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1. Amino acid and protein specificity of protein fatty acylation in Caenorhabditis elegans

   https://doi.org/10.1073/pnas.2307515121  

   Zhang, Bingsen; Yu, Yan; Fox, Bennett W; Liu, Yinong; Thirumalaikumar, Venkatesh P; Skirycz, Aleksandra; Lin, Hening; Schroeder, Frank C (January 2024, Proceedings of the National Academy of Sciences)

   Protein lipidation plays critical roles in regulating protein function and localization. However, the chemical diversity and specificity of fatty acyl group utilization have not been investigated using untargeted approaches, and it is unclear to what extent structures and biosynthetic origins ofS-acyl moieties differ fromN- andO-fatty acylation. Here, we show that fatty acylation patterns inCaenorhabditis elegansdiffer markedly between different amino acid residues. Hydroxylamine capture revealed predominant cysteineS-acylation with 15-methylhexadecanoic acid (isoC17:0), a monomethyl branched-chain fatty acid (mmBCFA) derived from endogenous leucine catabolism. In contrast, enzymatic protein hydrolysis showed that N-terminal glycine was acylated almost exclusively with straight-chain myristic acid, whereas lysine was acylated preferentially with two different mmBCFAs and serine was acylated promiscuously with a broad range of fatty acids, including eicosapentaenoic acid. Global profiling of fatty acylated proteins using a set of click chemistry–capable alkyne probes for branched- and straight-chain fatty acids uncovered 1,013S-acylated proteins and 510 hydroxylamine-resistantN- orO-acylated proteins. Subsets ofS-acylated proteins were labeled almost exclusively by either a branched-chain or a straight-chain probe, demonstrating acylation specificity at the protein level. Acylation specificity was confirmed for selected examples, including theS-acyltransferase DHHC-10. Last, homology searches for the identified acylated proteins revealed a high degree of conservation of acylation site patterns across metazoa. Our results show that protein fatty acylation patterns integrate distinct branches of lipid metabolism in a residue- and protein-specific manner, providing a basis for mechanistic studies at both the amino acid and protein levels. 

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2. Activity of bacteria isolated from bats against Pseudogymnoascus destructans in China

   https://doi.org/10.1111/1751-7915.13765  

   Li, Zhongle; Li, Aoqiang; Hoyt, Joseph R.; Dai, Wentao; Leng, Haixia; Li, Yanfei; Li, Wei; Liu, Sen; Jin, Longru; Sun, Keping; et al (February 2021, Microbial Biotechnology)

   Summary White‐nose syndrome, a disease that is caused by the psychrophilic fungusPseudogymnoascus destructans, has threatened several North America bat species with extinction. Recent studies have shown that East Asian bats are infected withP. destructansbut show greatly reduced infections. While several factors have been found to contribute to these reduced infections, the role of specific microbes in limitingP. destructansgrowth remains unexplored. We isolated three bacterial strains with the ability to inhibitP. destructans, namely,Pseudomonas yamanorumGZD14026,Pseudomonas brenneriXRD11711 andPseudomonas fragiGZD14479, from bats in China.Pseudomonas yamanorum, with the highest inhibition score, was selected to extract antifungal active substance. Combining mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy analyses, we identified the active compound inhibitingP. destructansas phenazine‐1‐carboxylic acid (PCA), and the minimal inhibitory concentration (MIC) was 50.12 μg ml⁻¹. Whole genome sequencing also revealed the existence of PCA biosynthesis gene clusters. Gas chromatography‐mass spectrometry (GC‐MS) analysis identified volatile organic compounds. The results indicated that 10 ppm octanoic acid, 100 ppm 3‐tert‐butyl‐4‐hydroxyanisole (isoprenol) and 100 ppm 3‐methyl‐3‐buten‐1‐ol (BHA) inhibited the growth ofP. destructans. These results support that bacteria may play a role in limiting the growth ofP. destructanson bats. 

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3. Substrate identification of putative NCS1 and NCS2 nucleobase transporters in Pseudomonas aeruginosa

   https://doi.org/10.1128/mbio.02434-24  

   Kennelly, Corey; Prindle, Arthur (December 2024, mBio)

   Mathee, Kalai; Dandekar, Ajai A (Ed.)

   ABSTRACT Pseudomonas aeruginosais an opportunistic pathogen that can salvage nucleobases from the environment to conserve nutrients that would otherwise be spent onde novonucleotide biosynthesis. However, little is known regarding the substrate specificity of the 13 putative nucleobase transporters inP. aeruginosa. Here, using a combination of genetic and chemical approaches, we report substrate identifications for 10 putative nucleobase transporters inP. aeruginosa. Specifically, we individually expressed each transporter in a genetic background lacking all 13 putative nucleobase transporters and quantified growth on a panel of 10 nucleobases as sole nitrogen sources. We confirmed these expression-based substrate identifications using targeted genetic knockouts. In a complementary approach, we utilized four toxic nucleobase antimetabolites to characterize antimicrobial activity in these same strains. We identified the sole allantoin transporter as well as transporters for guanine, xanthine, uric acid, cytosine, thymine, uracil, and dihydrouracil. Furthermore, we associated at least five nucleobase transporters with hypoxanthine, which has been recently reported to be an antibiofilm cue inP. aeruginosa. These results provide an initial characterization of the putative nucleobase transporters inP. aeruginosa, significantly advancing our understanding of nucleobase transport in this clinically relevant organism. IMPORTANCEPseudomonas aeruginosais a frequently multidrug-resistant opportunistic pathogen and one of the most common causes of healthcare-acquired infections. While nucleobases are known to support growth in nutrient-limited conditions, recent work showed that adenine and hypoxanthine can also decreaseP. aeruginosabiofilm formation by disrupting c-di-GMP metabolism. Thus, nucleobase transport may be relevant to multiple aspects ofP. aeruginosabiology and pathogenesis. However, there is currently little known about the transport of nucleobases inP. aeruginosa. Our work reports initial substrate identifications for 10 putative nucleobase transporters inP. aeruginosa, providing new tools to address previously difficult-to-test hypotheses relating to nucleobase transport in this organism. 

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4. Amination of polypropylene‐ g ‐(maleic anhydride) using reactive extrusion

   https://doi.org/10.1002/app.56085  

   Kay, Ian_P; Goddard, Julie_M (August 2024, Journal of Applied Polymer Science)

   Abstract We report synthesis of a radical scavenging aminated thermoplastic polymer through reactive extrusion of polyethyleneimine (PEI) with a polypropylene and polypropylene‐graft‐maleic anhydride (PP‐g‐MA) meltblend. The reaction was confirmed using acid orange 7 (AO7) amine density assay, toluidine blue O (TBO) carboxylic acid density assay, Fourier transform infrared spectroscopy (FTIR), and a migration assay. FTIR spectra revealed a reduction of the asymmetric stretching of the maleic anhydride (MA) carbonyl group at 1777 cm⁻¹and the emergence of the maleimide carbonyl peak at 1702 cm⁻¹. AO7 supported surface orientation of grafted amine groups by introduction of 7.22 nmol cm⁻²primary amines, corresponding to the reduction of surface carboxylic acids quantified by TBO from 12.46 nmol cm⁻²to 0.43 nmol cm⁻². After incubation (40°C, 10 days) in ethanol, acetic acid, and water, < 0.1 mg cm⁻²PEI migrated from the materials, supporting the covalent nature of the grafting. Antioxidant activity was demonstrated exhibiting 5.90 and 4.31 nmol Trolox_eqcm⁻²in aqueous and organic environments, respectively. Results indicate a successful condensation reaction during reactive extrusion, producing an aminated thermoplastic polymer with antioxidant activity for target applications such as food packaging, wastewater treatment, carbon capture, and others. 

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5. Regulation of tricarboxylate transport and metabolism in Acinetobacter baylyi ADP1

   https://doi.org/10.1128/aem.02111-23  

   Baugh, Alyssa C; Defalco, Justin B; Duscent-Maitland, Chantel V; Tumen-Velasquez, Melissa P; Laniohan, Nicole S; Figatner, Kayla; Hoover, Timothy R; Karls, Anna C; Elliott, Kathryn T; Neidle, Ellen L (February 2024, Applied and Environmental Microbiology)

   Cann, Isaac (Ed.)

   ABSTRACT Despite the significant presence of plant-derived tricarboxylic acids in some environments, few studies detail the bacterial metabolism oftrans-aconitic acid (Taa) and tricarballylic acid (Tcb). In a soil bacterium,Acinetobacter baylyiADP1, we discovered interrelated pathways for the consumption of Taa and Tcb. An intricate regulatory scheme tightly controls the transport and catabolism of both compounds and may reflect that they can be toxic inhibitors of the tricarboxylic acid cycle. The genes encoding two similar LysR-type transcriptional regulators, TcuR and TclR, were clustered on the chromosome withtcuAandtcuB, genes required for Tcb consumption. The genetic organization differed from that inSalmonella entericaserovar Typhimurium, in whichtcuAandtcuBform an operon with a transporter gene,tcuC. InA. baylyi,tcuCwas not cotranscribed withtcuAB. Rather,tcuCwas cotranscribed with a gene, designatedpacI, encoding an isomerase needed for Taa consumption. TcuC appears to transport Tcb andcis-aconitic acid (Caa), the presumed product of PacI-mediated periplasmic isomerization of Taa. Two operons,tcuC-pacIandtcuAB, were transcriptionally controlled by both TcuR and TclR, which have overlapping functions. We investigated the roles of the two regulators in activating transcription of both operons in response to multiple effector compounds, including Taa, Tcb, and Caa.IMPORTANCEIngestion of Taa and Tcb by grazing livestock can cause a serious metabolic disorder called grass tetany. The disorder, which results from Tcb absorption by ruminants, focuses attention on the metabolism of tricarboxylic acids. Additional interest stems from efforts to produce tricarboxylic acids as commodity chemicals. Improved understanding of bacterial enzymes and pathways for tricarboxylic acid metabolism may contribute to new biomanufacturing strategies. 

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