The emergence of serious infections due to community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has fueled interest in the contributions of specific staphylococcal virulence factors to clinical disease. To assess the contributions of agr-dependent factors to the fate of organisms in polymorphonuclear neutrophils (PMN), we examined the consequences for organism and host cells of feeding PMN with wild-type CA-MRSA (LAC) or CA-MRSA (LAC agr KO) at different multiplicities of infection (MOIs). Phagocytosed organisms rapidly increased the transcription of RNAIII in a time- and MOI-dependent fashion; extracellular USA300 (LAC) did not increase RNAIII expression despite having the capacity to respond to autoinducing peptide-enriched culture medium. HOCl-mediated damage and intracellular survival were the same in the wild-type and USA300 (LAC agr KO). PMN lysis by ingested USA300 (LAC) was time- and MOI-dependent and, at MOIs >1, required α-hemolysin (hla) as USA300 (LAC agr KO) and USA300 (LAC hla KO) promoted PMN lysis only at high MOIs. Taken together, these data demonstrate activation of the agr operon in human PMN with the subsequent production of α-hemolysin and PMN lysis. The extent to which these events in the phagosomes of human PMN contribute to the increased morbidity and mortality of infections with USA300 (LAC) merits further study.

Summary The acquisition and metabolism of iron (Fe) by the human pathogen Staphylococcus aureus is critical for disease progression. S. aureus requires Fe to synthesize inorganic cofactors called iron-sulfur (Fe-S) clusters, which are required for functional Fe-S proteins. In this study we investigated the mechanisms utilized by S. aureus to metabolize Fe-S clusters. We identified that S. aureus utilizes the Suf biosynthetic system to synthesize Fe-S clusters and we provide genetic evidence suggesting that the sufU and sufB gene products are essential. Additional biochemical and genetic analyses identified Nfu as a Fe-S cluster carrier, which aids in the maturation of Fe-S proteins. We find that deletion of the nfu gene negatively impacts staphylococcal physiology and pathogenicity. A nfu mutant accumulates both increased intracellular non-incorporated Fe and endogenous reactive oxygen species (ROS) resulting in DNA damage. In addition, a strain lacking Nfu is sensitive to exogenously supplied ROS and reactive nitrogen species. Congruous with ex vivo findings, a nfu mutant strain is more susceptible to oxidative killing by human polymorphonuclear leukocytes and displays decreased tissue colonization in a murine model of infection. We conclude that Nfu is necessary for staphylococcal pathogenesis and establish Fe-S cluster metabolism as an attractive antimicrobial target.

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Background: Esophageal squamous cell carcinoma (ESCC) is among the most prevalent causes of cancerrelated death in adults. Tumor microenvironment (TME) has been associated with therapeutic failure and lethal outcomes for patients. However, published reports on the heterogeneity and TME in ESCC are scanty. Methods: Five tumor samples and five corresponding non-malignant samples were subjected to scRNA-seq analysis. Bulk RNA sequencing data were retrieved in publicly available databases. Findings: From the scRNA-seq data, a total of 128,688 cells were enrolled for subsequent analyses. Gene expression and CNV status exhibited high heterogeneity of tumor cells. We further identified a list of tumorspecific genes and four malignant signatures, which are potential new markers for ESCC. Metabolic analysis revealed that energy supply-related pathways are pivotal in cancer metabolic reprogramming. Moreover, significant differences were found in stromal and immune cells between the esophagus normal and tumor tissues, which promoted carcinogenesis at both cellular and molecular levels in ESCC. Immune checkpoints, regarded as potential targets for immunotherapy in ESCC were significantly highly expressed in ESCC, including LAG3 and HAVCR2. Eventually, we constructed a cell-to-cell communication atlas based on cancer cells and immune cells and performed the flow cytometry, qRT-PCR, immunofluorescence, and immunohistochemistry analyses to validate the results. Interpretation: This study demonstrates a widespread reprogramming across multiple cellular elements within the TME in ESCC, particularly in transcriptional states, cellular functions, and cell-to-cell interactions. The findings offer an insight into the exploration of TME and heterogeneity in the ESCC and provide new therapeutic targets for its clinical management in the future.