Kwok, L.-Y. | bioRxiv Science

bioRxiv2020

Microbiota in milk from healthy and mastitis cows varies greatly in diversity, species richness and composition, as revealed by PacBio sequencing

Mastitis is the most economically important disease of dairy cows. This study used PacBio single-molecule real-time sequencing technology to sequence the full-length of the l6S rRNA from the microbiota in 27 milk samples (18 from mastitis and 9 from healthy cows; the cows were at different stages of lactation). We observed that healthy or late stage milk microbiota had significantly higher microbial diversity and richness. The community composition of the microbiota from different groups also varied greatly. In milk from healthy cows the microbiota was predominantly comprised of Lactococcus lactis, Acinetobacter johnsonii and Bacteroides dorei, while from mastitis cows it was predominantly comprised of Bacillus cereus, Clostridium cadaveris and Streptococcus suis. The prevalence of La. lactis and B. cereus in milk from healthy and mastitis cows was confirmed by digital droplets PCR. Differences in milk microbiota composition could suggest an important role for these microbes in protecting the host from mastitis. Based on the milk microbiota profiles, the Udder Health Index was constructed to predict the risk of bovine mastitis. Application of this predictive model could aid early identification and prevention of mastitis in dairy cows, though the model requires further optimisation using a larger dataset.

microbiology↗

bioRxiv2020

Probiotic consumption relieved human stress and anxiety symptoms via modulating the gut microbiota and neuroactive potential

Stress has been shown to disturb the balance of human intestinal microbiota and subsequently cause mental health problems, such as anxiety and depression. The gut microbial communities are able to synthesize and/or consume various neuroactive metabolites, and preliminary human studies have also demonstrated the ability of probiotics to modulate the levels of neurotransmitter. However, the study and interpretation of the biological significance of microbial neuroactive compounds have been hindered by the lack of dedicated reference databases and corresponding human intestinal microbiota reference genomes. Our previous study showed that ingesting the probiotic strain, Lactobacillus (L.) plantarum P-8, for 12 weeks could alleviate stress and anxiety of stressed adults. The current study was a follow-up work aiming to further elucidate mechanisms behind the observed beneficial effects by performing deep analysis of the fecal metagenomes of the probiotic (n = 43) and placebo (n = 36) groups. Comparing with the probiotic group, the gut microbiomes of the placebo group showed significantly higher Bray-Curtis dissimilarity between weeks 0 and 12 (p < 0.05). Comparing with week 0, the Shannon diversity index of the placebo group decreased significantly at week 12 (t-test; p < 0.05), but such decrease was non-significant for the probiotic group. Additionally, the fecal metagenomes of the probiotic group showed significant increases in the species-level genome bins (SGBs) of Bifidobacterium adolescent, Bifidobacterium longum, and Fecalibacterium prausnitzii increased, while decreases in the SGBs of Roseburia faeci and Fusicatenibacter saccharivorans. Furthermore, the 12-week probiotic supplementation enhanced the diversity of neurotransmitter-synthesizing and/or -consuming SGBs, and the levels of some predicted microbial neuroactive metabolites (short chain fatty acids, gamma-aminobutyric acid, arachidonic acid, and sphingomyelin et.al). In conclusion, this study revealed the potential mechanism of probiotics in alleviating stress and anxiety via the gut-brain axis. The modulation of the intestinal microbiota by probiotics is an attractive strategy for managing stress and anxiety.

neuroscience↗