Cutest Protist: Love Actually..or Splitsville?

Cutest Protist: Love Actually..or Splitsville?

If you go down in the woods today, you’re sure of a big surprise. No, not the Teddy Bear’s picnic. Giardiasis is a common and explosive form of diarrhea caused from drinking contaminated water from mountain streams and “clean water” sources, often during camping. Also known as Beaver Fever, wild animals and pets can get the runs too.  Giardia lamblia is wonderfully weird: 

• First described in 1681 by Antony van Leeuwenhoek who examined his own diarrhea under a microscope and wrote, “I have sometimes also seen animalcules a-moving very prettily; some of ‘em a bit bigger, others a bit less, than a blood globule… furnisht with sundry little paws, where with they made such a stir”.

• Despite the heart-shape in the left image, Giardia lacks a love life and reproduces only asexually, splitting inside the cyst into two cells (trophozoites) that are released within the intestine. 

• There are two identical and functional nuclei, which makes the stained Giardia look like it has two eyes (right image). Other organisms that have multiple sets of chromosomes house them in the same nucleus. The “smile” comes from the median body which organizes the cell’s skeleton (microtubules).

• Considered the most primitive of eukaryotes, Giardia was believed to have no mitochondria. But now it appears to have some remnants of them, called mitoplasts. Being anaerobic, they don’t respire or make ATP in their mitochondria. Other eukaryotes, even anaerobic ones, have mitochondria.

Henry Hall & His Orchestra – The Teddy Bear’s Picnic (1932)

IMAGES: Digitally colored scanning electron micrograph of Giardia cells in late stage of cell division, courtesy of CDC/ Dr. Edwin P. Ewing, Jr. (left). Stained Giardia looks like a smiley face with two nuclei eyes (right). More cute images:

#ScienceEveryday     #ScienceSunday  

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106 Responses to Cutest Protist: Love Actually..or Splitsville?

  1. Another lovely SEM (pun intended). I’ve never come across Guardia lamblia (through studies nor experience). You learn something new everyday.

  2. Jon Hiller says:

    Wonderful read while eating my pizza lol!

  3. Rajini Rao says:

    It’s actually the most common cause of diarrhea other than bacteria, and the most common cause in the US. 

  4. Rajini Rao says:

    Oops, sorry..skip that part about Leeuwenhoek then 🙂

  5. Well scientists are known to get carried away once they get hold of a microscope =P

  6. Pam Adger says:

    I used to work in a lab that studied Giardia. They had cute pictures of it all over the place…..

  7. Rajini Rao says:

    Isn’t it the cutest? They look so happy, and in love ;P

  8. Rajini Rao says:

    Err…have you had it on a field trip, Erin Kane ? The symptoms sound quite horrible.

  9. Not the kind of love I’d like to share that’s for sure ;P

  10. Rajini Rao says:

    This one looks a bit apologetic for all the trouble it’s caused:

  11. Rajini Rao says:

    Aww, sorry Erin Kane . Have a plush toy:

  12. Rajini Rao says:

    Just posted the link, M Monica ! 😀

  13. Rajini Rao says:

    Hiking/camping seems to be the most common time to get infected, Bobby Shaftoe . 

    Gnotic Pasta , with all the camping you do..ever caught this bug?

  14. Rajini Rao says:

    Because the cysts survive cold, they are also found in sources of drinking water, like wells and water storage tanks. I think I read somewhere that they survive chlorine. 

  15. Bill Carter says:

    Ah Giardia – we had an… intimate relationship for many years. First arrived in my guts in St. Petersburg, riding atop a delightful seaweed salad.

    … Egg burps.  Yea, don’t miss those.  Very tenacious little bugger.  I think the only thing that finally got rid of them was proper diet.  None of the unbelievable medicine I took was actually effective.  

  16. Rajini Rao says:

    That’s too bad, William Carter ! You must have been in the small percentage for whom the antibiotics do not work. I guess they tried metronidazole first. 

  17. Rajini Rao says:

    Have you tried those pumps that iodinate water while it passes through a cartridge? We used them when our kids were little and we travelled to tropical countries where the flora was different.

  18. Viet Le says:

    It also causes incredibly uncomfortable bloating. Caught it during my trip to Vietnam.

  19. NEY MELLO says:

    Rajini Rao ….Did I hear..”Beaver Fever”?!? 😀 😀

  20. prem mundada says:

    Nice post abt cause of illness

  21. Rajini Rao says:

    Yup, NEY MELLO . Does it mean something else? :O

    Drew Sowersby , do you happen to know why protozoans are now known as protists? I must have missed that class in school 🙂

  22. Viet Le says:

    Rajini Rao Drew Sowersby for Kingdom Protista, no?

  23. Rajini Rao says:

    That’s interesting about the well.

    Most people are asymptomatic with Giardia, Dan. Perhaps you have to get a large dose, or be susceptible at the time. 

  24. Rajini Rao says:

    Viet Le , we used to call them Protozoa. What happened to that name? I read the description protist with parenthetical “formerly known as protozoan”, and wondered why. 

  25. Bill Carter says:

    Rajini Rao – Forgot to mention this was way back in 1989 (yea, I’m that old) at the start of my round-the-world travels with my mom. We did take our own ceramic filter pump on subsequent trips through Asia (until a few Tibetan kids got hold of it, curiously took it apart and smashed the filter!)

  26. Rajini Rao says:

    The googles told me that “A protozoan is a heterotrophic protist” and that 7 subphyla of the kingdom of protista are protozoa. The protist kingdom includes protozoans and algae. 

  27. Rajini Rao says:

    You’re a young’un, William Carter 🙂

  28. Viet Le says:

    Rajini Rao  I think the kindgom has gone through some restructuring and renaming…protista, then they were lumped in with eukaryotes for a while then back to protista, then it was some other name, then back to protista…well you get the idea. I think it’s generally agreed upon now that it’s protozoa…but I could be wrong.

  29. Bill Carter says:

    You’re very sweet Rajini Rao 🙂

  30. Viet Le says:

    Rajini Rao hmmmm. Now I’m confused.

  31. Rajini Rao says:

    Viet Le , I think Protista is the Kingdom, as you said. The autotrophs in that kingdom are algae and the heterotrophs are protozoa (suggesting little animalcules). 

    At least, I hope that algae are protists phylogeny is rusty.

  32. Viet Le says:

    Rajini Rao rusty over here too.

  33. John Kampsen says:

    Strange little vermin, Rajini Rao . Happily this day, my innards are not overly populated with them. Hope you are well, young lady. We have quite a flu epidemic going on here !

  34. Rajini Rao Algae are nothing. In Catalan I’d say they are “un calaix de sastre”, a “taylor’s box” (I don’t think this expression exists in English). It’s an outdated term that includes lots of different things, spread in different Kingdoms.

  35. Rajini Rao says:

    John Kampsen , I’m flu-free and protist-free at the present, thanks for enquiring. Hope you are well too 🙂 

    Why tailor’s box, Víktor Bautista i Roca ? Like a purse perhaps.

  36. Rajini Rao says:

    Oh dear, Feisal Kamil . I shouldn’t have looked up the urban dictionary. Care for a demerit? NEY MELLO , too 🙂

  37. Rajini Rao says:

    Beaver’s carry them and contaminate mountain streams, (for those that do not look up urban dictionary) . It’s also called Colorado fever or such. 

  38. Rajini Rao says:

    I’m no doctor, but it could have been viral Feisal Kamil . Good morning and good weekend to you.

  39. Rajini Rao  It means a box where you put anything, a totum revolutum.

    Green algae are Plantae, red algae are Archaeplastida but not Plantae, some are Bikonta, closer to amoebas than anything else, and other are Chromista or Alveolata. Oh, and the blue-green algae are bacteria.

  40. In this context the right expression would be “algae are a polyphyletic group”. So, they are no group at all.

  41. Rajini Rao says:

    Especially since blue-green algae are cyanobacteria! 

  42. Rajini Rao Yes. In fact, even in the widest use of algae term blue-green algae are not included.

  43. Rajini Rao says:

    Víktor Bautista i Roca , I was just reading the tangled history of cyanobacteria classification: first they were thought to be plants, then protists (under Monera) and finally prokaryotes.

  44. Arizona Bob says:

    Gnotic Pasta Rajini Rao Same here…plenty of times I probably should have been sick with it here…but all of the similar gut problems I have had occured while traveling elsewhere.

  45. Rajini Rao says:

    We’ve been having fun with the Repoopulation story of fecal transplants, Jon Hiller . You’ve probably seen the punderstorm on Chad Haney ‘s post on this 🙂

  46. Mary T says:

    I used to drink from mountain streams, back in the late ’70’s, and suspect I may have had a mild case of it.  Now, I boil my water if I camp in the wilderness.

  47. Rajini Rao says:

    Thanks, Drew Sowersby . I figured it out…protists that are heterotrophs are called protozoa. Algae are protists but not protozoan since they can make their own food. 

  48. Rajini Rao says:

    Hah, yes..also #animalcules  in honor of Anton van Leeuwenhoek. 

  49. I think von Leewenhoek was the original bio-geek! Thanks!

  50. Rajini Rao says:

    I like the term bio-geek 🙂

  51. I love talking about giardia with my students.  It’s such a photographic microbe. I almost convinced my students to dress up as giardia for Halloween, but they chickened out.  (Or should I say, they pooped out?)

  52. Jim Carver says:

    Iodine is actually really effective for most things you might get in stream water. It’s more antiseptic than Cl,…only thing is, it stains everything and makes the water taste like shit.

    What we found at CU were these hand operated RO pumps. They didn’t put out a whole lot at once, but it was definitely enough to keep you going. I still carried the I tabs but I didn’t have to use them anymore. I could usually pack enough to keep me going for a while. Oh and btw, don’t drink your own piss like that guy did on a stupid survival show. That’s about dumber than drinking seawater. 🙂

  53. Jim Carver says:

    Those little Bio-Lites are good at boiling water also. You can fuel those by stuff just laying around…twigs and stuff. It’s powered by a small fan hooked to a battery and thermoelectric generator that can even charge your USB device. I’m sure you’ve probably seen it. They’re great for this in the woods. Seriously, it takes so little wood.

  54. Jim Carver Rajini Rao We back in India used to add iodine crystals in the drinking water storage tank but after few weeks we found out that there is some algae growth.

    We then stopped. Now I wonder what type it was.

  55. Rajini Rao says:

    mandar khadilkar , you probably saw brown algal blooms in those iodinated tanks. It turns out that many algae love to assimilate iodine and it can get up to 1% of their weight. It’s thought to be a defense mechanism to put off herbivores with the bad taste. There’s some data showing faster growth of algae with increasing iodine. Unfortunately, iodine is not as good in killing protozoans relative to bacteria and viruses.

  56. I thought that I was Sisyphus, until I read your comment, Keep rolling that stone Feisal Kamil I’m behind you all the way.

  57. Dave Lunt says:

    HI Rajini, very cool post. Actually, although Giardia (probably) reproduces asexually in much of its range, it can certainly reproduce sexually as well and this has been seen in South American wild populations. Its probably not quite true to say that all other eukaryotes have mitochondria, most do but there are some other amitochondrial groups- like microsporidia.

  58. Rajini Rao says:

    Dave Lunt , thanks, I was wondering about that. Usually, organisms reproduce sexually before forming spores, or in this case, cysts. But the reviews I read made no mention of sexual reproduction, which is odd.

    It’s interesting that microsporidia used to be considered protists too, but now they are classed as fungi. We were discussing the confusion over classification of cyanobacteria as well. My sense is that with simple unicellular organisms, the distinctions between the kingdoms are not that clear cut and there are shared features that make them difficult to classify. 

  59. Dave Lunt says:

    Yes, I understand why that was all you came across- complete asexuality is a very common view in papers and textbooks, but actual investigations find evidence of both sexual machinery and sexual recombination in populations e.g. doi:10.1016/j.cub.2007.10.020 One of the problems is that you can only really detect sexual recombination when the same person is infected with two different strains. Sounds nasty!

  60. Rajini Rao says:

    Sex: Is Giardia Doing It in the Dark?

    This paper shows that genes for genetic recombination exist in Giardia but they don’t see evidence for outcrossing yet. It’s important to know because this may help understand how meiosis and genetic recombination evolved.

    Giardia sex? Yes, but how and how much?


    Although Giardia is of practical importance as a pathogen and has theoretical importance in evolutionary biology, it is not known whether it ever reproduces sexually. Several recent papers have shed light on this problem, without completely solving it. One paper shows that nuclei in the encysted organism can temporarily fuse and exchange genes; this may explain the genetic similarity of the two nuclei in a cell. Another paper demonstrates that Giardia does undergo sexual reproduction with outcrossing. However, we still do not know whether this involves a meiotic or a parasexual cycle, when it occurs, or how common it is.


    Curiouser and curiouser! 

  61. Rajini Rao says:

    I see..there is evidence for meiotic recombination in genetic loci but we’ve not caught ’em at it. Very interesting.

  62. Rajini Rao making or keeping water potable is very expensive in my experience.

    After our experiment with iodine, we tried KMnO4 (potassium permanganate) . Few weeks were very good.

    But again, some other thingies start growing.

    Since then my mom who stays there by herself uses ceramic physical filters with storage bucket below.

    No chemicals beyond what got added from the public works system. That is mostly chlorine.

    She physically cleans the ceramic rods every week and in process removes top thin layer renewing the filter to some extent.

    I am sure the filter system will not work when microbes are very small.

    Interestingly, I read that most microbes are very susceptible to fluid pressure and surface tension and pH.

  63. Rajini Rao does is happen in nature that there is less frequent sexual reproduction to bring gene mutations and then asexual reproduction for mass production. This combination is good as it bring best of both the worlds.

    Think like in industrialization- different companies cross pollinate but there is a production line with identical items.

    So, from the same company, identical items produced but very different variation across companies.

  64. Rajini Rao says:

    mandar khadilkar yes, that’s right and a good  analogy to a business model too! Strictly speaking the recombination between genes brings genetic variation (instead of mutation..those are caused by damage and errors).

  65. Jim Carver says:

    Rajini Rao I’m usually rebuffed by biologists for stating the following: I think mutations might have been important in the earliest beginnings of life. They have a statistical probability of some have said 1% (at least back when I was in school) and I think that was way too high. I believe that was one reason why it took maybe a few billions of years before there was much progression. As time moved along, then recombination and HGT took on a very much larger role in evolution and is the one factor that dominates today.  This would account for the explosion of life that we begin seeing in the Paleozoic when things began to change. I don’t think the mutation theory can hold up to this. Of course that’s just a geologist’s point of view.

  66. Rajini Rao says:

    Jim Carver , mutations are always important for evolution. They are the source of the genetic variation. I was clarifying that recombination, or the swapping of genetic material, shuffles the genes and gives rise to variation in the combination of alleles (gene versions) that we carry. Mutations (or polymorphisms, actual changes in the base composition of DNA) arise from mistakes in copying, repair, radiation damage, etc. Now, I don’t know how the rate of mutagenesis has varied over time. There must have been eras where the bombardment of life forms with radiation was larger than it is now.  1% sounds very high to me.

  67. Jim Carver says:

    Rajini Rao It’s likely that real life as we know it didn’t start until the Proterozoic (the last Age of the Pre-cambrium) when oxygen was released by the cyanobacteria. That’s the accepted theory although there have been some other theories postulated about the release of free O2 by oxides in the Early Earth. I personally don’t subscribe to this theory since it has a lot of holes. So, speaking of holes, there were a lot of holes in this early atmosphere too. Big ones, that let a lot of UV in (the whole alphabet) and it was likely at first that some water was needed as a shield against the radiation. Plenty of radiation and mostly too much…plenty of opportunity, but not much change until the atmosphere was able to shield out a larger quantity.

  68. Rajini Rao thanks for correction. I almost forgot what I learnt in school that mutations are just error in ATCG sequences. Those will happen in any replication or even in normal life of a cell due to radiation or chemical agents or even some mixing with genetical materials (virus)?

    And swapping of genes or something as you call is different phenomenon is due to sexual reproduction.

    Don’t you think that mutations are more fundamental and much more primordial? It brings larger and constant supply of diversity?

  69. Rajini Rao says:

    You hit a hole in one with that explanation, Jim Carver . Thanks!

  70. Rajini Rao says:

    mandar khadilkar  viruses do cause mutations because of how and where they insert their DNA into the host genes. They can activate genes abnormally, or break them apart. And you’re right that mutations are very fundamental to the evolution of life. They are the source of constant supply of diversity.

  71. Sandi D says:

    Rajini Rao I wonder and the destruction of ??

  72. Jim Carver says:

    Sandra D No, not total deconstruction or it would be totally inviable. We’re just maybe knocking a side chain off or knocking things into a different position. If they are toasted there is no way.

    Of course there’s always the possibility those fragments could be incorporated into other structures, etc.

  73. Sandi D says:

    Jim Carver I understand but not total destruction but efficient to alter and re-alter, like re-creating but destroying the formation?

  74. Jim Carver says:

    You know what’s a ‘really bend your brain’? Try to imagine how mitochondria, found in eukaryotic cells that may have once be free organisms, are now the powerhouse of modern metabolism? That’s at least a theory and I’m sure Rajini knows more than I can recall. Wonder if it was a hostile takeover or a peaceful treaty? 🙂

  75. Rajini Rao says:

    Speaking about endosymbionts, like mitochondria, here is an extraordinary story of a bacteria that infects insects, gets into their sperm and egg so it can be transmitted to future generations, and even has its genes inserted into the host:

  76. Jim Carver says:

    Interesting…but that’s a lower form infecting a higher form. What if they are on equal ground?

  77. Rajini Rao says:

    Can’t think of an example off would be like cell fusion of a sort. Sometimes cells fuse to form a syncytium (multiple nuclei, no cell membranes between them). Most endosymbionts are prokaryotes (bacteria, cyanobacteria) that are incorporated into a larger eukaryotic cell. 

  78. Jim Carver says:

    The theories I heard about were mostly some kind of envelopment. Like an amoeba or something and then that died out leaving the mitochondria as a relict, not able to sustain itself in the outside world.

  79. Rajini Rao says:

    Actually, the prokaryote (bacterial ancestor) would have been engulfed by the larger cell and is what we now know as the mitochondrion. There is plenty of biochemical support for this. For example the outer membrane of the mito resembles that of the larger eukaryotic cell while the inner membrane has many of the lipids that bacteria have. The mitochondria have their own DNA and ribosomes, and have many similarities to bacteria. The ox phos reactions that take place on the inner mito membrane are the same as those on the bacterial membrane. Same analogies for chloroplasts. The endosymbiont theory is pretty well accepted, and I’m not aware of any viable alternative theories. 

  80. Jim Carver says:

    Oh, I guess they got it backwards back then. Oh well wouldn’t be the first time.

    I will read it back three times to make sure I have it right. 🙂

  81. Jim Carver says:

    Okay, on third reading, doesn’t it seem that there has been a lot of gene transfer here and how do you really know which happened when?

  82. Rajini Rao says:

    Here is the actual abstract, which make more sense (at least to me!): “Although common among bacteria, lateral gene transfer-the movement of genes between distantly related organisms-is thought to occur only rarely between bacteria and multicellular eukaryotes.

    However, the presence of endosymbionts, such as Wolbachia pipientis, within some eukaryotic germlines may facilitate bacterial gene transfers to eukaryotic host genomes. We therefore examined host genomes for evidence of gene transfer events from Wolbachia bacteria to their hosts. We found and confirmed transfers into the genomes of four insect and four nematode species that range from nearly the entire Wolbachia genome (>1 megabase) to short (<500 base pairs) insertions.

    Potential Wolbachia-to-host transfers were also detected computationally in three additional sequenced insect genomes. We also show that some of these inserted Wolbachia genes are transcribed within eukaryotic cells lacking endosymbionts. Therefore, heritable lateral gene transfer occurs into eukaryotic hosts from their prokaryote symbionts, potentially providing a mechanism for acquisition of new genes and functions.”


    They make an interesting point in the paper: when genomes are sequenced, “bacterial sequences” recognized by algorithms are typically thrown out because they are considered to be contaminants. They may actually be there for real, from lateral gene transfer. 

  83. Jim Carver says:

    Well that’s interesting isn’t it? While not giving really any credence here. It surely shows the researcher’s intuition about this.

  84. Jim Carver says:

    Rajini I can’t exactly tell you why. I’m not a biologist as you well know. But this just fits. It’s obviously don’t know the details.

  85. Jim Carver says:

    I’ll go one step further and maybe take it out on a limb.

    Researchers found that the transference of a resistant glyphosate gene didn’t occur in sterile soil. Once they used live soil from the garden or where ever, it was.  All the weeds got the gene without a direct genetic transfer. One that didn’t, got it anyway. Virus? Probably.

  86. Now that we are at genes etc, Jim Carver Rajini Rao did you follow the link bet TBT and Grand Children obesity (in mice)?

    While in US there is obesity in humans, there is strong evidence that mammals surrounding us are also obese. So, the link is just not life style.

  87. Jim Carver says:

    mandar khadilkar Interesting, have to follow that later when I’m more coherent. PS Don’t fall asleep on the squishy couch when watching the Ancient X-Files, it will mess up brain function for at least 12 hours, 😉

  88. I’m conflicted, sure, it looks cute – but cleaning three carpets after one of our dogs experienced explosive diarrhea (and I do mean explosive) after picking up a giardia infection from raccoon feces, well… no. Not a fan!

  89. Rajini Rao says:

    David Archer  Then you deserve the apology-faced Giardia or maybe even the plush toy in sympathy 🙂

  90. Pam Adger says:

    Rajini Rao Hahhaahaa!

  91. Wow, that Leeuwenhoek quote is amusing. He sounds like a fun character (although not a fun-guy).

  92. Rajini Rao says:

    Linda Baig , many of us carry Giardia and other microorganisms in us without symptoms. We can still pass the infection on to others, though. It may have to do with natural immunity or with the amount of the exposure to the germs. Also, the incidences of diarrhea are actually higher in places where sanitation is poor.

  93. Rajini Rao says:

    Yes, many people are asymptomatic. Only some develop giardiasis.

  94. Jim Carver says:

    Linda Baig This one is fairly easy to eliminate using several methods. A 1 uM cartridge filter works fine and I read where sand filters work also. The smaller stuff like bacteria and viruses are more problematic. Usually they recommend a combination of treatments. Those hand operated RO units are good. I have to say the membrane didn’t last very long on mine.

    You know what they sometimes say though? “You’re either eating bugs…or dead bugs.” 😉 (Well not always)

  95. A few years ago the Mexican government did a nationwide health study of food handling practices and found a few very interesting things, most noteworthy being the fact that, in spite of names like “Montezuma’s Revenge” and “Turista” Mexicans suffer an alarming amount of dysentery from eating restaurant and street food. So the assumption about locals’ resistance is somewhat mythical. It was just not news-worthy.

  96. Jim Carver says:

    Fortunately I have a few friends on here, otherwise I would think that everyone is a jerk. I think Firesign Theater said it best: “Inferior people should not be employed.” (They should be blocked.) 

  97. Rajini Rao says:

    It’s good to keep perspective 🙂

    I’m here for the science. And the foodie posts, and the puns, and ….

  98. Jim Carver says:

    Me too, and I make mistakes sometimes. You said they do have more problems in those areas. I said they are easy to get rid of unlike some smaller things, etc.

    That’s the third time I’ve been jumped on in as many days for trying to be helpful. Do I get a thanks Jim that’s really true? Noooo…I get you’re not addressing my wants, needs and desires.

    What she wanted was a personal consultation with the doctor. I think you should start charging for that. 🙂

  99. Rajini Rao says:

    Hahaha! I thought everyone knew that I’m not a “real” doctor 😉

  100. Jim Carver says:

    That’s right! “Not one that helps anyone” . 😉

    No, it really should be not one that gives immediate relief. But stick around…

  101. Daniel Kight says:

    Rajini Rao as anyone told you how pretty u r 2day

  102. Daniel Kight says:

    Well got to go to bed feed time comes early in the morning goodnight all

  103.  primitive of eukaryotes!?

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