellular life, but no sooner do the mats arise, than they fail: the same process that ensures their success – natural selection – , ensures their demise.” But even more problematic is that groups, once extant, must have some means of reproducing themselves, else they are of little evolutionary consequence.

Pondering this problem led Rainey to an ingenious solution. What if cheats could act as seeds – a germ line – for the next set of mats: while cheats destroy the mats, what about the possibility that they might also stand as their saviour? “It’s just a matter of perspective”, argues Rainey. The idea is beautifully simple, but counter-intuitive. Nonetheless, it offers potential solutions to profound problems such as the origins of reproduction, the soma / germ distinction – even the origin of development itself.

In their experiments the researchers compared how two different life cycles affected group (mat) evolution. In the first, the mats were allowed to reproduce via a two-phase life cycle in which mats gave rise to mat offspring via cheater cells that functioned as a kind of germ line. In the second, cheats were purged and mats reproduced by fragmentation. “The viability of the resulting bacterial mats, that is, their biological fitness, improved under both scenarios, provided we allowed mats to compete with each other,” explains Katrin Hammerschmidt of the New Zealand Institute for Advanced Study.

Surprisingly however, the researchers found that when cheats were part of the life cycle, the fitness of cellular collectives decoupled from that of the individual cells: that is, the most fit mats consisted of cells with relatively low individual fitness. “The selfish interests of individual cells in these collectives appear to have been conquered by natural selection working at the level of mats: individual cells ended up working for the common good. The resulting mats were thus more than a casual association of multiple cells. Instead, they developed into a new kind of biological entity – a multicellular organism whose fitness can no longer be explained by the fitness of the individual cells that comprise the collective” says Rainey.

“Life cycles consisting of two phases are surprisingly similar to the life cycles of most multicellular organisms that we know today. It is even possible that germ-line cells, i.e. egg and sperm cells, may have emerged during the course of evolution from such selfish cheating cells,” says Rainey.


Contact

Prof. Dr. Paul Rainey
Max Planck Institute for Evolutionary Biology, Plön

Email: rainey@evolbio.mpg.de


Original publication
Katrin Hammerschmidt, Caroline Rose, Ben Kerr and Paul B. Rainey

Life cycles, fitness decoupling and the evolution of multicellularity

Nature, 6 November 2014; 515, 75-79 (doi:10.1038/nature13884)

Prof. Dr. Paul Rainey | Max-Planck-Institute

More articles from Life Sciences:

nachricht Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute

nachricht Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>