Microbial communities are essential to the function of virtually all ecosystems and eukaryotes, including humans. However, it is still a major challenge to identify microbial cells active under natural conditions in complex systems. In this study, we developed a new method to identify and sort active microbes on the single-cell level in complex samples using stable isotope probing with heavy water (D 2 O) combined with Raman microspectroscopy. Incorporation of D 2 O-derived D into the biomass of autotrophic and heterotrophic bacteria and archaea could be unambiguously detected via C-D signature peaks in single-cell Raman spectra, and the obtained labeling pattern was confirmed by nanoscaleresolution secondary ion MS. In fast-growing Escherichia coli cells, label detection was already possible after 20 min. For functional analyses of microbial communities, the detection of D incorporation from D 2 O in individual microbial cells via Raman microspectroscopy can be directly combined with FISH for the identification of active microbes. Applying this approach to mouse cecal microbiota revealed that the host-compound foragers Akkermansia muciniphila and Bacteroides acidifaciens exhibited distinctive response patterns to amendments of mucin and sugars. By Ramanbased cell sorting of active (deuterated) cells with optical tweezers and subsequent multiple displacement amplification and DNA sequencing, novel cecal microbes stimulated by mucin and/ or glucosamine were identified, demonstrating the potential of the nondestructive D 2 O-Raman approach for targeted sorting of microbial cells with defined functional properties for singlecell genomics.ecophysiology | single-cell microbiology | carbohydrate utilization | nitrifier | Raman microspectroscopy M icroorganisms play a vital role in many environments. They mediate global biogeochemical cycles, catalyze biotechnological processes, and contribute to health and disease in the human body. The in situ study of microbial activity in natural and engineered ecosystems is therefore of great interest. For this purpose, several elegant methods have been established that use either transcriptional or translational activity of community members (i.e., metatranscriptomics, metaproteomics) (1-3) or the incorporation of isotopically labeled substrates into biomolecules (4-10) to infer the ecophysiology of microbes in such systems. However, these bulk techniques do not offer sufficient spatial resolution to study microbial activities at the micrometer scale. Therefore, important information can be overlooked because microbial communities are frequently spatially structured (e.g., biofilms) (11) and contain populations with life cycles (12,13). Furthermore, even apparently identical cells in clonal populations can have strongly divergent activities (14).Consequently, microbial ecophysiology is ideally studied also at the level of the single cell, but only a restricted number of approaches exist for determining physiological properties of individual cells in a microbial community. For exa...

Highlights d Mucispirillum schaedleri confers protection against Salmonella colitis in mice d Salmonella and M. schaedleri compete for anaerobic respiration substrates in the gut d M. schaedleri restricts Salmonella infection and inhibits virulence factor expression d Mucispirillum spp. are enriched in human gut mucosal samples

Shifts in gut microbiota composition have been associated with intestinal inflammation, but it remains unclear whether inflammation-associated bacteria are commensal or detrimental to their host. Here, we studied the lifestyle of the gut bacterium Mucispirillum schaedleri, which is associated with inflammation in widely used mouse models. We found that M. schaedleri has specialized systems to handle oxidative stress during inflammation. Additionally, it expresses secretion systems and effector proteins and can modify the mucosal gene expression of its host. This suggests that M. schaedleri undergoes intimate interactions with its host and may play a role in inflammation. The insights presented here aid our understanding of how commensal gut bacteria may be involved in altering susceptibility to disease.

Summary Bacterial degradation of the sugar sulfoquinovose (SQ, 6-deoxy-6-sulfoglucose) produced by plants, algae, and cyanobacteria, is an important component of the biogeochemical carbon and sulfur cycles. Here, we reveal a third biochemical pathway for primary SQ degradation in an aerobic Bacillus aryabhattai strain. An isomerase converts SQ to 6-deoxy-6-sulfofructose (SF). A novel transaldolase enzyme cleaves the SF to 3-sulfolactaldehyde (SLA), while the non-sulfonated C 3 -(glycerone)-moiety is transferred to an acceptor molecule, glyceraldehyde phosphate (GAP), yielding fructose-6-phosphate (F6P). Intestinal anaerobic bacteria such as Enterococcus gilvus , Clostridium symbiosum , and Eubacterium rectale strains also express transaldolase pathway gene clusters during fermentative growth with SQ. The now three known biochemical strategies for SQ catabolism reflect adaptations to the aerobic or anaerobic lifestyle of the different bacteria. The occurrence of these pathways in intestinal (family) Enterobacteriaceae and (phylum) Firmicutes strains further highlights a potential importance of metabolism of green-diet SQ by gut microbial communities to, ultimately, hydrogen sulfide.

Background The role of schools in the SARS-CoV-2 pandemic is much debated. We aimed to quantify reliably the prevalence of SARS-CoV-2 infections at schools detected with reverse-transcription quantitative polymerase-chain-reaction (RT-qPCR). Methods This nationwide prospective cohort study monitors a representative sample of pupils (grade 1–8) and teachers at Austrian schools throughout the school year 2020/2021. We repeatedly test participants for SARS-CoV-2 infection using a gargling solution and RT-qPCR. We herein report on the first two rounds of examinations. We used mixed-effects logistic regression to estimate odds ratios and robust 95% confidence intervals (95% CI). Findings We analysed data on 10,734 participants from 245 schools (9465 pupils, 1269 teachers). Prevalence of SARS-CoV-2 infection increased from 0·39% at round 1 (95% CI 028–0·55%, 28 September-22 October 2020) to 1·39% at round 2 (95% CI 1·04–1·85%, 10–16 November). Odds ratios for SARS-CoV-2 infection were 2·26 (95% CI 1·25–4·12, P = 0·007) in regions with >500 vs. ≤500 inhabitants/km 2 , 1·67 (95% CI 1·42–1·97, P <0·001) per two-fold higher regional 7-day community incidence, and 2·78 (95% CI 1·73–4·48, P <0·001) in pupils at schools with high/very high vs. low/moderate social deprivation. Associations of regional community incidence and social deprivation persisted in a multivariable adjusted model. Prevalence did not differ by average number of pupils per class nor between age groups, sexes, pupils vs. teachers, or primary (grade 1–4) vs. secondary schools (grade 5–8). Interpretation This monitoring study in Austrian schools revealed SARS-CoV-2 infection in 0·39%-1·39% of participants and identified associations of regional community incidence and social deprivation with higher prevalence. Funding BMBWF Austria.