#microtwjc Week 26 – the 1st birthday edition!

Euprymna scolopes

Next Tuesday marks the 1 year anniversary of #microtwjc – I can’t believe it’s come around so quickly!  Thank you to everyone who has been involved running the sessions, taking part in them and advertising them to colleagues.  Please continue!  It wouldn’t be half as much fun without you all

On to this week’s paper

This week I’ve chosen this paper in mBio by Heath-Heckman et al, because I am constantly amazed at the number of different ways the microbes that live in or on us affect us, our bodies and our behaviours (although I will admit to also being drawn to cute animals like the one above!)

Bacterial Bioluminescence Regulates Expression of a Host Cryptochrome Gene in the Squid-Vibrio Symbiosis

Elizabeth A. C. Heath-Heckman, Suzanne M. Peyer, Cheryl A. Whistler,Michael A. Apicella, William E. Goldman, Margaret J. McFall-Ngai

Importance

In mammals, biological rhythms of the intestinal epithelium and the associated mucosal immune system regulate such diverse processes as lipid trafficking and the immune response to pathogens. While these same processes are affected by the diverse resident microbiota, the extent to which these microbial communities control or are controlled by these rhythms has not been addressed. This study provides evidence that the presentation of three bacterial products (lipid A, peptidoglycan monomer, and blue light) is required for cyclic expression of a cryptochrome gene in the symbiotic organ. The finding that bacteria can directly influence the transcription of a gene encoding a protein implicated in the entrainment of circadian rhythms provides the first evidence for the role of bacterial symbionts in influencing, and perhaps driving, peripheral circadian oscillators in the host.

Abstract

The symbiosis between the squid Euprymna scolopes and its luminous symbiont, Vibrio fischeri, is characterized by daily transcriptional rhythms in both partners and daily fluctuations in symbiont luminescence. In this study, we sought to determine whether symbionts affect host transcriptional rhythms. We identified two transcripts in host tissues (E. scolopes cry1 [escry1] and escry2) that encode cryptochromes, proteins that influence circadian rhythms in other systems. Both genes cycled daily in the head of the squid, with a pattern similar to that of other animals, in which expression of certain cry genes is entrained by environmental light. In contrast, escry1 expression cycled in the symbiont-colonized light organ with 8-fold upregulation coincident with the rhythms of bacterial luminescence, which are offset from the day/night light regime. Colonization of the juvenile light organ by symbionts was required for induction of escry1 cycling. Further, analysis with a mutant strain defective in light production showed that symbiont luminescence is essential for cycling of escry1; this defect could be complemented by presentation of exogenous blue light. However, blue-light exposure alone did not induce cycling in nonsymbiotic animals, but addition of molecules of the symbiont cell envelope to light-exposed animals did recover significant cycling activity, showing that light acts in synergy with other symbiont features to induce cycling. While symbiont luminescence may be a character specific to rhythms of the squid-vibrio association, resident microbial partners could similarly influence well-documented daily rhythms in other systems, such as the mammalian gut.

There is a blogpost on this article available at mBiosphere.  If anyone else writes/has written a post on the article please don’t be shy about posting the link below.

Questions to think about this week…

1. Was the paper well written?
2. Were the methods sound?
3. Were there any other experiments you would like to see in there?
4. What do the results mean in a broader context?
5. What other influences do we know that commensal flora have on their hosts?

Please spread the word about Tuesday’s session – it would be great for the birthday edition to be busy

See you there

Image: Licenced under Creative Commons Attribution-Share Alike 3.0 Unported license by Nick Hobgood

Yay – we just got some publicity!

Just a quick post to say that #microtwjc has been featured in the Nature SpotOn NYC birthday celebration case studies here :)

Please pass the word on to your friends and colleagues and we hope to see you at our next session on Tuesday 30th April 8pm BST.

 

(Image by DROUET)

Week 25 #microtwjc: How do viruses enter your cells?

Watch this video to see why this paper is important: .https://www.youtube.com/watch?v=lIE_UElOk3c

I picked this paper: Host Cell Entry of Respiratory Syncytial Virus Involves Macropinocytosis Followed by Proteolytic Activation of the F Protein by Krzyzaniak et al, in PLoS Pathogens last week because of the depth and detail that they went to in order to determine one of the most basic and important processes in virus infection: cell entry.

Questions:

How important is it to find out how a virus enters a cell?

Could purification/concentration of the virus particles change how the virus enters?

Did they use the correct cells (not primary respiratory cells) and virus (not a clinical isolate) for their experiments?

Would you target this pathway as an antiviral strategy?

What would you do next?

#microtwjc week 24: A dilema of choices!

So people here is next week’s paper for discussion.

Microanatomy at Cellular Resolution and Spatial Order of Physiological Differentiation in a Bacterial Biofilm

I had a hard choice and I have decided on one of two stories (the other one was on phages) that caught my attention at the BACNET13 meeting I attended in Poland recently.

The wonderful images produced by the Hengge lab while dissecting the role of c-di-GMP in biofilm formation won. You will need to use the online material as well as the paper for this one.

We have discussed c-di-GMP and Biofilms sometime back and it is a subject that started my own journey into the fascinating world of Caulobacter crescentus as a young Post-Doc. Regine Hengge gave an excellent talk on this story at BACNET. The field of c-di-GMP itself played a central role at this meeting. What was clear to me is that the field has begun to move on from the biochemical characterisation of the components involved to returning to the underlying question of what c-di-GMP is regulating, why and how? Clearly exciting times are ahead for the field.

As per usual our discussion will focus on:

1) Did the paper read well?

2) Could you understand the regulatory network?

3) Would you have done anything differently?

4) where next?

#microtwjc week 23 – Easter Session on 2nd of April at 8 pm BST

Hi all!

I have chosen this paper, because I think it is an interesting topic and also because we have not had anything on Streptomyces yet. Furthermore since this work, is from a former student of my supervisor, and she is willing to attend the session and so will Paul. So we get some input from the researcher directly! 

Hopefully see many of you on the 2nd of April at 8 pm BST! 

Here it goes: http://www.nature.com/srep/2013/130123/srep01109/full/srep01109.html

Mammalian cell entry genes in Streptomyces may provide clues to the evolution of bacterial virulence

This week’s Journal Club is on a publication on how virulence might have evolved in bacteria. The non-pathogenic soil bacterium S. coelicolor, nevertheless in their genome you can find homologues of virulence loci. This paper investigates the mammalian cell entry locus (mce) in S. coelicolor, it has previously been characterised in M. tuberculosis. The study investigates its impact on cell survival, morphology and interaction with other soil organisms (A. polyphaga and Arabidopsis). The results suggest that the genes play an important role in survival in the environment and give hints into the evolution and selection as these genes as virulence factors.

Discussion points:

-          Was the publication easy to read/follow/understand?

-          Do you think this research is helping to understand how virulence evolved?

-          Which follow up experiments could be done based on the data presented?