https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49640 Wed 22 Nov 2023 15:41:08 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:29783 dif. In Escherichia coli, two tyrosine-family recombinases, XerC and XerD, bind to dif and carry out two pairs of sequential strand exchange reactions. However, what makes the reaction unique among site-specific recombination reactions is that the first step, XerD-mediated strand exchange, relies on interaction with the very C-terminus of the FtsK DNA translocase. FtsK is a powerful molecular motor that functions in cell division, co-ordinating division with clearing chromosomal DNA from the site of septation and also acts to position the dif sites for recombination. This is a model system for unlinking, separating and segregating large DNA molecules. Here we describe the molecular detail of the interaction between XerD and FtsK that leads to activation of recombination as deduced from a co-crystal structure, biochemical and in vivo experiments. FtsKγ interacts with the C-terminal domain of XerD, above a cleft where XerC is thought to bind. We present a model for activation of recombination based on structural data.]]> Wed 11 Apr 2018 17:12:14 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26208 Wed 11 Apr 2018 15:30:25 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:29110 oF₁ ATPase, helicases, viral dsDNA-packaging motors, bacterial chromosome translocases, myosin, kinesin, and dynein. In particular, dsDNA translocases are used to illustrate how these features relate to the motion mechanism and how nature elegantly evolved a revolution mechanism to avoid coiling and tangling during lengthy dsDNA genome transportation in cell division. Motor chirality and channel size are two factors that distinguish rotation motors from revolution motors. Rotation motors use right-handed channels to drive the right-handed dsDNA, similar to the way a nut drives the bolt with threads in same orientation; revolution motors use left-handed motor channels to revolve the right-handed dsDNA. Rotation motors use small channels (<2 nm in diameter) for the close contact of the channel wall with single-stranded DNA (ssDNA) or the 2-nm dsDNA bolt; revolution motors use larger channels (>3 nm) with room for the bolt to revolve. Binding and hydrolysis of ATP are linked to different conformational entropy changes in the motor that lead to altered affinity for the substrate and allow work to be done, for example, helicase unwinding of DNA or translocase directional movement of DNA.]]> Wed 11 Apr 2018 15:14:20 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:23206 Wed 11 Apr 2018 13:59:44 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30154 Wed 11 Apr 2018 11:04:38 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:16795 Wed 11 Apr 2018 10:46:19 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:25993 Wed 01 Feb 2017 16:53:40 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:48554 Tue 21 Mar 2023 15:37:49 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34802 Synechocystis, sp. PCC6803 is a member of the Tc1/mariner/IS630 superfamily, and is characterized by high transposition efficiency and a strong preference for TA target sequences. In this paper, we describe the design and application of a mini-ISY100 suicide vector for the in vivo creation of stable random transposon insertion libraries. The system was successfully applied in seven species belonging to four different orders of γ proteobacteria. In all cases, delivery using conjugation consistently showed the highest transposition efficiency compared to chemical transformation or electroporation. We determined the frequency of transposon insertions in all the species and proved the utility of the system by identifying genes involved in colony coloration in Shewanella oneidensis. The ease and the efficiency of the protocol developed here allow the creation of complete knock-out libraries in an extensive range of host microorganisms in less than a week with no requirement for preparatory modification.]]> Tue 03 Sep 2019 17:58:55 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49403 Thu 22 Feb 2024 11:32:12 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39702 Thu 22 Feb 2024 11:29:44 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43934 Thu 22 Feb 2024 11:11:02 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:41005 Thu 21 Jul 2022 10:51:15 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34848 Thu 16 May 2019 17:38:51 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:49928 polyethylene>nylon>polyester. The concentrations of adsorbed Pb and PFOS were 4-25% and 20-85% higher in aged MFs and varied among the polymer types. The increased contaminant adsorption was linked with the altered surface area and the hydrophobic/hydrophilic characteristics of the samples. Overall, the present study demonstrates that biofilms play a decisive role in contaminant-plastic interactions and significantly enhance the vector potential of MFs for toxic environmental contaminants. We anticipate that knowledge generated from this study will help refine the planetary risk assessment of MPs.]]> Thu 15 Jun 2023 12:09:35 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10871 5000 bp per second—and is powerful enough to remove other proteins from the DNA. In bacteria it is localised to the site of cell division, the septum, where it functions as a DNA pump at the late stages of the cell cycle, to expedite cytokinesis and chromosome segregation. The N terminus of the protein is involved in the cell-cycle-specific localisation and assembly of the cell-division machinery, whereas the C terminus forms the motor. The motor portion of FtsK has been studied by a combination of biochemistry, genetics, X-ray crystallography and single-molecule mechanical assays, and these will be the focus here. The motor can be divided into three subdomains: α, β and γ. The α and β domains multimerise to produce a hexameric ring with a central channel for dsDNA, and contain a RecA-like nucleotide-binding/hydrolysis fold. The motor is given directionality by the regulatory γ domain, which binds to polarised chromosomal sequences—5′-GGGNAGGG-3′, known as KOPS—to ensure that the motor is loaded onto DNA in a specific orientation such that subsequent translocation is always towards the region of the chromosome where replication usually terminates (the terminus), and specifically to the 28 bp dif site, located in this region. Once the FtsK translocase has located the dif site it then interacts with the XerCD site-specific recombinases to activate recombination.]]> Sat 24 Mar 2018 08:14:31 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:10662 Sat 24 Mar 2018 08:12:42 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:18361 Sat 24 Mar 2018 07:52:40 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:28354 Escherichia coli, complete unlinking of newly replicated sister chromosomes is required to ensure their proper segregation at cell division. Whereas replication links are removed primarily by topoisomerase IV, XerC/XerD-dif site-specific recombination can mediate sister chromosome unlinking in Topoisomerase IV-deficient cells. This reaction is activated at the division septum by the DNA translocase FtsK, which coordinates the last stages of chromosome segregation with cell division. It has been proposed that, after being activated by FtsK, XerC/XerD-dif recombination removes DNA links in a stepwise manner. Here, we provide a mathematically rigorous characterization of this topological mechanism of DNA unlinking. We show that stepwise unlinking is the only possible pathway that strictly reduces the complexity of the substrates at each step. Finally, we propose a topological mechanism for this unlinking reaction.]]> Sat 24 Mar 2018 07:25:12 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43435 P_app), with differences in ML retention and complexation amongst the chelants and the gut microbes. The decrease in ML permeability varied amongst the MLs. Chelating agents reduce intestinal absorption of MLs by forming complexes thereby making them less permeable. In the case of gut bacteria, the decrease in the intestinal permeability of MLs may be associated to a direct protection of the intestinal barrier against the MLs or indirect intestinal ML sequestration by the gut bacteria through adsorption on bacterial surface. Thus, both gut microbes and chelating agents can be used to decrease the intestinal permeability of MLs, thereby mitigating their toxicity.]]> Mon 19 Sep 2022 11:35:28 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:51765 Cd > Pb > As(III)>As(V) for E. coli; and Hg > Cd > As(III)>Pb > As(V) for the two Lactobacillus sp. Arsenite (AsIII) showed higher toxicity than arsenate (AsV) to gut bacteria. While As is an anion, Cd, Pb and Hg are cations and hence their binding capacity to the bacterial cell wall varied based on the charge dependent functional groups. However, the toxic effects of PTEs for a bacteria are controlled by their speciation and bioavailability.]]> Mon 18 Sep 2023 14:23:29 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39212 Lactobacillus acidophilus, Lactobacillus rhamnosus and Escherichia coli. Lead toxicity to these three microbes was also examined at various pH values. Bioaccessibility of Pb was measured using gastric and intestinal extractions. Both Pb spiked and Pb-contaminated shooting range field soils were used to measure Pb bioaccessibility in the presence and absence of gut microbes. The results indicated that Pb toxicity to gut microbes, as measured by LD₅₀ value, decreased with increasing pH, and was higher for Lactobacillus species. Gut microbes decreased the bioaccessible Pb; the effect was more pronounced at low pH, mimicking gastric conditions than in conditions closer to the intestine. Lead adsorption by these microbes increased at the higher pH tested, and E. coli adsorbed higher amounts of Pb than did the Lactobacillus species. The effect of gut microbes on reducing Pb bioaccessibility may be attributed to microbially-induced immobilization of Pb through adsorption, precipitation, and complexation reactions. The study demonstrates that bioaccessibility and subsequently bioavailability of metal(loid)s can be modulated by gut microbes, and it is important to undertake bioaccessibility measurements in the presence of gut microbes.]]> Fri 27 May 2022 11:09:22 AEST ]]>