Recent publications

Bioinformatic, phylogenetic and chemical analysis of the UV-absorbing compounds scytonemin and mycosporine-like amino acids from the microbial mat communities of Shark Bay, Australia

D’Agostino, P.M.a,bWoodhouse, J.N.a,cLiew, H.T.a,dSehnal, L.ePickford, R.fWong, H.L.aBurns, B.P.aNeilan, B.A.a,g

aSchool of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
bBiosystems Chemistry, Department of Chemistry and Center for Integrated Protein Science Munich (CIPSM), Technische Universität München, Garching, Germany
cDepartment of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Stechlin, Germany
dSchool of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore
eResearch Centre for Toxic Compounds in the Environment, Faculty of Science, Masaryk University, Kamenice 5, Brno, 625 00, Czech Republic
fBioanalytical Mass Spectrometry Facility, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW, Australia
gSchool of Environmental and Life Sciences, University of Newcastle, Newcastle, NSW, Australia

Shark Bay, Western Australia is a World Heritage area with extensive microbial mats and stromatolites. Microbial communities that comprise these mats have developed a range of mitigation strategies against changing levels of photosynthetically active and ultraviolet radiation, including the ability to biosynthesise the UV-absorbing natural products scytonemin and mycosporine-like amino acids (MAAs). To this end, the distribution of photoprotective pigments within Shark Bay microbial mats was delineated in the present study. This involved amplicon sequencing of bacterial 16S rDNA from communities at the surface and subsurface in three distinct mat types (smooth, pustular and tufted), and correlating this data with the chemical and molecular distribution of scytonemin and MAAs. Employing UV spectroscopy and MS/MS fragmentation, mycosporine-glycine, asterina and an unknown MAA were identified based on typical fragmentation patterns. Marker genes for scytonemin and MAA production (scyC and mysC) were amplified from microbial mat DNA and placed into phylogenetic context against a broad screen throughout 363 cyanobacterial genomes. Results indicate that occurrence of UV screening compounds is associated with the upper layer of Shark Bay microbial mats, and the occurrence of scytonemin is closely dependent on the abundance of cyanobacteria.

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Harnessing long-read amplicon sequencing to uncover NRPS and Type I PKS gene sequence diversity in polar desert soils

Benaud, N.aZhang, E.aVan Dorst, J.aBrown, M.V.bKalaitzis, J.A.aNeilan, B.A.bFerrari, B.C.a

aSchool of Biotechnology and Biomolecular Sciences, UNSW, Sydney, NSW 2052, Australia
bSchool of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia

The severity of environmental conditions at Earth’s frigid zones present attractive opportunities for microbial biomining due to their heightened potential as reservoirs for novel secondary metabolites. Arid soil microbiomes within the Antarctic and Arctic circles are remarkably rich in Actinobacteria and Proteobacteria, bacterial phyla known to be prolific producers of natural products. Yet the diversity of secondary metabolite genes within these cold, extreme environments remain largely unknown. Here, we employed amplicon sequencing using PacBio RS II, a third generation long-read platform, to survey over 200 soils spanning twelve east Antarctic and high Arctic sites for natural product-encoding genes, specifically targeting non-ribosomal peptides (NRPS) and Type I polyketides (PKS). NRPS-encoding genes were more widespread across the Antarctic, whereas PKS genes were only recoverable from a handful of sites. Many recovered sequences were deemed novel due to their low amino acid sequence similarity to known protein sequences, particularly throughout the east Antarctic sites. Phylogenetic analysis revealed that a high proportion were most similar to antifungal and biosurfactant-type clusters. Multivariate analysis showed that soil fertility factors of carbon, nitrogen and moisture displayed significant negative relationships with natural product gene richness. Our combined results suggest that secondary metabolite production is likely to play an important physiological component of survival for microorganisms inhabiting arid, nutrient-starved soils.

 

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Physiological responses of the freshwater N 2 -fixing cyanobacterium Raphidiopsis raciborskii to Fe and N availabilities

Fu, Q.-L.aYeung, A.C.Y.bFujii, M.aNeilan, B.A.cWaite, T.D.b

aDepartment of Civil and Environmental Engineering, Tokyo Institute of Technology, Ookayama, Tokyo, Japan
bSchool of Civil and Environmental Engineering, The University of New South Wales, Sydney, Australia
cSchool of Environmental and Life Sciences, The University of Newcastle, Newcastle, Australia

The cyanobacterium Raphidiopsis raciborskii is of environmental and social concern in view of its toxicity, bloom-forming characteristics and increasingly widespread occurrence. However, while availability of macronutrients and micronutrients such as N and Fe are critically important for the growth and metabolism of this organism, the physiological response of toxic and non-toxic strains of R. raciborskii to varying Fe and N availabilities remains unclear. By determining physiological parameters as a function of Fe and N availability, we demonstrate that R. raciborskii growth and N 2 -fixing activity are facilitated at higher Fe availability under N 2 -limited conditions with faster growth of the CS-506 (cylindrospermopsin-producing) strain compared with that of CS-509 (the non-toxic) strain. Radiolabelled Fe uptake assays indicated that R. raciborskii acclimated under Fe-limited conditions acquires Fe at significantly higher rates than under Fe replete conditions, principally via unchelated Fe(II) generated as a result of photoreduction of complexed Fe(III). While N 2 -fixation of both strains occurred during both day and night, the CS-506 strain overall exhibited higher N 2 -fixing and Fe uptake rates than the CS-509 strain under N-deficient and Fe-limited conditions. The findings of this study highlight that Fe availability is of significance for the ecological advantage of CS-506 over CS-509 in N-deficient freshwaters.

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Diagnosing water treatment critical control points for cyanobacterial removal: Exploring benefits of combined microscopy, next-generation sequencing, and cell integrity methods

Arash ZamyadiabCaitlin RomanisToby MillsBrett Neilan dFlorence Choo bLucila A. Coral beDeb Gale fGayle Newcombe gNick Crosbie hRichard Stuetz aRita K. Hendersonb

aWater Research Centre, School of Civil and Environmental Engineering, University of New South Wales (UNSW), Sydney, Australia
bBioMASS Lab, School of Chemical Engineering, UNSW, Sydney, Australia
cBGA Innovation Hub, and Civil, Mineral and Mining Engineering Department, Polytechnique Montréal, Montreal, Canada
dSchool of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
eChemistry and Biology Department, Universidade Tecnológica Federal do Paraná, Curitiba, Brazil
fSeqwater, Ipswich, Australia
gSouth Australian Water Corporation (SA Water), Adelaide, Australia
hMelbourne Water, Melbourne, Australia

A wide range of cyanobacterial species and their harmful metabolites are increasingly detected in water bodies worldwide, exacerbated by climate change and human activities. The resulting bloom conditions represent significant challenges to production of safe drinking water and cost effective water reuse, therefore their removal is a priority to ensure public safety. While current microscopic taxonomy identification methods provide valuable information about cell numbers during treatment, these methods are incapable of providing information about the fate of cells during treatment. The objectives of this study were to (1) identify the critical control points for breakthrough and accumulation of cells by investigating the fate of cells during treatment processes using a combination of taxonomy, cell integrity and next-generation sequencing (NGS), and (2) assess the impact of pre-treatment processes on breakthrough prevention at critical control points, and the benefits of cell integrity and NGS analysis for improved management purposes. This paper presents the results of an unprecedented cyanobacterial monitoring program conducted in four full scale water treatment plants located in three different climate zones. Cyanobacterial cell integrity and accumulation during operation process were assessed for the first time using next generation of gene sequencing methods. NGS analysis led to detection of cyanobacterial and melainabacteria orders in water samples that were not identified by microscopy. 80 ± 5% of cells were completely lysed post pre-oxidation (for both ozone and potassiumpermanganate). However unlike pre-ozonation, the remaining cells were undamaged cells with the potential to accumulate and grow within the plants post-KMnO4 treatment, particularly in clarifier sludge. To effectively monitor water quality, this study presents a synergistic approach coupling new and traditional analytical methods and demonstrates the importance of identifying critical points for managing accumulation of cyanobacteria within plants.

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Re-evaluation of paralytic shellfish toxin profiles in cyanobacteria using hydrophilic interaction liquid chromatography-tandem mass spectrometry

D’Agostino, P.M.a,b Boundy, M.J.cHarwood, T.D.cCarmichael, W.W.dNeilan, B.A.a,e,Wood, S.A.c

aSchool of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, 2052, Australia
bBiosystems Chemistry, Department of Chemistry and Center for Integrated Protein Science Munich (CIPSM), Technische Universität München, Garching, Germany
cCawthron Institute, 98 Halifax Street East, Private Bag 2, Nelson, 7010, New Zealand
dDepartment of Biological Sciences, Wright State University, Dayton, OH 45435, United States
eSchool of Environmental and Life Sciences, University of Newcastle, Newcastle, NSW, Australia

To date Paralytic shellfish toxin (PST) variants in cyanobacteria have primarily been characterized using high performance liquid chromatography coupled with fluorescence detection. In this study we re-evaluated the PST profiles of five cyanobacterial cultures (Dolichospermum circinale AWQC131C, Aphanizomenon sp. NH-5, Raphidiopsis raciborskii T3, Scytonema cf. crispum CAWBG524 and CAWBG72) and one environmental sample (Microseria wollei) using hydrophilic interaction liquid chromatography coupled with electrospray ionization tandem mass spectrometry. A total of 35 different PST variants were detected. D. circinale contained the highest number of variants (23), followed by S. cf. crispum CAWBG72 (21). Many of the variants detected in the cultures/environmental sample had not been reported from these strains previously: D. circinale (14 variants), S. cf. crispum CAWBG72 (16), S. cf. crispum CAWBG524 (9), Aphanizomenon sp. (9), R. raciborskii (7), and M. wollei (7). Of particular interest was the detection of M-toxins (Aphanizomenon sp., R. raciborskii, D. circinale). These have previously only been identified from shellfish where they were thought to be metabolites. Well-characterized PST variant profiles are essential for research investigating the genetic basis of PST production, and given that the toxicity of each variants differs, it will assist in refining risk assessments.

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Cyanobacterial Community Composition and Bacteria–Bacteria Interactions Promote the Stable Occurrence of Particle-Associated Bacteria

Jason N. Woodhouse1,2, Jennifer Ziegler2Hans-Peter Grossart2 and Brett A. Neilan3*
1Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
2School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
3School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW, Australia

Within meso/eutrophic freshwater ecosystems the dominance of cyanobacterial blooms during summer months has substantial impacts on ecosystem function with the production of toxins and subsequent induction of hypoxia altering food web structures and biogeochemical cycles. Cyanobacterial aggregates are extensively colonized by heterotrophic bacteria that provide the cyanobacteria with key nutrients and contribute towards remineralisation of organic matter. Here we sampled from five sites within a shallow eutrophic pond over a 6 months period, relating changes in the abundance of particle-associated heterotrophic taxa to phytoplankton abundance, toxin gene copies and physiochemical properties. The abundance of a majority of particle-associated bacteria were stable, in that they persisted despite perturbation. Cyanobacterial species abundance more likely correlated with stable rather than unstable bacteria and unstable bacteria were associated with allochthonous (terrestrial) organic matter. The occurrence of the most stable bacteria was correlated with large numbers of other bacteria suggesting bacteria-bacteria interactions have implications for the stable occurrence of microorganisms on particles. Freshwater ecosystems are frequently inundated with fresh nutrients in the form of surface runoff and experience an increasing number of high temperature days. In addition to increasing the severity and longevity of cyanobacterial blooms, run-off changes the nature of the particle-associated community compromising stability. This disruption has the potential to drive changes in the carbon and nitrogen cycles and requires further attention.

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Synthetic microbe communities provide internal reference standards for metagenome sequencing and analysis

Hardwick, S.A.a,b, Chen, W.Y.a,b, Wong, T.a, Kanakamedala, B.S.a, Deveson, I.W.a,b, Ongley, S.E.c,d, Santini, N.S.e,f, Marcellin, E.g, Smith, M.A.a,b, Nielsen, L.K.g, Lovelock, C.E.h, Neilan, B.A.c,d, Mercer, T.R.a,b,i

 

aGarvan Institute of Medical Research, Sydney, NSW 2010, Australia
bSt. Vincent’s Clinical School, Faculty of Medicine, UNSW Sydney, Sydney, NSW 2052, Australia
cSchool of Biotechnology and Biomolecular Sciences, UNSW Sydney, Sydney, NSW 2052, Australia
dSchool of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
eCentre for Marine Bioinnovation UNSW Sydney, Sydney, NSW 2052, Australia
fInstituto de Ecologia, Universidad Nacional Autonoma de Mexico, Mexico City, 04500, Mexico
gAustralian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia
hSchool of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia
iAltius Institute for Biomedical Sciences, Seattle, WA 98121, United States

 

The complexity of microbial communities, combined with technical biases in next-generation sequencing, pose a challenge to metagenomic analysis. Here, we develop a set of internal DNA standards, termed “sequins” (sequencing spike-ins), that together constitute a synthetic community of artificial microbial genomes. Sequins are added to environmental DNA samples prior to library preparation, and undergo concurrent sequencing with the accompanying sample. We validate the performance of sequins by comparison to mock microbial communities, and demonstrate their use in the analysis of real metagenome samples. We show how sequins can be used to measure fold change differences in the size and structure of accompanying microbial communities, and perform quantitative normalization between samples. We further illustrate how sequins can be used to benchmark and optimize new methods, including nanopore long-read sequencing technology. We provide metagenome sequins, along with associated data sets, protocols, and an accompanying software toolkit, as reference standards to aid in metagenomic studies.

 

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Insertions within the Saxitoxin Biosynthetic Gene Cluster Result in Differential Toxin Profiles

 School of Environmental and Life SciencesUniversity of Newcastle, Newcastle, NSW 2308, Australia
 School of Biotechnology and Biomolecular SciencesUniversity of New South Wales, Sydney, NSW 2052, Australia
§ Biosystems Chemistry, Department of Chemistry and Center for Integrated Protein Science Munich (CIPSM)Technische Universität München, Garching 85747, Germany
|| Bioanalytical Mass Spectrometry Facility, Mark Wainwright Analytical CentreUniversity of New South Wales, Sydney, NSW 2052, Australia
 Coastal and Freshwater GroupCawthron Institute, Nelson 7001, New Zealand

The neurotoxin saxitoxin and related paralytic shellfish toxins are produced by multiple species of cyanobacteria and dinoflagellates. This study investigates the two saxitoxin-producing strains of Scytonema crispum, CAWBG524 and CAWBG72, isolated in New Zealand. Each strain was previously reported to have a distinct paralytic shellfish toxin profile, a rare observation between strains within the same species. Sequencing of the saxitoxin biosynthetic clusters (sxt) from S. crispum CAWBG524 and S. crispum CAWBG72 revealed the largest sxt gene clusters described to date. The distinct toxin profiles of each strain were correlated to genetic differences in sxttailoring enzymes, specifically the open-reading frame disruption of the N-21 sulfotransferase sxtN, adenylylsulfate kinase sxtO, and the C-11 dioxygenase sxtDIOX within S. crispumCAWBG524 via genetic insertions. Heterologous overexpression of SxtN allowed for the proposal of saxitoxin and 3′-phosphoadenosine 5′-phosphosulfate as substrate and cofactor, respectively, using florescence binding assays. Further, catalytic activity of SxtN was confirmed by the in vitroconversion of saxitoxin to the N-21 sulfonated analog gonyautoxin 5, making this the first known report to biochemically confirm the function of a sxt tailoring enzyme. Further, SxtN could not convert neosaxitoxin to its N-21 sulfonated analog gonyautoxin 6, indicating paralytic shellfish toxin biosynthesis most likely occurs along a predefined route. In this study, we identified key steps toward the biosynthetic conversation of saxitoxin to other paralytic shellfish toxins.

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Understanding differential paralytic shellfish toxin profiles between two Scytonema crispum strains

 

Author: Alescia Cullen

A major reason cyanobacterial blooms are of nuisance is due to their ability to produce toxic compounds. One class of these compounds are the Paralytic Shellfish Toxins (PSTs), which encompass saxitoxin and its related analogues. Despite the identification of the putative genetics underlying biosynthesis of saxitoxin in 2008, biochemical confirmation of its products and analogues remains mostly uncharacterized. This study investigated two PST-producing strains of Scytonema crispum, CAWBG524 and CAWBG72, isolated in New Zealand. Genome sequencing of both strains revealed the largest sxt clusters described, with the highest abundance in transposases. While these two strains show high genetic similarity, their toxin profiles vastly vary. S. cripsum CAWBG524 only produces saxitoxin while S. crispum CAWBG72 produces a range of saxitoxin analogues that are sulphated at numerous positions. Further genome analysis correlated these variations to inactivating transposase insertions into genes encoding tailoring enzymes sxtN, sxtO and sxtDIOX, in S. crispum CAWBG524. These enzymes were predicted to be responsible for the production of sulphated analogues. To validate this hypothesis, we investigated the function of putative sulphotransferase SxtN via binding to proposed substrates and in vitro biochemical assays. Our results confirmed that SxtN acts as a N-sulfotransferase on the N21 position of saxitoxin yielding the monosulphated analogue gonyautoxin-5, thus explaining the lack of analogues in S. crispum CAWBG524. This is the first biochemical characterization of the biosynthesis of saxitoxin analogues using a putative sxt cluster.


Effects of indigenous soil cyanobacteria on seed germination and seedling growth of arid species used in restoration

Muñoz-Rojas, M.a,b,cChilton, A.d, Liyanage, G.S.c, Erickson, T.E.a,b, Merritt, D.J.a,b, Neilan, B.A.d,e, Ooi, M.K.J.c

aSchool of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia
bKings Park Science, Department of Biodiversity, Conservation and Attractions, Kings Park, WA 6005, Australia
cCentre for Ecosystem Science, School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia
dAustralian Centre for Astrobiology and School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
eSchool of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia

 

Background and aims: Cyanobacteria from biocrusts can enhance soil function and structure, a critical objective when restoring degraded dryland ecosystems. Large-scale restoration of biodiversity requires direct seeding of native plant species, and bio-priming seeds with cyanobacteria is a potential method of initiating enhanced soil functioning. The utility of cyanobacteria for improving soil is therefore dependent on whether target plant species remain unaffected during its application. Methods: Cyanobacteria from the genera Microcoleus and Nostoc were isolated from locally-sourced biocrust samples, and cultured under controlled conditions. A two-factor laboratory experiment was conducted including cyanobacteria and the culture growth medium (BG11) as factors. We bio-primed seeds of five species native to Western Australia, commonly used in dryland restoration, by soaking them in the cultures developed, and assessed germination and growth. Results: We found significant positive effects of seeds bio-primed with cyanobacteria on germination and seedling growth of two species, Senna notabilis and Acacia hilliana, respectively. Importantly, no significant negative effects of cyanobacteria were found for any of the species studied. Conclusions: Few studies of cyanobacteria effects on regeneration of native species exist. We found that the potential benefits of applying indigenous bacteria via bio-priming seeds would not inhibit plant establishment, and indeed may be beneficial for some species used in dryland restoration.

 

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Biocrust morphology is linked to marked differences in microbial community composition

Chilton, A.M.a, Neilan, B.A.a,b, Eldridge, D.J.c

aAustralian Centre for Astrobiology and School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia
bSchool of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
cCentre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia

Background and aims: Biocrust morphology is often used to infer ecological function, but morphologies vary widely in pigmentation and thickness. Little is known about the links between biocrust morphology and the composition of constituent microbial community. This study aimed to examine these links using dryland crusts varying in stage and morphology. Methods: We compared the microbial composition of three biocrust developmental stages (Early, Mid, Late) with bare soil (Bare) using high Miseq Illumina sequencing. We used standard diversity measures and network analysis to explore how microbe-microbe associations changed with biocrust stage. Results: Biocrust richness and diversity increased with increasing stage, and there were marked differences in the microbial signatures among stages. Bare and Late stages were dominated by Alphaproteobacteria, but Cyanobacteria was the dominant phylum in Early and Mid stages. The greatest differences in microbial taxa were between Bare and Late stages. Network analysis indicated highly-connected hubs indicative of small networks. Conclusions: Our results indicate that readily discernible biocrust features may be good indicators of microbial composition and structure. These findings are important for land managers seeking to use biocrusts as indicators of ecosystem health and function. Treating biocrusts as a single unit without considering crust stage is likely to provide misleading information on their functional roles.

 

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Heterologous expression and biochemical characterisation of cyanotoxin biosynthesis pathways

Alescia Cullen aLeanne A. PearsonaRabia MazmouzaTianzhe LiubAngela H. SoeriyadibSarah E. Ongleya and Brett A. Neilan *a
aSchool of Environmental and Life Sciences, University of Newcastle, Callaghan 2308, Australia
bSchool of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney 2052, Australia

Marine and freshwater cyanobacteria produce a variety of toxic compounds that pose a threat to the health of humans, livestock and natural ecosystems world-wide. Significant research efforts have been directed towards understanding the biosynthesis of these cyanotoxins in an attempt to reduce their deleterious effects on water quality and, more recently, to harness their biotechnological potential. While a variety of complementary methods (such as bioinformatic analyses and isotope feeding studies) have been employed over the last three decades to address knowledge gaps in this field, this review focuses on the utility of heterologous expression and biochemical studies, including emerging technologies for engineering and expressing complete cyanotoxin gene clusters.

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An In Vitro and In Vivo Study of Broad-Range Phosphopantetheinyl Transferases for Heterologous Expression of Cyanobacterial Natural Products

Tianzhe LiuRabia Mazmouz , and Brett A. Neilan* 
 School of Biotechnology and Biomolecular SciencesThe University of New South Wales, Sydney, NSW 2052, Australia
 School of Environmental and Life SciencesThe University of Newcastle, Callaghan, NSW 2308, Australia

Phosphopantetheinyl transferases catalyze the post-translational modification of carrier proteins involved in both primary and secondary metabolism. The functional expression of polyketide synthases and nonribosomal peptide synthetases requires the activation of all carrier protein domains by phosphopantetheinyl transferases. Here we describe the characterization of five bacterial phosphopantetheinyl transferases by their substrate specificity and catalytic efficiency of four cyanobacterial carrier proteins. Comparative in vitro phosphopantetheinylation analysis showed Sfp possesses the highest catalytic efficiency over various carrier proteins. In vivo coexpression of phosphopantetheinyl transferases with carrier proteins revealed a broad range substrate specificity of phosphopantetheinyl transferases; all studied phosphopantetheinyl transferases were capable of converting apo– carrier proteins, sourced from diverse biosynthetic enzymes, to their active holo form. Phosphopantetheinyl transferase coexpression with the hybrid nonribosomal peptide synthetases/polyketide synthases responsible for microcystin biosynthesis confirmed that the higher in vitro activity of Sfp translated in vivo to a higher yield of production.

 

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Genome variation in nine co-occurring toxic Cylindrospermopsis raciborskii strains

Willis, A.aWoodhouse, J.N.b,f, Ongley, S.E.b,c, Jex, A.R.d,e, Burford, M.A.a, Neilan, B.A.b,c

aAustralian Rivers Institute, Griffith University, QLD, Australia
bSchool of Biotechnology and Biomolecular Sciences, University of New South Wales, NSW, Australia
cSchool of Environmental and Life Sciences, The University of Newcastle, NSW, Australia
dFaculty of Veterinary and Agricultural Sciences, University of Melbourne, VIC, Australia
ePopulation Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia
fLeibniz-Institute of Freshwater Ecology and Inland Fisheries, Alte Fischerhütte 2, OT Neuglobsow, Stechlin, 16775, Germany

 

Cyanobacteria form harmful algal blooms and are highly adapted to a range of habitats, in part due to their phenotype plasticity. This plasticity is partially the result of co-existence of multiple strains within a single population. The toxic cyanobacterium Cylindrospermopsis raciborskii has remarkable phenotypic plasticity, strain variation and environmental adaptation resulting in an expansion of its global range. To understand the genetic basis of the high level of plasticity within a C. raciborskii population, the genomes of nine co-occurring strains were compared. The strains differed in morphology, toxin cell quotas and physiology, despite being obtained from a single water sample. Comparative genomics showed that three coiled strains were 3.9 Mbp in size, with 3544 ± 11 genes, while straight strains were 3.8 Mbp in size, with 3485 ± 20 genes. The core proteome comprised 86% of the genome and consisted of 2891 orthologous groups (OGs), whereas the variable genome comprised ∼14% (847 OGs), and the strain specific genome only ∼1% (433 OGs).There was a high proportion of variable strain-specific genes for the very closely related strains, which may underpin strain differentiation. The variable genes were associated with environmental responses and adaptation, particularly phage defence, DNA repair, membrane transport, and stress, illustrative of the adaptability of the strains in response to environmental and biological stressors. This study shows that high genomic variability exists between co-occurring strains and may be the basis of strain phenotypic differences and plasticity of populations. Therefore management and prediction of blooms of this harmful species requires different approaches to capture this strain variability.

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Microbial diversity of speleothems in two southeast Australian limestone cave arches

Vardeh, D.P.a, Woodhouse, J.N.a,b, Neilan, B.A.a,c

aSchool of Biotechnology and Biomolecular Sciences, Australian Centre for Astrobiology, University of New South Wales (UNSW), Sydney, Australia
bLeibnitz-Institute of Freshwater Ecology and Inland Fisheries, Germany
cSchool of Environmental and Life Sciences, University of Newcastle, Australia

Peculiar cave structures, nicknamed lobsters, and shaped by drip water, wind, aeolian particles and microbial biofilms, are described from cave entrance arches at Jenolan and Wombeyan caves in southeast Australia. Subaerial biofilms on rock surfaces support complex microbial assemblages adapted to temperature, desiccation, and low irradiance stress. The community composition of active and inactive speleothems was elucidated by next generation sequencing. Active biofilms showed high abundances of cyanobacterial taxa, morphologically and phylogenetically belonging to the genera Chroococcidiopsis and Gloeocapsa, representing an endolithic lifestyle in desiccated and low light conditions. Significant differences were found between caves and between actively accreting and inactive and weathered structures. Functional taxa putatively occupying the same niches were found on active structures in both locations. A temporal succession is proposed, with dominance shifting from Chroococcales to Actinomycetales and highly desicca-tion-resistant and oligotrophic Rubrobacterales with decreasing water availability.

 

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Mechanisms and Effects Posed by Neurotoxic Products of Cyanobacteria/Microbial Eukaryotes/Dinoflagellates in Algae Blooms: a Review

Mello FD1Braidy N2Marçal H3Guillemin G4Nabavi SM5Neilan BA6

1.School of Biotechnology and Biomolecular Sciences The University of New South Wales Sydney Australia
2.Centre for Healthy Brain Ageing, School of Psychiatry, Faculty of Medicine The University of New South Wales Sydney Australia
3.Graduate School of Biomedical Engineering, Faculty of Engineering The University of New South Wales Sydney Australia
4.Neuropharmacology group, MND and Neurodegenerative diseases Research Centre Macquarie University Sydney Australia
5.Applied Biotechnology Research Center Baqiyatallah University of Medical Sciences Tehran Iran
6.School of Environmental and Life Sciences The University of Newcastle Callaghan Australia

Environmental toxins produced by cyanobacteria and dinoflagellates have increasingly become a public health concern due to their ability to damage several tissues in humans. In particular, emerging evidence has called attention to the neurodegenerative effects of the cyanobacterial toxin β-N-methylamino-l-alanine (BMAA). Furthermore, other toxins such as anatoxin, saxitoxin, microcystin, nodularin and ciguatoxin also have a different range of effects on human tissues, including hepatotoxicity, neurotoxicity and gastrointestinal irritation. However, the vast majority of known environmental toxins have not yet been examined in the context of neurodegenerative disease. This review aims to investigate whether neurotoxic mechanisms can be demonstrated in all aforementioned toxins, and whether there exists a link to neurodegeneration. Management of toxin exposure and potential neuroprotective compounds is also discussed. Collectively, all aforementioned microbial toxins are likely to exert some form of neuronal damage, with many of their modes of action consistent with neurodegeneration. This is important in advancing our current understanding of the cytotoxic potential of environmental toxins upon human brain function, particularly in the context of age-related neurodegenerative disease.

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