Noninvasive Analysis of Peptidoglycan from Living Animals.

The role of the intestinal microbiota in host health is increasingly revealed in its contributions to disease states. The host-microbiome interaction is multifactorial and dynamic. One of the factors that has recently been strongly associated with host physiological responses is peptidoglycan from bacterial cell walls. Peptidoglycan from gut commensal bacteria activates peptidoglycan sensors in human cells, including the nucleotide-binding oligomerization domain-containing protein 2. When present in the gastrointestinal tract, both the polymeric form (sacculi) and depolymerized fragments can modulate host physiology, including checkpoint anticancer therapy efficacy, body temperature and appetite, and postnatal growth. To utilize this growing area of biology toward therapeutic prescriptions, it will be critical to directly analyze a key feature of the host-microbiome interaction from living hosts in a reproducible and noninvasive way. Here we show that metabolically labeled peptidoglycan/sacculi can be readily isolated from fecal samples collected from both mice and humans. Analysis of fecal samples provided a noninvasive route to probe the gut commensal community including the metabolic synchronicity with the host circadian clock. Together, these results pave the way for noninvasive diagnostic tools to interrogate the causal nature of peptidoglycan in host health and disease.

Non-invasive Analysis of Peptidoglycan from Living Animals.

The role of the intestinal microbiota in host health is increasingly revealed in its contributions to disease states. The host-microbiome interaction is multifactorial and dynamic. One of the factors that has recently been strongly associated with host physiological responses is peptidoglycan from bacterial cell walls. Peptidoglycan from gut commensal bacteria activate peptidoglycan sensors in human cells, including the Nucleotide-binding oligomerization domain containing protein 2 (NOD2). When present in the gastrointestinal tract, both the polymeric form (sacculi) and de-polymerized fragments can modulate host physiology, including checkpoint anticancer therapy efficacy, body temperature and appetite, and postnatal growth. To leverage this growing area of biology towards therapeutic prescriptions, it will be critical to directly analyze a key feature of the host-microbiome interaction from living hosts in a reproducible and non-invasive way. Here we show that metabolically labeled peptidoglycan/sacculi can be readily isolated from fecal samples collected from both mice and humans. Analysis of fecal samples provided a non-invasive route to probe the gut commensal community including the metabolic synchronicity with the host circadian clock. Together, these results pave the way for non-invasive diagnostic tools to interrogate the causal nature of peptidoglycan in host health and disease.

Real-time non-invasive fluorescence imaging of gut commensal bacteria to detect dynamic changes in the microbiome of live mice.

In mammals, gut commensal microbiota interact extensively with the host, and the same interactions can be dysregulated in diseased states. Animal imaging is a powerful technique that is widely used to diagnose, measure, and track biological changes in model organisms such as laboratory mice. Several imaging techniques have been discovered and adopted by the research community that provide dynamic, non-invasive assessment of live animals, but these gains have not been universal across all fields of biology. Herein, we describe a method to non-invasively image commensal bacteria based on the specific metabolic labeling of bacterial cell walls to illuminate the gut bacteria of live mice. This tagging strategy may additionally provide unprecedented insight into cell wall turnover of gut commensals, which has implications for bacterial cellular growth and division, in a live animal.

Reciprocal Interactions Between the Gut Microbiome and Mammary Tissue Mast Cells Promote Metastatic Dissemination of HR+ Breast Tumors.

Establishing commensal dysbiosis, defined as an inflammatory gut microbiome with low biodiversity, before breast tumor initiation, enhances early dissemination of hormone receptor-positive (HR+) mammary tumor cells. Here, we sought to determine whether cellular changes occurring in normal mammary tissues, before tumor initiation and in response to dysbiosis, enhanced dissemination of HR+ tumors. Commensal dysbiosis increased both the frequency and profibrogenicity of mast cells in normal, non-tumor-bearing mammary tissues, a phenotypic change that persisted after tumor implantation. Pharmacological and adoptive transfer approaches demonstrated that profibrogenic mammary tissue mast cells from dysbiotic animals were sufficient to enhance dissemination of HR+ tumor cells. Using archival HR+ patient samples, we determined that enhanced collagen levels in tumor-adjacent mammary tissue positively correlated with mast cell abundance and HR+ breast cancer recurrence. Together, these data demonstrate that mast cells programmed by commensal dysbiosis activate mammary tissue fibroblasts and orchestrate early dissemination of HR+ breast tumors.