Biology subjects

Mao, X.

Publications and source records attributed to Mao, X..

At least 73 records · Page 4Linked to original sources

bioRxiv2021

A spatiotemporal steroidogenic regulatory network in human fetal adrenal glands and gonads

Human fetal adrenal glands produce substantial amounts of dehydroepiandrosterone (DHEA), which is one of the most important precursors of sex hormones. However, the underlying biological mechanism remains largely unknown. Herein, we sequenced human fetal adrenal glands and gonads from 7 to 14 GW via the 10x Genomics single-cell transcriptome techniques and reconstructed their location information by Spatial Transcriptome, conducted COOL-seq for the MC2R+ inner zone steroidogenic cells during the time window of sex differentiation (8-12GW). We found that relative to gonads, adrenal glands begin to synthesize steroids early. The coordination among steroidogenic cells and multiple nonsteroidogenic cells promotes adrenal cortex construction and steroid synthesis. Notably, during the time window of sex differentiation (8-12 GW), key enzyme gene expression shifts to accelerate DHEA synthesis in males and cortisol synthesis in females. Furthermore, high SST+ expressions in the adrenal gland and testis amplify androgen synthesis in males. Our research highlights the robustness of the action of fetal adrenal glands on gonads to modify the process of sexual differentiation.

systems biology↗

bioRxiv2021

Structural Basis of Substrate Recognition by the Mitochondrial ADP/ATP Transporter

Specific import of ADP and export of ATP by ADP/ATP carrier (AAC) across the inner mitochondrial membrane are crucial for sustainable energy supply in all eukaryotes. However, mechanism for highly specific substrate recognition in the dynamic transport process remains largely elusive. Here, unguided MD simulations of 22 microseconds in total reveal that AAC in ground c-state uses the second basic patch (K91K95R187), tyrosine ladder (Y186Y190Y194), F191 and N115 in the upper region of the cavity to specifically recognize ADP and confer selectivity for ADP over ATP. Mutations of these residues in yeast AAC2 reduce ADP transport across the L. lactis membrane and induce defects in OXPHOS and ATP production in yeast. Sequence analyses also suggest that AAC and other adenine nucleotide transporters use the upper region of the cavity, rather than the central binding site to discriminate their substrates. Identification of the new site unveils the unusually high substrate specificity of AAC, and together with central binding site support early biochemical findings about existence of two substrate binding sites. Our results imply that using different sites for substrate recognition and conformational transition could be a smart strategy for transporters to cope with substrate recognition problem in the highly dynamic transport process.

biophysics↗

bioRxiv2021

Bacterial DNA on the skin surface overrepresents the viable skin microbiome

The skin microbiome provides vital contributions to human health. However, the spatial organization and viability of its bacterial components remain unclear. Here we apply culturing, imaging, and molecular approaches to human and mouse skin samples, and find that the skin surface is colonized by fewer viable bacteria than predicted by bacterial DNA levels. Instead, viable skin-associated bacteria are predominantly located in hair follicles and other cutaneous invaginations. Furthermore, we show that the skin microbiome has a uniquely low fraction of viable bacteria as compared to other human microbiome sites, indicating that most bacterial DNA on the skin surface is not associated with viable cells Additionally, a small number of bacterial families dominate each skin site and traditional sequencing methods overestimate both the richness and diversity of the skin microbiome. Finally, we performed an in-vivo skin microbiome perturbation-recovery study using human volunteers. Bacterial 16S rRNA gene sequencing revealed that, while the skin microbiome is remarkably stable even in the wake of aggressive perturbation, repopulation of the skin surface is driven by the underlying viable population. Our findings help explain the dynamics of skin microbiome perturbation, as bacterial DNA on the skin surface can be transiently perturbed but is replenished by a stable underlying viable population. These results address multiple outstanding questions in skin microbiome biology with significant implications for future efforts to study and manipulate it. Significance statementThis study provides a crucial update to the skin microbiome paradigm by showing that viable bacteria of the skin microbiome are primarily localized to hair follicles and other sub-cutaneous structures rather than the skin surface. The native distribution of skin-associated bacteria has not been previously evaluated, and here we show that the skin surface has few intact bacteria while deeper structures are replete with bacterial contents. We used orthogonal approaches to evaluate the source of bacterial DNA and the dynamics of bacterial repopulation on the skin surface to develop an updated model of the skin microbiome. By adjusting the current understanding of the skin microbiome to match this model, we will be able to address outstanding questions in the field.

microbiology↗

bioRxiv2021

Neurotoxins subvert the allosteric activation mechanism of SARM1 to induce neuronal loss

SARM1 is an inducible TIR-domain NAD+ hydrolase that mediates pathological axon degeneration. SARM1 is activated by an increased ratio of NMN to NAD+, which competes for binding to an allosteric activating site. When NMN binds, the TIR domain is released from autoinhibition, activating its NAD+ hydrolase activity. The discovery of this allosteric activating site led us to hypothesize that other NAD+-related metabolites might also activate SARM1. Here we show that the nicotinamide analogue 3-acetylpyridine (3-AP), first identified as a neurotoxin in the 1940s, is converted to 3-APMN which activates SARM1 and induces SARM1-dependent NAD+ depletion, axon degeneration and neuronal death. Systemic treatment with 3-AP causes rapid SARM1-dependent death, while local application to peripheral nerve induces SARM1-dependent axon degeneration. We also identify a related pyridine derivative, 2-aminopyridine, as another SARM1-dependent neurotoxin. These findings identify SARM1 as a candidate mediator of environmental neurotoxicity, and furthermore, suggest that SARM1 agonists could be developed into selective agents for neurolytic therapy.

neuroscience↗

bioRxiv2021

New cellular models of undifferentiated pleomorphic sarcoma and malignant peripheral nerve sheath tumor

Undifferentiated pleomorphic sarcoma (UPS) and malignant peripheral nerve sheath tumor (MPNST) are aggressive soft tissue sarcomas that do not respond well to current treatment modalities. The limited availability of UPS and MPNST cell lines makes it challenging to identify potential therapeutic targets in a laboratory setting. Understanding the urgent need for improved treatments for these tumors and the limited cellular models led us to generate additional cell lines to study these rare cancers further. Patient-derived tumors were used to establish 5 new UPS models, including one radiation-associated UPS--UPS060.1, UPS271.1, UPS511, UPS0103, and RIS620--and 3 new models of MPNST--MPNST007, MPNST3813E, and MPNST4970. This study examined the utility of the new cell lines as sarcoma models by assessing tumorigenic potential and mutation status for known sarcoma-related genes. All the cell lines formed colonies and migrated in vitro. The in vivo tumorigenic potential of each cell line was determined by either subcutaneous injection of cells or implantation of tumor tissue into immunocompromised mice. UPS060.1, UPS271.1, and UPS511 cells formed tumors in mice upon subcutaneous injection. UPS0103 and RIS620 tumor implants formed tumors in vivo, as did MPNST007 and MPNST3813E tumor implants. Mutation analysis of a panel of genes frequently mutated in sarcomas showed that two of the three MPNST cell lines had NF1 mutations. Two of the three MPNST cell lines had mutations in polycomb repressive complex 2 members. These new cellular models provide the scientific community with powerful tools for detailed studies of sarcomagenesis and investigate novel therapies for UPS and MPNST.

cancer biology↗

bioRxiv2021

Edaravone activates the GDNF/RET neurotrophic signaling pathway and protects mRNA-induced motor neurons from iPS cells.

BackgroundSpinal cord motor neurons (MNs) from human iPS cells (iPSCs) have wide applications in disease modeling and therapeutic development for amyotrophic lateral sclerosis (ALS) and other MN-associated neurodegenerative diseases. We need highly efficient MN differentiation strategies for generating iPSC-derived disease models that closely recapitulate the genetic and phenotypic complexity of ALS. An important application of these models is to understand molecular mechanisms of action of FDA-approved ALS drugs that only show modest clinical efficacy. Novel mechanistic insights will help us design optimal therapeutic strategies together with predictive biomarkers to achieve better efficacy. MethodsWe induce efficient MN differentiation from iPSCs in 4 days using synthetic mRNAs coding two transcription factors (Ngn2 and Olig2) with phosphosite modification. These MNs after extensive characterization were applied in electrophysiological and neurotoxicity assays as well as transcriptomic analysis, to study the neuroprotective effect and molecular mechanisms of edaravone, an FDA-approved drug for ALS, for improving its clinical efficacy. ResultsWe generate highly pure and functional mRNA-induced MNs (miMNs) from normal and ALS iPSCs, as well as embryonic stem cells. Edaravone alleviates H2O2-induced neurotoxicity and electrophysiological dysfunction in miMNs, demonstrating its neuroprotective effect that was also found in the glutamate-induced miMN neurotoxicity model. Guided by the transcriptomic analysis, we show a previously unrecognized effect of edaravone to induce the GDNF receptor RET and the GDNF/RET neurotrophic signaling in vitro and in vivo, suggesting a clinically translatable strategy to activate this key neuroprotective signaling. Notably, edaravone can replace required neurotrophic factors (BDNF and GDNF) to support long-term miMN survival and maturation, further supporting the neurotrophic function of edaravone-activated signaling. Furthermore, we show that edaravone and GDNF combined treatment more effectively protects miMNs from H2O2-induced neurotoxicity than single treatment, suggesting a potential combination strategy for ALS treatment. ConclusionsThis study provides methodology to facilitate iPSC differentiation and disease modeling. Our discoveries will facilitate the development of optimal edaravone-based therapies for ALS and potentially other neurodegenerative diseases. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/443325v2_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@cd0bc9org.highwire.dtl.DTLVardef@1c0c0b6org.highwire.dtl.DTLVardef@1ac0952org.highwire.dtl.DTLVardef@1980f5b_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2021

Aplp1 and the Aplp1-Lag3 Complex facilitates transmission of pathologic alpha-synuclein

Pathologic -synuclein (-syn) spreads from cell-to-cell, in part, through binding to the lymphocyte-activation gene 3 (Lag3). Here we report that amyloid {beta} precursor-like protein 1 (Aplp1) forms a complex with Lag3 that facilitates the binding, internalization, transmission, and toxicity of pathologic -syn. Deletion of both Aplp1 and Lag3 eliminates the loss of dopaminergic neurons and the accompanying behavioral deficits induced by -syn preformed fibrils (PFF). Anti-Lag3 prevents the internalization of -syn PFF by disrupting the interaction of Aplp1 and Lag3, and blocks the neurodegeneration induced by -syn PFF in vivo. The identification of Aplp1 and the interplay with Lag3 for -syn PFF induced pathology advances our understanding of the molecular mechanism of cell-to-cell transmission of pathologic -syn and provides additional targets for therapeutic strategies aimed at preventing neurodegeneration in Parkinsons disease and related -synucleinopathies. One Sentence SummaryAplp1 forms a complex with Lag3 that facilitates the binding, internalization, transmission, and toxicity of pathologic -synuclein. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=94 SRC="FIGDIR/small/442157v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1d746bforg.highwire.dtl.DTLVardef@65acb2org.highwire.dtl.DTLVardef@12cf2f0org.highwire.dtl.DTLVardef@19d6e_HPS_FORMAT_FIGEXP M_FIG Aplp1 and the Aplp1-Lag3 complex facilitates transmission of pathologic -synuclein. Aplp1 is a receptor that drives pathologic -syn transmission, and genetic depletion of Aplp1 can significantly reduce the -synuclein pathogenesis. Aplp1 and Lag3 forms an Aplp1-Lag3 complex that accounts for substantial binding of pathologic -syn to cortical neurons. Together Aplp1 and Lag3 play a major role in pathologic -syn internalization, transmission and toxicity. Double knockout of Aplp1 and Lag3 and or a Lag3 antibody that disrupts the Aplp1 and Lag3 complex almost completely blocks -syn PFF-induced neurodegeneration. C_FIG

neuroscience↗

bioRxiv2021

Constitutively active SARM1 variants found in ALS patients induce neuropathy

In response to injury, neurons activate a program of organized axon self-destruction initiated by the NAD+ hydrolase SARM1. In healthy neurons SARM1 is autoinhibited, but single amino acid changes can abolish autoinhibition leading to constitutively-active SARM1 enzymes that promote degeneration when expressed in cultured neurons. To investigate whether naturally-occurring human variants might similarly disrupt SARM1 autoinhibition and potentially contribute to risk for neurodegenerative disease, we assayed the enzymatic activity of 29 rare SARM1 alleles identified among 8,507 amyotrophic lateral sclerosis (ALS) patients. Ten missense variants or small in-frame deletions exhibit constitutive NADase activity, including more than half of those that are unique to the ALS patients or that occur in multiple patients. Expression of these constitutively active ALS-associated SARM1 alleles in cultured dorsal root ganglion (DRG) neurons is pro-degenerative and cytotoxic. Intrathecal injection of an AAV expressing the common SARM1 reference allele is innocuous to mice, but a construct harboring SARM1V184G, the constitutively active variant found most frequently in the ALS patients, causes axon loss, motor dysfunction, and sustained neuroinflammation. These results implicate rare hypermorphic SARM1 alleles as candidate genetic risk factors for ALS and other neurodegenerative conditions.

neuroscience↗

bioRxiv2021

The histologic phenotype of lung cancers may be driven by transcriptomic features rather than genomic characteristics

Histology plays an essential role in therapeutic decision-making for lung cancer patients. However, the molecular determinants of lung cancer histology are largely unknown. We conducted whole-exome sequencing(WES) and microarray profiling on 19 micro-dissected tumor regions of different histologic subtypes from 9 patients with lung cancers of mixed histology. A median of 68.9% of point mutations and 83% of copy number aberrations were shared between different histologic components within the same tumors. Furthermore, different histologic components within the tumors demonstrated similar subclonal architecture. On the other hand, transcriptomic profiling revealed shared pathways between the same histologic subtypes from different patients, which was supported by the analyses of the transcriptomic data from 141 cell lines and 343 lung cancers of different histologic subtypes. These data suggest that histology of lung cancers may be determined at the transcriptomic level rather than the genomic level.

genomics↗

bioRxiv2020

The jasmine (Jasminum sambac) genome and flower fragrances

Jasminum sambac, a world-renowned plant appreciated for its exceptional flower fragrance, is of cultural and economic importance. However, the genetic basis of its fragrance is largely unknown. Here, we present the first de novo genome of J. sambac with 550.12 Mb (scaffold N50 = 40.1 Mb) assembled into 13 pseudochromosomes. Terpene synthase genes associated with flower fragrance are significantly amplified in the form of gene clusters through tandem duplications in the genome. Eleven homolog genes within the SABATH super-family were identified as related to phenylpropanoid/benzenoid compounds. Several key genes regulating jasmonate biosynthesis were duplicated causing increased copy numbers. Furthermore, multi-omics analyses identified various aromatic compounds and the key genes involved in fragrance biosynthesis pathways. Our genome of J. sambac offers a basic genetic resource for studying floral scent biosynthesis and provides an essential foundation for functional genomic research and variety improvements in Jasminum.

plant biology↗

bioRxiv2020

Barnacle-Inspired Paste for Instant Hemostatic Tissue Sealing

Whilst sealing damaged tissues by adhesives has potential advantages over suturing or stapling, existing tissue adhesives cannot form rapid or robust adhesion on tissues covered with body fluids such as blood. In contrast, the glues of barnacles, consisting of a lipid-rich matrix and adhesive proteins, and can strongly adhere to wet and contaminated surfaces. Here we report a barnacle-inspired paste capable of forming instant robust hemostatic sealing of diverse tissues. The paste is composed of a hydrophobic oil matrix and bioadhesive microparticles to implement the barnacle-inspired mechanism to repel blood through the hydrophobic matrix. Subsequently, the bioadhesive microparticles crosslink with underlying tissues under gentle pressure. The barnacle-inspired paste can provide tough (interfacial toughness over 300 J m-2) and strong (shear and tensile strength over 70 kPa, burst pressure over 350 mmHg) hemostatic sealing of a broad range of tissues within five seconds. We validate in vitro and in vivo biocompatibility and biodegradability of the barnacle-inspired paste in rodent models. We further demonstrate potential applications of the barnacle-inspired paste for instant hemostatic sealing in ex vivo porcine aorta, in vivo rat liver and heart models.

bioengineering↗

bioRxiv2020

A fish-specific new gene evolves new functions in cichlid fishes

Deciphering why some lineages produce spectacular radiations while others do not provides important insights into biodiversity, but the molecular basis underlying this process remains largely unknown. Here, we identified a lineage-restricted gene, which we named lg. Combined omics analyses showed that lg is under positive selection in the most species-rich lineage of cichlid fishes, the modern haplochromine (MH) lineage, indicating its evolutionary advantage. Using transgenic zebrafish, we functionally showed that a cichlid fish-specific upstream insertion of lg can drive new and strong eGFP expression in tissues noted for adaptation in the MH lineage, but not in other lineages. Furthermore, the deletion of three MH-specific SNPs within this region can reconstitute weak and limited expression patterns similar to those in non-MH lineages. We thus demonstrated that a series of cis-regulatory changes in an advantageous gene are linked with a gain of expression that is related to an astonishingly adaptive radiative lineage.

evolutionary biology↗

bioRxiv2020

Luteolin transforms the BMDM polarity to regulate the expression of inflammatory factors

ABSTRACTMacrophage are indispensable regulator cells in inflammatory response. Macrophage polarization and its secreted inflammatory factors have affinity with the outcomes of inflammation. Luteolin, a flavonoid abundant in plants has anti-inflammatory activity, but whether luteolin can manipulate M1/M2 polarization of BMDM to suppress inflammation is still veiled. The purpose of this study was to observe the effects of luterolin on the polarity of BMDM derived from C57BL/6 mice and the expression of inflammatory factors, to explore the mechanism of luteolin regulating the BMDM polarity. M1-polarized BMDM were induced by LPS+IFN-γ, M2-polarization were stimulated with IL-4. BMDM morphology was observed by laser confocal microscopy; levels of BMDM differentiation and CD11c or CD206 on membrane surface were assessed by FCM; mRNA and protein of M1/M2-type inflammatory factors were performed by qPCR and ELISA, respectively; the expression of p-STAT1 and p-STAT6 protein pathways was detected by Western-blotting. The isolated mouse bone marrow cells were successfully differentiated into BMDM, LPS+IFN-γ induced BMDM M1-phenotype polarization, and IL-4 induced its M2-phenotype polarization. After M1-polarized BMDM treated with luteolin, M1-type pro-inflammatory factors including IL-6, TNF-α□iNOS, CD86 were down-regulated while M2-type anti-inflammatory factors including IL-10, Arg1, CD206 were up-regulated; the expression of M1-type surface marker CD11c decreased, nevertheless, M2-type marker CD206 increased; levels of inflammatory signaling protein p-STAT1 and p-STAT6 were attenuated and enhanced respectively. Our study suggests luteolin may transform BMDM polarity through p-STAT1/6 to regulate the expression of inflammatory mediators, thereby inhibiting inflammation. Naturally occurring luteolin hold promise as an anti-inflammatory and immunomodulatory agent.View Full Text

immunology↗

bioRxiv2020

Population genetics of sugar kelp in the Northwest Atlantic region using genome-wide markers

An assessment of genetic diversity of marine populations is critical not only for the understanding and preservation of natural biodiversity but also for its economic potential. As commercial demand rises for marine resources, it is critical to generate baseline information for monitoring wild populations. Furthermore, anthropogenic stressors on the coastal environment, such as warming sea surface temperatures and overharvesting of wild populations, are leading to the destruction of keystone marine species such as kelps. In this study, we conducted a fine-scale genetic analysis using genome-wide high-density markers on Northwest Atlantic sugar kelp species, Saccharina latissima and putative species, Saccharina angustissima. The population structure for a total of 149 samples from the Gulf of Maine (GOM) and Southern New England (SNE) was investigated using AMOVA, Fst, admixture, and PCoA. Genome-wide association analyses were conducted for six morphological traits, and the extended Lewontin and Krakauer (FLK) test was used to detect selection signatures. Our results indicate that the GOM region is moderately more heterogeneous than SNE. While admixture was observed between regions, these results confirm that Cape Cod acts as a biogeographic barrier for sugar kelp gene flow. We detected one significant SNP (P-value=2.03x10-7) associated with stipe length, and 243 SNPs with higher-than-neutral differentiation. The findings of this study provide fundamental knowledge on sugar kelp population genetics for future monitoring, managing and potentially restoring wild populations, as well as assisting in selective breeding to improve desirable traits for cultivation and bioenergy production.

genetics↗

bioRxiv2019

Bacteriological Monitoring and Evaluation of Cleaning-disinfection of Computer-related Equipment in an Obstetric and Gynecology Hospital

It is already known that computer keyboards and mouses in hospitals are contaminated with different kinds of bacteria. However, the mouse pad has been neglected with regard to both research and regular cleaning and disinfection in hospitals. In our study, we monitored and evaluated the bacteriology degrees of 74 computers keyboards, mouses and mouse pads from six departments. The results showed that before cleaning-disinfection, the contamination rate of the mouse pad ranked second following the keyboards. Enterococcus Faecium was cultured from the mouse pads. The computer-related equipment in the wards and outpatient rooms were much more contaminated than that in the operating rooms. Acinetobacter spp. was only isolated from the doctors computers. After cleaning-disinfection, 4 strains of MRSA were isolated from the keyboards and the mouses, one and 3 were cultured at day 3 and day 5 after cleaning-disinfection, respectively. One strain of Pseudomonas Aeruginosa was isolated from the mouses at day 3 after cleaning-disinfection. These demonstrated that the bacterial contamination of the mouse pads must be as emphasized as that of the keyboards and mouses. Furthermore, It is better to clean and disinfect the computer-related equipment(keyboards, mouses, mouse pads) at least once a day.

scientific communication and education↗

bioRxiv2019

Why does a flying fish taxi on sea surface before take-off? A hydrodynamic interpretation

Flying fish have been observed jumping out of warm ocean waters worldwide. Before take-off, the flying fish are seen to taxi on the water surface by rapidly beating their semi-submerged tail fins, which process may help them airborne with enough speed to glide over a long distance. To understand the underlying physical mechanisms, here, we study a flying fish, 0.25 m in length and 0.191 kg in weight, considering both its underwater swimming and surface taxiing locomotion. Its hydrodynamic characteristics are numerically studied by computational fluid dynamics (CFD). Underwater, the fish is assumed to swim at a constant speed of 10 m s-1. Different critical frequencies are identified for various maximum deflected angles, ranging from{theta} 0 = 10{degrees} to 30{degrees}, at which the fish reaches cruising states, when the horizontal forces are balanced. The corresponding minimum power required for cruising swimming is 350 W, obtained at a deflected angle of 10{degrees} and a critical frequency of 145 Hz. In contrast, in the taxiing stage, the minimum power required for a stead-state locomotion at 10 m s-1 is 36 W, occurring at a deflected angle of 15{degrees} and a frequency of 50 Hz. We note that the power is significantly smaller than the swimming locomotion. Further, by increasing the flapping power, we find that larger speeds can be achieved. In specific, when the power is brought up to 350 W, it can reach a speed of 16.5 m s-1. Clearly, from the direct comparison between the two locomotive modes, it is apparently evidenced that the flying fish can be further accelerated by taxiing along the water surface.

zoology↗

bioRxiv2019

Comparative investigation into formycin A and pyrazofurin A biosynthesis reveals branch pathways for the construction of C-nucleoside scaffolds

Formycin A (FOR-A) and pyrazofurin A (PRF-A) are purine-related C-nucleoside antibiotics, in which ribose and a pyrazole-derived base are linked by a C-glycosidic bond, however, the logic underlying the biosynthesis of these molecules has remained largely unexplored. Here, we report the discovery of the pathways for FOR-A and PRF-A biosynthesis from diverse actinobacteria, and demonstrate that their biosynthesis is initiated by a lysine N6-monooxygenase. Moreover, we show that the forT and prfE (individually related to FOR-A and PRF-A biosynthesis) mutants are correspondingly capable of accumulating the unexpected pyrazole-related intermediates, compound 11 and 9a. We also decipher the enzymatic basis of ForT/PrfE for the C-glycosidic bond formation in FOR-A/PRF-A biosynthesis. To our knowledge, ForT/PrfE represents the first example of {beta}-RFA-P ({beta}-ribofuranosyl-aminobenzene 5-phosphate) synthase-like enzymes governing C-nucleoside scaffold construction in natural product biosynthesis. These data establish a foundation for combinatorial biosynthesis of related purine nucleoside antibiotics, and also open the way for target-directed genome mining of PRF-A/FOR-A related antibiotics.\n\nIMPORTANCEFormycin A (FOR-A) and pyrazofurin A (PRF-A) are well known for their unusual chemical structures and remarkable biological activities. Actually, deciphering FOR-A/PRF-A biosynthesis will not only expand biochemical repertoire for novel enzymatic reactions, but also permit the target-oriented genome mining of FOR-A/PRF-A related C-nucleoside antibiotics.

biochemistry↗

bioRxiv2019

Mechanical stress compromises multicomponent efflux complexes in bacteria

Physical forces have long been recognized for their effects on the growth, morphology, locomotion, and survival of eukaryotic organisms1. Recently, mechanical forces have been shown to regulate processes in bacteria, including cell division2, motility3, virulence4, biofilm initiation5,6, and cell shape7,8, although it remains unclear how mechanical forces in the cell envelope lead to changes in molecular processes. In Gram-negative bacteria, multicomponent protein complexes that form rigid links across the cell envelope directly experience physical forces and mechanical stresses applied to the cell. Here we manipulate tensile and shear mechanical stress in the bacterial cell envelope and use single-molecule tracking to show that shear (but not tensile) stress within the cell envelope promotes disassembly of the tripartite efflux complex CusCBA, a system used by E. coli to resist copper and silver toxicity, thereby making bacteria more susceptible to metal toxicity. These findings provide the first demonstration that mechanical forces, such as those generated during colony overcrowding or bacterial motility through submicron pores, can inhibit the contact and function of multicomponent complexes in bacteria. As multicomponent, trans-envelope efflux complexes in bacteria are involved in many processes including antibiotic resistance9, cell division10, and translocation of outer membrane components11, our findings suggest that the mechanical environment may regulate multiple processes required for bacterial growth and survival.

biophysics↗