Final Post

MetaRNA has come to an end. The MetaRNA fellows received an excellent education at their institutions and are now ready for new challenges in academia and industry. At this occasion, the fellows would like to thank their advisors and the European Commission for excellent support.


MetaRNA at 10th Young Scientists Symposium 2017

Last year, MetaRNA presented at the 9th Young Scientist Symposium 2016 . This year, Stefano Piccolo – one of the MetaRNA fellow – participates again…but on the other side as part of the organizing committee of the 10th edition of Young Scientist Symposium at IECB in Pessac (Bordeaux – France).

The experience during the last edition of Young Scientist Symposium was so great, that this year Stefano, from the MetaRNA consortium, is part of the organizing committee, and he is looking for the best speakers and sponsors that they can attract.


YYS 2017 organizing committee
From left: Dr. Nina KHRISTENKO, Dr. Josephine ABI-GHANEM, Léonie CUSSOL, Dr. Nassima Meriem GUEDDOUDA, Clémence RABIN, Mégane BORNERIE, Alba HERRERO, Laura BARTOLUCCI,
In font: Stefano PICCOLO (our MetaRNA fellow)

For this 10th edition of the conference, there are two novel features:

  • Round-table career session, with permanent researcher in industry and academia;
  • Three competitive prizes for the best talks and poster by IdEx – Bordeaux University.
    • One of the talk IdEx prize will be attribute by all participants


I hope this year will be even more exciting than before. See you there and do not forget to register!


Young Scientist Symposium 2017


METABOLIC OSCILLATIONS: Cellular decision-making

For this post as part of the “Metabolic oscillations” series, Josi Buerger introduces us to the publications that inspired the creation of this ITN network. The series will focus on the underlying concepts, explain the four main publications stretching from 2010 to 2016, and lay out how the Fellows’ efforts will push this work forward into 2017.

Regulation is at the heart of the cell

Within the cell, genes and proteins are regulated. There are two reasons for this: firstly, a cell can respond to its environment by changing or regulating its internal state. Secondly, it is much more cost-effective if this change happens by modulating existing structures instead of tearing everything down and creating it from scratch. Consider how much less effort it is to dim the lights in the evening as opposed to dismantling the electrical circuits and then reconstruct them in the morning…

The ability to regulate internal states is the basic concept of the first publication featured as part of our “Metabolic oscillations” series, Bacterial adaptation through distributed sensing of metabolic fluxes.  In today’s post we’ll discuss the basic concept of cells responding to their environment and use a textbook example: carbon source utilization. Or, in more laymen’s terms: cells have food preferences.

Cells have food preferences.

Weird, isn’t it? But Escherichia coli’s sweet tooth is one of the cornerstone experiments in the field of microbiology dating back to 1957 (Cohen & Monod). Also there is a link between preferring one type of food and changing cellular metabolism to suit the preference. For example, E. coli loves glucose (a type of sugar). When glucose passes through the outer membrane of the cell, it activates a number of other processes which all help the cell to preferentially eat the glucose.


You can see this in the image on the right: the blue line indicates E. coli cell growth in an environment where both glucose and acetate is available. The total amount of glucose is indicated by the dotted line, which decreases as the cells consume it to grow. Once all the glucose is consumed, the cells are forced to switch to acetate, indicated by the drawn-through line (Image modified from Kotte et al., 2010).

How to sense acetate?

So far, so good.  Yet as always in biology, the picture becomes more complicated as soon as you zoom in on the details.

For glucose, there is an elegant link between transport and regulation. But even though cellular behaviour to acetate is well-documented, it is unknown how cells detect acetate. Generally, there are two main detection systems: membrane-based sensing as with glucose, or transcription-factor based sensing where the molecule is recognised by a specific sensing modules. Neither system has been found for acetate, despite decades of interest.

Here’s the cool bit about Bacterial adaptation through distributed sensing of metabolic fluxes.  The researchers show that the preference of glucose to acetate can be explained by elements of the cell that we already know about. There isn’t some undiscovered acetate sensing system, but rather the elements of the cell can behave in more ways than we thought!

The details? Well, you will just have to wait for our next post…..



Kotte, Oliver, Judith B. Zaugg, and Matthias Heinemann. “Bacterial adaptation through distributed sensing of metabolic fluxes.” Molecular systems biology 6.1 (2010): 355.


SERIES INTRODUCTION: The ups and downs of metabolism

New year, new series on the metaRNA blog!

For the upcoming posts on “Metabolic oscillations”, Josi Buerger introduces us to the publications that inspired the creation of this ITN network. The series will focus on the underlying concepts, explain the four main publications stretching from 2010 to 2016, and lay out how the Fellows’ efforts will push this work forward into 2017.


Life isn’t static. It can’t be – in biological systems, stagnation means death.

Even though cells are rules by homeostasis, this continuous fine-tuning of cellular processes is anything but static.

Homeostasis: Self-regulation to maintain internal equilibrium.

For example, the human body strives to maintain 37 °C as its internal temperature via heat-loss (sweating) or heat retention (goose-bumps).

But remember, the cell itself cannot think or make decision like our human minds. Individual cells don’t have a brain that acts as the central decision maker. Some argue that cellular fate is encoded in its DNA and this should be seen as a “brain” of sorts. However, the cell must still be able to respond to external events or internal catastrophes above and beyond the determination of the DNA code.

So how is this possible? What kind of situation requires immediate and total cellular responses? And what does this response look like?

The following four papers have been chosen as the features of our new series to answer these questions:

  1. Bacterial adaptation through distributed sensing of metabolic fluxes
  2. Functioning of a metabolic flux sensor in Escherichia coli
  3. Phenotypic bistability in Escherichia coli’s central carbon metabolism
  4. Autonomous metabolic oscillations robustly gate the early and late cell cycle

Join in as we explore cellular decision-making!

Functional mining of transporters using synthetic selections

After our successful Meet the Fellows series, we are starting a new project: The metaRNA Fellows will introduce papers new and old that they find interesting or inspiring. Today, Josi Buerger starts  with a recent publication on riboswitches.

On this blog, we have talked at length about aptamers and biosensors. There has been a post on aptamers in general, the specific SPINACH aptamer, and an application on how biosensors can be targeted to specific cells.

Today I want to introduce a biosensor for the vitamin thiamine. This biosensor detects a phosphorylated version of the thiamine molecule and this detection is sensitive enough to sense the very low thiamine concentrations inside the cell. A recent publication describes how this biosensor can explore bacterial biodiversity and how this has ramifications for the discovery of new drug targets.


The thiamine biosensor consists of a riboswitch which is placed in front of a gene that makes a bacterial cell resistant to antibiotics. When thiamine is present, the riboswitch is turned ON and the bacteria cell can survive the antibiotic. However, if there is no thiamine present in the cell, the resistance gene can not be utilised and the cell is killed by the antibiotic. This has the distinct advantage that those cells that do not have  thiamine are killed by the riboswitch-modulated system.

Riboswitch: An RNA molecules that switches conformation upon binding of a particular target molecules. Riboswitches are often used to control gene expression.

This riboswitch was used to look at how bacterial cells transport thiamine from their environments through the cell wall into the cell. The image on the right is a nice representation of this – transporters are a hole in the cell membrane that can allotransporterw particular molecules to enter or exit the cell. There are particular strains of E. coli that do not have a naturally occurring importer for thiamine and instead synthesise whatever they need. The trick for the selection system here is that the strain is engineered to lose its biosynthetic capability, so that it is dependent on external thiamine – but it can’t take up the external thiamine!

In order to survive, the cell is exposed to a “metagenomic library” which is a pool of many fragments of DNA from many different microorganisms. Then, the cell randomly takes up bits of this external DNA. If it manages to take up a gene that encodes a transporter, voila! It can survive.

So where does the riboswitch come in? There are countless types of transporters in the metagenomic gene pool and some of them are non-specific. But as this study wanted to find highly specific and efficient thiamine transporters, it needed to increase the amount of thiamine required for survival. Therefore, coupling the presence of thiamine to the ability to survive high levels of antibiotics can do just that. The image below shows how the cells survive only if they manage to find a transporter from the metagenomic library. Furthermore, this transporter has to be functional.


From Genee et al., 2016

So what are the results of the riboswitch selection? The researchers found a type of thiamine transporters that was previously undiscovered. In particular, this type of thiamine transporter, called PnuT, is prevalent in bacteria of the human gut. Moreover, some known human pathogens have only the new transporter type for their thiamine uptake and therefore, their survival depends on it. This means that the Pnu transporters constitutes an interesting new drug target for human health.

The publication is a nice example of how synthetic biology, cell metabolism, and metagenomic DNA can all come together and point to a new direction for drug targets.


Genee, Hans J., et al. “Functional mining of transporters using synthetic selections.” Nature Chemical Biology 12.12 (2016): 1015-1022.

MetaRNA at the 9th Young Scientist Symposium 2016

On the 26th and 27th May 2016, MetaRNA was present at 9th Young Scientist Symposium 2016 in IECB – Pessac (France). Stefano briefs us on the topics that were discussed at this meeting and tells us a little about what he presented there.

Mixing chemistry and biology, the YSS, as the name suggests, is organised for young researchers from both disciplines and from all over the world. With several oral sessions and two poster sessions, PhD students got the opportunity to present their work, discuss the presented research among themselves and with invited researchers from industry and academia.

MetaRNAers Stefano and Sara at the poster session.

All the talks presented an interdisciplinary research approach by combining both chemistry and biology.. This year, we had talks concerning:

  •    Nucleic Acids
  •    Supramolecular Chemistry
  •    Chemistry of 5 senses
  •    Pharmaceutical Chemistry
  •    Genomics
  •    Cancer and Physiology
  •    Career, Industry, Scientific Journalism

I had the opportunity to present some of my results of my PhD project in the first session. My talk was titled Biophysical characterisation of RNA-metabolite complexes by native mass spectrometry.

Stefano giving his talk at YSS.

A few of the MetaRNA members will soon meet again in Bordeaux at the Aptamers in Bordeaux with talks from Beatrix Suess, Jean-Jacques Toulmé, Günter Mayer and posters from Adrien Boussebayle and Stefano Piccolo.

See you soon!

Sara and Stefano


Cell Penetrating Peptides: A System for Delivery

One aspect of design of RNA molecules that serve specific functions is figuring out how to get those molecules inside the cell. In this post, Adrien delves into a system used for drug delivery, known as CPP, or cell-penetrating peptides. Analogues of such technology may be used for delivering RNA molecules developed in vitro into cells.

The ability to have a drug that can be taken up to a very specific location in the body is a long-standing problem. In 1906, the concept of the “magic bullet” was imagined by Paul Ehrlich (a Nobel Laureate for his work in immunology). This concept supposes that we could have what is known as  a magic bullet bring a drug, in a specific way, toward the active site of the drug.

Paul Ehrlich is considered the father of chemotherapy.

The field of drug delivery systems has improved during the last century and there are several types of nano-carriers which are already developed. One of these systems is the Cell Penetrating Peptides (or CPP). CPP are short peptides that are designed to carry molecules (nucleic acids, fluorophore, proteins…) inside the cells by going through the membrane.

Continue reading Cell Penetrating Peptides: A System for Delivery

Facebook, mySpace, Twitter, and RNA-based metabolic sensors: Remnants of ancient control machinery or ever-present control mechanism?

Social media and riboswitches? They might be more related than you think…. Today, Ruben talks about the ancient origins of riboswitches and poses interesting questions about their future.

If you were a teenager in the early 2000s, you probably used mySpace as your first social media. You might have even posted Emo-inspired pictures and used glittery GIFs. However, unfortunately for mySpace, Facebook was created in 2004 and soon after it started to rapidly overtake mySpace´s users, until 2008 when Facebook became the most used social platform worldwide. Other social media such as Twitter also remain active because it is specialized in a different type of social interaction: less about personal social connections and more about staying informed by following topics, conversations and people. These differences allowed Twitter to conserve their niche on an ever-growing sea of social media options.

This analogy came to my mind while reading about different sensing molecules. In order to survive and reproduce, organism have evolved mechanisms to sense and translate environmental signals as efficiently as possible. It is generally recognized that many of these mechanisms are protein-based molecules, which regulate gene expression in response to a chemical signal (e.g. transcription factors).

Although these protein-based sensing mechanisms explained the regulation of certain biological processes, they are not the only mechanism in action.This is often seen in the lack of correlation between transcriptome and proteome data. Insights into unknown interactions of RNA with metabolites led to the discovery of RNA sensing molecules able to control their own activity, so called: Riboswitches (Templeton et al., 2004).

Continue reading Facebook, mySpace, Twitter, and RNA-based metabolic sensors: Remnants of ancient control machinery or ever-present control mechanism?


It’s appearing all over the place : CRISPR/Cas9. The method has boomed since its 2012 breakthrough moment. Adam Mol walks us through this technology.

Currently, more and more discussions are appearing about CRISPR/Cas9. This technology can be used to edit the genome of almost any organism and the most controversial seems to be editing the genes of human embryos. How does this system works? CRISPR (Clustered Regularly Interspaced Short Palindromic Repeat) sequences and CRISPR-associated (Cas) genes were found in a wide variety of bacteria and archaea. The enzyme Cas9 is a DNA endonucleas
e found in many bacteria, where it functions as part of a defense system against invading DNA molecules, e.g. from viruses. The CRISPR/Cas9 system allows for specific genome disruption and replacement in a flexible and simple system, resulting in high specificity and low cell toxicity (Harrison et al., 2014; Peng et al., 2015).


Fig. 1 CRISPR/Cas9 in action (from Pennisi, 2013; modified)

The CRISPR/Cas9 genome editing system requires the co-expression of a Cas9 protein with a guide RNA. The crRNA and tracrRNA can be fused together to create a chimeric, single-guide RNA (sgRNA). Cas9 has two active sites that each cleave one strand of a double-stranded DNA molecule. The enzyme is guided to the target DNA by an sgRNA that contains a sequence that matches the sequence to be cleaved, which is demarcated by PAM (protospacer-adjacent motif) sequence. (There also exists a RNA-targeting CRISPR/Cas9 complex, called RCas9, that can edit RNA! by J. Doudna; O’Connell et al., 2014).


Fig. 2 Schematic of the RNA-guided Cas9 nuclease (from Ran et al., 2013)

Continue reading CRISPS/CAS9

Defining Life

What is Life? Why should we care about defining it? As biologists, our research tends to focus on the details, not the bigger picture. Today, Josi Buerger steps back and looks at how the basic concept of “Life” affects topics from conservation to astrobiology.


The Life Sciences, though young in comparison to other disciplines, have made incredible progress in explaining the tangible world around us. Yet even at the most fundamental level, biological processes remain a mystery. Basic questions remain unanswered: Why did living systems evolve on this planet? Could it have taken radically different forms? Why do organisms display such complexity and diversity?

The fact that we can ask and discuss these questions surely indicates that defining life is unnecessary – we all know what it means and know it when we see it. Our efforts should be aimed at understanding biological processes, not quibbling over a definition…

There are two main concerns why scientists should care about definitions: Firstly, even if we do not fully understand biological processes, there are scenarios where we need to be able to identify and label them. Space exploration comes to mind, or the deep ocean. Secondly, arguing about definitions may not be traditional examples of the “Scientific Method”, but there are concrete examples where definitions affects experimental design: in early evolutionary biology, dentifying life forms from interacting organic material is vital. Or consider the construction of “minimal genomes”: does a self-replicating plasmid suffice as a minimal organism, or does it require a more complex cellular set-up?

Continue reading Defining Life