Ana M Valdes and colleagues discuss strategies for modulating the gut microbiota through diet and probiotics

https://www.bmj.com/content/bmj/361/bmj.k2179.full.pdf

Role of the gut microbiota in nutrition and health

Background It has been recognized that a number of mechanisms mediating the health benefits of beneficial bacterial cells do require viability. However, new terms such as paraprobiotic or postbiotic have emerged to denote that non-viable microbial cells, microbial fractions, or cell lysates might also offer physiological benefits to the host by providing additional bioactivity. Scope and approach This review provides an overview of the postbiotic concept, evidence of their health benefits and possible signaling pathways involved in their protective effects, as well as perspectives for applications in foods and pharmaceuticals. Key findings and conclusions Postbiotics refers to soluble factors (products or metabolic byproducts), secreted by live bacteria, or released after bacterial lysis, such as enzymes, peptides, teichoic acids, peptidoglycan-derived muropeptides, polysaccharides, cell surface proteins, and organic acids. These postbiotics have drawn attention because of their clear chemical structure, safety dose parameters, long shelf life and the content of various signaling molecules which may have anti-inflammatory, immunomodulatory, anti-obesogenic, antihypertensive, hypocholesterolemic, anti-proliferative, and antioxidant activities. These properties suggest that postbiotics may contribute, to the improvement of host health by improving specific physiological functions, even though the exact mechanisms have not been entirely elucidated.

Postbiotics: An evolving term within the functional foods field

Aquaculture is an important food producing sector to fulfill nutritional food demand of a continuously growing population. However, disease outbreak has become a major problem in aquaculture which cause huge economic loss to aquaculture industries. The use of expensive chemotherapeutic drugs for treatment have negative impacts on the aquatic environment. So there is a growing concern to find other safe, non-antibiotic based and eco-friendly alternative for the treatment of the diseases. The use of probiotics is a promising alternative approach for the control of infectious agents and treatment of diseases. The benefits of probiotic include stimulation of growth, improved digestion, enhanced immune response and recuperate the water quality as well. Probiotics concoct the fish to fight against various pathogens and improves the overall health as they show anti-bacterial, anti-fungal and anti-viral properties. The use of probiotics in aquaculture is a recent trend and its efficacy in aquatic environment has not been studied extensively. This review paper provides the current knowledge of the use of probiotics in aquaculture, selection criteria, types of probiotics used in aquaculture, their mode of action and administrative methods of probiotics in aquaculture.

Probiotics in aquaculture: a promising emerging alternative approach.

Honey bees are essential pollinators threatened by colony losses linked to the spread of parasites and pathogens. Here, we report a new approach for manipulating bee gene expression and protecting bee health. We engineered a symbiotic bee gut bacterium, Snodgrassella alvi, to induce eukaryotic RNA interference (RNAi) immune responses. We show that engineered S. alvi can stably recolonize bees and produce double-stranded RNA to activate RNAi and repress host gene expression, thereby altering bee physiology, behavior, and growth. We used this approach to improve bee survival after a viral challenge, and we show that engineered S. alvi can kill parasitic Varroa mites by triggering the mite RNAi response. This symbiont-mediated RNAi approach is a tool for studying bee functional genomics and potentially for safeguarding bee health.

https://hal.archives-ouvertes.fr/hal-02498542/document

Engineered symbionts activate honey bee immunity and limit pathogens

Engineering Microbial Living Therapeutics: The Synthetic Biology Toolbox.

Designer probiotics for the prevention and treatment of human diseases.

Engineering probiotics for therapeutic applications: recent examples and translational outlook.

The EvgS/EvgA two-component system of Escherichia coli is activated in response to low pH and alkali metals and regulates many genes, including those for the glutamate-dependent acid resistance system and a number of efflux pumps. EvgS, the sensor kinase, is one of five unconventional histidine kinases (HKs) in E. coli and has a large periplasmic domain and a cytoplasmic PAS domain in addition to phospho-acceptor, HK and dimerization, internal receiver, and phosphotransfer domains. Mutations that constitutively activate the protein at pH 7 map to the PAS domain. Here, we built a homology model of the periplasmic region of EvgS, based on the structure of the equivalent region of the BvgS homologue, to guide mutagenesis of potential key residues in this region. We show that histidine 226 is required for induction and that it is structurally colocated with a proline residue (P522) at the top of the predicted transmembrane helix that is expected to play a key role in passing information to the cytoplasmic domains. We also show that the constitutive mutations in the PAS domain can be further activated by low external pH. Expression of the cytoplasmic part of the protein alone also gives constitutive activation, which is lost if the constitutive PAS mutations are present. These findings are consistent with a model in which EvgS senses both external and internal pH and is activated by a shift from a tight inactive to a weak active dimer, and we present an analysis of the purified cytoplasmic portion of EvgS that supports this.IMPORTANCE One of the ways bacteria sense their environment is through two-component systems, which have one membrane-bound protein to do the sensing and another inside the cell to turn genes on or off in response to what the membrane-bound protein has detected. The membrane-bound protein must thus be able to detect the stress and signal this detection event to the protein inside the cell. To understand this process, we studied a protein that helps E. coli to survive exposure to low pH, which it must do before taking up residence in the gastrointestinal tract. We describe a predicted structure for the main sensing part of the protein and identify some key residues within it that are involved in the sensing and signaling processes. We propose a mechanism for how the protein may become activated and present some evidence to support our proposal.

/pdf/structural-and-functional-analysis-of-the-escherichia-coli-rnbu14mhwc.pdf

Structural and Functional Analysis of the Escherichia coli Acid-Sensing Histidine Kinase EvgS.

The human microbiome is composed of a collection of dynamic microbial communities that inhabit various anatomical locations in the body. Accordingly, the coevolution of the microbiome with the host has resulted in these communities playing a profound role in promoting human health. Consequently, perturbations in the human microbiome can cause or exacerbate several diseases. In this Review, we present our current understanding of the relationship between human health and disease development, focusing on the microbiomes found across the digestive, respiratory, urinary, and reproductive systems as well as the skin. We further discuss various strategies by which the composition and function of the human microbiome can be modulated to exert a therapeutic effect on the host. Finally, we examine technologies such as multiomics approaches and cellular reprogramming of microbes that can enable significant advancements in microbiome research and engineering.

Microbiome and Human Health: Current Understanding, Engineering, and Enabling Technologies

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ggn2.10038

Nikhil Aggarwal

Papers

Designer probiotics for the prevention and treatment of human diseases.

Engineering probiotics for therapeutic applications: recent examples and translational outlook.

Structural and Functional Analysis of the Escherichia coli Acid-Sensing Histidine Kinase EvgS.

Microbiome and Human Health: Current Understanding, Engineering, and Enabling Technologies

Future trends in synthetic biology in Asia