Smoking Hot Marine Fungi: Deep sea vent marine fungi culturing and study

 Marine fungi are known to be well studied in accessible habitats such as tropical mangrove forest, estuarine or open ocean. Deep sea marine fungi on the other hand are not widely studied as they are challenging to sample from the deep sea due to cost and a lack of expedition expertise.

In previous years, scientists have assembled evidence of deep sea fungi communities and diversity and are also studying their ecological role in the environment. The role of marine fungi in brackish water, tidal zones and estuarine habitats is an agent of degrading organic matter such as micro and macro algae. The paper mentions that the role of marine algae seems to have been underestimated, perhaps overshadowed by other major degrading agents such as bacteria, E.huxleyi virus, etc.

There are several factors that makes deep-sea sampling challenging. As we know that the majority of organic matter from planktonic to hard multicellular living organisms sink to the bottom floor, finding its way to the deep sea.  It makes up the sample in the deep-sea ecosystem, so the deep sea habitat doesn’t necessarily consist its original sample. Many organic samples might come from a variety of different origin. As the result of this, deep sea fungi sample may contain sample the from upper layer. The paper mentions that decaying algae, higher plants and wood found in the deep sea may contain fungi from the previous habitats carried by attaching to the matter, in which case samples might not be endemic to the system. But so far Burgaud et.al (2009) mention that there are a scarce number of deep sea samples of marine Fungi and the sea Vent fungi sample is a novel sample.

Studies employed culture-independent methods combined with SSU rRNA to survey microeukaryotes diversity in extreme environments such as samples in acidic and iron river. This method reveals new fungal phylotypes with a fungal specific primer and reveals diversity of fungi in extreme environments, which can be applied to sample deep sea vent fungal diversity. Burgaud et.al (2009) collected samples of 210 fungal growth of which 42 samples yield to isolation of fungi. The hydrothermal samples gathered were mostly from shrimp and mussels with some from tubeworms, other animals and abiotic surfaces, for which 33% of the isolated strains belonged to new phylotypes. Burgaud et.al (2009) also mentions that there is no previous report of culturing filamentous fungi from deep-sea vent ecosystem.

Samples of filamentous fungi from the deep sea vent were cultured and observed to discriminate individuals of filamentous fungi for their ability to live in deep-sea hydrothermal ecosystems. The 18s rRNA sequence indicate the presence of Ascomycota and Basidiomycota in the culture collection which were represented by Pezyzomycotina subphylum (of Ascomycota) and Tilletiopsis pallescens (close to Basidomycota).

Little is known about deep sea marine fungi’s role in the ecosystem – there is one case of Carponia-like parasitic fungi in a mussel hill of Fiji basin reported, causing tissue deterioration on deep sea mussel (but this is a rare case). Mussel samples were relatively healthy despite the presence of fungi, which proves that they were not a strict saprophyte and that fungi may be a parasite or opportunistic pathogen.

This paper has an interesting and novel experiment (and observations) which could be considered a breakthrough when looking at deep sea fungal samples and culturing methods. Even though there is no independent method section, it seems that the method is merged with results and introduction, which gives a unique guideline while adding brief method in the result section. Though not all readers may enjoy this style I personally do and, overall, I feel it is a very interesting paper and an important read for marine fungi enthusiasts.

Reviewed paper:

Burgaud G et al.,(2009) “Diversity of culturable marine filamentous fungi from deep-sea hydrothermal vents”. Environ Microbiol. 2009 Jun;11(6):1588-600., Link https://www.ncbi.nlm.nih.gov/pubmed/19239486