Proteomes of Lactobacillus delbrueckii subsp. bulgaricus LBB.B5 Incubated in Milk at Optimal and Low Temperatures

Comparative Genomics Analysis Provides New Insights into High Ethanol Tolerance of Lactiplantibacillus pentosus LTJ12, a Novel Strain Isolated from Chinese Baijiu

Lactic acid bacteria have received a significant amount of attention due to their probiotic characteristics. The species Lactiplantibacillus plantarum and Lactiplantibacillus pentosus are genotypically closely related, and their phenotypes are so similar that they are easily confused and mistaken. In the previous study, an ethanol-resistant strain, LTJ12, isolated from the fermented grains of soy sauce aroma type baijiu in North China, was originally identified as L. plantarum through a 16S rRNA sequence analysis. Here, the genome of strain LTJ12 was further sequenced using PacBio and Illumina sequencing technology to obtain a better understanding of the metabolic pathway underlying its resistance to ethanol stress. The results showed that the genome of strain LTJ12 was composed of one circular chromosome and three circular plasmids. The genome size is 3,512,307 bp with a GC content of 46.37%, and the number of predicted coding genes is 3248. Moreover, by comparing the coding genes with the GO (Gene Ontology), COG (Cluster of Orthologous Groups) and KEGG (Kyoto Encyclopedia of Genes and Genomes) databases, the functional annotation of the genome and an assessment of the metabolic pathways were performed, with the results showing that strain LTJ12 has multiple genes that may be related to alcohol metabolism and probiotic-related genes. Antibiotic resistance gene analysis showed that there were few potential safety hazards. Further, after conducting the comparative genomics analysis, it was found that strain LTJ12 is L. pentosus but not L. plantarum, but it has more functional genes than other L. pentosus strains that are mainly related to carbohydrate transport and metabolism, transcription, replication, recombination and repair, signal transduction mechanisms, defense mechanisms and cell wall/membrane/envelope biogenesis. These unique functional genes, such as gene 2754 (encodes alcohol dehydrogenase), gene 3093 (encodes gamma-D-glutamyl-meso-diaminopimelate peptidase) and some others may enhance the ethanol tolerance and alcohol metabolism of the strain. Taken together, L. pentosus LTJ12 might be a potentially safe probiotic with a high ethanol tolerance and alcohol metabolism. The findings of this study will also shed light on the accurate identification and rational application of the Lactiplantibacillus species.

Lactobacillus delbrueckii alleviates depression-like behavior through inhibiting toll-like receptor 4 (TLR4) signaling in mice

Background

The intestinal flora can influence behavior through the microbiota-gut-brain axis and is closely related to the occurrence and development of nervous system diseases such as depression. Probiotics like Lactobacillus may regulate the balance of the intestinal flora and play an active role in preventing and treating depression.

Methods

Eight-week-old C57BL/6J mice (n=32) were randomly and equally divided into a normal control group, a control + Lac group, a model group, and a model + Lac group. The model and model + Lac groups were intraperitoneally injected with 1.2 mg/kg lipopolysaccharide for 7 days, and the behavior of the mice was assessed 24 hours later. The normal and model groups received intragastric administration of saline daily, while the control + Lac and model + Lac groups were given 10⁹ cfu Lac intragastrically daily for 7 days. The inhibitory effect of Lac and its fermentation products on depression-related bacteria were examined in vitro.

Results

Lac effectively inhibited the production of depression-like behaviors in mice. The expression levels of zonula occludens-1 (ZO-1) and E-cadherin in the small intestine in the model group were significantly decreased, but Lac abrogated this effect. Overactivation of microglia and decreased expression of dopamine transporter (DAT) in brain tissues, which are closely related to depression, were also abrogated by Lac treatment. Furthermore, the expression of toll-like receptor 4 (TLR4) and nod-like receptor protein-3 (NLRP3), as well as the level of interleukin-1 beta (IL-1β) in the intestine and brain, were all significantly increased; however, these effects were subsequently abrogated by Lac. Moreover, Lac inhibited dysbiosis through its metabolites.

Conclusions

Lac has a remarkable antidepressant function, which it performs through the inhibition of dysbiosis (via its metabolites) and pattern recognition receptor TLR4 signaling.

Yeast Fermentation at Low Temperatures: Adaptation to Changing Environmental Conditions and Formation of Volatile Compounds

Yeast plays a key role in the production of fermented foods and beverages, such as bread, wine, and other alcoholic beverages. They are able to produce and release from the fermentation environment large numbers of volatile organic compounds (VOCs). This is the reason for the great interest in the possibility of adapting these microorganisms to fermentation at reduced temperatures. By doing this, it would be possible to obtain better sensory profiles of the final products. It can reduce the addition of artificial flavors and enhancements to food products and influence other important factors of fermented food production. Here, we reviewed the genetic and physiological mechanisms by which yeasts adapt to low temperatures. Next, we discussed the importance of VOCs for the food industry, their biosynthesis, and the most common volatiles in fermented foods and described the beneficial impact of decreased temperature as a factor that contributes to improving the composition of the sensory profiles of fermented foods.

FTIR micro-spectroscopy using synchrotron-based and thermal source-based radiation for probing live bacteria

Fourier transform infrared (FTIR) spectroscopy has proven to be a non-invasive tool to analyse cells without the hurdle of employing exogenous dyes or probes. Nevertheless, the study of single live bacteria in their aqueous environment has long remained a big challenge, due to the strong infrared absorption of water and the small size of bacteria compared to the micron-range infrared wavelengths of the probing photons. To record infrared spectra of bacteria in an aqueous environment, at different spatial resolutions, two setups were developed. A custom-built attenuated total reflection inverted microscope was coupled to a synchrotron-based FTIR spectrometer, using a germanium hemisphere. With such a setup, a projected spot size of 1 × 1 μm² was achieved, which allowed spectral acquisition at the single-cell level in the 1800-1300 cm^-1 region. The second setup used a demountable liquid micro-chamber with a thermal source-powered FTIR microscope, in transmission geometry, for probing clusters of a few thousands of live cells in the mid-IR region (4000-975 cm^-1). Both setups were applied for studying two strains of a model lactic acid bacterium exhibiting different cryo-resistances. The two approaches allowed the discrimination of both strains and revealed population heterogeneity among bacteria at different spatial resolutions. The multivariate analysis of spectra indicated that the cryo-sensitive cells presented the highest cell heterogeneity and the highest content of proteins with the α-helix structure. Furthermore, the results from clusters of bacterial cells evidenced phosphate and peptidoglycan vibrational bands associated with the cell envelope, as potential markers of resistance to environmental conditions. Graphical Abstract.