Multispecies communities:interspecies interactions influence growth on saliva as sole nutritional source

Human oral bacteria live in multispecies communities in the biofilm called dental plaque. This review focuses on the interactions of seven species and the ability of each species individually and together with other species to grow on saliva as the sole source of nutrient. Community formation in biofihns in flow cells is monitored using species-specific fluorophore-conjugated immunoglobulin Gy and images are captured by confocal microscopy. Early colonizing veillonellae emerge from this review of interspecies interactions in saliva as a critical genus that guides the development of multispecies communities. Highly selective interspecies recognition is evident as initial colonizers pair with early and middle colonizers to form multispecies communities that grow on saliva.

A systematic understanding of microbial reductive dechlorination towards an improved“one health”soil bioremediation:A review and perspective

Chlorinated organic pollutants(COPs),both emerging and traditional,are typical persistent pollutants that harm soil health worldwide.Dechlorinators mediated reductive dechlorination is the optimal way to completely remove COPs from anaerobic soil through a redox reaction driven by electron transfer during microbial anaerobic respiration.Generally,the dechlorinated depletion of COPs in situ often interacts with multiple element biogeochemical activities,e.g.,methanogenesis,sulfate reduction,iron reduction,and denitrification.Elucidating the relevance of biogeochemical cycles between COPs and multiple elements and the coupled mechanisms involved,thus,helps to develop effective pollution control strategies with the balance between pollution degradation and element cycles in heterogeneous soil,ultimately contributing to“one health”goal.In this review,we summarized the microbial-chemical coupling redox processes and the driving factors,elucidated the interspecies metabolites exchange and electron transfer mechanisms within COP-dechlorinating communities,and further proposed a detailed design,construction,and analysis framework of engineering COP-dechlorinating microbiomes via“top-down”selfassembly and“bottom-up”synthesis to pave the way from laboratory to practical field application.Especially,we delve into the major challenges and perspectives surrounding the design of state-of-the-art synthetic microbial communities.Our goal is to improve the understanding of the microbial-mediated coupling between reductive dechlorination and element biogeochemical cycling,with a particular focus on the implications for health-integrated soil bioremediation under the“one health”concept.

Towards applications of genome-scale metabolic model-based approaches in designing synthetic microbial communities

Background:Synthetic microbial communities,with different strains brought together by balancing their nutrition and promoting their interactions,demonstrate great advantages for exploring complex performance of communities and for further biotechnology applications.The potential of such microbial communities has not been explored,due to our limited knowledge of the extremely complex microbial interactions that are involved in designing and controlling effective and stable communities.Results:Genome-scale metabolic models(GEM)have been demonstrated as an effective tool for predicting and guiding the investigation and design of microbial communities,since they can explicitly and efficiently predict the phenotype of organisms from their genotypic data and can be used to explore the molecular mechanisms of microbehabitats and microbe-microbe interactions.In this work,we reviewed two main categories of GEM-based approaches and three uses related to design of synthetic microbial communities:predicting multi-species interactions,exploring environmental impacts on microbial phenotypes,and optimizing community-level performance.Conclusions:Although at the infancy stage,GEM-based approaches exhibit an increasing scope of applications in designing synthetic microbial communities.Compared to other methods,especially the use of laboratory cultures,GEM-based approaches can greatly decrease the trial-and-error cost of various procedures for designing synthetic communities and improving their functionality,such as identifying community members,determining media composition,evaluating microbial interaction potential or selecting the best community configuration.Future efforts should be made to overcome the limitations of the approaches,ranging from quality control of GEM reconstructions to community-level modeling algorithms,so that more applications of GEMs in studying phenotypes of microbial communities can be expected.

Delivery of an Rhs-family nuclease effector reveals direct penetration of the gram-positive cell envelope by a type VI secretion system in Acidovorax citrulli

The type VI secretion system(T6SS)is a double-tubular nanomachine widely found in gram-negative bacteria.Its spear-like Hcp tube is capable of penetrating a neighboring cell for cytosol-to-cytosol protein delivery.However,gram-positive bacteria have been considered impenetrable to such T6SS action.Here we report that the T6SS of a plant pathogen,Acidovorax citrulli(AC),could deliver an Rhsfamily nuclease effector RhsB to kill not only gram-negative but also gram-positive bacteria.Using bioinformatic,biochemical,and genetic assays,we systematically identified T6SS-secreted effectors and determined that RhsB is a crucial antibacterial effector.RhsB contains an N-terminal PAAR domain,a middle Rhs domain,and an unknown C-terminal domain.RhsB is subject to self-cleavage at both its N-and C-terminal domains and its secretion requires the upstream-encoded chaperone EagT2 and VgrG3.The toxic Cterminus of RhsB exhibits DNase activities and such toxicity is neutralized by either of the two downstream immunity proteins,RimB1 and RimB2.Deletion of rhsB significantly impairs the ability of killing Bacillus subtilis while ectopic expression of immunity proteins RimB1 or RimB2 confers protection.We demonstrate that the AC T6SS not only can effectively outcompete Escherichia coli and B.subtilis in planta but also is highly potent in killing other bacterial and fungal species.Collectively,these findings highlight the greatly expanded capabilities of T6SS in modulating microbiome compositions in complex environments.