A synthetic microbial consortium protects against obesity by regulating vitamin B6 metabolism.

Constructing synthetic microbial consortia is a challenging task but holds enormous potential for various applications. Our previous droplet-based microfluidic approach allowed for the isolation of bacteria that could utilize metabolites from an engineered bacterium BsS-RS06551 with anti-obesity potential, facilitating the construction of synthetic microbial consortia. Here, we identified a strain of Bifidobacterium pseudocatenulatum JJ3 that interacted with BsS-RS06551, and in vitro coculture showed that BsS-RS06551 was likely to interact with JJ3 through five dipeptides. Pathway analysis revealed that the vitamin B6 metabolism pathway was enriched in the coculture of BsS-RS06551 and JJ3 compared with the individual culture of BsS-RS06551. Additionally, we confirmed that the administration of JJ3 significantly alleviated obesity and related disorders in mice fed a high-fat diet. Notably, continuous ingestion of the synthetic microbial consortium comprising BsS-RS06551 and JJ3 not only exhibited a more pronounced impact on alleviating obesity compared to the individual administration of BsS-RS06551 or JJ3 but also enriched the population of Bifidobacterium longum and perturbed the vitamin B6 metabolism pathway in the gut. Synthetic microbial consortia represent a promising frontier for synthetic biology, and our strategy provides guidance for constructing and applying such consortia.

Single-cell microfluidics enabled dynamic evaluation of drug combinations on antibiotic resistance bacteria.

The rapid spread of antibiotic resistance has become a significant threat to global health, yet the development of new antibiotics is outpaced by emerging new resistance. To treat multidrug-resistant bacteria and prolong the lifetime of existing antibiotics, a productive strategy is to use combinations of antibiotics and/or adjuvants. However, evaluating drug combinations is primarily based on end-point checkerboard measurements, which provide limited information to study the mechanism of action and the discrepancies in the clinical outcomes. Here, single-cell microfluidics is used for rapid evaluation of the efficacy and mode of action of antibiotic combinations within 3 h. Focusing on multidrug-resistant Acinetobacter baumannii, the combination between berberine hydrochloride (BBH, as an adjuvant) and carbapenems (meropenem, MEM) or ß-lactam antibiotic is evaluated. Real-time tracking of individual cells to programmable delivered antibiotics reveals multiple phenotypes (i.e., susceptible, resistant, and persistent cells) with fidelity. Our study discovers that BBH facilitates the accumulation of antibiotics within cells, indicating synergistic effects (FICI = 0.5). For example, the combination of 256 mg/L BBH and 16 mg/L MEM has a similar killing effect (i.e., the inhibition rates >90%) as the MIC of MEM (64 mg/L). Importantly, the synergistic effect of a combination can diminish if the bacteria are pre-stressed with any single drug. Such information is vital for understanding the underlying mechanisms of combinational treatments. Overall, our platform provides a promising approach to evaluate the dynamic and heterogenous response of a bacterial population to antibiotics, which will facilitate new drug discovery and reduce emerging antibiotic resistance.

A droplet-based microfluidic approach to isolating functional bacteria from gut microbiota.

Metabolic interactions within gut microbiota play a vital role in human health and disease. Targeting metabolically interacting bacteria could provide effective treatments; however, obtaining functional bacteria remains a significant challenge due to the complexity of gut microbiota. Here, we developed a facile droplet-based approach to isolate and enrich functional gut bacteria that could utilize metabolites from an engineered butyrate-producing bacteria (EBPB) of anti-obesity potential. This involves the high throughput formation of single-bacteria droplets, followed by culturing "droplets" on agar plates to form discrete single-cell colonies. This approach eliminates the need for sophisticated s instruments to sort droplets and thus allows the operation hosted in a traditional anaerobic chamber. In comparison to the traditional culture, the droplet-based approach obtained a community of substantially higher diversity and evenness. Using the conditioned plates containing metabolites from the EBPB supernatant, we obtained gut bacteria closely associated or interacting with the EBPB. These include anaerobic Lactobacillus and Bifidobacterium, which are often used as probiotics. The study illustrates the potential of our approach in the search for the associated bacteria within the gut microbiota and retrieving those yet-to-be cultured.