Marine fungi are one of the most understudied an poorly understood marine microbe, this can be partially blamed on the poor sampling method previously used to identify marine fungi. Many early marine fungi studied used cultured based methods, but many species have specific nutrient requirements making them uncultureable in the lab, and therefore many studies may have massively underestimated the amount of marine fungi present. Culture-independent studies need to be more widely used to be able to sample marine fungi comprehensively.
Picard 2017 produced one of the comprehensive marine fungi studies to date sampling year round at 4 sites (in North Carolina), consisting of sediment samples and samples from the plankton zone.
Ion torrent sequencing was conducted on samples from all 4 sites. The sequences were then taxanomically assigned using 2 methods 1) BLAST+MEGAN and 2) the ribosomal database project. Followed by phylogentic placement.
Over the 4 sample sites; Priver's Island (plankton), Town marsh (wetland sediments), Bird shoal (intertidal sediments) and Cape lookout bight (sediment core), some interesting fungal diversity patterns emerged.
For all sites Ascomycota was the most speciose phylum, however most recovered taxa was found in relativly low abundances. It was observed that over the seasons the relative abundances of the most dominant phyla was altered, this was especially evident in the plankton sample and the intertidal sediments with a clear domination of the Ascomycota in winter and fall but in spring there is a relatively equal abundance of the 7 major groups identified in this study (Ascomycota, Basidiomycota, Blastocladiomycota, Chytridiomycota, Entromophthoromycota, Neocallimastigomycorta and Zygomycota), this even abundance seen in spring may be related to the spring diatom blooms, as we know that many marine fungi species are parasites to planktonic species, with the relatively stable populations seen in the sediment samples it added further evidence that fungal groups in the plankton can only thrive in the presence of blooming plankton.
The last major findings were that oxygen deficient marine sediments had the fewest number of OTU's, and had an especially high number of species belonging to zoosporic linages.
This paper offers a great insight in the distribution of marine fungi and there year long distribution changes within the marine fungi. The authors fully acknowledge some of the limitations in this study mainly the selection of an appropriate DNA marker and the corresponding primer pair, as well as this this study although one of the most comprehensive study on marine fungi, it still do not an exhaustive catalogue of the marine fungi from these sites. With many novel fungal groups being found it shows the amount of work still needed in marine fungi, and our current techniques still may not be sufficient for sampling marine fungi, but this paper offers a unique look into sampling marine fungi.
This study is very recent and actually dated 2017, so it has no citing as yet, but it does provide a milestone in the understanding of marine fungi, and will hopefully be used in the future to further sample marine fungi and start to understand their functional role in these systems.
reviewed paper: Picard, K. T. (2017). Coastal marine habitats harbor novel early-diverging fungal diversity. Fungal Ecology, 25, 1–13. doi:10.1016/j.funeco.2016.10.006 http://www.sciencedirect.com/science/article/pii/S1754504816301180
Hi Natasha, Thanks for your review I think it’s really interesting how due to the difficulty in culturing fungi it lead to the misunderstanding that there were not playing important roles in the marine environment.
ReplyDeleteIn light of today’s lecture with Michael he mentioned how studying the same area continually for a number of years can allow the authors to provide a more definite statements about communities and trends in abundance of organisms, because this may vary between years and seasons. This change in abundance was highlighted in the paper due to the fungi abundance changing in response to phytoplankton blooms which occur in spring due to their parasitic lifestyle. However the sample sites were only sampled in a single year, do you think the finding of the study may be strengthen by looking at potential changes annually or do you think this is not needed?
Also I was wondering if you would be able to describe the method of BLAST+MEGAN in a bit more detail as I have not come across this before,
Thanks
Alisha
Hi Alisha,
ReplyDeleteI think that a time series study looking at marine fungi would definitely strengthen out understanding of these communities. This study has strength in the fact that is explored marine fungal communities over a range of environments, but i agree with you adding a time series element to these studies would be great for our understanding of marine fungi communities. Although it does appear to that there still need some refinements to the sampling of marine fungi to ensure we are fully encapsulating marine fungi.
BLAST and MEGAN are databases that give statistical comparisons between and 'unknown' sequence to known/ published ones. BLAST is used for nucleotide and protein analysis to find out what organism a genome or gene sequence belongs to or the function of a protein. Where as MEGAN compared metagenomic sequences to a database to determine a communities functional capabilities. I hope this answers your questions.
Thanks
Nnatasha-lea