Field of Science

MM09 answer: Hoplonympha - loaded with bacteria

ResearchBlogging.orgI'm really behind on the answers. I'll do the easier one first, so MM08 will be next.

Remember this myserious organism from a while ago? Johan got it: it's Hoplonympha, a parabasalian gut endosymbiont! (Opisthokont was also on the right track)

Hoplonympha. top: SEM of whole organism (F indicates flagella), the long strips are actually ectosymbiotic bacteria, as evident in the TEM cross section on the bottom. CM - cytoplasmic [inner] membrane, OM - outer membrane, SL - S-layer. Note that unlike in Streblomastix (an oxymonad), the host cell is substantially more convoluted. (Image from Ohkuma 2008 Tr Microbiol(free access), originally from Noda et al. 2005 Env Microbiol)

A Streblomastix wannabe. Although in a completely different clade. Not too surprising, considering the similarity of their habitats, that such a strong evolutionary convergence may occur. Note that unlike Streblo, this organism also seems to contain bacterial endosymbionts inside it. It's quite a jungle of symbiotic relationships there in the termite and cockroach guts!

What are those bacteria doing? For one thing, Parabaslians are anaerobes, containing highly derived relict mitochondria called hydrogenosomes -- which, as their name suggests, generate hydrogen gas. Bare hydrogen is a relatively rare commodity in nature, so there's plenty of bacteria that crave it for their own metabolic exercises. Many of the symbiotic bacteria are methanogens, and use the hydrogen gas in their methane production pathways.

The exact functions of some other bacteria in this bizzare and complex ecosystem aren't well understood (Ohkuma 2008 Tr Microbiol). For many obligate anaerobes, however, the gut of various animals became a rare haven from the oxygen pollution their ancestors have wrecked the environment with a couple billion years ago. In termites and wood-eating roaches you have the extra advantage of free poorly digested (by the host) carbon sources entering in the form of wood cellulose. It's a nice deal: you nibble on yummy cellulose and the host is happy with your excrement. Of course, as with any nice deal, a hungry horde of other creatures congregates around the fun. So we end up with something like this:

A sample of the complex interactions between the gut protists, bacteria and the host. For more info, read the source Ohkuma 2008 Tr Microbiol, a freely accessible pdf of which was found by Johan.

And it's likely only the beginning of the story. And yes, the cellulose digestion is predominantly done by the protists, not the bacteria. Apparently, removal of bacteria by antibiotics did not stop the cellulose digestion, whereas a removal of the gut protists wrecks it.

Since it's meaningless to look at organisms without at least considering their place in The Tree, Hoplonympha seem to form a sister clade to Eucomonympha, which together group cozily with the Trichonymphidae, with some peculiar Staurojoeninidae getting in the way:
You may recognise Trichonympha, Eucomonympha, and Cochlosoma in the Trichomonads. Trichonympha are NOT Trichomonads, but are Hypermastigotes. Just sayin'. Trichomonads tend to be a little less 'hyper' with their karyomastigont (nucleus + flagellar apparatus) multiplication. Turns out we're steadily building up quite a collection of Parabasalians here...we have these people to partly blame: (Carpenter, Chow & Keeling 2009 JEM)

There's a really cool Parabasalian with ectosymbiotic bacteria that act much like flagella, propelling the organism by beating in a synchronised fashion. This partly where Margulis gets her "spirochaete = flagellum" fantasies from, where spirochaetes mafically became attached to the proto-eukaryote and somehow became its flagellum. Which is obviously eukaryotic, and devoid of DNA, and not even barely spirochaete-like, but never mind. Or, as TC-S would say: the eukaryotic flagellum differs from a spirochaete "in every visible respect possible" for a subcellular structure. =D We'll look at this cool organism at some other time, so I'll leave you in suspense for now.

Before I finally shut up, there's a slightly annoying gap in our exploration of Hypermastigotes: While we've by now glanced at Trichonympha, Eucomonympha and Hoplonympha, what about this mysterious Staurojoenina thing between them? Guess what, it also has ectosymbiotic bacteria!

Staurojoenina. The things on its ass in the SEM are spirochaetes, while the rest of it is covered in rod-shaped bacteria, with some flagellar tufts towards the anterior. Also littered with endosymbionts. Kind of cute, but Eucomonympha and Trichonympha are fuzzier. (Stingl et al. 2004 Microbiol)

Now to write up MM08 (a really cool one), and you guys still need to figure out MM10!


CARPENTER, K., CHOW, L., & KEELING, P. (2009). Morphology, Phylogeny, and Diversity of
(Parabasalia: Hypermastigida) of the Wood-Feeding Cockroach
Journal of Eukaryotic Microbiology, 56 (4), 305-313 DOI: 10.1111/j.1550-7408.2009.00406.x

Noda, S., Inoue, T., Hongoh, Y., Kawai, M., Nalepa, C., Vongkaluang, C., Kudo, T., & Ohkuma, M. (2006). Identification and characterization of ectosymbionts of distinct lineages in Bacteroidales attached to flagellated protists in the gut of termites and a wood-feeding cockroach Environmental Microbiology, 8 (1), 11-20 DOI: 10.1111/j.1462-2920.2005.00860.x

OHKUMA, M. (2008). Symbioses of flagellates and prokaryotes in the gut of lower termites Trends in Microbiology, 16 (7), 345-352 DOI: 10.1016/j.tim.2008.04.004

Stingl, U. (2004). Symbionts of the gut flagellate Staurojoenina sp. from Neotermes cubanus represent a novel, termite-associated lineage of Bacteroidales: description of 'Candidatus Vestibaculum illigatum' Microbiology, 150 (7), 2229-2235 DOI: 10.1099/mic.0.27135-0


  1. Or, as TC-S would say: the eukaryotic flagellum differs from a spirochaete "in every visible respect possible" for a subcellular structure.

    I thought that there was supposed to be a quite spooky resemblance between the "9 + 2" arrangement of microtubules in a cilium and the arrangement of tubules in a spirochaete? Though if there is, I've always wondered if some form of lateral gene transfer rather than full endosymbiotic origin might be the best explanation.

  2. I was unaware of the 9+2 thing, although I have read somewhere that mathematically/physically, that is the arrangement that makes the most sense considering the size and structure of the microtubules. Something like the optimal way to pack them into a compact membranous sheath, with enough space for motor proteins. In which case, a convergence would be thoroughly unsurprising (spirochaetes don't use tubulin, presumably?). I'll go look for it...

  3. Yeah, I read here in Mitchell 2007 that the 9+2 arrangement may have been optimal for motility for structural reasons:

    He also has a discussion about it here (2004):

  4. Necrotizing fasciitis (NF), commonly known as flesh-eating disease or flesh-eating bacteria, is a rare infection of the deeper layers of skin and subcutaneous tissues, easily spreading across the fascial plane within the subcutaneous tissue.

    Type I describes a polymicrobial infection, whereas Type II describes a monomicrobial infection. Many types of bacteria can cause necrotizing fasciitis (e.g., Group A streptococcus (Streptococcus pyogenes), Staphylococcus aureus, Vibrio vulnificus, Clostridium perfringens, Bacteroides fragilis). Such infections are more likely to occur in people with compromised immune systems.
    Historically, Group A streptococcus made up most cases of Type II infections. However, since at least 2001, another serious form of monomicrobial necrotizing fasciitis has been observed with increasing frequency.In these cases, the bacterium causing it is methicillin-resistant Staphylococcus aureus (MRSA), a strain of S. aureus that is resistant to methicillin, the antibiotic used in the laboratory that determines the bacterium's sensitivity to flucloxacillin or nafcillin that would be used for treatment clinically.


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