Mammalian cell surfaces are decorated with complex glycoconjugates that terminate with negatively charged sialic acids. Commensal and pathogenic bacteria can use host-derived sialic acids for a competitive advantage, but require a functional sialic acid transporter to import the sugar into the cell. This work investigates the sodium sialic acid symporter (SiaT) from Staphylococcus aureus (SaSiaT). We demonstrate that SaSiaT rescues an Escherichia coli strain lacking its endogenous sialic acid transporter when grown on the sialic acids N-acetylneuraminic acid (Neu5Ac) or N-glycolylneuraminic acid (Neu5Gc). We then develop an expression, purification and detergent solubilization system for SaSiaT and demonstrate that the protein is largely monodisperse in solution with a stable monomeric oligomeric state. Binding studies reveal that SaSiaT has a higher affinity for Neu5Gc over Neu5Ac, which was unexpected and is not seen in another SiaT homolog. We develop a homology model and use comparative sequence analyses to identify substitutions in the substrate-binding site of SaSiaT that may explain the altered specificity. SaSiaT is shown to be electrogenic, and transport is dependent upon more than one Na+ ion for every sialic acid molecule. A functional sialic acid transporter is essential for the uptake and utilization of sialic acid in a range of pathogenic bacteria, and developing new inhibitors that target these transporters is a valid mechanism for inhibiting bacterial growth. By demonstrating a route to functional recombinant SaSiaT, and developing the in vivo and in vitro assay systems, our work underpins the design of inhibitors to this transporter.

The alarming rise in superbugs that are resistant to drugs of last resort, including vancomycin-resistant enterococci and staphylococci, has become a significant global health hazard. Here we report the click chemistry synthesis of an unprecedented class of shapeshifting vancomycin dimers (SVDs) that display potent activity against bacteria that are resistant to the parent drug, including the ESKAPE pathogens, vancomycin-resistant Enterococcus (VRE), methicillin-resistant Staphylococcus aureus (MRSA) as well as vancomycin-resistant S. aureus (VRSA). The shapeshifting modality of the dimers is powered by a click-linked bullvalene core, hence exploiting the dynamic covalent rearrangements of the fluxional carbon cage and creating ligands with the capacity to inhibit bacterial cell wall biosynthesis. The new shapeshifting antibiotics are not disadvantaged by the common mechanism of vancomycin resistance resulting from the alteration of the C-terminal dipeptide with the corresponding D-Ala-D-Lac depsipeptide. Further, evidence suggests that the shapeshifting ligands destabilize the complex formed between the flippase MurJ and lipid II, inferring the potential for a new mode of action for polyvalent glycopeptides. The SVDs show little propensity for acquired resistance by enterococci, suggesting that this new class of shapeshifting antibiotic will display durable antimicrobial activity not prone to rapidly acquired clinical resistance.

Amino acids are an essential building block of all life and are commonly incorporated into extending polypeptide chains to produce proteins. Lysine is one such amino acid and is classified as basic and positively charged at physiological pH due to the presence of an additional amino chemical group on the side chain. Lysine has two main biosynthetic pathways, namely the diaminopimelate and α-aminoadipate pathways, which employ different enzymes and substrates and are found in different organisms. Lysine catabolism occurs through one of several pathways, the most common of which is the saccharopine pathway. Lysine plays several roles in humans, most importantly proteinogenesis, but also in the crosslinking of collagen polypeptides, uptake of essential mineral nutrients, and in the production of carnitine, which is key in fatty acid metabolism. Furthermore, lysine is often involved in histone modifications, and thus, impacts the epigenome. Due to the importance of lysine in several biological processes, a lack of lysine can lead to several disease states including; defective connective tissues, impaired fatty acid metabolism, anaemia, and systemic protein-energy deficiency. In juxtaposition to this, an overabundance of lysine, caused by ineffective catabolism, can cause severe neurological issues.

A series of gold(I) (4a – 4h, 5a – 5b) and silver(I) (3a – 3h) complexes of 1,2,4-triazolylidene and imidazolylidene based N-heterocyclic carbene ligands were prepared and the antibacterial activities...

Galectins are a family of glycan-binding molecules with a characteristic affinity for ß-Dglycosides that mediate a variety of important cellular functions, including immune and inflammatory responses. Galectin-11 (LGALS-11) has been recently identified as a mediator induced specifically in animals against gastrointestinal nematodes and can interfere with parasite growth and development. Here, we report that at least two natural genetic variants of LGALS-11 exist in sheep, and demonstrate fundamental differences in anti-parasitic activity, correlated with their ability to dimerise. This study improves our understanding of the role of galectins in the host immune and inflammatory responses against parasitic nematodes and provides a basis for genetic studies toward selective breeding of animals for resistance to parasites.

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The main goal of this study was to screen different lignocellulosic materials for their ability to support the cell growth of the yeast Komagataella pastoris and the production of xylitol. Several lignocellulosic materials, namely banana peels, brewer’s spent grains (BSGs), corncobs, grape pomace, grape stalks, and sawdust, were subjected to dilute acid hydrolysis to obtain sugar rich solutions that were tested as feedstocks for the cultivation of K. pastoris. Although the culture was able to grow in all the tested hydrolysates, a higher biomass concentration was obtained for banana peels (15.18 ± 0.33 g/L) and grape stalks (14.58 ± 0.19 g/L), while the highest xylitol production (1.51 ± 0.07 g/L) was reached for the BSG hydrolysate with a xylitol yield of 0.66 ± 0.39 g/g. Cell growth and xylitol production from BSG were improved by detoxifying the hydrolysate using activated charcoal, resulting in a fourfold increase of the biomass production, while xylitol production was improved to 3.97 ± 0.10 g/L. Moreover, concomitant with arabinose consumption, arabitol synthesis was noticed, reaching a maximum concentration of 0.82 ± 0.05 g/L with a yield on arabinose of 0.60 ± 0.11 g/g. These results demonstrate the feasibility of using lignocellulosic waste, especially BSG, as feedstock for the cultivation of K. pastoris and the coproduction of xylitol and arabitol. Additionally, it demonstrates the use of K. pastoris as a suitable microorganism to integrate a zero-waste biorefinery, transforming lignocellulosic waste into two high-value specialty chemicals with high market demand.

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