Microalgae as a Source of Mycosporine-like Amino Acids (MAAs); Advances and Future Prospects

Mycosporine-like amino acids (MAAs), are secondary metabolites, first reported in 1960 and found to be associated with the light-stimulated sporulation in terrestrial fungi. MAAs are nitrogenous, low molecular weight, water soluble compounds, which are highly stable with cyclohexenone or cycloheximine rings to store the free radicals. Microalgae are considered as a good source of different kinds of MAAs, which, in turn, has its own application in various industries due to its UV absorbing, anti-oxidant and therapeutic properties. Microalgae can be easily cultivated and requires a very short generation time, which makes them environment friendly source of biomolecules such as mycosporine-like amino acids. Modifying the cultural conditions along withmanipulation of genes associated with mycosporine-like amino acids biosynthesis can help to enhance MAAs synthesis and, in turn, can make microalgae suitable bio-refinery for large scale MAAs production. This review focuses on properties and therapeutic applications of mycosporine like amino acids derived from microalgae. Further attention is drawn on various culture and genetic engineering approaches to enhance the MAAs production in microalgae.

Methods in Microbial Biodiscovery

This review presents an account of the microbial biodiscovery methodology developed and applied in our laboratory at The University of Queensland, Institute for Molecular Bioscience, with examples drawn from our experiences studying natural products produced by Australian marine-derived (and terrestrial) fungi and bacteria.

Genome-scale phylogenetic analyses confirm Olpidium as the closest living zoosporic fungus to the non-flagellated, terrestrial fungi

The zoosporic obligate endoparasites, Olpidium, hold a pivotal position to the reconstruction of the flagellum loss in fungi, one of the key morphological transitions associated with the colonization of land by the early fungi. We generated genome and transcriptome data from non-axenic zoospores of Olpidium bornovanus and used a metagenome approach to extract phylogenetically informative fungal markers. Our phylogenetic reconstruction strongly supported Olpidium as the closest zoosporic relative of the non-flagellated terrestrial fungi. Super-alignment analyses resolved Olpidium as sister to the non-flagellated terrestrial fungi, whereas a super-tree approach recovered different placements of Olpidium, but without strong support. Further investigations detected little conflicting signal among the sampled markers but revealed a potential polytomy in early fungal evolution associated with the branching order among Olpidium, Zoopagomycota and Mucoromycota. The branches defining the evolutionary relationships of these lineages were characterized by short branch lengths and low phylogenetic content and received equivocal support for alternative phylogenetic hypotheses from individual markers. These nodes were marked by important morphological innovations, including the transition to hyphal growth and the loss of flagellum, which enabled early fungi to explore new niches and resulted in rapid and temporally concurrent Precambrian diversifications of the ancestors of several phyla of fungi.

New endosymbiotic relationships between Mucoromycota and Burkholderiaceae representatives

Mucoromycota representatives are known to harbour two types of endohyphal bacteria (EHB) – Burkholderia related endobacteria (BRE) and Mycoplasma related endobacteria (MRE). While both BRE and MRE occur in fungi representing all subphyla of Mucoromycota, their distribution is not well studied. Therefore, it is difficult to resolve the evolutionary history of these associations in favour of one of the two alternative hypotheses explaining their origin: “early invasion” and “late invasion”. Our main goal was to fill this knowledge gap by surveying Mucoromycota fungi for presence of EHB. We screened 196 fungal strains from 16 genera using PCR-based approach to detect bacterial 16S rDNA gene, complemented with FISH imaging to confirm presence of bacteria within the hyphae. We detected Burkholderiaceae in ca. 20% of fungal strains. Some of these bacteria clustered phylogenetically with previously described BRE clades whereas others grouped with free-living Paraburkholderia. Importantly, the latter were detected in Umbelopsidales, which previously were not known to harbour endobacteria. Our results suggest that this group of EHB is recruited from the environment, supporting the late invasion scenario. This pattern complements the early invasion scenario apparent in the BRE clade of EHB. IMPORTANCE Bacteria living within fungal hyphae present an example of one of the most intimate relationships between fungi and bacteria. Even though there are several well-described examples of such partnerships, their prevalence within fungal kingdom remains unknown. Our study focused on early divergent terrestrial fungi in the phylum Mucoromycota. We found that ca. 20% of the strains tested, harboured bacteria from the family Burkholderiaceae. Not only did we confirm the presence of bacteria from previously described endosymbiont clades, we also identified new group of endohyphal Burkholderiaceae representing the genus Paraburkholderia. We established that more than half of the screened Umbelopsis strains were positive for bacteria from this new group. We also determined that, while previously described BRE codiverged with their fungal hosts, Paraburkholderia symbionts did not.

Evaluation of seasonal dynamics of fungal DNA assemblages in a flow-regulated stream in a restored forest using eDNA metabarcoding

Investigation of the seasonal variation in the fungal community is essential for understanding biodiversity and its ecosystem functions. However, the conventional sampling method, with substrate removal and high spatial heterogeneity of community compositions, makes surveying the seasonality of fungal communities challenging. Recently, water environmental DNA (eDNA) analysis, including both aquatic and terrestrial species, has been explored for its usefulness in biodiversity surveys. Examining eDNA may allow for the survey of the community over time with less disturbance to the ecosystem. In this study, we assessed whether seasonality of fungal communities can be detected with monitoring of eDNA in a flow-regulated stream in a restored forest. We conducted monthly water sampling in the stream over two years, and used DNA metabarcoding to estimate the taxonomic and functional groups of fungal eDNA in the water. The river water contained taxonomically and functionally diverse DNA from both aquatic and terrestrial fungi, such as plant decomposers, parasites, and mutualists. The DNA assemblages showed a distinct annual periodicity, meaning that the assemblages were similar to each other regardless of the year, in the same sampling season. These seasonal changes were partially explained by temperature alterations. Furthermore, the strength of the one-year periodicity may vary across functional groups. Our results suggest that forest streams act as a “natural trap” for fungal DNA and that studies of fungal DNA in stream water may provide information on the temporal variation of fungal communities inhabiting not only water but also the surrounding ecosystem.

An comparative analysis of airborne and terrestrial fungi in show caves Novoafonskaya (Caucasus) and Ali-Sadr (Iran)

Caves are considered as ecosystems isolated from the surface in varying degrees. Hypogean habitats are mostly A study of cultivated species of microfungi in two show caves Novoafonskaya (Caucasus) and Ali-Sadr (Iran) was carried out. The species composition of fungi has been analyzed in the air and cave sediments along the excursion route. Species identification was performed using standard approaches and cultivation methods. Jaccard index was applied to estimate similarity of communities of different biotopes. The species diversity of microfungi was higher in the Novoafonskaya cave where 50 species of microfungi were identified. Only 38 species were isolated from the Ali-Sadr cave. Representatives of Ascomycota predominated in fungal communities. The greatest species diversity was noted in the genera Alternaria, Aspergillus, Fusarium, Penicillium, and Trichoderma. Species Alternaria alternata, Cladosporium cladosporioides, Cladosporium herbarum, Pseudogymnoascus pannorum, Oidiodendron tenuissimum and Penicillium chrysogenum were identified in all biotopes of both caves. Comparison of two biotopes of the caves using the Jaccard index revealed a high similarity in the species composition in the soil and air of the Novoafonskaya cave (KJ = 0.64). On the contrary, the species composition of fungi was different in Ali-Sadr cave (KJ = 0.22), which may be explained by intensive propagules input from the surface due to the cave morphology features and the arrangement of excursion route.

Genome-scale phylogenetic analyses confirm Olpidium as the closest living zoosporic fungus to the non-flagellated, terrestrial fungi

The zoosporic obligate endoparasites, Olpidium, hold a pivotal position to the reconstruction of the flagellum loss in fungi, one of the key morphological transitions associated with the colonization of land by the early fungi. We generated genome and transcriptome data from non-axenic zoospores of Olpidium bornovanus and used a metagenome approach to extract phylogenetically informative fungal markers. Our phylogenetic reconstruction strongly supported Olpidium as the closest zoosporic relative of the non-flagellated terrestrial fungi. Super-alignment analyses resolved Olpidium as sister to the non-flagellated terrestrial fungi, whereas a super-tree approach recovered different placements of Olpidium, but without strong support. Further investigations detected little conflicting signal among the sampled markers but revealed a potential polytomy in early fungal evolution associated with the branching order among Olpidium, Zoopagomycota and Mucoromycota. The branches defining the evolutionary relationships of these lineages were characterized by short branch lengths and low phylogenetic content and received equivocal support for alternative phylogenetic hypotheses from individual markers. These nodes were marked by important morphological innovations, including the transition to hyphal growth and the loss of flagellum, which enabled early fungi to explore new niches and resulted in rapid and temporally concurrent Precambrian diversifications of the ancestors of several phyla of fungi.

Extracellular Enzymes and Bioactive Compounds from Antarctic Terrestrial Fungi for Bioprospecting

Antarctica, one of the harshest environments in the world, has been successfully colonized by extremophilic, psychrophilic, and psychrotolerant microorganisms, facing a range of extreme conditions. Fungi are the most diverse taxon in the Antarctic ecosystems, including soils. Genetic adaptation to this environment results in the synthesis of a range of metabolites, with different functional roles in relation to the biotic and abiotic environmental factors, some of which with new biological properties of potential biotechnological interest. An overview on the production of cold-adapted enzymes and other bioactive secondary metabolites from filamentous fungi and yeasts isolated from Antarctic soils is here provided and considerations on their ecological significance are reported. A great number of researches have been carried out to date, based on cultural approaches. More recently, metagenomics approaches are expected to increase our knowledge on metabolic potential of these organisms, leading to the characterization of unculturable taxa. The search on fungi in Antarctica deserves to be improved, since it may represent a useful strategy for finding new metabolic pathways and, consequently, new bioactive compounds.

Further evidence for fungivory in the Lower Devonian (Lochkovian) of the Welsh Borderland, UK

The recent demonstrations that widespread mid-Palaeozoic Prototaxites and other nematophytes had fungal affinities indicate that terrestrial fungi were important elements in carbon cycling in the Early Devonian. Here, we provide evidence for their participation in the recycling of nutrients by early terrestrial invertebrates. Evidence is in the form of coprolites, both those associated with nematophytes or containing their fragmentary remains. Cylindrical coprolites consistently associated with fungal mats are placed in a new ichnospecies, Bacillafaex myceliorum. Their contents are granular to amorphous, suggestive of complete digestion of the ingested hyphae, with the inference of possession of chitinases in the digestive tracts of the consumers. A further single example comprises a cluster of cylindrical bodies attached to the lower surface of a Nematothallus fragment. Here, homogenisation was less complete, with traces of hyphae remaining. Terrestrial animal fossils have not been found at the locality, but scorpions, pseudoscorpions, Opiliones, mites, centipedes (carnivores) and millipedes, and Collembola (detritivores) have been recorded from the slightly younger Rhynie cherts. Studies of fungivory in extant arthropods have concentrated on Collembola and, to a lesser extent, mites, but their faecal pellets are much smaller than the fossil examples. Millipedes, based on body size and faeces of extant forms, are considered more realistic producers, but little is known about fungal feeding in these animals. Regardless of the affinities of the producers, the diversity in morphology, sizes, aggregations, and composition of nematophyte-containing examples suggests that fungivory was an important component of carbon cycling in early terrestrial ecosystems.