Selective disrupted gray matter volume covariance of amygdala subregions in schizophrenia.

Objective: Although extensive structural and functional abnormalities have been reported in schizophrenia, the gray matter volume (GMV) covariance of the amygdala remain unknown. The amygdala contains several subregions with different connection patterns and functions, but it is unclear whether the GMV covariance of these subregions are selectively affected in schizophrenia. Methods: To address this issue, we compared the GMV covariance of each amygdala subregion between 807 schizophrenia patients and 845 healthy controls from 11 centers. The amygdala was segmented into nine subregions using FreeSurfer (v7.1.1), including the lateral (La), basal (Ba), accessory-basal (AB), anterior-amygdaloid-area (AAA), central (Ce), medial (Me), cortical (Co), corticoamygdaloid-transition (CAT), and paralaminar (PL) nucleus. We developed an operational combat harmonization model for 11 centers, subsequently employing a voxel-wise general linear model to investigate the differences in GMV covariance between schizophrenia patients and healthy controls across these subregions and the entire brain, while adjusting for age, sex and TIV. Results: Our findings revealed that five amygdala subregions of schizophrenia patients, including bilateral AAA, CAT, and right Ba, demonstrated significantly increased GMV covariance with the hippocampus, striatum, orbitofrontal cortex, and so on (permutation test, P< 0.05, corrected). These findings could be replicated in most centers. Rigorous correlation analysis failed to identify relationships between the altered GMV covariance with positive and negative symptom scale, duration of illness, and antipsychotic medication measure. Conclusion: Our research is the first to discover selectively impaired GMV covariance patterns of amygdala subregion in a large multicenter sample size of patients with schizophrenia.

Microalgae Octapeptide IIAVEAGC Alleviates Oxidative Stress and Neurotoxicity in 6-OHDA-Induced SH-SY5Y Cells by Regulating the Nrf2/HO-1and Jak2/Stat3 Pathways.

Neurodegenerative diseases are characterized by the progressive loss of selectively vulnerable populations of neurons, and many factors are involved in its causes. Neurotoxicity and oxidative stress, are the main related factors. The octapeptide Ile-Ile-Ala-Val-Glu-Ala-Gly-Cys (IEC) was identified from the microalgae Isochrysis zhanjiangensis and exhibited potential anti-oxidative stress activity. In this study, the stability of α-synaptic protein binding to IEC was modeled using molecular dynamics, and the results indicated binding stabilization within 60 ns. Oxidative stress in neurons is the major cause of α-synaptic protein congestion. Therefore, we next evaluated the protective effects of IEC against oxidative stress and neurotoxicity in 6-ohdainduced Parkinson's disease (PD) model SH-SY5Y cells in vitro. In oxidative stress, IEC appeared to increase the expression of the antioxidant enzymes HO-1 and GPX through the antioxidant pathway of Nrf2, and molecular docking of IEC with Nrf2 and GPX could generate hydrogen bonds. Regarding apoptosis, IEC protected cells by increasing the Bcl-2/Bax ratio, inhibiting the caspase cascade, acting on p53, and modulating the Jak2/Stat3 pathway. The results indicated that IEC exerted neuroprotective effects through the inhibition of α-synaptic protein aggregation and antioxidant activity. Therefore, microalgal peptides have promising applications in the prevention and treatment of neurodegenerative diseases.

Neuroprotection of Truncated Peptide IIAVE from Isochrysis zhanjiangensis: Quantum Chemical, Molecular Docking, and Bioactivity Studies.

Parkinson's disease (PD) is a progressive neurodegenerative disorder of the elderly for which there is no cure or disease-modifying therapy. Mitochondrial dysfunction and oxidative stress play a central role in dopaminergic neurodegeneration in PD. Therefore, antioxidants are considered a promising neuroprotective approach. In in vivo activity studies, 6-OHDA-induced oxidative stress in SH-SY5Y cells was established as a model of PD for cellular experiments. IIAVE (Ile-Ile-Ala-Val-Glu) was derived from Isochrysis zhanjiangensis octapeptide (IIAVEAGC), which has a small molecular weight. The structure and antioxidant activity of IIAVE were tested in a previous study and proved to have good antioxidant potential. In this study, the chemical properties of IIAVE were calculated using quantum chemical methods, including frontier molecular orbital (FMO), molecular electrostatic potential (MEP), natural population analysis (NPA), and global reactivity properties. The interaction of IIAVE with Bcl-2 and DJ-1 was investigated using the molecular docking method. The results showed that IIAVE promoted the activation of the Keap1/Nrf2 pathway and up-regulated the expression of the superoxide dismutase 1 (SOD-1) protein by inhibiting the level of reactive oxygen species (ROS) in cells. In addition, IIAVE inhibits ROS production and prevents 6-OHDA-induced oxidative damage by restoring mitochondrial membrane potential. Furthermore, IIAVE inhibited cell apoptosis by increasing the Bcl-2/Bax ratio and inhibiting the activation of Caspase-9 and Caspase-3. Thus, IIAVE may become a potential drug for the treatment and prevention of PD.

Individualized Texture Similarity Network in Schizophrenia.

BACKGROUND: Structural covariance network disruption has been considered an important pathophysiological indicator for schizophrenia. Here, we introduced a novel individualized structural covariance network measure, referred to as a texture similarity network (TSN), and hypothesized that the TSN could reliably reveal unique intersubject heterogeneity and complex dysconnectivity patterns in schizophrenia. METHODS: The TSN was constructed by measuring the covariance of 180 three-dimensional voxelwise gray-level co-occurrence matrix feature maps between brain areas in each participant. We first tested the validity and reproducibility of the TSN in characterizing the intersubject variability in 2 longitudinal test-retest healthy cohorts. The TSN was further applied to elucidate intersubject variability and dysconnectivity patterns in 10 schizophrenia case-control datasets (609 schizophrenia cases vs. 579 controls) as well as in a first-episode depression dataset (69 patients with depression vs. 69 control participants). RESULTS: The test-retest analysis demonstrated higher TSN intersubject than intrasubject variability. Moreover, the TSN reliably revealed higher intersubject variability in both chronic and first-episode schizophrenia, but not in depression. The TSN also reproducibly detected coexistent increased and decreased TSN strength in widespread brain areas, increased global small-worldness, and the coexistence of both structural hyposynchronization in the central networks and hypersynchronization in peripheral networks in patients with schizophrenia but not in patients with depression. Finally, aberrant intersubject variability and covariance strength patterns revealed by the TSN showed a missing or weak correlation with other individualized structural covariance network measures, functional connectivity, and regional volume changes. CONCLUSIONS: These findings support the reliability of a TSN in revealing unique structural heterogeneity and complex dysconnectivity in patients with schizophrenia.

Spectrum-Weighted Fusion Cooperative Detection Algorithm Based on Double Thresholds for Underwater Acoustic Networks.

Spectrum-sensing technology is crucial for the development of underwater acoustic communication networks and plays a key role in detecting spectrum holes and channel occupancy. Energy detection technology, as the fundamental spectrum sensing technology in cognitive radio, has reached a mature level of development. Its application in hydroacoustic communications can significantly enhance the utilization of the hydroacoustic spectrum. However, due to the complexity of the hydroacoustic channel compared with that of the radio channel, the traditional double-threshold energy detection technique faces challenges such as fixed threshold values and limited flexibility. To address this, we propose a model for the hydroacoustic channel that incorporates a weight factor based on the signal-to-noise ratio in the algorithm. This allows for adaptive threshold values based on the user's signal-to-noise environment, reducing false detection rates and improving overall detection performance. Through simulation experiments and comparisons, our proposed signal-to-noise weighted collaborative spectrum-sensing technique demonstrates superior detection performance compared with other spectrum-sensing techniques.

Activated carbon modified titanium dioxide/bismuth trioxide adsorbent: One-pot synthesis, high removal efficiency of organic pollutants, and good recyclability.

Considerable endeavors have focused on tightly combining adsorption with photocatalysis in designing composite materials for environmental pollution treatment. Recent advances in coupling titanium dioxide/bismuth trioxide (TiO2/Bi2O3) with activated carbon (AC) show significantly enhanced photocatalytic performance but face critical limitations including low adsorption capacity and multi-step synthesis. In this work, we introduce a one-pot synthesis of activated carbon modified TiO2/Bi2O3 composite materials (TiO2/Bi2O3/AC). Thanks to the integrated adsorbent/photocatalyst system, TiO2/Bi2O3/AC shows a drastically enhanced removal efficiency for sulfamethazine (>81%), far beyond the corresponding value of the reported AC/TiO2/Bi2O3 adsorbent (<40%). Notably, the removal rates of other typical pollutants including tetracyclines, methyl orange, and rhodamine B are as high as >98%. Furthermore, TiO2/Bi2O3/AC obtains >80% of its adsorption rate for the fifth cycle after simple photo-regeneration without any other post-treatments. Kinetic analysis and photoelectric characterization are carried out to provide insight into adsorption mechanism. Therefore, this work demonstrates a considerable potential to design and construct other multifunctional adsorbents with advanced performance.

Research Progress of Treatment Technology and Adsorption Materials for Removing Chromate in the Environment.

Cr is used extensively in industry, so the number of Cr (VI) hazards is increasing. The effective control and removal of Cr (VI) from the environment are becoming an increasing research priority. In order to provide a more comprehensive description of the research progress of chromate adsorption materials, this paper summarizes the articles describing chromate adsorption in the past five years. It summarizes the adsorption principles, adsorbent types, and adsorption effects to provide methods and ideas to solve the chromate pollution problem further. After research, it is found that many adsorbents reduce adsorption when there is too much charge in the water. Besides, to ensure adsorption efficiency, there are problems with the formability of some materials, which impact recycling.

Mechanisms of Antitumor Invasion and Metastasis of the Marine Fungal Derivative Epi-Aszonalenin A in HT1080 Cells.

Epi-aszonalenin A (EAA) is an alkaloid that is isolated and purified from the secondary metabolites of coral symbiotic fungi and has been shown to have good atherosclerotic intervention activity and anti-angiogenic activity in our previous studies. In the present study, antiangiogenic activity was used as a basis of an intensive study of its mechanism of action against tumor metastasis and invasion. Invasive metastatic pairs are a hallmark of malignancy, and the dissemination of tumor cells is the most dangerous process in the development of tumors. The results of cell wound healing and the Transwell chamber assay showed that EAA interfered well with PMA-induced migration and invasion of HT1080 cells. Western blot and the ELISA assay showed that EAA decreased MMPs and vascular endothelial growth factor (VEGF) activity and inhibited the expression of N-cadherin and hypoxia-inducible factor-1α (HIF-1α) by regulating the phosphorylation of downstream mitogen-activated protein kinase (MAPK), PI3K/AKT, and NF-κB pathways. Simultaneous molecular docking results revealed that the mimic coupling between the EAA and MMP-2/-9 molecules formed a stable interaction. The results of this study provide a research basis for the inhibition of tumor metastasis by EAA, and together with previous studies, confirm the potential pharmacology and drug potential for this class of compound for application in angiogenesis-related diseases and further improve the availability of coral symbiotic fungi.

Comparative in silico and in vitro study of the stability and biological activity of an octapeptide from microalgae Isochrysis zhanjiangensis and its truncated short peptide.

In this study, the structural characteristics and active sites of the octapeptide (IIAVEAGC), the pentapeptide (IIAVE) and tripeptide (AGC) were studied in silica and in vitro. The quantum mechanics results show that the pentapeptide has better structural features. In addition, the docking of three peptides with Keap1 was compared through molecular docking, indicating that the potential molecular mechanism may show antioxidant activity by occupying the Nrf2 binding site on Keap1. The above results are consistent with the cell (SH-SY5Y cell) experiment. In the cell experiment, the three peptides can reduce the damage of hydrogen peroxide to cells under a non-toxic effect. Among them, pentapeptide has better activity than the other two peptides, and can inhibit the production of reactive oxygen species and reduce the potential damage to the mitochondrial membrane. Interestingly, these three peptides can promote the nuclear expression of Nrf2 and inhibit the PI3K, MAPK, and NF-κB signaling pathways' corresponding influence, but their influence degree is different. This study can provide a theoretical basis for the structure-activity relationship of the active peptide, and also broaden the field of vision for the application of the polypeptide from the microalgal Isochrysis zhanjiangensis in food.

Research Progress on Up-Conversion Fluorescence Probe for Detection of Perfluorooctanoic Acid in Water Treatment.

Perfluorooctanoic acid (PFOA) is a new type of organic pollutant in wastewater that is persistent, toxic, and accumulates in living organisms. The development of rapid and sensitive analytical methods to detect PFOA in environmental media is of great importance. Fluorescence detection has the advantages of high efficiency and low cost, in which fluorescent probes have excellent fluorescence properties, excellent bio-solubility, and remarkable photostability. It is necessary to review the fluorescence detection routes for PFOA. In addition, the up-conversion of fluorescent materials (UCNPs), as fluorescent materials to prepare fluorescent probes with, has significant advantages and also attracts the attention of researchers, however, reviews related to their application in detecting PFOA and comparing them with other routes are rare. Furthermore, there are many strategies to improve the performance of up-conversion fluorescent probes including SiO2 modification and amino modification. These strategies can enhance the detection effect of PFOA. Thus, this work reviews the types of fluorescence detection, the design, and synthesis of UCNPs, their recognition mechanism, properties, and their application progress. Moreover, the development trend and prospects of these detection probes are given.

A Study on Doping and Compound of Zinc Oxide Photocatalysts.

As an excellent semiconductor photocatalyst, zinc oxide is widely used in the field of photocatalysis and is regarded as one of the most reliable materials to solve environmental problems. However, because its band gap energy limits the absorption of visible light and reduces the efficiency of catalytic degradation, it needs to be doped with other substances or compounded with other substances and precious metal. This paper summarizes the research on this aspect at home and abroad in recent years, introduces the doping of transition metal ions by zinc oxide, the compounding of zinc oxide with precious metals or other semiconductors, and the prospect of further improving the catalytic efficiency of zno photocatalyst is also put forward.

Visualizing germination of microbiota endospores in the mammalian gut.

Transmission of bacterial endospores between the environment and people and the following germination in vivo play critical roles in both the deadly infections of some bacterial pathogens and the stabilization of the commensal microbiotas in humans. Our knowledge about the germination process of different bacteria in the mammalian gut, however, is still very limited due to the lack of suitable tools to visually monitor this process. We proposed a two-step labeling strategy that can image and quantify the endospores' germination in the recipient's intestines. Endospores collected from donor's gut microbiota were first labeled with fluorescein isothiocyanate and transplanted to mice via gavage. The recipient mice were then administered with Cyanine5-tagged D-amino acid to label all the viable bacteria, including the germinated endospores, in their intestines in situ. The germinated donor endospores could be distinguished by presenting two types of fluorescent signals simultaneously. The integrative use of cell-sorting, 16S rDNA sequencing, and fluorescence in situ hybridization (FISH) staining of the two-colored bacteria unveiled the taxonomic information of the donor endospores that germinated in the recipient's gut. Using this strategy, we investigated effects of different germinants and pre-treatment interventions on their germination, and found that germination of different commensal bacterial genera was distinctly affected by various types of germinants. This two-color labeling strategy shows its potential as a versatile tool for visually monitoring endospore germination in the hosts and screening for new interventions to improve endospore-based therapeutics.

Mechanism analysis of octapeptide from microalgae, Isochrysis zhanjiangensis for suppressing vascular injury and angiogenesis in human umbilical vein endothelial cell.

Incorporating microalgae active peptides into functional foods is one of the hottest topics in algae research. Ile-Ile-Ala-Val-Glu-Ala-Gly-Cys (IEC) is a novel octapeptide isolated from the microalgae, Isochrysis Zhanjiangensis that inhibits the vascular injury, angiogenesis and has a protective effect on cardiovascular diseases. In this study, IEC can suppress ROS production and inhibit pro-inflammatory factors through the Nrf2/SOD/HO-1 and NF-κB signaling pathways. Additionally, IEC inhibits angiogenesis by reducing the expression of MMP2 and MMP9 via the PI3K/AKT, NF-κB, and MAPK pathways. Molecular docking also demonstrated that IEC possesses an excellent docking effect with SOD, Bcl-2 and VEGFR-2. In conclusion, this study not only provides a new idea for the prevention of cardiovascular diseases, but also proves the possibility of octapeptide (IEC) in functional food and drugs, and further improves the use value of microalgae (Isochrysis Zhanjiangensis).

Potential anti-skin aging effect of a peptide AYAPE isolated from Isochrysis zhanjiangensis on UVB-induced HaCaT cells and H2O2-induced BJ cells.

AYAPE (Ala-Tyr-Ala-Pro-Glu) is a pentapeptide isolated from Isochrysis zhanjiangensis, previous studies have proved that this pentapeptide has antioxidant and inflammatory activities. In this study, we determined the anti-skin aging bioactivity of AYAPE with UVB-induced human immortalized keratinocytes (HaCaT) and H2O2-induced human skin fibroblasts (BJ cells) as models. The results showed that AYAPE against UVB-induced photoaging on HaCaT cells via alleviating DNA damage, reducing intracellular reactive oxygen (ROS) levels, down regulating phosphorylation of proteins in MAPK/AP-1 signaling pathways. In addition, AYAPE attenuated senescence related effectors expression in H2O2-induced BJ cells. Furthermore, p53 showed an important role in regulation effect of AYAPE in both two cells, and AYAPE showed a directly combination with p53 by molecular docking. These results demonstrated that AYAPE is potential to against skin aging by decreasing matrix metalloproteinase-1 (MMP-1) production, inhibiting inflammation and apoptosis, and attenuating fibroblast senescence.

Pentapeptide AYP from Isochrysis Zhanjiangensis Exhibits Antiangiogenic Activity in HT1080 Cells and HUVECs by Suppressing Migration and Invasion In Vitro.

Microalgae are important biological sources of marine active peptides and renewable biological resources. Isochrysis zhanjiangensis has been widely used in biological ultrafiltration membranes and aquaculture. However, there are relatively few studies on its component structure and diverse activities. In this study, the mechanism of action of previously isolated pentapeptides (AYP, Ala-Tyr-Ala-Pro-Glu) on inflammation and tumor angiogenesis was evaluated. The results showed that AYP could effectively inhibit the invasion and migration of human umbilical vein endothelial cells (HUVECs) and HT1080 cells by downregulating the expression of MMP-2/-9, independent of cytotoxicity. Especially after 100 µM AYP treatment, the ability to inhibit migration was about 67.7% ± 1.9 for HT1080 cells and 63.6% ± 1.3 for HUVECs, respectively. In addition, the activity of iNOS and COX-2 was decreased by inhibiting the oversecretion of VEGF in HT1080 cells induced by CoCl2 and the activation of VEGFR-2 in HUVECs and by regulating PI3K/AKT and Ras/MAPK signaling pathways. It can prevent inflammation and block tumor angiogenesis. Therefore, AYP is expected to become a drug or functional food to prevent and treat tumor angiogenesis.

A systematic review of the mental health risks and resilience among pollution-exposed adolescents.

Pollution is harmful to human physical health and wellbeing. What is less well established is the relationship between adolescent mental health - a growing public health concern - and pollution. In response, we systematically reviewed studies documenting associations between pollution and mental health in adolescents. We searched Africa Wide, Medline, PsycArticles, PsycInfo, PubMed, CINAHL, ERIC, SciELO, Scopus, and Web of Science Core Collection for studies published up to 10 April 2020 that investigated exposure to any pollutant and symptoms of anxiety; depression; disruptive, impulse-control, and conduct disorders; neurodevelopmental disorders; psychosis; or substance abuse in 10-24-year-olds (i.e., adolescents as per expanded and more inclusive definition of adolescence). This identified 2291 records and we assessed 128 papers for inclusion. We used a narrative synthesis to coalesce the studies' findings. This review is registered on PROSPERO, CRD42020176664. Seventeen studies from Asia, Europe, the Middle East, and North America were included. Air and water pollution exposure was associated with elevated symptoms of depression, generalised anxiety, psychosis, and/or disruptive, impulse control and conduct disorder. Exposure to lead and solvents was associated with neurodevelopmental impairments. Most studies neglected factors that could have supported the mental health resilience of adolescents exposed to pollution. Notwithstanding the limited quality of most reviewed studies, results suggest that pollution exposure is a risk to adolescent mental health. High-quality research is urgently required, including the factors and processes that protect the mental health of pollution-exposed adolescents. Studies with adolescents living in low- and lower middle-income countries and the southern hemisphere must be prioritized.

In Situ Visualization of PD-L1-Specific Glycosylation on Tissue Sections.

Immune checkpoint therapy has provided a weapon against cancer, but its response rate has been extremely low due to the lack of effective predictors. Herein, we developed a FRET strategy based on lectin for glycan labeling and an aptamer for PD-L1 antigen recognition for visualization of PD-L1-specific glycosylation (FLAG). The FLAG strategy combines the PD-L1 aptamer, which efficiently labels the PD-L1 polyantigen with smaller steric hindrance than the PD-L1 antibody, and metabolism-free lectin labeling for glycosylation. As a result, the FLAG strategy enables in situ visualization of PD-L1-specific glycosylation on the tissue section while maintaining the spatial context and tissue architecture. Due to nonmetabolic labeling, the FLAG strategy revealed that the tissue level of PD-L1-specific glycosylation is correlated with the efficacy of PD-1/PD-L1 therapy. Overall, the FLAG strategy provides a powerful tool for revealing the significance of PD-L1 glycosylation, offering the unprecedented potential for immunophenotypic differential analysis to predict the immunotherapy response.

Mechanism Analysis of Antiangiogenic d-Isofloridoside from Marine Edible Red algae Laurencia undulata in HUVEC and HT1080 cell.

Laurencia undulata, as one of the most biologically active species in the genus Laurencia, is an edible folk herb red algae. Among them, d-isofloridoside (DIF, 940.68 Da) is isolated from Laurencia undulata, which has antioxidant and matrix metalloproteinases (MMP) inhibitory activities. However, its mechanism of action on tumor angiogenesis has not yet been reported. In this study, we have studied the mechanism of DIF on tumor metastasis and angiogenesis in HT1080 cell and human vascular endothelial cell (HUVEC). The results show that DIF can reduce the activity of MMP-2/9, and can inhibit the expression of hypoxia-inducible factor-1α (HIF-1α) by regulating the downstream PI3K/AKT and mitogen-activated protein kinases (MAPK) pathways, thereby down-regulating the production of vascular endothelial growth factor (VEGF) in CoCl2-induced HT1080 cell. In addition, DIF can inhibit the activation of VEGF receptor (VEGFR-2), regulate downstream PI3K/AKT, MAPK, nuclear factor-kappa B (NF-κB) signal pathways, activate apoptosis, and thus down-regulate the production of platelet-derived growth factor (PDGF) in VEGF-induced HUVEC. In conclusion, our research shows that DIF has the potential to develop into a tumor-preventing functional food and tumor angiogenesis inhibitor, and it can provide theoretical guidance for the high-value comprehensive utilization of edible red algae Laurencia undulata.

Imaging the in vivo growth patterns of bacteria in human gut Microbiota.

How to study the unculturable bacteria in the laboratory is one of the major challenges in human gut microbiota research. The resulting lack of microbiology knowledge of this "dark matter" greatly hinders further understanding of our gut microbiota. Here, to characterize the in vivo growth and division of human gut bacteria, we report the integrative use of STAMP (sequential tagging with D-amino acid-based metabolic probes) and fluorescence in situ hybridization (FISH) in a human microbiota-associated mouse model. After stable colonization of the human fecal microbiotas in germ-free mice, two fluorescent D-amino acid probes were sequentially administered by gavage, and the dually labeled peptidoglycan of the bacteria provided a chronological recording of their cell wall syntheses. Following taxonomic identification with FISH staining, the growth patterns of 32 species, including 5 currently unculturables, were identified. Surprisingly, we found that many bacterial species in the human microbiota were significantly shorter than those in the mouse gut microbiota. An imaging database for gut bacteria ̶ Microbiome Atlas was built for summarizing STAMP imaging of bacteria from different microbiotas, which can be contributed by the microbiota research community worldwide. This integrative imaging strategy and the database will promote our understanding of the bacterial cytology in gut microbiotas and facilitate communications among cellular microbiologists.

Biodistributions of l,d-Transpeptidases in Gut Microbiota Revealed by In Vivo Labeling with Peptidoglycan Analogs.

By catalyzing a 3-3 cross-link in peptidoglycan, l,d-transpeptidases (Ldts) can cause resistance to ß-lactams in some pathogens in vitro. However, the prevalence of Ldt and Ldt-mediated responses to different ß-lactams in vivo have never been explored. Here, we apply an in vivo metabolic labeling strategy to study their biodistributions and Ldt-induced bacterial responses to ß-lactams in the mouse gut microbiota. A tetrapeptide-based fluorescent probe that functions as a substrate for Ldts in Gram-positive bacteria efficiently labels ∼18% of total gut bacteria after gavage, suggesting Ldts' high prevalence in gut microbiota. The cellular distributions of 3-3 cross-links on three gut bacterial species were then identified with the aid of fluorescence in situ hybridization to identify the bacterial taxa. After oral administration of two ß-lactams, ampicillin and meropenem, only the latter efficiently inhibits the tetrapeptide labeling, suggesting that Ldts may be able to cause resistance to some ß-lactams in the mammalian gut.