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Streptococcus pyogenes (Group A Streptococcus , GAS) is a Gram-positive bacterium that inflicts both superficial and life-threatening diseases on its human host. Analysis of fitness using a transposon mutant library revealed that genes predicted to be involved in vitamin B 6 acquisition are associated with fitness in whole human blood. Vitamin B 6 is essential for all life and is important for many cellular functions. In several streptococcal species, it has been shown that mutants in B 6 acquisition exhibited reduced virulence phenotypes and were attenuated during infection. In GAS, B 6 acquisition is believed to be controlled by the pdxR-pdxKU locus, where PdxR is a positive regulator of pdxKU , which encodes for a B 6 -substrate kinase and permease, respectively. Mutants in the regulator (Δ pdxR ) and salvage machinery (Δ pdxKU ) both exhibited modest growth defects when grown in oxygenated conditions with limited vitamin B 6 precursors. ∆ pdxR and ∆ pdxKU mutants also exhibited an impaired ability to survive when challenged with whole human or mouse blood. This defect was characterized by reduced survival in the presence of human neutrophil-like HL60s, primary polymorphonuclear leukocytes, and antimicrobial peptide LL-37. Promoter analysis showed that PdxR is an autoregulator and activated pdxKU in the absence of B 6 . Interestingly, ∆ pdxR and ∆ pdxKU mutants were not attenuated in mouse models of infection, suggesting a species-specific impact on virulence. Overall, it appears that pdxR-pdxKU is associated with GAS vitamin B 6 metabolism as well as pathogen survival during encounters with the human innate immune system.IMPORTANCEBacterial pathogens such as Streptococcus pyogenes (Group A Streptococcus , GAS) must be able to obtain needed nutrients in their human host. Vitamin B 6 or pyridoxal 5' phosphate is essential for all life and is important for many cellular functions. In other streptococcal pathogens, B 6 acquisition has been shown to be important for their ability to cause disease. Here, we show that loss of the putative vitamin B 6 salvage pathway locus pdxR-pdxKU affects GAS pathogenesis when encountering innate immune responses from phagocytic neutrophils and antimicrobial peptides within the host. pdxR- pdxKU may contribute to oxygen tolerance through B 6 ; however, there appear to be other mechanisms for salvaging vitamin B 6 . Overall, pdxR-pdxKU is associated with GAS resistance to the human innate immune response and oxygen tolerance and contributes modestly to B 6 metabolism.

Streptococcus pyogenes [group A streptococcus (GAS)] is a human pathogen capable of infecting diverse tissues. To successfully infect these sites, GAS must detect available nutrients and adapt accordingly. The phosphoenolpyruvate transferase system (PTS) mediates carbohydrate uptake and metabolic gene regulation to adapt to the nutritional environment. Regulation by the PTS can occur through phosphorylation of transcriptional regulators at conserved PTS-regulatory domains (PRDs). GAS has several PRD-containing stand-alone regulators with regulons encoding both metabolic genes and virulence factors [PRD-containing virulence regulators (PCVRs)]. One is RofA, which regulates the expression of virulence genes in multiple GAS serotypes. It was hypothesized that RofA is phosphorylated by the PTS in response to carbohydrate levels to coordinate virulence gene expression. In this study, the RofA regulon of M1T1 strain 5448 was determined using RNA sequencing. Two operons were consistently differentially expressed across growth in the absence of RofA; the pilus operon was downregulated, and the capsule operon was upregulated. This correlated with increased capsule production and decreased adherence to keratinocytes. Purified RofA-His was phosphorylated in vitro by PTS proteins EI and HPr, and phosphorylated RofA-FLAG was detected in vivo when GAS was grown in low-glucose C medium. Phosphorylated RofA was not observed when C medium was supplemented 10-fold with glucose. Mutations of select histidine residues within the putative PRDs contributed to the in vivo phosphorylation of RofA, although phosphorylation of RofA was still observed, suggesting other phosphorylation sites exist in the protein. Together, these findings support the hypothesis that RofA is a PCVR that may couple sugar metabolism with virulence regulation., Competing Interests: The authors declare no conflict of interest.

Microbially-induced corrosion is the acceleration of corrosion induced by bacterial biofilms. The bacteria in the biofilms oxidize metals on the surface, especially evident with iron, to drive metabolic activity and reduce inorganic species such as nitrates and sulfates. Coatings that prevent the formation of these corrosion-inducing biofilms significantly increase the service life of submerged materials and significantly decrease maintenance costs. One species in particular, a member of the Roseobacter clade, Sulfitobacter sp., has demonstrated iron-dependent biofilm formation in marine environments. We have found that compounds that contain the galloyl moiety can prevent Sulfitobacter sp. biofilm formation by sequestering iron, thus making a surface unappealing for bacteria. Herein, we have fabricated surfaces with exposed galloyl groups to test the effectiveness of nutrient reduction in iron-rich media as a non-toxic method to reduce biofilm formation.

Bacterial pathogens rely on a complex network of regulatory proteins to adapt to hostile and nutrient-limiting host environments. The phosphoenolpyruvate phosphotransferase system (PTS) is a conserved pathway in bacteria that couples transport of sugars with phosphorylation to monitor host carbohydrate availability. A family of structurally homologous PTS-regulatory-domain-containing virulence regulators (PCVRs) has been recognized in divergent bacterial pathogens, including Streptococcus pyogenes Mga and Bacillus anthracis AtxA. These paradigm PCVRs undergo phosphorylation, potentially via the PTS, which impacts their dimerization and their activity. Recent work with predicted PCVRs from Streptococcus pneumoniae (Mga Spn ) and Enterococcus faecalis (MafR) suggest they interact with DNA like nucleoid-associating proteins. Yet, Mga binds to promoter sequences as a homo-dimeric transcription factor, suggesting a bi-modal interaction with DNA. High-resolution crystal structures of 3 PCVRs have validated the domain structure, but also raised additional questions such as how ubiquitous are PCVRs, is PTS-mediated histidine phosphorylation via potential PCVRs widespread, do specific sugars signal through PCVRs, and do PCVRs interact with DNA both as transcription factors and nucleoid-associating proteins? Here, we will review known and putative PCVRs based on key domain and functional characteristics and consider their roles as both transcription factors and possibly chromatin-structuring proteins., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Rom, Hart and McIver.)

Only 28% of individuals suffering from psychiatric disorders seek care from mental health specialists. In this paper, the authors describe how the de facto PCP mental health care system gained ground when it seemed the financing and organizational structure of managed care would have predicted the opposite result. They argue that the new realities of mental health practice require new approaches to improving behavioral health treatment. These approaches, they believe, will maximize the benefit of care delivered in and accessed through the primary care office.

Patients with inflammatory bowel disease are susceptible to thromboembolism and recently small vessel thrombosis has been implicated as an aetiological factor in Crohn's disease. This study therefore investigated platelet function in 104 patients with inflammatory bowel disease of whom eight had previous thromboembolism. Thirty five patients had reproducible spontaneous platelet aggregation of more than 30% (0 in controls) (p < 0.0001). A further 20 patients showed hypersensitivity of platelets to low concentrations of aggregating agents (p < 0.001). Plasma thromboxane B2 and beta thromboglobulin levels were significantly higher than controls (p < 0.001 and p < 0.001), but platelet lifespan studies were normal. There was no correlation with disease activity. Patients with inflammatory bowel disease have abnormal platelet activity, which may contribute to the inflammatory process.