Microbiota and host immune responses: a love-hate relationship

A complex relationship between the microbiota and the host emerges early at birth and continues throughout life. The microbiota includes the prokaryotes, viruses and eukaryotes living among us, all of which interact to different extents with various organs and tissues in the body, including the immune system. Although the microbiota is most dense in the lower intestine, its influence on host immunity extends beyond the gastrointestinal tract. These interactions with the immune system operate through the actions of various microbial structures and metabolites, with outcomes ranging from beneficial to deleterious for the host. These differential outcomes are dictated by host factors, environment, and the type of microbes or products present in a specific ecosystem. It is also becoming clear that the microbes are in turn affected and respond to the host immune system. Disruption of this complex dialogue between host and microbiota can lead to immune pathologies such as inflammatory bowel diseases, diabetes and obesity. This review will discuss recent advances regarding the ways in which the host immune system and microbiota interact and communicate with one another

The interplay between inflammation and microbial activities in colorectal cancer

The microbiota affects host immune health by influencing immune system development and promoting tolerogenic immune responses, effects that have the potential to influence vaccine and cancer immunotherapy efficacy. Disruption of the delicate homeostatic balance between the host and microbiota can lead to intestinal diseases such as inflammatory bowel diseases (IBD) and colorectal cancer (CRC) and also extra-intestinal pathologies such as metabolic syndrome and autoimmune diseases. This dissertation focuses on the impact of the microbiota on host intestinal immune responses in relation to inflammation and carcinogenesis. The aim of the first project was to evaluate the role of the microbiota in modulating systemic neutrophil numbers and function in the developing zebrafish. Using a gnotobiotic approach we demonstrated colonization of germ-free (GF) zebrafish with a conventional microbiota increased neutrophil numbers and myeloperoixidase expression, altered neutrophil localization and migratory behavior and improved neutrophil recruitment to extra-intestinal injury. We showed that neutrophil migratory behavior was mediated through the acute phase response protein serum amyloid A (SAA), which was also induced by the microbiota. In vitro experiments revealed SAA exposure activated nuclear factor (NF)-κB in zebrafish cells, and NF-κB was also required within neutrophils for SAA-dependent migration. The goal of the second project was to evaluate the ability of CRC-associated microbes to induce inflammation and CRC in genetically susceptible gnotobiotic mice. Fusobacterium nucleatum and Escherichia coli that contain the genotoxic island, polyketide synthase (pks) are part of the altered microbiota that is associated with human CRC. We mono-associated ApcMin/+;Il10-/- mice with either F. nucleatum or E. coli and found only pks+ E. coli had the capacity to induce inflammation and tumorigenesis. Next, we examined the functional role of human biofilm associated microbes in CRC development using ApcMin/+;Il10-/- mice. We found that biofilm forming microbes promoted tumorigenesis, suggesting bacterial organization also plays a role in CRC pathogenesis. Taken together these studies stress the importance of balance in host-microbiota interactions. Elucidating host and microbial factors that contribute to disease states has the potential to transform how diseases are prevented and treated.Doctor of Philosoph

Microbiota as a mediator of cancer progression and therapy

Complex and intricate circuitries regulate cellular proliferation, survival, and growth, and alterations of this network through genetic and epigenetic events result in aberrant cellular behaviors, often leading to carcinogenesis. Although specific germline mutations have been recognized as cancer inducers, the vast majority of neoplastic changes in humans occur through environmental exposure, lifestyle, and diet. An emerging concept in cancer biology implicates the microbiota as a powerful environmental factor modulating the carcinogenic process. For example, the intestinal microbiota influences cancer development or therapeutic responses through specific activities (immune responses, metabolites, microbial structures, and toxins). The numerous effects of microbiota on carcinogenesis, ranging from promoting, preventing, or even influencing therapeutic outcomes, highlight the complex relationship between the biota and the host. In this review, we discuss the latest findings on this complex microbial interaction with the host and highlight potential mechanisms by which the microbiota mediates such a wide impact on carcinogenesis

Could a Swimming Creature Inform Us on Intestinal Diseases? Lessons from Zebrafish:

Understanding a complex pathology such as inflammatory bowel disease, where host genetics (innate and adaptive immunity, barrier function) and environmental factors (microbes, diet, and stress) interact together to influence disease onset and severity, requires multipronged approaches to model these numerous variables. Researchers have typically relied on preclinical models of mouse and rat origin to push the boundary of knowledge further. However, incorporation of novel vertebrate models may contribute to new knowledge on specific aspects of intestinal homeostasis. An emerging literature has seen the use of zebrafish as a novel animal system to study key aspects of host–microbe interactions in the intestine. In this review, we briefly introduce components of host–microbiota interplay in the developing zebrafish intestine and summarize key lessons learned from this animal system; review important chemically induced and genetically engineered zebrafish models of intestinal immune disorders; and discuss perspectives and limitations of the zebrafish model system

Global pattern of nest predation is disrupted by climate change in shorebirds

Ongoing climate change is thought to disrupt trophic relationships, with consequences for complex interspecific interactions, yet the effects of climate change on species interactions are poorly understood, and such effects have not been documented at a global scale. Using a single database of 38,191 nests from 237 populations, we found that shorebirds have experienced a worldwide increase in nest predation over the past 70 years. Historically, there existed a latitudinal gradient in nest predation, with the highest rates in the tropics; however, this pattern has been recently reversed in the Northern Hemisphere, most notably in the Arctic. This increased nest predation is consistent with climate-induced shifts in predator-prey relationships

CAFF Technical Report No. 21 - ARCTIC BIRDS INTERNATIONAL BREEDING CONDITIONS SURVEY BULLETIN No. 11

CAFF Technical Report No. 21 - ARCTIC BIRDS INTERNATIONAL BREEDING CONDITIONS SURVEY BULLETIN No. 1

SEM and AFM studies of two-phase magnetic alkali borosilicate glasses

The morphology and composition of four types of two-phase alkali borosilicate glasses with magnetic atoms prepared by inductive melting have been studied. The results of scanning electron microscopy point to uniform distribution of Na, Si, and O atoms in these samples whilemagnetic iron atoms formball-shaped agglomerates. The magnetic properties of these agglomerates have been confirmed by magnetic force microscopy. Atomic force microscopy had shown that in these samples two different morphological structures, drop-like and dendrite net, are formed. The formation of dendrite-like structure is a necessary condition for production of porous magnetic glasses. The obtained results allowus to optimize the melting and heat treatment processes leading to production of porous alkali borosilicate glasses withmagnetic properties. The first results for nanocompositematerials on the basis ofmagnetic glasses containing the embedded ferroelectrics KH2PO4 demonstrate the effect of applied magnetic field on the ferroelectric phase transition. The morphology and composition of four types of two-phase alkali borosilicate glasses with magnetic atoms prepared by inductive melting have been studied. The results of scanning electron microscopy point to uniform distribution of Na, Si, and O atoms in these samples whilemagnetic iron atoms formball-shaped agglomerates. The magnetic properties of these agglomerates have been confirmed by magnetic force microscopy. Atomic force microscopy had shown that in these samples two different morphological structures, drop-like and dendrite net, are formed. The formation of dendrite-like structure is a necessary condition for production of porous magnetic glasses. The obtained results allowus to optimize the melting and heat treatment processes leading to production of porous alkali borosilicate glasses withmagnetic properties. The first results for nanocompositematerials on the basis ofmagnetic glasses containing the embedded ferroelectrics KH2PO4 demonstrate the effect of applied magnetic field on the ferroelectric phase transition.DAA

Synthesis, structure, and visible-light-driven activity of o-YbFeO3/h-YbFeO3/CeO2 photocatalysts

Received: 29.09.2021. Revised: 27.11.2021. Accepted: 30.11.2021. Available online: 02.12.2021.Photo-Fenton-like oxidation of organic substances is one of the key advanced oxidation processes based on the reversible Fe2+↔Fe3+ transition and the generation of a strong oxidant ·OH in the presence of H2O2 and is currently considered as a promising method for the purification of polluted aqueous media. However, the absence of effective and stable photocatalysts of this process, operating under the action of visible light, necessitates the exploratory studies, mainly among iron oxides and ferrites of various compositions and structures. In this work, using the method of solution combustion followed by heat treatment in air the heterojunction nanocomposites based on ytterbium orthoferrite and cerium dioxide of the composition o-YbFeO3/h-YbFeO3/CeO2 (0–20 mol.%) with high absorption in the visible region and advanced photo-Fentonlike activity were obtained. The nanocomposites were studied by EDS, SEM, XRD, BET, and DRS methods. The photo-Fenton-like activity of the nanocomposites was investigated during the degradation of methyl violet under the action of visible (λmax = 410 nm) radiation. As a result, the formation of I-type heterojunction based on stable rhombic (55.4–79.0 nm) and metastable hexagonal (19.5–24.0 nm) modifications of ytterbium orthoferrite (o-YbFeO3 and h-YbFeO3, respectively) and cubic cerium dioxide CeO2 (13.2–19.2 nm) nanocrystals was established. It was shown that the obtained nanocomposites had foamy morphology and were characterized by a specific surface in the range of 9.1–25.0 m2/g, depending on the CeO2 content. It was found that nanocrystalline components were chemically and phase-pure, uniformly spatially distributed over the nanocomposite, and had multiple contacts with each other. Based on this fact and the established electronic structure of the nanocomposite components, the formation of I-type heterojunction with the participation of o-YbFeO3 (Eg = 2.15 eV), h-YbFeO3 (Eg = 2.08 eV), and CeO2 (Eg = 2.38 eV) was shown, the presence of which increased photocatalytic activity of the resulting nanocomposite. The optimal content of CeO2 in the nanocomposite was 5%, and the o-YbFeO3/h-YbFeO3/CeO2–5% sample was characterized by the highest rate constant of photo-Fenton-like degradation of methyl violet under the action of visible light equal to k = 0.138 min–1, which was 2.5 to 5 times higher than for nanocomposites based on ytterbium orthoferrite. The obtained results obtained indicate that the developed nanocomposites can be considered as a promising basis for the advanced oxidation processes for the purification of aqueous media from organic pollutants.This work is supported by the Grant of President of the Rus-sian Federation МК-795.2021.1.3. The XRD, SEM, and EDS studies were performed on the equipment of the Engineer-ing Center of Saint Petersburg State Institute of Technology