Ascophyllum nodosum
is considered one of the most successful intertidal algae in the North Atlantic
Ocean, this algae can be the dominant organism in estuaries, salt marshes and
even highly exposed rocky intertidal. So what is the secret to its success in
this wide variety of biological niches? It plays host to a complex symbiotic
system which includes the four core members; A. nodosum; Vertebrata lanosa which is in turn associated with the
red algal parasite Choreocolax
polysiphoniae and the obligate endosymbiont fungus Mycophycias ascophylli.
Fungi are often found in partnership with photosynthetic
organisms, often as parasites. The partnership between A. nodosum and the fungus M.
ascophylli would suggest forming lichen; however this is rejected by some
lichenologists. Lichens can tolerate rapid and extreme fluctuations in
temperature and moisture, like A. nodosum.
These environments are too extreme for many species which allows A. nodosum to exploit a lot of available
niches.
The paper in review is the latest paper as part of an 11
paper ongoing study into Ascophyllum and its symbionts to understand the
physiology, ecology and success of A.
nodosum. As we looked at the relationship with M. ascophylli in the lecture, I thought it would be interesting to
look at the other symbionts in the relationship to create a more rounded
picture so this paper focuses on the interaction with V. lanosa.
The study used amplitude fluorimetry of chlorophyll a
fluorescence from photosystem II (PSII) to measure the maximum quantum yield of
photosystem II [QY(II)max] in the thallus of both symbionts. Treatments of
attached, detached (but in the same medium) or separate were measured in the
field and in the laboratory, over a 7 day period.
Their findings included:
-
When attached to A. nodosum, V. lanosa has much higher photosynthetic capability
when thaullus is submerged in water, unsurprisingly.
-
Over the 7 day period A. nodosum was found to have similar photosynthetic capability
whether attached to V. lanosa or not,
or even in the same medium.
-
V. lanosa
was found to have much less photosynthetic capability when unattached from A. nodosum and when in a separate
medium, these results became clear within the first 24 hours of the 7 day
period. QY(II)max was always higher in V. lanosa when attached to A.
nodosum, no significant decline over the 7 day period.
-
The second lab test was to measure the
fluorescence in V. lanosa. Results of
QY(II)max
came back similar to previous experiment. Similarly, in this experiment V. lanosa shown signs of significant
decline in fluorescence when unattached to A.
nodosum and when alone.
This experiment focused on A. nodosum and V. lanosa
as symbionts; however it is important to remember this in association to the
other symbionts such as M. ascophylli.
Previous papers have shown that zygotes of A.
nodosum grew faster and were more tolerant to desiccation once infected by M. ascophylli. M. ascophylli is always
present in A. nodosum, which could be
suggesting that the symbiotic relationship between M. ascophylli and V. lanosa
may have similar physiological basis as V.
lanosa and A. nodosum.
Previous studies have explored the physiological
relationship of A. nodosum and V. lanosa such
as nutrient and other materials transferred between the symbionts. However,
this paper shows how strong this relationship is with regards to physiological
basis for the symbiotic relationship in both lab and field conditions. Highlighting
that V. lanosa unattached and not in the same culture has less success than
when attached to A. nodosum.
It would be interesting to see if A. nodosum photosynthetic capability is affected at different
temperatures. The samples measured in the field were collected in winter at air
temperature of 13C. We understand A.
nodosum is tolerant at a wide range of temperatures, but it would be
interesting to find out if the symbionts are as tolerant and if photosynthetic
capability is temperature influenced at all.
It is well understood A.
nodosum has inducible chemical defences which are employed when an individual
suffers physical damage. I’ve found little knowledge on the role of this fungal
symbionts role in the chemical defence of A.
nodosum, it would be interesting to understand the function of these microbial
symbionts on A. nodosums chemical defence,
which in turn is key to its survival and success.
I felt the research was done well; the paper was an easy
read and very interesting. The only criticism I have towards the paper itself is
the results section, which to me, is too wordy and I believe some aspects
should be in the discussion.
Garbary, D. J., Miller, A. G., & Scrosati, R. A. (2014).
Ascophyllum nodosum and its symbionts: XI. The epiphyte Vertebrata lanosa
performs better photosynthetically when attached to Ascophyllum than when
alone. Algae, 29(4), 321. https://www.researchgate.net/profile/Ricardo_Scrosati/publication/268577790_Ascophyllum_nodosum_and_its_symbionts_XI_The_epiphyte_Vertebrata_lanosa_performs_better_photosynthetically_when_attached_to_Ascophyllum_than_when_alone/links/54916dfa0cf222ada858bcf0.pdf
Extra reading:
The controversy of is A nodosm as a lichen:
Garbary, D. J. (2009). Why
is Ascophyllum nodosum not a lichen. Int
Lichen Newsl, 41,
34-35. https://www.researchgate.net/publication/233794753_Why_is_Ascophyllum_nodosum_not_a_lichen?el=1_x_8&enrichId=rgreq-77a8488c8a9d3c1aa09277e8a1013cc2-XXX&enrichSource=Y292ZXJQYWdlOzI2ODU3Nzc5MDtBUzoxNzUzNDU0MzcyNTc3MjhAMTQxODgxNzAxODEyMw==
Hey Ellie,
ReplyDeleteReally nice blog! You mentioned that this paper focused on the symbiont V.lanosa, but also reminded us that M. ascophylli is always present within the macrophyte. Was there any statistical analyses which looked at the individual effect, as well as the interactive effect of these two symbionts on the algae? Did they ever look at the photosynthetic rate of the plant without M. ascophylli and with only V.lanosa, or does this paper not cover this in anyway?
Thanks,
Harriet.
Hi Harriet,
DeleteThank you for your questions, sorry for the delayed response. This study did not include any statistical analysis of M. ascophylli, the main focus of the paper was interaction with V. lanosa (also known as Polysiphonia lanosa). However, I was also interested in the relationship between M. ascophylli and V. lanosa and how this mutualistic relationship works with A. nodosum. So you might be interested in looking at these previous papers from the extensive study into A. nodosum.
This study by Xu et al, (2008) looks into the structural relationship of A. nodosum and M. ascophylli, although does not talk much about V. lanosa, except for mentioning it as part of the symbiotic relationship again.
Xu, H., Deckert, R. J., & Garbary, D. J. (2008). Ascophyllum and its symbionts. X. Ultrastructure of the interaction between A. nodosum (Phaeophyceae) and Mycophycias ascophylli (Ascomycetes). Botany, 86(2), 185-193. http://www.nrcresearchpress.com/doi/abs/10.1139/B07-122
Garbary et al (2005) is an interesting paper on the morphological relationship between M. ascophylli and V. lanosa, showing how this mutualistic relationship provides protection for A. nodosum and how the host provides nutrients to the symbionts.
The study also shows V. lanosa as an independent photosynthetic organism, their results suggest that the settlement of V. lanosa is not reliant on biochemical dependency but ecological factors.
Garbary, D. J., Deckert, R. J., & Hubbard, C. B. (2005). Ascophyllum and its symbionts. VII. Three-way interactions among Ascophyllum nodosum (Phaeophyceae), Mycophycias ascophylli (Ascomycetes) and Vertebrata lanosa (Rhodophyta). ALGAE-INCHON-, 20(4), 353. https://www.researchgate.net/profile/David_Garbary/publication/233870753_Ascophyllum_and_Its_Symbionts_VII_Three-way_Interactions_Among_Ascophyllum_nodosum_Phaeophyceae_Mycophycias_ascophylli_Ascomycetes_and_Vertebrata_lanosa_Rhodophyta/links/0912f50c7a6a51abcc000000.pdf
Interesting stuff and luckily there seems to be a wealth of information. I hope I’ve answered your questions!
Many thanks,
Ellie
Hi Ellie,
DeleteYou've gone above and beyond answering my question - so thank you! I especially like the Garbary et al., (2005) paper that you have included, so thank you for showing me this as it's really great.
Harriet
Hi Elle,
ReplyDeleteThanks for your post - these emerging insights into the fungal role of marine holobionts is really exciting stuff. While not a marine example, you might be interested in a paper that came out this year that might change the paradigm of lichenisation. The authors describe that on top of the ascomycote mycobiont and algal symbiont, they have found evidence of a basidiomycote yeast living in the lichen cortex. Lichens may be even more complicated consortia than previously imagined, and it would be fascinating to see if this holds true for marine species.
Thanks,
Davis
Spribille, T., Tuovinen, V., Resl, P., Vanderpool, D., Wolinski, H., Aime, M. C., ... & Mayrhofer, H. (2016). Basidiomycete yeasts in the cortex of ascomycete macrolichens. Science, 353(6298), 488-492. http://science.sciencemag.org/content/353/6298/488
Hi Davis,
DeleteThanks very much for the paper, really interesting read to help understand the complexity of lichens and the changing definition of lichens.
The knowledge of lichen structure is expanding, and like you say will be interesting to see if this transfers to marine examples. Whilst reading the paper you sent I also came across this paper:
Jones, E. G., & Choeyklin, R. (2008, December). Ecology of marine and freshwater basidiomycetes. In British Mycological Society Symposia Series(Vol. 28, pp. 301-324). Academic Press. http://www.sciencedirect.com/science/article/pii/S0275028708800185
This paper talks about the ecology of some of the few examples of aquatic basidiomycetes and their role in the marine environment. While it mainly focuses on the distribution of basidiomycetes in the aquatic environment, it is a step in the right direction to understand the physiology and biochemistry of marine basidiomycetes.
Here is to ever-changing microbiology!
Many thanks,
Ellie
Hi Elle,
ReplyDeleteYou mentioned that the fungal symbiont (V. lanosa ) had a higher 'fitness' in terms of photosynthesis rates when attached to algae, i was wondering your opinion on why this is the case? Do you think that this is a mutalistic or parasitic relationship. One though i had was is this relationship comparable to the one seen in coral and zooxanthellae, where increased photosynthesis rates are induced so they can provide the host with the products, this could be especially prevalent in the winter months. I think a way forward for studying the algae and the fungal symbionts is to look at the genome of the fungi to see if there is any reduction, indicating any enslavement of the fungi by the algae, like other fungi species and bacteria. Although i understand that sampling the fungi genome is very difficult, as i mentioned in my blog post 'Marine coastal environments unveil a new world of marine fungi'.
Thanks
Natasha
Hi Natasha,
DeleteInteresting question, the paper says fungi are often found in parasitic partnership with photosynthetic organisms however I do not think this is necessarily the case with this particular example. It has been shown in previous literature that photosynthates and inorganic nutrients are transferred, in both directions, between V. lanosa and A. nodosum, this combinded with the results that A. nodosum can do well, although not as well, when separate from V. lanosa and the higher photosynthetic rates from V. lanosa when attached to A. nodosum suggests to me that the relationship is mutualistic. Another interesting result showed that A. nodosum was not negatively affected by the addition of V. lanosa which suggests the relationship is not parasitic.
The paper describes the relationship as ‘virtually obligate association’ which I would agree with based on their findings and previous literature.
I haven’t seen anything to suggest that photosynthetic rates are induced so that these nutrients can be transferred to the host, however I do not personally think this relationship has been as well studied as Corals and zooxanthellae. I would say that it is definitely a possibility to the relationship and could be a potential for future research to look at. I would also agree that if it is possible to isolate the genomes of fungi to study that way that would be an efficient way of studying it.
I hope I’ve answered your questions!
Many thanks,
Ellie