Recent studies have shown that the gut microbiota modulates the physical and psychological functions of the host through several modes of action. One of them is mediating the production of active neurotransmitters, such as serotonin and gamma-aminobutyric acid (GABA). GABA is the major inhibitory neurotransmitter in the central nervous system. Here, we analyzed the relationship between fecal GABA concentration and microbial composition in more than 70 human participants. The gut microbiome composition was analyzed using next-generation sequencing based on 16S ribosomal RNA. High-performance liquid chromatography was used to evaluate the neurotransmitters GABA and glutamate. The GABA level was detected in a broad range (0–330 µg/g feces). The participants’ samples were classified into high (>100 µg/g), medium (10–100 µg/g), and low (<10 µg/g) groups, based on fecal GABA concentration. The results reveal that the microbiome of the high-GABA samples had lower alpha diversity than the other samples. Beta diversity analysis showed significant (p < 0.05) separation between the high-GABA samples and others. Furthermore, we surveyed the abundance of specific GABA producer biomarkers among the microbiomes of tested samples. The family Bifidobacteriaceae exhibited high abundance in the microbiome of the high-GABA group. This study demonstrated that Bifidobacterium abundance was associated with high fecal GABA content in healthy human subjects. These results may aid the development of potential probiotics to improve microbial GABA production, which can support the maintenance of the physical and psychiatric health of the host.

Background Bifidobacteria are gram-positive, probiotic, and generally regarded as safe bacteria. Techniques such as transformation, gene knockout, and heterologous gene expression have been established for Bifidobacterium, indicating that this bacterium can be used as a cell factory platform. However, there are limited previous reports in this field, likely because of factors such as the highly anaerobic nature of this bacterium. Bifidobacterium adolescentis is among the most oxygen-sensitive Bifidobacterium species. It shows strain-specific gamma-aminobutyric acid (GABA) production. GABA is a potent bioactive compound with numerous physiological and psychological functions. In this study, we investigated whether B. adolesentis could be used for mass production of GABA. Results The B. adolescentis 4–2 strain isolated from a healthy adult human produced approximately 14 mM GABA. It carried gadB and gadC, which encode glutamate decarboxylase and glutamate GABA antiporter, respectively. We constructed pKKT427::Pori-gadBC and pKKT427::Pgap-gadBC plasmids carrying gadBC driven by the original gadB (ori) and gap promoters, respectively. Recombinants of Bifidobacterium were then constructed. Two recombinants with high production abilities, monitored by two different promoters, were investigated. GABA production was improved by adjusting the fermentation parameters, including the substrate concentration, initial culture pH, and co-factor supplementation, using response surface methodology. The optimum initial cultivation pH varied when the promoter region was changed. The ori promoter was induced under acidic conditions (pH 5.2:4.4), whereas the constitutive gap promoter showed enhanced GABA production at pH 6.0. Fed-batch fermentation was used to validate the optimum fermentation parameters, in which approximately 415 mM GABA was produced. The conversion ratio of glutamate to GABA was 92–100%. Conclusion We report high GABA production in recombinant B. adolescentis. This study provides a foundation for using Bifidobacterium as a cell factory platform for industrial production of GABA.

A series of new Escherichia coli entry vectors (pIIS18-SapI, pIIS18-BsmBI, pIIS18-BsaI, pIIS18-BfuAI-1, and pIIS18-BfuAI-2) was constructed based on a modified pUC18 backbone, which carried newly designed multiple cloning sites, consisting of two facing type IIS enzyme cleavage sites and one blunt-end enzyme cleavage site. These vectors are useful for seamless gene cloning.

Mounting evidence elucidates the impact of gut microbiota on the maintenance of host's physical and psychological conditions. The gut microbiota can produce its effects through neural, endocrine, and immune pathways. Specific gut members, such as lactobacilli and bifidobacteria, have shown unique abilities to affect the host's mental health, and hence, they are called psychobiotics. Several studies, on both rodents and humans, have confirmed the role of Bifidobacterium in the regulation of anxiety, mood, cognition, and pain. Here, we summarize the currently available evidence that suggests the roles of bifidobacteria in gut microbiota-brain communication and highlight the prospects of this research field. The action of Bifidobacterium has been found to be strain specific. We discuss here the currently reported mechanisms of action of different Bifidobacterium strains. However, more strategic investigations are needed to fully understand the detailed mechanisms of action of Bifidobacterium as psychobiotic bacteria.

Methicillin-resistant Staphylococcus aureus (MRSA) has a major public health concern. It can be identified throughout the chain of production for poultry, which raises questions regarding potential transmission from farm to consumer. MRSA has zoonotic significance and can be transmitted to humans and poultry. Several studies have been carried out on MRSA on poultry, but this study was conducted to find out the whole scenario of MRSA at the farm level. A total of 100 samples were collected randomly from different poultry farms and retail shops in Khulna city to investigate this study. MRSA was isolated and identified by culturing antibiotic susceptibility testing, and polymerase chain reaction (PCR). Among the 100 samples, 57% were positive for S. aureusand 80.70% of the isolated S. aureus showed hemolysis on blood agar. Among the 57 isolates, 78.94% were MRSA (oxacillin) and 19.29% were vancomycin-resistant Staphylococcus aureus (VRSA) phenotypically. Surprisingly, 59.64% of S. aureus results showed a positive mecA gene. It is also concerning that 60% of broiler meat and 53.84% of farm personnel were infected with MRSA. The present study revealed that MRSA could be transmitted from poultry to humans.