Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Surprising role of bacterial genes in evolution

12.10.2016

We generally think of inheritance as the genetic transfer from parent to offspring and that evolution moves toward greater complexity. But there are other ways that genes are transferred between organisms.

Sometimes a "host" organism can obtain genes from another organism that resides within its own cell (called an endosymbiont) through a process known as endosymbiotic gene transfer. At other times, an organism can obtain genes from a creature that lives in the surrounding environment, or from something that it eats, which is called horizontal gene transfer.


This micrograph of the single-celled Paulinella shows the the photosynthetic "machinery" in green.

Credit: Eva Nowack

Furthermore, some levels of gene transfer can result in extensive loss of genes and genome reduction, especially for organisms that live as endosymbionts. For the first time, researchers have demonstrated that horizontal gene transfer may play a dominant role in compensating for genome reduction in an endosymbiont, and that this may be a key feature in the evolutionary transformation of an endosymbiont into an organelle (a longstanding organ inside a cell that often has specialized functions).

The research, published in the October 10 on-line edition of the Proceedings of the National Academy of Sciences, was conducted as a collaboration between scientists at Carnegie's Department of Plant Biology*, Rutgers University and Heinrich-Heine-Universität in Düsseldorf.

Specialized organelles called chloroplasts, which occur in plants and algae, are critical for performing the process of photosynthesis, and thus manufacturing sugars, starch and oils. These organelles originated more than 1 billion years ago when a photosynthetic bacterium, called a cyanobacterium, was engulfed by a host organism called a protist. There was a subsequent massive loss of genes from the genome of the cyanobacterium. Some of the lost cyanobacterial genes were transferred to the nucleus of the host cell through endosymbiotic gene transfer, while others were completely lost. This genome reduction was accompanied by the loss of many endosymbiont genes critical for the chain of enzymatic reactions involved in the biosynthesis of various essential compounds. How the host compensated for this gene reduction was only partially known.

Surprising results that shed light on the evolution of organelles from endosymbionts were obtained using the green, single-celled organism Paulinella chromatophora. Carnegie co-author Arthur Grossman explained: "We have recently proposed that the loss of genes from the photosynthetic organelle of P. chromatophora, which is called a chromatophore (originally an endosymbiotic cyanobacterium that was engulfed by a Paulinella species 60-200 million years ago), was in many cases compensated for by genes coming from neighboring bacteria in the environment. These new genes were integrated into the host nucleus and the proteins made from these genes were routed into chromatophores, where they compensate for the loss of genes."

Lead author Eva Nowack remarked: "Of the at least 229 genes in the P. chromatophora nucleus that were acquired from various bacteria, only about 25% are of cyanobacterial origin and may have originated from endosymbiotic gene transfer. Excitingly, many of the remainder were acquired through horizontal gene transfer, representing genes from a variety of bacteria. Many of these bacteria-derived genes produce proteins that fill in gaps in chromatophore localized biosynthetic pathways. The original genes that filled the gaps were lost as a consequence of chromatophore genome reduction. This result suggests a dominant role for horizontal gene transfer in compensating for endosymbiont genome reduction."

Furthermore, researchers found that a sister (ancestral) organism to P. chromatophora does not have a chromatophore and feeds on a variety of different bacteria, much like the way that white blood cells consume invading bacteria. In this new work, it is hypothesized that this method of feeding, called phagotrophy, may allow for the acquisition of different bacterial genes through horizontal gene transfer. In this way, the process of feeding facilitated bacterial gene selection as the cyanobacterial endosymbiont became a permanent resident within the phagotrophic host during early stages of chromatophore evolution.

###

* Authors on the paper are Eva C.M. Nowack, Dana C. Price, Debashish Bhattacharya, Anna Singer, Michael Melkonian, and Arthur R. Grossman This study was supported by National Science Foundation grant MCB-10370 (to A.R.G.), EF 08-27023 and OCE 11-29203 (to D.B.), and Deutsche Forschungsgemeinschaft Grant NO 1090/1-1 (to E.C.M.N.)

The Carnegie Institution for Science is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

Arthur Grossman | EurekAlert!

More articles from Life Sciences:

nachricht Lethal combination: Drug cocktail turns off the juice to cancer cells
12.12.2018 | Universität Basel

nachricht Smelling the forest – not the trees
12.12.2018 | Universität Konstanz

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

New discoveries predict ability to forecast dementia from single molecule

12.12.2018 | Health and Medicine

CCNY-Yale researchers make shape shifting cell breakthrough

12.12.2018 | Physics and Astronomy

Pain: Perception and motor impulses arise in the brain independently of one another

12.12.2018 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>