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Background Inhibitory control (IC) is critical to keep long-term goals in everyday life. Bidirectional relationships between IC deficits and obesity are behind unhealthy eating and physical exercise habits. Methods We studied gut microbiome composition and functionality, and plasma and faecal metabolomics in association with cognitive tests evaluating inhibitory control (Stroop test) and brain structure in a discovery (n=156), both cross-sectionally and longitudinally, and in an independent replication cohort (n=970). Faecal microbiota transplantation (FMT) in mice evaluated the impact on reversal learning and medial prefrontal cortex (mPFC) transcriptomics. Results An interplay among IC, brain structure (in humans) and mPFC transcriptomics (in mice), plasma/faecal metabolomics and the gut metagenome was found. Obesity-dependent alterations in one-carbon metabolism, tryptophan and histidine pathways were associated with IC in the two independent cohorts. Bacterial functions linked to one-carbon metabolism (thyX,dut, exodeoxyribonuclease V), and the anterior cingulate cortex volume were associated with IC, cross-sectionally and longitudinally. FMT from individuals with obesity led to alterations in mice reversal learning. In an independent FMT experiment, human donor's bacterial functions related to IC deficits were associated with mPFC expression of one-carbon metabolism-related genes of recipient's mice. Conclusion These results highlight the importance of targeting obesity-related impulsive behaviour through the induction of gut microbiota shifts. ; This work was partially supported by research grants FIS (PI15/01934 and PI18/01022) from the Instituto de Salud Carlos III from Spain, SAF2015- 65878-R and #AEI-SAF2017-84060-R-FEDER from Ministry of Economy and Competitiveness, Prometeo/2018/A/133 from Generalitat Valenciana, Spain; and also by Fondo Europeo de Desarrollo Regional (FEDER) funds, European Commission (FP7, NeuroPain #2013-602891), the Catalan Government (AGAUR, #SGR2017-669, ICREA Academia Award 2015), the Spanish Instituto de Salud Carlos III (RTA, #RD16/0017/0020), the Spanish Ministry of Science, Innovation and Universities (RTI2018-099200-B-I00), the Catalan Goverment (Agency for Management of University and Research Grants [2017SGR696] and Department of Health [STL002/16/00250]; the European Regional Development Fund (project No. 01.2.2-LMT-K-718-02-0014) under grant agreement with the Research Council of Lithuania (LMTLT); and the Project ThinkGut (EFA345/19) 65% co-financed by the European Regional Development Fund (ERDF) through the Interreg V-A SpainFrance-Andorra programme (POCTEFA 2014-2020). MA-R is funded by a predoctoral Río Hortega contract from the Instituto de Salud Carlos III (ISCIII, CM19/00190), co-funded by the European Social Fund "Investing in your future". OC-R is funded by the Miguel Servet Program from the Instituto de Salud Carlos III (ISCIII CP20/00165), co-funded by the Europeran Social Fund "Investing in your future". JM-P is funded by the Miguel Servet Program from the Instituto de Salud Carlos III (ISCIII CP18/00009), co-funded by the European Social Fund "Investing in your future". JS is funded by a predoctoral PERIS contract (SLT002/16/00250) from the Catalan Government. MJ is a professor under the "Serra Hunter" programme (Generalitat de Catalunya).

Background: Inhibitory control (IC) is critical to keep long-term goals in everyday life. Bidirectional relationships between IC deficits and obesity are behind unhealthy eating and physical exercise habits. Methods: We studied gut microbiome composition and functionality, and plasma and faecal metabolomics in association with cognitive tests evaluating inhibitory control (Stroop test) and brain structure in a discovery (n=156), both cross-sectionally and longitudinally, and in an independent replication cohort (n=970). Faecal microbiota transplantation (FMT) in mice evaluated the impact on reversal learning and medial prefrontal cortex (mPFC) transcriptomics. Results: An interplay among IC, brain structure (in humans) and mPFC transcriptomics (in mice), plasma/faecal metabolomics and the gut metagenome was found. Obesity-dependent alterations in one-carbon metabolism, tryptophan and histidine pathways were associated with IC in the two independent cohorts. Bacterial functions linked to one-carbon metabolism (thyX,dut, exodeoxyribonuclease V), and the anterior cingulate cortex volume were associated with IC, cross-sectionally and longitudinally. FMT from individuals with obesity led to alterations in mice reversal learning. In an independent FMT experiment, human donor's bacterial functions related to IC deficits were associated with mPFC expression of one-carbon metabolism-related genes of recipient's mice. Conclusion: These results highlight the importance of targeting obesity-related impulsive behaviour through the induction of gut microbiota shifts. ; This work was partially supported by research grants FIS (PI15/01934 and PI18/01022) from the Instituto de Salud Carlos III from Spain, SAF2015-65878-R and #AEI-SAF2017-84060-R-FEDER from Ministry of Economy and Competitiveness, Prometeo/2018/A/133 from Generalitat Valenciana, Spain; and also by Fondo Europeo de Desarrollo Regional (FEDER) funds, European Commission (FP7, NeuroPain #2013-602891), the Catalan Government (AGAUR, #SGR2017-669, ICREA Academia Award 2015), the Spanish Instituto de Salud Carlos III (RTA, #RD16/0017/0020), the Spanish Ministry of Science, Innovation and Universities (RTI2018-099200-B-I00), the Catalan Goverment (Agency for Management of University and Research Grants [2017SGR696] and Department of Health [STL002/16/00250]; the European Regional Development Fund (project No. 01.2.2-LMT-K-718-02-0014) under grant agreement with the Research Council of Lithuania (LMTLT); and the Project ThinkGut (EFA345/19) 65% co-financed by the European Regional Development Fund (ERDF) through the Interreg V-A Spain-France-Andorra programme (POCTEFA 2014-2020). MA-R is funded by a predoctoral Río Hortega contract from the Instituto de Salud Carlos III (ISCIII, CM19/00190), co-funded by the European Social Fund "Investing in your future". OC-R is funded by the Miguel Servet Program from the Instituto de Salud Carlos III (ISCIII CP20/00165), co-funded by the Europeran Social Fund "Investing in your future". JM-P is funded by the Miguel Servet Program from the Instituto de Salud Carlos III (ISCIII CP18/00009), co-funded by the European Social Fund "Investing in your future". JS is funded by a predoctoral PERIS contract (SLT002/16/00250) from the Catalan Government. MJ is a professor under the "Serra Hunter" programme (Generalitat de Catalunya).

Cover -- Half Title -- Title Page -- Copyright Page -- Dedication -- Table of Contents -- Foreword: Learn from Others -- About BGI and Prof. Yang -- Acknowledgments -- Chapter 1: Introduction -- Chapter 2: Evolution of Life on Earth -- What is Life? -- Again, What is Life? -- Chapter 3: Adaptation of Life to Extreme Conditions -- What is Hibernation? -- Cell Biology and Genomics of Adaptation -- Chapter 4: Homo Sapiens ("Us"): Strengths and Weaknesses -- Musculoskeletal System -- Digestive System -- Respiratory System -- Urinary System -- Endocrine System -- Cardiovascular System -- Lymphatic System -- Nervous System -- Sensory Nervous System -- Human Eye (Vision) -- Human Ear (Hearing) -- Human Touch -- Human Taste -- Human Smell -- Spatial Navigation -- What is Pain? -- Sapiens Challenges and Weaknesses -- What is it That Kills Homo Sapiens? -- The Human Brain, The Big Differentiator -- Chapter 5: The Human Microbiome: How Our Health is Impacted by Microorganisms -- Diabetes and Intestinal Microbes -- Intestinal Microorganisms and Immune System -- The Role of the Appendix -- Intestinal Microorganisms and Antibiotic Use -- Intestinal Microbiology and Neurodevelopment -- Intestinal Microorganisms and Obesity -- Intestinal Microorganisms and Hypertension -- Intestinal Microbes and Chronic Inflammatory Bowel Disease -- Intestinal Microorganisms and Tumors -- Intestinal Microbes and Neurobehavioral Diseases -- Intestinal Microbiology and Biological Clock -- Intestinal Microbes and Human Mental Health -- Chapter 6: Animals with Connection to Human Knowledge, Health, and Performance -- 6A. Human Knowledge -- HGP specific Model Organisms -- Biomedical Model Organisms -- The Fruit Fly (Drosophila melanogaster) -- The Mouse (Mus musculus) -- California Sea Slug (Aplysia californica) -- The Zebrafish (Danio rerio) -- 6B. Human Health.

This study investigated the effects of Cordyceps militaris (CM) on intestinal barrier function and gut microbiota in a pig model. A total of 160 pigs were randomly allocated to either a control group (fed the basal diet) or a CM group (fed the basal diet supplemented with 300 mg/kg CM). CM improved intestinal morphology and increased the numbers of goblet cells and intraepithelial lymphocytes. CM also elevated the expression of zona occluden-1, claudin-1, mucin-2 and secretory immunoglobulin A. Furthermore, the mucosal levels of pro-inflammatory cytokines were downregulated while the levels of anti-inflammatory cytokines were upregulated in the CM group. Mechanistically, CM downregulated the expression of key proteins of the TLR4/MyD88/NF-κB signaling pathway. Moreover, CM altered the colonic microbial composition and increased the concentrations of acetate and butyrate. In conclusion, CM can modulate the intestinal barrier function and gut microbiota, which may provide a new strategy for improving intestinal health.

Background: Infectious gastroenteritis (IGE) is caused by numerous bacterial, viral, and parasitic pathogens. A history of IGE has been shown in previous studies to increase the risk of developing chronic gastrointestinal disorders and other chronic conditions. As bacteria and viruses represent the majority of pathogen-specific causes of IGE, post-infectious studies have primarily focused on these organisms. The objective of this study was to investigate an association between a history of parasite-associated IGE and the subsequent development of chronic post-infectious gastrointestinal and non-gastrointestinal disorders in a military population.

Titanium dioxide (TiO2) is commonly used as a food additive (E171 in the EU) for its whitening and opacifying properties. However, a risk of intestinal barrier disruption, including dysbiosis of the gut microbiota, is increasingly suspected because of the presence of a nano-sized fraction in this additive. We hypothesized that food-grade E171 and Aeroxyde P25 (identical to the NM-105 OECD reference nanomaterial in the European Union Joint Research Centre) interact with both commensal intestinal bacteria and transient food-borne bacteria under non-UV-irradiated conditions. Based on differences in their physicochemical properties, we expect a difference in their respective effects. To test these hypotheses, we chose a panel of eight Grampositive/Gram-negative bacterial strains, isolated from different biotopes and belonging to the species Escherichia coli, Lactobacillus rhamnosus, Lactococcus lactis (subsp. lactis and cremoris), Streptococcus thermophilus, and Lactobacillus sakei. Bacterial cells were exposed to food-grade E171 vs. P25 in vitro and the interactions were explored with innovative (nano) imaging methods. The ability of bacteria to trap TiO2 was demonstrated using synchrotron UV fluorescence imaging with single cell resolution. Subsequent alterations in the growth profiles were shown, notably for the transient food-borne L. lactis and the commensal intestinal E. coli in contact with food-grade TiO2. However, for both species, the reduction in cell cultivability remained moderate, and the morphological and ultrastructural damages, observed with electron microscopy, were restricted to a small number of cells. E. coli exposed to food-grade TiO2 showed some internalization of TiO2 (7% of cells), observed with high-resolution nano-secondary ion mass spectrometry (Nano-SIMS) chemical imaging. Taken together, these data show that E171 may be trapped by commensal and transient food-borne bacteria within the gut. In return, it may induce some physiological alterations in the most sensitive species, with a putative impact on gut microbiota composition and functioning, especially after chronic exposure.

Avian intestinal spirochetosis (AIS) results from the colonization of the ceca and colorectum of poultry by pathogenic Brachyspira species. The number of cases of AIS has increased since the 2006 European Union ban on the use of antibiotic growth promoters, which, together with emerging antimicrobial resistance in Brachyspira, has driven renewed interest in alternative intervention strategies. Probiotics have been reported as protecting livestock against infection with common enteric pathogens, and here we investigate which aspects of the biology of Brachyspira they antagonize in order to identify possible interventions against AIS. The cell-free supernatants (CFS) of two Lactobacillus strains, Lactobacillus reuteri LM1 and Lactobacillus salivarius LM2, suppressed the growth of Brachyspira pilosicoli B2904 in a pH-dependent manner. In in vitro adherence and invasion assays with HT29-16E three-dimensional (3D) cells and in a novel avian cecal in vitro organ culture (IVOC) model, the adherence and invasion of B. pilosicoli in epithelial cells were reduced significantly by the presence of lactobacilli (P < 0.001). In addition, live and heat-inactivated lactobacilli inhibited the motility of B. pilosicoli, and electron microscopic observations indicated that contact between the lactobacilli and Brachyspira was crucial in inhibiting both adherence and motility. These data suggest that motility is essential for B. pilosicoli to adhere to and invade the gut epithelium and that any interference of motility may be a useful tool for the development of control strategies.

We thank Manuel Kulagin for technical help, Pierre Bonnaventure for portal vein blood sampling, Francisco Sepulveda for technical assistance in GS-MS acquisition, and Dorothee Hahne (Metabolomics Australia, University of Western Australia) for human samples SCFA isolation, acquisition, and analysis. We also thank Cristina Cartoni (Phenotyping Unit, EPFL) for Milliplex analysis, Jessica Dessimoz and her team from the Histology Core Facility (EPFL), Miguel Garcia and his team from the Flow Cytometry Core Facility (EPFL), and staff from the EPFL CPG animal house for excellent animal care. The computations were partially performed at the Vital-IT Center for high-performance computing of the SIB Swiss Institute of Bioinformatics (http://www.vital-it.ch). The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 310948. Funding for A.W.W. and a subset of the 16S rRNA gene sequencing was provided by the Wellcome Trust (grant number WT 098051). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ; Peer reviewed ; Publisher PDF

OBJECTIVES: Recent studies have reported altered fecal microbiota composition together with increased intestinal permeability (IP) and inflammation in individuals consuming military food rations in austere environments, but could not separate effects of the highly processed, commercially sterile ration-based diets from environmental factors. This study aimed to determine how the U.S. Meal, Ready-to-Eat (MRE) food ration affects fecal microbiota composition and IP. METHODS: In this parallel-arm trial, 60 adults (95% male, 18–61 yr) were randomly assigned to consume their usual diet for 31d (CON), or a strictly controlled MRE-only diet for 21d then their usual diet for 10d (MRE). Fecal samples were collected at baseline (BL, days -8–0), and during (INT, days 1–21) and after (POST, days 22–31) the intervention period to measure microbiota composition by 16S rDNA sequencing. On days 0, 10, 21 and 31 IP was measured by dual-sugar absorption test, and circulating markers of bacterial translocation from the gut lumen (LPS-binding protein (LBP)) and inflammation (hsCRP) were measured. RESULTS: During INT, carbohydrate (CON vs MRE: 44% vs 50% energy) and fiber (19 vs 26 g/d) intakes were lower in CON relative to MRE, whereas protein intake was higher (18% vs. 13% energy) (P ≤ 0.01). Body weight increased over time in CON, but transiently decreased during INT in MRE (P = 0.001). Changes in fecal microbiota composition differed over time between groups (P ≤ 0.01), with random forest models discriminating the fecal microbiota of MRE and CON samples during INT with 88% accuracy. The most discriminant genera included multiple bacteria used in food production (Lactobacillus, Lactococcus, Streptococcus, Leuconostoc) which were less abundant in MRE, and the inflammation-associated genus Sutterella which transiently increased in MRE during INT. IP and hsCRP were both lower (25% and 16%, respectively) in MRE relative to CON on day 21 (P < 0.05), but did not differ before or after. LBP did not differ between groups at any time. ...

Titanium dioxide (TiO2) is commonly used as a food additive (E171 in the EU) for its whitening and opacifying properties. However, a risk of intestinal barrier disruption, including dysbiosis of the gut microbiota, is increasingly suspected because of the presence of a nano-sized fraction in this additive. We hypothesized that food-grade E171 and Aeroxyde P25 (identical to the NM-105 OECD reference nanomaterial in the European Union Joint Research Centre) interact with both commensal intestinal bacteria and transient food-borne bacteria under non-UV-irradiated conditions. Based on differences in their physicochemical properties, we expect a difference in their respective effects. To test these hypotheses, we chose a panel of eight Gram-positive/Gram-negative bacterial strains, isolated from different biotopes and belonging to the species Escherichia coli, Lactobacillus rhamnosus, Lactococcus lactis (subsp. lactis and cremoris), Streptococcus thermophilus, and Lactobacillus sakei. Bacterial cells were exposed to food-grade E171 vs. P25 in vitro and the interactions were explored with innovative (nano)imaging methods. The ability of bacteria to trap TiO2 was demonstrated using synchrotron UV fluorescence imaging with single cell resolution. Subsequent alterations in the growth profiles were shown, notably for the transient food-borne L. lactis and the commensal intestinal E. coli in contact with food-grade TiO2. However, for both species, the reduction in cell cultivability remained moderate, and the morphological and ultrastructural damages, observed with electron microscopy, were restricted to a small number of cells. E. coli exposed to food-grade TiO2 showed some internalization of TiO2 (7% of cells), observed with high-resolution nano-secondary ion mass spectrometry (Nano-SIMS) chemical imaging. Taken together, these data show that E171 may be trapped by commensal and transient food-borne bacteria within the gut. In return, it may induce some physiological alterations in the most sensitive species, with a ...

Teming Zhang,1,* Zheng Han,1,* Arvine Chandoo,1,* Xincheng Huang,1 Xiangwei Sun,1 Lele Ye,2 Changyuan Hu,3 Xiangyang Xue,2 Yingpeng Huang,1 Xian Shen,1 Wenjun Chang,4 Xiaoming Lin5 1Department of General Surgery, Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, People's Republic of China; 2Department of Microbiology and Immunology, Institute of Molecular Virology and Immunology, Institute of Tropical Medicine, Wenzhou Medical University, Wenzhou, People's Republic of China; 3Department of Gastrointestinal Surgery, The First Affiliated Hospital, Wenzhou Medical University, Wenzhou, People's Republic of China; 4Department of Environmental Hygiene, Second Military Medical University, Shanghai People's Republic of China; 5Department of Thoracic Surgery, The First Affiliated Hospital of Wenzhou Medical University, Nanbaixiang, Wenzhou, People's Republic of China *These authors contributed equally to this work Background and aim: Periostin is a protein from the Fascilin family. It is commonly present in normal tissues and is responsible for cell adhesion. Evidence has emerged showing that changes in periostin expression play an important role in tumor initiation, development, and progression. This study aims to investigate the effect of periostin in gastric cancer (GC) patients who underwent gastrectomy. Seven hundred and forty-seven GC patients who underwent gastrectomy between December 2006 and July 2011 were included in this study. Methods: Seven hundred and forty-seven cancer tissues and 70 paired adjacent normal tissues were collected. Periostin expression was evaluated by immunohistochemistry. The Gene Expression Omnibus database was used to study the association between the mRNA level and patient's overall survival. The tumor microenvironment was also studied. Results: Periostin expression in stroma was downregulated in tumor tissues but it was upregulated in the epithelial cells. After dividing the tissues according to the Lauren Classification, we found that periostin expression in stroma and epithelial cells was higher in intestinal type than in diffuse type (P<0.001 and P=0.010, respectively). Periostin was an independent predictor of lymph node (LN) metastasis in GC patients. The study of CD163(+) tumor-associated macrophages (TAMs) revealed that in diffuse type GC, periostin expression was associated with CD163(+) TAMs. Conclusion: We found that the periostin expression can predict LN metastasis in patients undergoing curative gastrectomy. Intestinal type GC patients with high periostin level had both a favorable survival and lesser LN metastasis. Keywords: lymph node metastasis, tumor microenvironment, tissue microarray, cell adhesion, Lauren Classification

Titanium dioxide (TiO 2 ) is commonly used as a food additive (E171 in the EU) for its whitening and opacifying properties. However, a risk of intestinal barrier disruption, including dysbiosis of the gut microbiota, is increasingly suspected because of the presence of a nano-sized fraction in this additive. We hypothesized that food-grade E171 and Aeroxyde P25 (identical to the NM-105 OECD reference nanomaterial in the European Union Joint Research Centre) interact with both commensal intestinal bacteria and transient food-borne bacteria under non-UV-irradiated conditions. Based on differences in their physicochemical properties, we expect a difference in their respective effects. To test these hypotheses, we chose a panel of eight Gram-positive/Gram-negative bacterial strains, isolated from different biotopes and belonging to the species Escherichia coli, Lactobacillus rhamnosus, Lactococcus lactis (subsp. lactis and cremoris), Streptococcus thermophilus, and Lactobacillus sakei. Bacterial cells were exposed to food-grade E171 vs. P25 in vitro and the interactions were explored with innovative (nano)imaging methods. The ability of bacteria to trap TiO 2 was demonstrated using synchrotron UV fluorescence imaging with single cell resolution. Subsequent alterations in the growth profiles were shown, notably for the transient food-borne L. lactis and the commensal intestinal E. coli in contact with food-grade TiO 2 . However, for both species, the reduction in cell cultivability remained moderate, and the morphological and ultrastructural damages, observed with electron microscopy, were restricted to a small number of cells. E. coli exposed to food-grade TiO 2 showed some internalization of TiO 2 (7% of cells), observed with high-resolution nano-secondary ion mass spectrometry (Nano-SIMS) chemical imaging. Taken together, these data show that E171 may be trapped by commensal and transient food-borne bacteria within the gut. In return, it may induce some physiological alterations in the most sensitive species, with a putative impact on gut microbiota composition and functioning, especially after chronic exposure.

International audience ; Titanium dioxide (TiO 2) is commonly used as a food additive (E171 in the EU) for its whitening and opacifying properties. However, a risk of intestinal barrier disruption, including dysbiosis of the gut microbiota, is increasingly suspected because of the presence of a nano-sized fraction in this additive. We hypothesized that food-grade E171 and Aeroxyde P25 (identical to the NM-105 OECD reference nanomaterial in the European Union Joint Research Centre) interact with both commensal intestinal bacteria and transient food-borne bacteria under non-UV-irradiated conditions. Based on differences in their physicochemical properties, we expect a difference in their respective effects. To test these hypotheses, we chose a panel of eight Gram-positive/Gram-negative bacterial strains, isolated from different biotopes and belonging to the species Escherichia coli, Lactobacillus rhamnosus, Lactococcus lactis (subsp. lactis and cremoris), Streptococcus thermophilus, and Lactobacillus sakei. Bacterial cells were exposed to food-grade E171 vs. P25 in vitro and the interactions were explored with innovative (nano)imaging methods. The ability of bacteria to trap TiO 2 was demonstrated using synchrotron UV fluorescence imaging with single cell resolution. Subsequent alterations in the growth profiles were shown, notably for the transient food-borne L. lactis and the commensal intestinal E. coli in contact with food-grade TiO 2. However, for both species, the reduction in cell cultivability remained moderate, and the morphological and ultrastructural damages, observed with electron microscopy, were restricted to a small number of cells. E. coli exposed to food-grade TiO 2 showed some internalization of TiO 2 (7% of cells), observed with high-resolution nano-secondary ion Frontiers in Microbiology | www.frontiersin.org 1 April 2018 | Volume 9 | Article 794

International audience ; Titanium dioxide (TiO 2) is commonly used as a food additive (E171 in the EU) for its whitening and opacifying properties. However, a risk of intestinal barrier disruption, including dysbiosis of the gut microbiota, is increasingly suspected because of the presence of a nano-sized fraction in this additive. We hypothesized that food-grade E171 and Aeroxyde P25 (identical to the NM-105 OECD reference nanomaterial in the European Union Joint Research Centre) interact with both commensal intestinal bacteria and transient food-borne bacteria under non-UV-irradiated conditions. Based on differences in their physicochemical properties, we expect a difference in their respective effects. To test these hypotheses, we chose a panel of eight Gram-positive/Gram-negative bacterial strains, isolated from different biotopes and belonging to the species Escherichia coli, Lactobacillus rhamnosus, Lactococcus lactis (subsp. lactis and cremoris), Streptococcus thermophilus, and Lactobacillus sakei. Bacterial cells were exposed to food-grade E171 vs. P25 in vitro and the interactions were explored with innovative (nano)imaging methods. The ability of bacteria to trap TiO 2 was demonstrated using synchrotron UV fluorescence imaging with single cell resolution. Subsequent alterations in the growth profiles were shown, notably for the transient food-borne L. lactis and the commensal intestinal E. coli in contact with food-grade TiO 2. However, for both species, the reduction in cell cultivability remained moderate, and the morphological and ultrastructural damages, observed with electron microscopy, were restricted to a small number of cells. E. coli exposed to food-grade TiO 2 showed some internalization of TiO 2 (7% of cells), observed with high-resolution nano-secondary ion Frontiers in Microbiology | www.frontiersin.org 1 April 2018 | Volume 9 | Article 794