-
Proceedings of the National Academy of... Aug 2023The cell envelope of Gram-negative bacteria consists of three distinct layers: the cytoplasmic membrane, a cell wall made of peptidoglycan (PG), and an asymmetric outer...
The cell envelope of Gram-negative bacteria consists of three distinct layers: the cytoplasmic membrane, a cell wall made of peptidoglycan (PG), and an asymmetric outer membrane (OM) composed of phospholipid in the inner leaflet and lipopolysaccharide (LPS) glycolipid in the outer leaflet. The PG layer has long been thought to be the major structural component of the envelope protecting cells from osmotic lysis and providing them with their characteristic shape. In recent years, the OM has also been shown to be a load-bearing layer of the cell surface that fortifies cells against internal turgor pressure. However, whether the OM also plays a role in morphogenesis has remained unclear. Here, we report that changes in LPS synthesis or modification predicted to strengthen the OM can suppress the growth and shape defects of mutants with reduced activity in a conserved PG synthesis machine called the Rod complex (elongasome) that is responsible for cell elongation and shape determination. Evidence is presented that OM fortification in the shape mutants restores the ability of MreB cytoskeletal filaments to properly orient the synthesis of new cell wall material by the Rod complex. Our results are therefore consistent with a role for the OM in the propagation of rod shape during growth in addition to its well-known function as a diffusion barrier promoting the intrinsic antibiotic resistance of Gram-negative bacteria.
Topics: Lipopolysaccharides; Cell Wall; Cell Membrane; Cytoskeleton; Cell Cycle; Escherichia coli; Peptidoglycan
PubMed: 37607228
DOI: 10.1073/pnas.2301987120 -
Applied Microbiology and Biotechnology Mar 2024The massive usage of phthalate esters (PAEs) has caused serious pollution. Bacterial degradation is a potential strategy to remove PAE contamination. So far, an... (Review)
Review
The massive usage of phthalate esters (PAEs) has caused serious pollution. Bacterial degradation is a potential strategy to remove PAE contamination. So far, an increasing number of PAE-degrading strains have been isolated, and the catabolism of PAEs has been extensively studied and reviewed. However, the investigation into the bacterial PAE uptake process has received limited attention and remains preliminary. PAEs can interact spontaneously with compounds like peptidoglycan, lipopolysaccharides, and lipids on the bacterial cell envelope to migrate inside. However, this process compromises the structural integrity of the cells and causes disruptions. Thus, membrane protein-facilitated transport seems to be the main assimilation strategy in bacteria. So far, only an ATP-binding-cassette transporter PatDABC was proven to transport PAEs across the cytomembrane in a Gram-positive bacterium Rhodococcus jostii RHA1. Other cytomembrane proteins like major facilitator superfamily (MFS) proteins and outer membrane proteins in cell walls like FadL family channels, TonB-dependent transporters, and OmpW family proteins were only reported to facilitate the transport of PAEs analogs such as monoaromatic and polyaromatic hydrocarbons. The functions of these proteins in the intracellular transport of PAEs in bacteria await characterization and it is a promising avenue for future research on enhancing bacterial degradation of PAEs. KEY POINTS: • Membrane proteins on the bacterial cell envelope may be PAE transporters. • Most potential transporters need experimental validation.
Topics: Phthalic Acids; Membrane Transport Proteins; ATP-Binding Cassette Transporters; Bacteria; Esters; Dibutyl Phthalate; China
PubMed: 38536521
DOI: 10.1007/s00253-024-13105-6 -
Annual Review of Entomology Jan 2024Bacteriocytes are host cells specialized to harbor symbionts in certain insect taxa. The adaptation, development, and evolution of bacteriocytes underlie insect... (Review)
Review
Bacteriocytes are host cells specialized to harbor symbionts in certain insect taxa. The adaptation, development, and evolution of bacteriocytes underlie insect symbiosis maintenance. Bacteriocytes carry enriched host genes of insect and bacterial origin whose transcription can be regulated by microRNAs, which are involved in host-symbiont metabolic interactions. Recognition proteins of peptidoglycan, the bacterial cell wall component, and autophagy regulate symbiont abundance in bacteriocytes. Horizontally transferred genes expressed in bacteriocytes influence the metabolism of symbiont peptidoglycan, which may affect the bacteriocyte immune response against symbionts. Bacteriocytes release or transport symbionts into ovaries for symbiont vertical transmission. Bacteriocyte development and death, regulated by transcriptional factors, are variable in different insect species. The evolutionary origin of insect bacteriocytes remains unclear. Future research should elucidate bacteriocyte cell biology, the molecular interplay between bacteriocyte metabolic and immune functions, the genetic basis of bacteriocyte origin, and the coordination between bacteriocyte function and host biology in diverse symbioses.
Topics: Animals; Peptidoglycan; Hemiptera; Insecta; Bacteria; Symbiosis
PubMed: 38270981
DOI: 10.1146/annurev-ento-010323-124159 -
Science Advances Aug 2023poses a severe public health problem as one of the vital causative agents of healthcare- and community-acquired infections. There is a globally urgent need for new...
poses a severe public health problem as one of the vital causative agents of healthcare- and community-acquired infections. There is a globally urgent need for new drugs with a novel mode of action (MoA) to combat biofilms and persisters that tolerate antibiotic treatment. We demonstrate that a benzonaphthopyranone glycoside, chrysomycin A (ChryA), is a rapid bactericide that is highly active against persisters, robustly eradicates biofilms in vitro, and shows a sustainable killing efficacy in vivo. ChryA was suggested to target multiple critical cellular processes. A wide range of genetic and biochemical approaches showed that ChryA directly binds to GlmU and DapD, involved in the biosynthetic pathways for the cell wall peptidoglycan and lysine precursors, respectively, and inhibits the acetyltransferase activities by competition with their mutual substrate acetyl-CoA. Our study provides an effective antimicrobial strategy combining multiple MoAs onto a single small molecule for treatments of persistent infections.
Topics: Humans; Staphylococcus aureus; Aminoglycosides; Anti-Bacterial Agents; Staphylococcal Infections; Biofilms
PubMed: 37540745
DOI: 10.1126/sciadv.adg5995 -
Sleep Advances : a Journal of the Sleep... 2023Herein the major accomplishments, trials and tribulations, and epiphanies experienced by James M. Krueger over the course of his career in sleep research are presented....
Herein the major accomplishments, trials and tribulations, and epiphanies experienced by James M. Krueger over the course of his career in sleep research are presented. They include the characterization of a) the supranormal EEG delta waves occurring during NREMS post sleep loss, b) Factor S as a muramyl peptide, c) the physiological roles of cytokines in sleep regulation, d) multiple other sleep regulatory substances, e) the dramatic changes in sleep over the course of infectious diseases, and f) sleep initiation within small neuronal/glial networks. The theory that the preservation of brain plasticity is the primordial sleep function is briefly discussed. These accomplishments resulted from collaborations with many outstanding scientists including James M. Krueger's mentors (John Pappenheimer and Manfred Karnovsky) and collaborators later in life, including Charles Dinarello, Louis Chedid, Mark Opp, Ferenc Obal jr., Dave Rector, Ping Taishi, Linda Toth, Jeannine Majde, Levente Kapas, Eva Szentirmai, Jidong Fang, Chris Davis, Sandip Roy, Tetsuya Kushikata, Fabio Garcia-Garcia, Ilia Karatsoreos, Mark Zielinski, and Alok De, plus many students, e.g. Jeremy Alt, Kathryn Jewett, Erika English, and Victor Leyva-Grado.
PubMed: 37954093
DOI: 10.1093/sleepadvances/zpad039 -
Current Opinion in Microbiology Apr 2024Our ability to control the growth of Gram-negative bacterial pathogens is challenged by rising antimicrobial resistance and requires new approaches. Endolysins are... (Review)
Review
Our ability to control the growth of Gram-negative bacterial pathogens is challenged by rising antimicrobial resistance and requires new approaches. Endolysins are phage-derived enzymes that degrade peptidoglycan and therefore offer potential as antimicrobial agents. However, the outer membrane (OM) of Gram-negative bacteria impedes the access of externally applied endolysins to peptidoglycan. This review highlights recent advances in the discovery and characterization of natural endolysins that can breach the OM, as well as chemical and engineering approaches that increase antimicrobial efficacy of endolysins against Gram-negative pathogens.
Topics: Anti-Bacterial Agents; Peptidoglycan; Endopeptidases; Anti-Infective Agents; Gram-Negative Bacteria; Bacteriophages
PubMed: 38350268
DOI: 10.1016/j.mib.2024.102433 -
Science Advances Jul 2023Semiconductor-based biointerfaces are typically established either on the surface of the plasma membrane or within the cytoplasm. In Gram-negative bacteria, the...
Semiconductor-based biointerfaces are typically established either on the surface of the plasma membrane or within the cytoplasm. In Gram-negative bacteria, the periplasmic space, characterized by its confinement and the presence of numerous enzymes and peptidoglycans, offers additional opportunities for biomineralization, allowing for nongenetic modulation interfaces. We demonstrate semiconductor nanocluster precipitation containing single- and multiple-metal elements within the periplasm, as observed through various electron- and x-ray-based imaging techniques. The periplasmic semiconductors are metastable and display defect-dominant fluorescent properties. Unexpectedly, the defect-rich (i.e., the low-grade) semiconductor nanoclusters produced in situ can still increase adenosine triphosphate levels and malate production when coupled with photosensitization. We expand the sustainability levels of the biohybrid system to include reducing heavy metals at the primary level, building living bioreactors at the secondary level, and creating semi-artificial photosynthesis at the tertiary level. The biomineralization-enabled periplasmic biohybrids have the potential to serve as defect-tolerant platforms for diverse sustainable applications.
Topics: Periplasm; Biomineralization; Cell Membrane; Cytoplasm; Photosynthesis
PubMed: 37478187
DOI: 10.1126/sciadv.adg5858 -
ACS Infectious Diseases Dec 2023Here, we employed an integrated metabolomics and transcriptomics approach to investigate the molecular mechanism(s) of action of ceftazidime/avibactam against a...
Here, we employed an integrated metabolomics and transcriptomics approach to investigate the molecular mechanism(s) of action of ceftazidime/avibactam against a pan-drug-resistant clinical isolate from a patient with urinary tract infection. Ceftazidime/avibactam induced time-dependent perturbations in the metabolome and transcriptome of the bacterium, mainly at 6 h, with minimal effects at 1 and 3 h. Metabolomics analysis revealed a notable reduction in essential lipids involved in outer membrane glycerolipid biogenesis. This disruption effect extended to peptidoglycan and lipopolysaccharide biosynthetic pathways, including lipid A and -antigen assembly. Importantly, ceftazidime/avibactam not only affected the final steps of peptidoglycan biosynthesis in the periplasm, a common mechanism of ceftazidime action, but also influenced the synthesis of lipid-linked intermediates and early stages of cytoplasmic peptidoglycan synthesis. Furthermore, ceftazidime/avibactam substantially inhibited central carbon metabolism (e.g., the pentose phosphate pathway and tricarboxylic acid cycle). Consistently, the dysregulation of genes governing these metabolic pathways aligned with the metabolomics findings. Certain metabolomics and transcriptomics signatures associated with ceftazidime resistance were also perturbed. Consistent with the primary target of antibiotic activity, biochemical assays also confirmed the direct impact of ceftazidime/avibactam on peptidoglycan production. This study explored the intricate interactions of ceftazidime and avibactam within bacterial cells, including their impact on cell envelope biogenesis and central carbon metabolism. Our findings revealed the complexities of how ceftazidime/avibactam operates, such as hindering peptidoglycan formation in different cellular compartments. In summary, this study confirms the existing hypotheses about the antibacterial and resistance mechanisms of ceftazidime/avibactam while uncovering novel insights, including its impact on lipopolysaccharide formation.
Topics: Humans; Ceftazidime; Klebsiella pneumoniae; Transcriptome; Lipopolysaccharides; Peptidoglycan; Klebsiella Infections; beta-Lactamases; Anti-Bacterial Agents; Gene Expression Profiling; Carbon
PubMed: 37878861
DOI: 10.1021/acsinfecdis.3c00264 -
Frontiers in Cellular and Infection... 2023Most bacteria divide through a highly conserved process called binary fission, in which there is symmetric growth of daughter cells and the synthesis of peptidoglycan at... (Review)
Review
Most bacteria divide through a highly conserved process called binary fission, in which there is symmetric growth of daughter cells and the synthesis of peptidoglycan at the mid-cell to enable cytokinesis. During this process, the parental cell replicates its chromosomal DNA and segregates replicated chromosomes into the daughter cells. The mechanisms that regulate binary fission have been extensively studied in several model organisms, including , and . These analyses have revealed that a multi-protein complex called the divisome forms at the mid-cell to enable peptidoglycan synthesis and septation during division. In addition, rod-shaped bacteria form a multi-protein complex called the elongasome that drives sidewall peptidoglycan synthesis necessary for the maintenance of rod shape and the lengthening of the cell prior to division. In adapting to their intracellular niche, the obligate intracellular bacteria discussed here have eliminated one to several of the divisome gene products essential for binary fission in . In addition, genes that encode components of the elongasome, which were mostly lost as rod-shaped bacteria evolved into coccoid organisms, have been retained during the reductive evolutionary process that some coccoid obligate intracellular bacteria have undergone. Although the precise molecular mechanisms that regulate the division of obligate intracellular bacteria remain undefined, the studies summarized here indicate that obligate intracellular bacteria exhibit remarkable plasticity in their cell division processes.
Topics: Escherichia coli; Peptidoglycan; Bacterial Proteins; Cell Division; Cytokinesis
PubMed: 37876871
DOI: 10.3389/fcimb.2023.1205488 -
Nature Communications Aug 2023Peptidoglycan (PG) is an essential structural component of the bacterial cell wall that is synthetized during cell division and elongation. PG forms an extracellular...
Peptidoglycan (PG) is an essential structural component of the bacterial cell wall that is synthetized during cell division and elongation. PG forms an extracellular polymer crucial for cellular viability, the synthesis of which is the target of many antibiotics. PG assembly requires a glycosyltransferase (GT) to generate a glycan polymer using a Lipid II substrate, which is then crosslinked to the existing PG via a transpeptidase (TP) reaction. A Shape, Elongation, Division and Sporulation (SEDS) GT enzyme and a Class B Penicillin Binding Protein (PBP) form the core of the multi-protein complex required for PG assembly. Here we used single particle cryo-electron microscopy to determine the structure of a cell elongation-specific E. coli RodA-PBP2 complex. We combine this information with biochemical, genetic, spectroscopic, and computational analyses to identify the Lipid II binding sites and propose a mechanism for Lipid II polymerization. Our data suggest a hypothesis for the movement of the glycan strand from the Lipid II polymerization site of RodA towards the TP site of PBP2, functionally linking these two central enzymatic activities required for cell wall peptidoglycan biosynthesis.
Topics: Cryoelectron Microscopy; Escherichia coli; Peptidoglycan; Molecular Biology; Anti-Bacterial Agents; Glycosyltransferases; Peptidyl Transferases
PubMed: 37620344
DOI: 10.1038/s41467-023-40483-8