bNutrient germination of spores of Bacillus species occurs through germinant receptors (GRs) in spores' inner membrane (IM) in a process stimulated by sublethal heat activation. Bacillus subtilis spores maximum germination rates via different GRs required different 75°C heat activation times: 15 min for L-valine germination via the GerA GR and 4 h for germination with the L-asparagine-glucose-fructose-K ؉ mixture via the GerB and GerK GRs, with GerK requiring the most heat activation. In some cases, optimal heat activation decreased nutrient concentrations for half-maximal germination rates. Germination of spores via various GRs by high pressure (HP) of 150 MPa exhibited heat activation requirements similar to those of nutrient germination, and the loss of the GerD protein, required for optimal GR function, did not eliminate heat activation requirements for maximal germination rates. These results are consistent with heat activation acting primarily on GRs. However, (i) heat activation had no effects on GR or GerD protein conformation, as probed by biotinylation by an external reagent; (ii) spores prepared at low and high temperatures that affect spores' IM properties exhibited large differences in heat activation requirements for nutrient germination; and (iii) spore germination by 550 MPa of HP was also affected by heat activation, but the effects were relatively GR independent. The last results are consistent with heat activation affecting spores' IM and only indirectly affecting GRs. The 150-and 550-MPa HP germinations of Bacillus amyloliquefaciens spores, a potential surrogate for Clostridium botulinum spores in HP treatments of foods, were also stimulated by heat activation. Spores of Bacillus species can remain dormant for long periods in the absence of suitable growth conditions (1, 2). However, if specific nutrients are sensed, spores can rapidly become metabolically active in the process of germination followed by outgrowth. The specific nutrients that trigger spore germination are termed germinants, and these molecules are sensed by germinant receptors (GRs) located in spores' inner membrane (IM). Bacillus subtilis spores have three functional GRs: GerA, which responds to L-alanine or L-valine alone, and GerB and GerK, which together are essential for germination with a mixture of L-asparagine, Dglucose, D-fructose, and K ϩ (termed AGFK), with all four components of the mixture required; neither GerB nor GerK alone triggers germination with any nutrient germinant (1, 3). There is also a variant of the GerB GR, termed GerB*, that responds to L-asparagine alone, although GerB* action can be stimulated by glucose via GerK (3). All GRs in B. subtilis spores appear to be located together in a small cluster in the IM termed the germinosome, and formation of this structure is dependent on the GerD protein, which is also in the IM (2, 4). Since gerD spores do not form a germinosome and exhibit extremely slow GR-dependent germination (4), germinosome formation may be essential for rapid GR-dependent germinatio...
Phagocytosed Borrelia burgdorferi (Bb), the Lyme disease spirochete, induces a robust and complex innate immune response in human monocytes, in which TLR8 cooperates with TLR2 in the induction of NF-κB-mediated cytokine production, whereas TLR8 is solely responsible for transcription of IFN-β through IRF7. We now establish the role of Bb RNA in TLR8-mediated induction of IFN-β. First, using TLR2-transfected HEK.293 cells, which were unable to phagocytose intact Bb, we observed TLR2 activation by lipoprotein-rich borrelial lysates and TLR2 synthetic ligands but not in response to live spirochetes. Purified Bb RNA, but not borrelial DNA, triggered TLR8 activation. Neither of these 2 ligands induced activation of TLR7. Using purified human monocytes we then show that phagocytosed live Bb, as well as equivalent amounts of borrelial RNA delivered into the phagosome by polyethylenimine (PEI), induces transcription of IFN-β and secretion of TNF-α. The cytokine response to purified Bb RNA was markedly impaired in human monocytes naturally deficient in IRAK-4 and in cells with knockdown TLR8 expression by small interfering RNA. Using confocal microscopy we provide evidence that TLR8 colocalizes with internalized Bb RNA in both early (EEA1) and late endosomes (LAMP1). Live bacterial RNA staining indicates that spirochetal RNA does not transfer from the phagosome into the cytosol. Using fluorescent dextran particles we show that phagosomal integrity in Bb-infected monocytes is not affected. We demonstrate, for the first time, that Bb RNA is a TLR8 ligand in human monocytes and that transcription of IFN-β in response to the spirochete is induced from within the phagosomal vacuole through the TLR8-MyD88 pathway.
A major event in the nutrient germination of spores of Bacillus species is release of the spores' large depot of dipicolinic acid (DPA). This event is preceded by both commitment, in which spores continue through germination even if germinants are removed, and loss of spore heat resistance. The latter event is puzzling, since spore heat resistance is due largely to core water content, which does not change until DPA is released during germination. We now find that for spores of two Bacillus species, the early loss in heat resistance during germination is most likely due to release of committed spores' DPA at temperatures not lethal for dormant spores. Loss in spore acid resistance during germination also paralleled commitment and was also associated with the release of DPA from committed spores at acid concentrations not lethal for dormant spores. These observations plus previous findings that DPA release during germination is preceded by a significant release of spore core cations suggest that there is a significant change in spore inner membrane permeability at commitment. Presumably, this altered membrane cannot retain DPA during heat or acid treatments innocuous for dormant spores, resulting in DPA-less spores that are rapidly killed.
Internalization and degradation of live Bb within phagosomal compartments of monocytes, macrophages and dendritic cells (DCs), allows for the release of lipoproteins, nucleic acids and other microbial products, triggering a broad and robust inflammatory response. Toll-like receptors (TLRs) are key players in the recognition of spirochetal ligands from whole viable organisms (i.e., vita-PAMPs). Herein we will review the role of endosomal TLRs in the response to the Lyme disease spirochete.
Introduction Diabetes is the leading cause of end-stage renal disease (ESRD) in the United States (US), with 37 million having chronic kidney disease. Despite national guidelines recommendations for diabetic nephropathy screening with urine albumin-to-creatinine ratio (UACR), less than 50% receive full screening. Our Internal Medicine residents led a quality improvement project to increase diabetic nephropathy screening rate with UACR in our resident clinic by 50% in one academic year. Methods We conducted the resident-led quality improvement project from July 2021 to April 2022. We reviewed the electronic medical records (EMR) from our clinic pre-intervention July 2020 to June 2021 and compared this to post intervention July 2021 to March 2022 determining the nephropathy screening rates in patients with diabetes. Our interventions included resident education, pre and post surveys to test foundational knowledge, adding UACR in the affordable laboratory order form and establishing normal reference range of UACR in the EMR. Results We collected 217 patients with diabetes, 27% were uninsured, 38% had Medicare/Medicaid and 90% identified as Hispanic. Comparing pre to post intervention, there was a significant change of 45 (20.7%) vs 71 (32.7%) patients screened for diabetic nephropathy with a UACR. The correct average score of knowledge-based questions was 82% on the pre survey, which increased to 88% in the post survey. Conclusion Our study showed promising results on improving diabetic nephropathy screening. The comprehensive approach including resident education about diabetic nephropathy screening with UACR and more so facilitating the order set in the EMR were key to achieve this goal.
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