Interspecies interactions are essential for the persistence and development of any kind of complex community, and microbial biofilms are no exception. Multispecies biofilms are structured and spatially defined communities that have received much attention due to their omnipresence in natural environments. Species residing in these complex bacterial communities usually interact both intra- and interspecifically. Such interactions are considered to not only be fundamental in shaping overall biomass and the spatial distribution of cells residing in multispecies biofilms, but also to result in coordinated regulation of gene expression in the different species present. These communal interactions often lead to emergent properties in biofilms, such as enhanced tolerance against antibiotics, host immune responses, and other stresses, which have been shown to provide benefits to all biofilm members not only the enabling sub-populations. However, the specific molecular mechanisms of cellular processes affecting spatial organization, and vice versa, are poorly understood and very complex to unravel. Therefore, detailed description of the spatial organization of individual bacterial cells in multispecies communities can be an alternative strategy to reveal the nature of interspecies interactions of constituent species. Closing the gap between visual observation and biological processes may become crucial for resolving biofilm related problems, which is of utmost importance to environmental, industrial, and clinical implications. This review briefly presents the state of the art of studying interspecies interactions and spatial organization of multispecies communities, aiming to support theoretical and practical arguments for further advancement of this field.

Microorganisms frequently co-exist in matrix-embedded multispecies biofilms. Within biofilms, interspecies interactions influence the spatial organization of member species, which likely play an important role in shaping the development, structure and function of these communities. Here, a reproducible four-species biofilm, composed of Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus, was established to study the importance of individual species spatial organization during multispecies biofilm development. We found that the growth of species that are poor biofilm formers, M. oxydans and P. amylolyticus, were highly enhanced when residing in the four-species biofilm. Interestingly, the presence of the low-abundant M. oxydans (0.5% of biomass volume) was observed to trigger changes in the composition of the four-species community. The other three species were crucially needed for the successful inclusion of M. oxydans in the four-species biofilm, where X. retroflexus was consistently positioned in the top layer of the mature four-species biofilm. These findings suggest that low abundance key species can significantly impact the spatial organization and hereby stabilize the function and composition of complex microbiomes.

Great efforts have been made to the investigation of defects in silicon carbide for their attractive optical and spin properties. However, most of the researches are implemented at low and room temperature. Little is known about the spin coherent property at high temperature. Here, we experimentally demonstrate coherent control of divacancy defect spins in silicon carbide above 550 K. The spin properties of defects ranging from room temperature to 600 K are investigated, in which the zero-field-splitting is found to have a polynomial temperature dependence and the spin coherence time decreases as the temperature increases. Moreover, as an example of application, we demonstrate a thermal sensing using the Ramsey method at about 450 K. Our experimental results would be useful for the investigation of high temperature properties of defect spins and silicon carbide-based broad-temperature range quantum sensing.

Oscillospira is a class of organism that often appears in high-throughput sequencing data but has not been purely cultured and is widely present in the animal and human intestines. There is a strong association between variation in Oscillospira abundance and obesity, leanness, and human health. In addition, a growing body of studies has shown that Oscillospira is also implicated in other diseases, such as gallstones and chronic constipation, and has shown some correlation with the positive or negative changes in its course. Sequencing data combined with metabolic profiling indicate that Oscillospira is likely to be a genus capable of producing short-chain fatty acids (SCFAs) such as butyrate, which is an important reference indicator for screening “next-generation probiotics “. Considering the positive effects of Oscillospira in some specific diseases, such as obesity-related metabolic diseases, it has already been characterized as one of the next-generation probiotic candidates and therefore has great potential for development and application in the future food, health care, and biopharmaceutical products.

Environmental microbes frequently live in multispecies biofilms where mutualistic relationships and co-evolution may occur, defining spatial organization for member species and overall community functions. In this context, intrinsic properties emerging from microbial interactions, such as efficient organization optimizing growth and activities in multispecies biofilms, may become the object of fitness selection. However, little is known on the nature of underlying interspecies interactions during establishment of a predictable spatial organization within multispecies biofilms. We present a comparative metatranscriptomic analysis of bacterial strains residing in triple-species and four-species biofilms, aiming at deciphering molecular mechanisms underpinning bacterial interactions responsible of the remarkably enhanced biomass production and associated typical spatial organization they display. Metatranscriptomic profiles concurred with changes in micro-site occupation in response to the addition/removal of a single species, being driven by both cooperation, competition, and facilitation processes. We conclude that the enhanced biomass production of the four-species biofilm is an intrinsic community property emerging from finely tuned space optimization achieved through concerted antagonistic and mutualistic interactions, where each species occupies a defined micro-site favoring its own growth. Our results further illustrate how molecular mechanisms can be better interpreted when supported by visual imaging of actual microscopic spatial organization, and we propose phenotypic adaptation selected by social interactions as molecular mechanisms stabilizing microbial communities.

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Microorganisms frequently coexist in complex multispecies communities, where they distribute non-randomly, reflective of the social interactions that occur. It is therefore important to understand how social interactions and local spatial organization influences multispecies biofilm succession. Here the localization of species pairs was analyzed in three dimensions in a reproducible four-species biofilm model, to study the impact of spatial positioning of individual species on the temporal development of the community. We found, that as the biofilms developed, species pairs exhibited distinct intermixing patterns unique to the four-member biofilms. Higher biomass and more intermixing were found in four-species biofilms compared to biofilms with fewer species. Intriguingly, in local regions within the four member biofilms where Microbacterium oxydans was scant, both biomass and intermixing of all species were lowered, compared to regions where M. oxydans was present at typical densities. Our data suggest that Xanthomonas retroflexus and M. oxydans, both low abundant biofilm-members, intermixed continuously during the development of the four-species biofilm, hereby facilitating their own establishment. In turn, this seems to have promoted distinct spatial organization of Stenotrophomonas rhizophila and Paenibacillus amylolyticus enabling enhanced growth of all four species. Here local intermixing of bacteria advanced the temporal development of a multi-species biofilm.