https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:54089 Wed 28 Feb 2024 15:38:05 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:54983 Wed 27 Mar 2024 16:31:58 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:36697 Wed 24 Jun 2020 18:17:11 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:34828 Wed 15 May 2019 14:31:20 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:50347 Wed 06 Mar 2024 14:52:04 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:43986 Wed 05 Oct 2022 14:36:29 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37008 Wed 05 Aug 2020 14:09:13 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:34853 Wed 04 Dec 2019 10:17:27 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:54546 Tue 27 Feb 2024 20:42:03 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:36295 Tue 24 Mar 2020 09:23:30 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:35275 Tue 21 Mar 2023 15:56:55 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37098 Tue 18 Aug 2020 09:48:42 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:34123 Dolichospermum circinale (formerly Anabaena circinalis) is responsible for neurotoxic saxitoxin-producing blooms in Australia. Previous studies have reported distinct isolates of toxic D. circinale producing different saxitoxin analogues at varying amounts, but the mechanisms responsible remain poorly understood. To assess the characteristics that may be responsible for this variance, a morphological, molecular and chemical survey of 28 Anabaena isolates was conducted. Morphological characteristics, presence or absence of saxitoxin biosynthetic genes and toxin amount and profile were assessed. The 28 isolates were collected from 16 locations. A correlation between the size of the isolates and its reported toxicity or geographical location could not be found. Molecular screening for the presence of several sxt genes revealed eight out of the 28 strains harboured the sxt gene cluster and all tailoring genes except sxtX. Furthermore, the presence of PSTs was correlated with the presence of the sxt cluster using quantitative pre-column oxidation high performance liquid chromatography with fluorescence detection (HPLC-FLD) and LC-MS/MS. Interestingly, isolates differed in the amount and type of toxins produced, with the eight toxic strains containing the core and tailoring biosynthetic genes while non-toxic strains were devoid of these genes. Moreover, the presence of sxt tailoring genes in toxic strains correlated with the biosynthesis of analogues. A greater understanding of toxin profile/quantity from distinct sites around Australia will aid the management of these at-risk areas and provide information on the molecular control or physiological characteristics responsible for toxin production.]]> Tue 12 Feb 2019 13:12:12 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39953 Microcystis aeruginosa has been linked to toxic blooms worldwide. In addition to producing hepatotoxic microcystins, many strains are capable of synthesising a variety of biologically active compounds, including protease and phosphatase inhibitors, which may affect aquatic ecosystems and pose a risk to their use. This study explored the distribution, composition and conservation of known secondary metabolite (SM) biosynthesis gene clusters in the genomes of 27 M. aeruginosa strains isolated from six different Koppen-Geiger climates. Our analysis identified gene clusters with significant homology to nine SM biosynthesis gene clusters spanning four different compound classes: non-ribosomal peptides, hybrid polyketide-non-ribosomal peptides, cyanobactins and microviridins. The aeruginosin, microviridin, cyanopeptolin and microcystin biosynthesis gene clusters were the most frequently observed, but hybrid polyketide-non-ribosomal peptide biosynthesis clusters were the most common class overall. Although some biogeographic relationships were observed, taxonomic markers and geography were not reliable indicators of SM biosynthesis cluster distribution, possibly due to previous genetic deletions or horizontal gene transfer events. The only cyanotoxin biosynthesis gene cluster identified in our screening study was the microcystin synthetase (mcy) gene cluster, suggesting that the production of non-microcystin cyanotoxins by this taxon, such as anatoxin-a or paralytic shellfish poison analogues, is either absent or rare.]]> Thu 30 Jun 2022 14:50:32 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:55832 Thu 27 Jun 2024 12:21:19 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:51203 Thu 24 Aug 2023 14:58:35 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37155 Thu 21 Oct 2021 12:44:49 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:20249 Sat 24 Mar 2018 07:59:57 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:22178 Sat 24 Mar 2018 07:16:24 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:24839 Coelosphaerium sp., Synechococcus sp., Oscillatoria sp. and Chroococcus sp. to environmentally relevant concentrations of Cr⁶⁺, Cd²⁺ and Zn²⁺was assessed based on fluorescence change as a proxy for growth reduction. At 24 h exposure, the growth reduction inthe cyanobacteria followed the order: Zn²⁺ < Cr⁶⁺ ≤ Cd²⁺. Of the four cyanobacteria, Synechococcus was the most sensitive for Cr⁶⁺, where as Chroococcus was the most sensitive for Cd²⁺ and Zn²⁺. Sensitivity was gradually decreased by 96 h implying the acquisition of tolerance by cyanobacteria to heavy metal ions with prolonged exposure.]]> Sat 24 Mar 2018 07:11:19 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37448 Mon 30 Nov 2020 10:12:19 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:32385 Mon 23 Sep 2019 13:27:12 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37587 Mon 22 Feb 2021 11:59:53 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:48515 mcyA-J. The recent establishment of a cyanotoxin heterologous expression system in Escherichia coli has provided the means to study microcystin biosynthesis in a genetically tractable, rapidly growing host. Using this system, we demonstrate that deletion of the ABC-transporter, mcyH, and dehydrogenase, mcyI, abolishes microcystin production, while deletion of the O-methyltransferase, mcyJ, results in the production of the demethylated (DM) toxin [D-Asp³ , DMAdda ⁵]microcystin-LR. Both methylated and DM toxin variants were heterologously produced at high titers and efficiently exported into the extracellular medium, enabling easy purification. The results show that the mcy gene cluster can be engineered in E. coli to study the function of its individual components and direct the synthesis of particular microcystin variants. This technology could potentially be applied to other natural products of ecological and biomedical significance.]]> Mon 20 Mar 2023 16:46:36 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:36931 Mon 20 Jul 2020 10:49:41 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:41064 Mon 08 Aug 2022 14:59:49 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:38846 Raphidiopsis raciborskii is an invasive bloom-forming cyanobacteria with the flexibility to utilize atmospheric and fixed nitrogen. Since nitrogen-fixation has a high requirement for iron as an ezyme cofactor, we hypothesize that iron availability would determine the success of the species under nitrogen-fixing conditions. This study compares the proteomic response of cylindrospermopsin-producing and non-toxic strains of R. racibroskii to reduced iron concentrations, under nitrogen-fixing conditions, to examine any strain-specific adaptations that might increase fitness under these conditions. We also compared their proteomic responses at exponential and stationary growth phases to capture the changes throughout the growth cycle. Overall, the toxic strain was more competitive under Fe-starved conditions during exponential phase, with upregulated growth and transport-related proteins. The non-toxic strain showed reduced protein expression across multiple primary metabolism pathways. We propose that the increased expression of porin proteins during the exponential growth phase enables toxic strains to persist under Fe-starved conditions with this ability providing a potential explanation for the increased fitness of cylindrospermoipsin-producing strains during unfavourable environmental conditions.]]> Mon 06 May 2024 13:15:09 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:39205 3) compared with enzymes from other organisms. The size of the active site did not correlate well with substrate size, however, the "Gatekeeper" amino acid residues within the active site were strongly correlated to enzyme phylogeny. Our study provides unprecedented insight into the distribution, diversity, and molecular evolution of cyanobacterial type III PKSs, which could facilitate the discovery, characterization, and exploitation of novel enzymes, biochemical pathways, and specialized metabolites from this biosynthetically talented clade of microorganisms.]]> Fri 27 May 2022 09:52:31 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:34852 Fri 20 May 2022 15:28:54 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:50084 Fri 14 Jul 2023 11:41:19 AEST ]]>