The relationship between major depressive disorder (MDD) and personality disorders is complex, with implications for diagnosis and treatment. We sought to explore the relationship between these ...disorders quantitatively in an inpatient setting.
We conducted a structured observational study exploring symptoms of depression and selected neurocognitive functions over the span of an inpatient admission in those with depression and personality disorders. Sixty inpatients presenting with symptoms of depression completed ratings of mood and neurocognitive function. Diagnosis was confirmed by structured clinical interview (SCID-5-RV) at discharge and used to allocate patients to one of the two groups for analysis: those with MDD-only and those with a personality disorder (with or without MDD).
On admission, observer-based ratings of depression were significantly higher in the MDD-only group while subjective ratings were higher in the personality disorder group. Depression rating scores lessened in both groups during the admission, but at discharge, the personality disorder group continued to report higher subjective ratings. The personality disorder group also rated themselves as more cognitively impaired than the MDD-only group and unlike the MDD-only group, they did not report subjective improvements in cognitive function over the course of admission. Objective assessment of cognitive function demonstrated improvements in both groups.
In this study, the presence of a personality disorder was associated with greater subjective severity of depressive symptomatology and selected neurocognitive functioning, despite similar or lower objective severity in comparison with those with MDD. This finding has implications for understanding the patient journey through health care settings.
D-cycloserine is an antibiotic which targets sequential bacterial cell wall peptidoglycan biosynthesis enzymes: alanine racemase and D-alanine:D-alanine ligase. By a combination of structural, ...chemical and mechanistic studies here we show that the inhibition of D-alanine:D-alanine ligase by the antibiotic D-cycloserine proceeds via a distinct phosphorylated form of the drug. This mechanistic insight reveals a bimodal mechanism of action for a single antibiotic on different enzyme targets and has significance for the design of future inhibitor molecules based on this chemical structure.
Accumulating evidence suggests that peptidoglycan, consistent with a bacterial cell wall, is synthesized around the chloroplasts of many photosynthetic eukaryotes, from glaucophyte algae to ...early-diverging land plants including pteridophyte ferns, but the biosynthetic pathway has not been demonstrated. Here, we employed mass spectrometry and enzymology in a two-fold approach to characterize the synthesis of peptidoglycan in chloroplasts of the moss Physcomitrium (Physcomitrella) patens. To drive the accumulation of peptidoglycan pathway intermediates, P. patens was cultured with the antibiotics fosfomycin, D-cycloserine, and carbenicillin, which inhibit key peptidoglycan pathway proteins in bacteria. Mass spectrometry of the trichloroacetic acid-extracted moss metabolome revealed elevated levels of five of the predicted intermediates from uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) through the uridine diphosphate N-acetylmuramic acid (UDP-MurNAc)-D,L-diaminopimelate (DAP)-pentapeptide. Most Gram-negative bacteria, including cyanobacteria, incorporate meso-diaminopimelic acid (D,L-DAP) into the third residue of the stem peptide of peptidoglycan, as opposed to L-lysine, typical of most Gram-positive bacteria. To establish the specificity of D,L-DAP incorporation into the P. patens precursors, we analyzed the recombinant protein UDP-N-acetylmuramoyl-L-alanyl-D-glutamate-2,6-diaminopimelate ligase (MurE) from both P. patens and the cyanobacterium Anabaena sp. (Nostoc sp. strain PCC 7120). Both ligases incorporated D,L-DAP in almost complete preference to L-Lys, consistent with the mass spectrophotometric data, with catalytic efficiencies similar to previously documented Gram-negative bacterial MurE ligases. We discuss how these data accord with the conservation of active site residues common to DL-DAP-incorporating bacterial MurE ligases and of the probability of a horizontal gene transfer event within the plant peptidoglycan pathway.
is a gram-negative bacterial pathogen that causes challenging nosocomial infections. β-lactam targeting of penicillin-binding protein (PBP)-mediated cell wall peptidoglycan (PG) formation is a ...well-established antimicrobial strategy. Exposure to carbapenems or zinc (Zn)-deprived growth conditions leads to a rod-to-sphere morphological transition in
, an effect resembling that caused by deficiency in the RodA-PBP2 PG synthesis complex required for cell wall elongation. While it is recognized that carbapenems preferentially acylate PBP2 in
and therefore block the transpeptidase function of the RodA-PBP2 system, the molecular details underpinning cell wall elongation inhibition upon Zn starvation remain undefined. Here, we report the X-ray crystal structure of
PBP2, revealing an unexpected Zn coordination site in the transpeptidase domain required for protein stability. Mutations in the Zn-binding site of PBP2 cause a loss of bacterial rod shape and increase susceptibility to β-lactams, therefore providing a direct rationale for cell wall shape maintenance and Zn homeostasis in
. Furthermore, the Zn-coordinating residues are conserved in various β- and γ-proteobacterial PBP2 orthologs, consistent with a widespread Zn-binding requirement for function that has been previously unknown. Due to the emergence of resistance to virtually all marketed antibiotic classes, alternative or complementary antimicrobial strategies need to be explored. These findings offer a perspective for dual inhibition of Zn-dependent PG synthases and metallo-β-lactamases by metal chelating agents, considered the most sought-after adjuvants to restore β-lactam potency against gram-negative bacteria.
Factors influencing trainees' decisions about choosing and remaining in higher training subspecialties have not been widely researched. We administered telephone questionnaires to higher specialist ...trainees in the north-east of England to ascertain what influences these decisions. Thematic analysis was employed to develop overall constructs.
Twenty-seven trainees were interviewed, resulting in six overall constructs. These were: supervisory experiences; perceived work-life balance; career prospects; training and working environments; interest in the chosen subspecialty; and previous experience within the chosen subspecialty. Most trainees interviewed felt they had made the right specialty choice.
This study demonstrates the particular importance of exposure to a specialty and perceptions of the supervisory experience in determining trainees' choices of, and decisions to remain in, a particular psychiatric specialty. Factors highlighted in this study must inform training, recruitment and workforce planning in order to bolster the recruitment and retention of trainees into higher specialty training.
Rationale
Anthropogenic organic inputs to freshwaters can exert detrimental effects on aquatic ecosystems, raising growing concern for both environmental conservation and water security. Current ...regulation by the EU water framework directive (European Union, 2000/60/EC) relates to organic pollution by monitoring selected micropollutants; however, aquatic ecosystem responses require a comprehensive understanding of dissolved organic matter (DOM) composition. The introduction of high‐resolution mass spectrometry (HRMS) is set to greatly increase our understanding of the composition of DOM of both natural and anthropogenic origin derived from diffuse and point sources.
Methods
DOM was extracted from riverine and treated sewage effluent using solid‐phase extraction (SPE) and analysed using dissolved organic carbon analysis, direct‐infusion high‐resolution mass spectrometry (DI‐HRMS) and high‐performance liquid chromatography (HPLC)/HRMS. The data obtained were analysed using univariate and multivariate statistics to demonstrate differences in background DOM, anthropogenic inputs and in‐river mixing. Compound identifications were achieved based on MS2 spectra searched against on‐line databases.
Results
DI‐HRMS spectra showed the highly complex nature of all DOM SPE extracts. Classification and visualisation of extracts containing many thousands of individual compounds were achieved using principal component analysis (PCA) and hierarchical cluster analysis. Kruskal‐Wallis analyses highlighted significant discriminating ions originating from the sewage treatment works for more in‐depth investigation by HPLC/HRMS. The generation of MS2 spectra in HPLC/HRMS provided the basis for identification of anthropogenic compounds including; pharmaceuticals, illicit drugs, metabolites and oligomers, although many thousands of compounds remain unidentified.
Conclusions
This new approach enables comprehensive analysis of DOM in extracts without any preconceived ideas of the compounds which may be present. This approach has the potential to be used as a high throughput, qualitative, screening method to determine if the composition of point sources differs from that of the receiving water bodies, providing a new approach to the identification of hitherto unrecognised organic contribution to water bodies.
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Branched Lipid II, required for the formation of indirectly crosslinked peptidoglycan, is generated by MurM, a protein essential for high-level penicillin resistance in the human pathogen ...Streptococcus pneumoniae. We have solved the X-ray crystal structure of Staphylococcus aureus FemX, an isofunctional homolog, and have used this as a template to generate a MurM homology model. Using this model, we perform molecular docking and molecular dynamics to examine the interaction of MurM with the phospholipid bilayer and the membrane-embedded Lipid II substrate. Our model suggests that MurM is associated with the major membrane phospholipid cardiolipin, and experimental evidence confirms that the activity of MurM is enhanced by this phospholipid and inhibited by its direct precursor phosphatidylglycerol. The spatial association of pneumococcal membrane phospholipids and their impact on MurM activity may therefore be critical to the final architecture of peptidoglycan and the expression of clinically relevant penicillin resistance in this pathogen.
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•S. aureus FemX structure generated an improved homology model of S. pneumoniae MurM•A Lipid II binding site in MurM was identified by docking and molecular dynamics•Modeling indicates cardiolipin is enriched at the MurM protein:membrane interface•Enzyme assays show that phospholipids influence MurM activity
With an improved homology model of MurM, York et al., use docking and molecular dynamics studies to identify a potential Lipid II binding site and simulate how MurM interacts with this membrane-embedded substrate. Cardiolipin, a membrane phospholipid, was also found to associate with MurM and upregulate its enzymatic activity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The human pathogen Mycobacterium tuberculosis is the causative agent of pulmonary tuberculosis (TB), a disease with high worldwide mortality rates. Current treatment programs are under significant ...threat from multi-drug and extensively-drug resistant strains of M. tuberculosis, and it is essential to identify new inhibitors and their targets. We generated spontaneous resistant mutants in Mycobacterium bovis BCG in the presence of 10× the minimum inhibitory concentration (MIC) of compound 1, a previously identified potent inhibitor of mycobacterial growth in culture. Whole genome sequencing of two resistant mutants revealed in one case a single nucleotide polymorphism in the gene aspS at (535)GAC>(535)AAC (D179N), while in the second mutant a single nucleotide polymorphism was identified upstream of the aspS promoter region. We probed whole cell target engagement by overexpressing either M. bovis BCG aspS or Mycobacterium smegmatis aspS, which resulted in a ten-fold and greater than ten-fold increase, respectively, of the MIC against compound 1. To analyse the impact of inhibitor 1 on M. tuberculosis AspS (Mt-AspS) activity we over-expressed, purified and characterised the kinetics of this enzyme using a robust tRNA-independent assay adapted to a high-throughput screening format. Finally, to aid hit-to-lead optimization, the crystal structure of apo M. smegmatis AspS was determined to a resolution of 2.4 Å.
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Teixobactin is a new promising antibiotic that targets cell wall biosynthesis by binding to lipid II and has no detectable resistance thanks to its unique but yet not fully understood mechanism of ...operation. To aid in the structure-based design of teixobactin analogues with improved pharmacological properties, we present a 3D structure of native teixobactin in membrane mimetics and characterise its binding to lipid II through a combination of solution NMR and fast (90 kHz) magic angle spinning solid state NMR. In NMR titrations, we observe a pattern strongly suggesting interactions between the backbone of the C-terminal "cage" and the pyrophosphate moiety in lipid II. We find that the N-terminal part of teixobactin does not only act as a membrane anchor, as previously thought, but is actively involved in binding. Moreover, teixobactin forms a well-structured and specific complex with lipid II, where the N-terminal part of teixobactin assumes a β conformation that is highly prone to aggregation, which likely contributes to the antibiotic's high bactericidal efficiency. Overall, our study provides several new clues to teixobactin's modes of action.
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Survival in the human host requires bacteria to respond to unfavorable conditions. In the important Gram-positive pathogen
, cell wall biosynthesis proteins MurM and MurN are tRNA-dependent amino ...acyl transferases which lead to the production of branched muropeptides. We demonstrate that wild-type cells experience optimal growth under mildly acidic stressed conditions, but Δ
strain displays growth arrest and extensive lysis. Furthermore, these stress conditions compromise the efficiency with which alanyl-tRNA
synthetase can avoid noncognate mischarging of tRNA
with serine, which is toxic to cells. The observed growth defects are rescued by inhibition of the stringent response pathway or by overexpression of the editing domain of alanyl-tRNA
synthetase that enables detoxification of tRNA misacylation. Furthermore, MurM can incorporate seryl groups from mischarged Seryl-tRNA
into cell wall precursors with exquisite specificity. We conclude that MurM contributes to the fidelity of translation control and modulates the stress response by decreasing the pool of mischarged tRNAs. Finally, we show that enhanced lysis of Δ
pneumococci is caused by LytA, and the
operon influences macrophage phagocytosis in a LytA-dependent manner. Thus, MurMN attenuates stress responses with consequences for host-pathogen interactions. Our data suggest a causal link between misaminoacylated tRNA accumulation and activation of the stringent response. In order to prevent potential corruption of translation, consumption of seryl-tRNA
by MurM may represent a first line of defense. When this mechanism is overwhelmed or absent (Δ
), the stringent response shuts down translation to avoid toxic generation of mistranslated/misfolded proteins.
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