Coarsening Dynamics of Domains in Lipid Membranes

We investigate isothermal diffusion and growth of micron-scale liquid domains within membranes of free-floating giant unilamellar vesicles with diameters between 80 and 250 Am. Domains appear after a rapid temperature quench, when the membrane is cooled through a miscibility phase transition such that coexisting liquid phases form. In membranes quenched far from a miscibility critical point, circular domains nucleate and then progress within seconds to late stage coarsening in which domains grow via two mechanisms 1), collision and coalescence of liquid domains, and 2), Ostwald ripening. Both mechanisms are expected to yield the same growth exponent, alpha = 1/3, where domain radius grows as time(alpha). We measure alpha = 0.28 +/- 0.05, in excellent agreement. In membranes close to a miscibility critical point, the two liquid phases in the membrane are bicontinuous. A quench near the critical composition results in rapid changes in morphology of elongated domains. In this case, we measure alpha = 0.50 +/- 0.16, consistent with theory and simulation

Anti-microbial Functions of group 3 innate lymphoid cells in gut-associated lymphoid tissues are regulated by G-protein-coupled receptor 183

Summary: The intestinal tract is constantly exposed to various stimuli. Group 3 innate lymphoid cells (ILC3s) reside in lymphoid organs and in the intestinal tract and are required for immunity to enteric bacterial infection. However, the mechanisms that regulate the ILC3s in vivo remain incompletely defined. Here, we show that GPR183, a chemotactic receptor expressed on murine and human ILC3s, regulates ILC3 migration toward its ligand 7α,25-dihydroxycholesterol (7α,25-OHC) in vitro, and GPR183 deficiency in vivo leads to a disorganized distribution of ILC3s in mesenteric lymph nodes and decreased ILC3 accumulation in the intestine. GPR183 functions intrinsically in ILC3s, and GPR183-deficient mice are more susceptible to enteric bacterial infection. Together, these results reveal a role for the GPR183-7α,25-OHC pathway in regulating the accumulation, distribution, and anti-microbial and tissue-protective functions of ILC3s and define a critical role for this pathway in promoting innate immunity to enteric bacterial infection. : Chu et al. demonstrate that GPR183 and its ligand 7α,25-OHC regulate the accumulation, distribution, and anti-microbial and tissue-protective functions of group 3 innate lymphoid cells, thus revealing a critical role for this pathway in promoting innate immunity against enteric bacterial infection. Keywords: group 3 innate lymphoid cells, GPR183, mesenteric lymph node, intestine, accumulation, distribution, anti-microbia

Gut Microbiome Dysbiosis in Antibiotic-Treated COVID-19 Patients is Associated with Microbial Translocation and Bacteremia

Although microbial populations in the gut microbiome are associated with COVID-19 severity, a causal impact on patient health has not been established. Here we provide evidence that gut microbiome dysbiosis is associated with translocation of bacteria into the blood during COVID-19, causing life-threatening secondary infections. We first demonstrate SARS-CoV-2 infection induces gut microbiome dysbiosis in mice, which correlated with alterations to Paneth cells and goblet cells, and markers of barrier permeability. Samples collected from 96 COVID-19 patients at two different clinical sites also revealed substantial gut microbiome dysbiosis, including blooms of opportunistic pathogenic bacterial genera known to include antimicrobial-resistant species. Analysis of blood culture results testing for secondary microbial bloodstream infections with paired microbiome data indicates that bacteria may translocate from the gut into the systemic circulation of COVID-19 patients. These results are consistent with a direct role for gut microbiome dysbiosis in enabling dangerous secondary infections during COVID-19

Dysregulation of ILC3s unleashes progression and immunotherapy resistance in colon cancer

Group 3 innate lymphoid cells (ILC3s) regulate immunity and inflammation, yet their role in cancer remains elusive. Here, we identify that colorectal cancer (CRC) manifests with altered ILC3s that are characterized by reduced frequencies, increased plasticity, and an imbalance with T cells. We evaluated the consequences of these changes in mice and determined that a dialogue between ILC3s and T cells via major histocompatibility complex class II (MHCII) is necessary to support colonization with microbiota that subsequently induce type-1 immunity in the intestine and tumor microenvironment. As a result, mice lacking ILC3-specific MHCII develop invasive CRC and resistance to anti-PD-1 immunotherapy. Finally, humans with dysregulated intestinal ILC3s harbor microbiota that fail to induce type-1 immunity and immunotherapy responsiveness when transferred to mice. Collectively, these data define a protective role for ILC3s in cancer and indicate that their inherent disruption in CRC drives dysfunctional adaptive immunity, tumor progression and immunotherapy resistance

Effect of antimicrobial administration on fecal microbiota of critically ill dogs: dynamics of antimicrobial resistance over time

Abstract Background Multidrug resistance in companion animals poses significant risks to animal and human health. Prolonged antimicrobial drug (AMD) treatment in animals is a potential source of selection pressure for antimicrobial resistance (AMR) including in the gastrointestinal microbiota. We performed a prospective study of dogs treated for septic peritonitis, pyometra, or bacterial pneumonia and collected repeated fecal samples over 60 days. Bacterial cultures and direct molecular analyses of fecal samples were performed including targeted resistance gene profiling. Results Resistant Escherichia coli increased after 1 week of treatment (D1:21.4% vs. D7:67.9% P < 0.001) and returned to baseline proportions by D60 (D7:67.9% vs D60:42.9%, P = 0.04). Dogs with septic peritonitis were hospitalized significantly longer than those with pneumonia or pyometra. Based on genetic analysis, Simpson’s diversity index significantly decreased after 1 week of treatment (D1 to D7, P = 0.008), followed by a gradual increase to day 60 (D1 and D60, P = 0.4). Detection of CTX-M was associated with phenotypic resistance to third-generation cephalosporins in E. coli (OR 12.1, 3.3–68.0, P < 0.001). Lincosamide and macrolide-resistance genes were more frequently recovered on days 14 and 28 compared to day 1 (P = 0.002 and P = 0.004 respectively). Conclusion AMR was associated with prescribed drugs but also developed against AMDs not administered during the study. Companion animals may be reservoirs of zoonotic multidrug resistant pathogens, suggesting that veterinary AMD stewardship and surveillance efforts should be prioritized. Graphical abstrac

Utilizing a reductionist model to study host-microbe interactions in intestinal inflammation

Abstract Background The gut microbiome is altered in patients with inflammatory bowel disease, yet how these alterations contribute to intestinal inflammation is poorly understood. Murine models have demonstrated the importance of the microbiome in colitis since colitis fails to develop in many genetically susceptible animal models when re-derived into germ-free environments. We have previously shown that Wiskott-Aldrich syndrome protein (WASP)-deficient mice (Was−/−) develop spontaneous colitis, similar to human patients with loss-of-function mutations in WAS. Furthermore, we showed that the development of colitis in Was−/− mice is Helicobacter dependent. Here, we utilized a reductionist model coupled with multi-omics approaches to study the role of host-microbe interactions in intestinal inflammation. Results Was−/− mice colonized with both altered Schaedler flora (ASF) and Helicobacter developed colitis, while those colonized with either ASF or Helicobacter alone did not. In Was−/− mice, Helicobacter relative abundance was positively correlated with fecal lipocalin-2 (LCN2), a marker of intestinal inflammation. In contrast, WT mice colonized with ASF and Helicobacter were free of inflammation and strikingly, Helicobacter relative abundance was negatively correlated with LCN2. In Was−/− colons, bacteria breach the mucus layer, and the mucosal relative abundance of ASF457 Mucispirillum schaedleri was positively correlated with fecal LCN2. Meta-transcriptomic analyses revealed that ASF457 had higher expression of genes predicted to enhance fitness and immunogenicity in Was−/− compared to WT mice. In contrast, ASF519 Parabacteroides goldsteinii’s relative abundance was negatively correlated with LCN2 in Was−/− mice, and transcriptional analyses showed lower expression of genes predicted to facilitate stress adaptation by ASF519 in Was−/−compared to WT mice. Conclusions These studies indicate that the effect of a microbe on the immune system can be context dependent, with the same bacteria eliciting a tolerogenic response under homeostatic conditions but promoting inflammation in immune-dysregulated hosts. Furthermore, in inflamed environments, some bacteria up-regulate genes that enhance their fitness and immunogenicity, while other bacteria are less able to adapt and decrease in abundance. These findings highlight the importance of studying host-microbe interactions in different contexts and considering how the transcriptional profile and fitness of bacteria may change in different hosts when developing microbiota-based therapeutics. Video abstrac

Utilizing a reductionist model to study host-microbe interactions in intestinal inflammation

Abstract Background The gut microbiome is altered in patients with inflammatory bowel disease, yet how these alterations contribute to intestinal inflammation is poorly understood. Murine models have demonstrated the importance of the microbiome in colitis since colitis fails to develop in many genetically susceptible animal models when re-derived into germ-free environments. We have previously shown that Wiskott-Aldrich syndrome protein (WASP)-deficient mice (Was−/−) develop spontaneous colitis, similar to human patients with loss-of-function mutations in WAS. Furthermore, we showed that the development of colitis in Was−/− mice is Helicobacter dependent. Here, we utilized a reductionist model coupled with multi-omics approaches to study the role of host-microbe interactions in intestinal inflammation. Results Was−/− mice colonized with both altered Schaedler flora (ASF) and Helicobacter developed colitis, while those colonized with either ASF or Helicobacter alone did not. In Was−/− mice, Helicobacter relative abundance was positively correlated with fecal lipocalin-2 (LCN2), a marker of intestinal inflammation. In contrast, WT mice colonized with ASF and Helicobacter were free of inflammation and strikingly, Helicobacter relative abundance was negatively correlated with LCN2. In Was−/− colons, bacteria breach the mucus layer, and the mucosal relative abundance of ASF457 Mucispirillum schaedleri was positively correlated with fecal LCN2. Meta-transcriptomic analyses revealed that ASF457 had higher expression of genes predicted to enhance fitness and immunogenicity in Was−/− compared to WT mice. In contrast, ASF519 Parabacteroides goldsteinii’s relative abundance was negatively correlated with LCN2 in Was−/− mice, and transcriptional analyses showed lower expression of genes predicted to facilitate stress adaptation by ASF519 in Was−/−compared to WT mice. Conclusions These studies indicate that the effect of a microbe on the immune system can be context dependent, with the same bacteria eliciting a tolerogenic response under homeostatic conditions but promoting inflammation in immune-dysregulated hosts. Furthermore, in inflamed environments, some bacteria up-regulate genes that enhance their fitness and immunogenicity, while other bacteria are less able to adapt and decrease in abundance. These findings highlight the importance of studying host-microbe interactions in different contexts and considering how the transcriptional profile and fitness of bacteria may change in different hosts when developing microbiota-based therapeutics. Video abstrac

Immune regulation by fungal strain diversity in inflammatory bowel disease

The fungal microbiota (mycobiota) is an integral part of the complex multi-kingdom microbial community colonizing the mammalian gastrointestinal tract and plays an important role in immune regulation(1–6). Although aberrant mycobiota changes have been linked to several diseases including inflammatory bowel disease (IBD)(3–9), it is currently unknown whether fungal species captured by deep sequencing represent living organisms and whether specific fungi have functional consequences for disease development in affected individuals. Here we developed a translational platform for the functional exploration of the mycobiome at a fungal strain- and patient-specific level. Combining high-resolution mycobiota-sequencing, fungal culturomics and genomics, CRISPR/Cas9-based fungal strain editing system, in vitro functional immunoreactivity assays and in vivo models, this platform allows to explore host-fungal crosstalk within the human gut. We discovered a rich genetic diversity of opportunistic Candida albicans strains that dominated the colonic mucosa of IBD patients. Among these human gut-derived isolates, strains with high immune cell-damaging capacity (HD strains) reflect disease features of individual ulcerative colitis patients and aggravated intestinal inflammation in vivo through IL-1β-dependent mechanisms. Niche-specific inflammatory immunity and Th17 antifungal responses by HD strains in the gut were dependent upon the C. albicans secreted peptide toxin candidalysin during the transition from a benign commensal to a pathobiont state. These findings unveil the strain-specific nature of host-fungal interactions in the human gut and highlight new diagnostic and therapeutic targets for diseases of inflammatory origin