2-Heptyl-3-hydroxy-4(1H)-quinolone (PQS) is a quorum-sensing signal molecule used by Pseudomonas aeruginosa. The structural similarity between 3-hydroxy-2-methyl-4(1H)-quinolone, the natural substrate for the 2,4-dioxygenase, Hod, and PQS prompted us to investigate whether Hod quenched PQS signaling. Hod is capable of catalyzing the conversion of PQS to N-octanoylanthranilic acid and carbon monoxide. In P. aeruginosa PAO1 cultures, exogenously supplied Hod protein reduced expression of the PQS biosynthetic gene pqsA, expression of the PQS-regulated virulence determinants lectin A, pyocyanin, and rhamnolipids, and virulence in planta. However, the proteolytic cleavage of Hod by extracellular proteases, competitive inhibition by the PQS precursor 2-heptyl-4(1H)-quinolone, and PQS binding to rhamnolipids reduced the efficiency of Hod as a quorum-quenching agent. Nevertheless, these data indicate that enzyme-mediated PQS inactivation has potential as an antivirulence strategy against P. aeruginosa.
Human milk oligosaccharides (HMOs) are complex sugars that occur naturally in human breast milk and provide many beneficial functions. Most formula products lack HMOs or contain only the most abundant HMO, 2′-fucosyllactose; however, benefits of HMOs come from multiple sugars. We therefore developed a mixture of five HMOs (5HMO-Mix) mimicking the natural concentrations of the top five HMOs (5.75 g/L total, comprising 52% 2′-fucosyllactose, 13% 3-fucosyllactose, 26% lacto-N-tetraose, 4% 3′-sialyllactose, and 5% 6′-sialyllactose) representing the groups of neutral, neutral-fucosylated, and sialylated HMOs. We conducted the first multicenter, randomized, controlled, parallel-group clinical study assessing the safety, tolerability, and effect on growth of formula containing the 5HMO-Mix in healthy infants. We enrolled 341 subjects aged ≤14 days; 225 were randomized into groups fed either with infant formula containing 5HMO-Mix (5HMO-Mix) or infant formula without HMOs (IF) for 4 months, with the others exclusively breastfed. There were no differences in weight, length, or head circumference gain between the two formula groups. The 5HMO-Mix was well tolerated, with 5HMO-Mix and breastfed infants producing softer stools at a higher stool frequency than the control formula group. Adverse events were equivalent in all groups. We conclude that the 5HMO-Mix at 5.75 g/L in infant formula is safe and well tolerated by healthy term infants during the first months of life.
BackgroundBacteria of the genus Arthrobacter are ubiquitous in soil environments and can be considered as true survivalists. Arthrobacter sp. strain Rue61a is an isolate from sewage sludge able to utilize quinaldine (2-methylquinoline) as sole carbon and energy source. The genome provides insight into the molecular basis of the versatility and robustness of this environmental Arthrobacter strain.ResultsThe genome of Arthrobacter sp. Rue61a consists of a single circular chromosome of 4,736,495 bp with an average G + C content of 62.32%, the circular 231,551-bp plasmid pARUE232, and the linear 112,992-bp plasmid pARUE113 that was already published. Plasmid pARUE232 is proposed to contribute to the resistance of Arthrobacter sp. Rue61a to arsenate and Pb2+, whereas the linear plasmid confers the ability to convert quinaldine to anthranilate. Remarkably, degradation of anthranilate exclusively proceeds via a CoA-thioester pathway. Apart from quinaldine utilization, strain Rue61a has a limited set of aromatic degradation pathways, enabling the utilization of 4-hydroxy-substituted aromatic carboxylic acids, which are characteristic products of lignin depolymerization, via ortho cleavage of protocatechuate. However, 4-hydroxyphenylacetate degradation likely proceeds via meta cleavage of homoprotocatechuate. The genome of strain Rue61a contains numerous genes associated with osmoprotection, and a high number of genes coding for transporters. It encodes a broad spectrum of enzymes for the uptake and utilization of various sugars and organic nitrogen compounds. A. aurescens TC-1 is the closest sequenced relative of strain Rue61a.ConclusionsThe genome of Arthrobacter sp. Rue61a reflects the saprophytic lifestyle and nutritional versatility of the organism and a strong adaptive potential to environmental stress. The circular plasmid pARUE232 and the linear plasmid pARUE113 contribute to heavy metal resistance and to the ability to degrade quinaldine, respectively.
Human milk oligosaccharides (HMOs) are unique components of human breast milk. Their large-scale production by fermentation allows infant formulas to be fortified with HMOs, but current fermentation processes require lactose as a starting material, increasing the costs, bioburden, and environmental impact of manufacturing. Here we report the development of an Escherichia coli strain that produces 2′-fucosyllactose (2′-FL), the most abundant HMO, de novo using sucrose as the sole carbon source. Strain engineering required the expression of a novel glucose-accepting galactosyltransferase, overexpression of the de novo UDP-d-galactose and GDP-l-fucose pathways, the engineering of an intracellular pool of free glucose, and overexpression of a suitable α(1,2)-fucosyltransferase. The export of 2′-FL was facilitated using a sugar efflux transporter. The final production strain achieved 2′-FL yields exceeding 60 g/L after fermentation for 84 h. This efficient strategy facilitates the lactose-independent production of HMOs by fermentation, which will improve product quality and reduce the costs of manufacturing.
Arthrobacter nitroguajacolicus Rü 61a, which utilizes quinaldine as sole source of carbon and energy, was shown to contain a conjugative linear plasmid of approximately 110 kb, named pAL1. It exhibits similarities with other linear plasmids from Actinomycetales in that it has proteins covalently attached to its 59 ends. Southern hybridization with probes for the genes encoding quinaldine 4-oxidase and N-acetylanthranilate amidase indicated that pAL1 contains the gene cluster encoding the degradation of quinaldine to anthranilate. A mutant of strain Rü 61a that had lost pAL1 indeed could not convert quinaldine, but was still able to grow on anthranilate. Conjugative transfer of pAL1 to the plasmid-less mutant of strain Rü 61a and to Arthrobacter nicotinovorans DSM 420 (pAO1) occurred at frequencies of 5?4610 "4 and 2?0610per recipient, respectively, and conferred the ability to utilize quinaldine. Five other quinaldine-degrading Gram-positive strains were isolated from soil samples; 16S rDNA sequence analysis suggested the closest relationship to different Arthrobacter species. Except for strain K2-29, all isolates contained a pAL1-like linear plasmid carrying genes encoding quinaldine conversion. A 478 bp fragment that on pAL1 represents an intergenic region showed 100 % sequence identity in all isolates harbouring a pAL1-like plasmid, suggesting horizontal dissemination of the linear plasmid among the genus Arthrobacter. INTRODUCTIONBacteria of the genus Arthrobacter are considered to be ubiquitous in soil and have been found to be among the predominant members of culturable communities from several terrestrial subsurface environments (Crocker et al., 2000). Among the explanations advanced for their ubiquity or even predominance in soil are their resistance to desiccation and nutrient depletion, and their nutritional versatility. Arthrobacter spp. utilize a wide and varied range of natural as well as xenobiotic compounds and thus may play a significant role in the mineralization of organic matter in the environment (Cacciari & Lippi, 1987).Arthrobacter nitroguajacolicus strain Rü61a (formerly assigned to the species Arthrobacter ilicis) utilizes quinaldine (2-methylquinoline), a constituent of coal tar, as sole source of carbon and energy (Hund et al., 1990). Degradation via the anthranilate pathway ( Fig. 1) is initiated by the oxidation of quinaldine to 1H-4-oxoquinaldine, catalysed by quinaldine 4-oxidase (Qox). 1H-4-oxoquinaldine 3-monooxygenase subsequently generates 1H-3-hydroxy-4-oxoquinaldine, which undergoes 2,4-dioxygenolytic ring cleavage to form carbon monoxide and N-acetylanthranilate. This unusual mode of ring cleavage is catalysed by a cofactor-less 2,4-dioxygenase that does not share any similarity with aromatic ring cleavage dioxygenases, but seems to belong to the a/b-hydrolase fold superfamily of proteins (Fetzner, 2002). In the next step, an amidase (Amq) catalyses the hydrolysis of N-acetylanthranilate to anthranilate. We have characterized the gene cluster encoding this 'upper part' of th...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.