Showing posts with label @Blastocystis. Show all posts
Showing posts with label @Blastocystis. Show all posts

Wednesday, May 5, 2021

The 3rd Blastocystis Conference will be AWESOME!

 Hi everyone,

We're currently going through the abstracts submitted for the upcoming Blastocystis conference, which will be held exclusively online.

The scientific quality of the abstracts is very high, and participants in this year's conference are in for a veritable treat! 

Expect important and potentially game-changing updates on host-pathogen interactions, cell biology and evolution, epidemiology, intestinal ecology, diagnosis and molecular characterisation.

Use this opportunity to obtain answers to all of your Blastocystis questions.

We are very much overwhelmed about the interest for this event and the support.


Thursday, March 25, 2021

Dear all,

This is to remind you that the 3rd International Blastocystis Conference ( will take place virtually between 2nd to 4th of June 2021 and currently both the registration ( and the abstract submissions are open (, with the deadlines for abstract submission and early-bird registration approaching soon: April 15th, 2021.

Participants from LMICs will receive a 20% discount in their registration fees. Please contact the Conference Secretariat ( to register at the discounted rate.

 For frequent updates, please follow us on twitter: @Blastocystis21 . Please do also spread the word! 

We look forward to seeing you (even virtually) in June 2021.


Thursday, January 14, 2021

3rd International Blastocystis Conference - abstract submission open!

Hi Everyone, and a very Happy New Year!

Please note that abstract submission and registration for the 3rd International Blastocystis Conference (virtual, 2nd to 4th of June) is now OPEN! Click here to register and share your Blastocystis research!

We have registration fees as low as € 15 for early birds!

For Twitter users, please also follow @Blastocystis21 for updates.

Monday, November 2, 2020

Update on 3rd International Blastocystis Conference 2021 2-4 of June 2021


I would like to draw your attention to updates on the 3rd International Blastocystis Conference, which is very much ON, although in the virtual format.

Please go here for information.

I really hope that you will support the conference by your presence and active participation!

"Even though we wanted to see you in person in the beautiful Chania next year, we have decided for everyone’s safety to convert the 3rd International Blastocystis Conference into a virtual conference. The conference will take place between 2nd and 4th of June 2021 and we will make sure that it will also be tailored in the various time zones."

Thursday, February 20, 2020

Free access to fresh articles on Blastocystis - subtypes and lifecycle

Anyone with the links below can access our recent articles on Blastocystis for free over the next 50 days.

Please go here to download
Preempting Pandora’s Box: Blastocystis Subtypes Revisited

Please go here to download
Blastocystis - Parasite of the Month 

Both have been published in the March 2020 issue of Trends in Parasitology.

Happy reading!  

Thursday, January 30, 2020

Pre-empting Pandora's Box - Update on Blastocystis Subtypes and Reference Data

Back in 2006, when we came up with the subtype terminology for Blastocystis, the spectrum of and boundaries between Blastocystis subtypes were quite clear and distinct. Since then, the genetic make-up of Blastocystis has appeared to be an even bigger universe than we (or at least I) expected, and we may be far from having explored the entire 'galaxy' yet.

New technologies make it easier to sequence DNA, and sequences attributed to Blastocystis are accumulating in the publicly available databases with great speed. While this situation is one of the things that stimulate research (genetic diversity, co-evolution, host specificity, parasite-host-microbiome interaction, etc.), issues have emerged when it comes quality-controlling DNA sequences and putting taxonomic identifiers on these sequences.

For Blastocystis, the main taxonomic identifier is the 'subtype'. In 2013, 17 subtypes of Blastocystis had been acknowledged based on SSU rDNA analysis, and since then, quite a few more have been suggested by independent researchers all around the world. While it's great to see the field advance and more and more researchers 'checking in' on Blastocystis, care should be taken to ensure that Blastocystis terminology remains a useful one. And this... is not an easy task!

Some things are relatively straightforward though. For instance, sequence quality control. A simple BLAST query in GenBank (NCBI Database) should tell you whether your sequence is Blastocystis or something else. Like banana. Or asparagus. DNA sequence chimeras are sequences where one piece of DNA is combined with a piece of DNA from another strain/species/genus/etc., which can happen during PCR-based amplification of DNA. Suppose you have a sequence that is 75% Blastocystis and 25% banana. If you BLAST such a sequence, you might get Blastocystis as the top hit, but with a modest amount of sequence identity - maybe 85%. If you're not cautious, you might jump to the conclusion that this might be a new subtype, since 85% similarity is a lot less than the 95-97% similarity that is used pragmatically to delimit the boundary between subtypes. But if you look carefully at the alignment of the query sequence and the reference sequence, you'll probably note that a large part of the sequence aligns very well to the most similar reference sequence, while a minor part of it has great dissimilarity. This should be a warning sign, and you should try and BLAST only the bit of the sequence not aligning up well... and when you do this, you might end up with... banana! In which case you would have to discard this part of the sequence. Please also see one of my recent posts for more on this. If you do not check for chimeras, you might end up including chimeric DNA sequences in your phylogenetic analyses that will distort and confuse the interpretation and - in the worst case - lead to erroneous calling of new subtypes.

What is less easy is to set a 'one-fits-all' threshold for sequence similarity... how similar can Blastocystis DNA sequences be to be considered the same subtype? When do you have evidence of a 'new' subtype? It's difficult to know, as long as the data available in public databases is so limited as it is. Moreover, researchers do not always use the same genetic markers. It's still common practice to amplify and sequence only about 1/3 of the SSU rRNA gene and use that as a taxonomic identifier. But if it's not the same 1/3 then it gets tricky to compare data. Moreover, we actually need near-complete SSU rDNA sequences (at least 1600 bp or so) to be able to infer robust phylogenetic relationships between reference sequences and sequences potentially reflecting new subtypes. Obviously, this is because variation can exist across the entire SSU rRNA gene.

One subtype that has proven particularly challenging is ST14, a subtype which is common in larger herbivourous mammals, is very difficult to delimit. It may easily be confused with other subtypes, if sufficiently long sequences are not used for investigation. To this end, we try to keep a pragmatic approach to Blastocystis subtype terminology, and it may turn out that it would be more practical and relevant to refer to ST24 and ST25 as ST14 (see figure below). For now, we suggest keeping them as separate subtypes. Near-complete Blastocystis SSU rDNA sequences from a lot of larger herbivorous mammals will help us resolve the taxonomy in the top part of the tree shown in the figure above.

In terms of acquiring near-complete SSU rDNA sequences, I would personally recommend MinION sequencing of PCR products obtained by the universal eukaryotic primers RD5 + RD3. And if DNA from cultures isused (yes, it IS possible to culture Blastocystis not only from human hosts, but also from a variety of animals), then then MinION sequencing and analysis of the data output should be a straight-forward and relative cost-effective task.

Figure. As of January 2020, 'real' Blastocystis subtypes are most likely subtypes 1–17, 21, 23–26. This simplified phylogeny gives and indication of the relatedness of the subtypes and the relative host specificity. Humans can host subtypes 1–9 and also 12; when subtypes other than 1–4 are encountered in human samples, this may reflect cases of zoonotic transmission.

Graham Clark and I just published an article in Trends in Parasitology on this, and we concluded that some of the newly proposed subtypes are in fact invalid. Invalid subtypes (subtypes 18, 19, 20, 22) typically reflected DNA sequence chimeras.

In the figure above, you can see the subtypes identified to date that we consider valid.

We also provided updated guidelines on Blastocystis subtyping. One very important thing to include here is reference sequence data. It would be very useful if our wonderful Blasto colleagues could all try and use the same reference sequences when they develop multiple sequence alignments for phylogenetic analyses. We have already done all the work for you, so all there is to it, is to download the sequences from London School of Hygiene and Tropical Medicine's server available here and align them with your own DNA sequences. It would make life easier for all of us!


Corrected proofs of the article can be downloaded here.

Thanks for reading!

Tuesday, April 9, 2019

Blastocystis PhD position available with Tasos

Hi all,

Just spreading the word: 

There is a funded PhD opportunity (!!!) in Dr Tsaousis' lab on Blastocystis:

'Identifying the parasitic or passenger role of Blastocystis, in patients with gastrointestinal disease'

available for September 16th start!  


Deadline for applications is 22 April.

Find more info here

Special issue on Blastocystis, Pneumocystis and microsporidia in 'Frontiers'

The online journal 'Frontiers in Microbiology - Infectious Diseases' will be publishing a special issue on Blastocystis, Pneumocystis and microsporidia as opportunistic eukaryotes and controversial pathogens.

Please go and see the call for papers here.

Topics editors include Olga Matos, Lihua Xiao and myself.

(Blastocystis images towards the right courtesy of Marianne Lebbad)

Tuesday, February 19, 2019

The role of Blastocystis and other 'apathogenic' gut parasites in health and disease - how to proceed?

If you're interested in reading my most recent paper

Pinning down the role of common luminal intestinal parasitic protists in human health and disease – status and challenges

published recently in Parasitology, you can read it for free here.

Thank you for taking an interest.

Saturday, November 10, 2018

2nd International Blastocystis Conference Wrap-Up - Part III

I asked around for some more take-home messages from a couple of the keynote speakers present at the 2nd International Blastocystis Conference last month in Bogotรก. Here's a summary:

Kevin Tan:
  • Blastocystis is a species complex and as such, it is difficult to generalize on its roles in health and disease.
  • Studies are revealing that intra-subtype variations are associated with different phenotypes, so it is likely that we will require more resolution (allelic) when studying the effects of Blastocystis on the host.
  • Recent metagenomics studies on stools of healthy individuals associate the presence of Blastocystis with a diverse bacterial microbiota, but more studies are required on diseased groups to identify their possible associations with rare/ pathogenic isolates (e.g. ST7 isolates).
  • Recent work on rodent models are shedding light on possible pathogenic effects of acute Blastocystis infections.
  • More studies on the cell and molecular biology of Blastocystis are required to better understand the molecular basis for Blastocystis-host interactions (identify virulence factors, adaptation strategies etc).
  • It is very likely that more surprises are in store for the curious and observant Blastocystis researcher!

Kevin Tan giving his keynote

Kevin Tan taking questions - here probably expanding on Blastocystis ploidy...

Andrew Roger:
  • We shouldn’t try to generalize about characteristics of ‘Blastocystis’ based on studies of individual isolates. This is a category error — Blastocystis comprises many many different organisms with different genetic makeups. There is variation not just between subtypes, but within subtypes. So we shouldn’t say “Blastocystis is a commensal/parasite” because different Blastocystis isolates could be commensals or parasites depending on the host, the genetic makeup of the parasite and the microbiota with which they interact.
  • In microbiome studies, colonization with Blastocystis in general seems to correlate with a different composition of the prokaryotic microbiota in hosts.
  • We know virtually NOTHING about the basic cell biology of Blastocystis (Kevin Tan’s group is making important inroads into understanding this).
  • We know virtually NOTHING about how Blastocystis interacts with (or responds to) other microbes and the host immune system.
  • There may be an important impact of host diet on Blastocystis colonization and ‘behaviour'.
  • The diversity of Blastocystis in humans and animals is huge — new lineages are being continuously revealed.

Andrew Roger about to give his keynote

Andrew Roger taking questions from the audience