Two‐Component Systems in Microbial Communities: Approaches and Resources for Generating and Analyzing Metagenomic Data Sets

Milk microbiome diversity and bacterial group prevalence in a comparison between healthy Holstein Friesian and Rendena cows

Dry and early lactation periods represent the most critical phases for udder health in cattle, especially in highly productive breeds, such as the Holstein Friesian (HF). On the other hand, some autochthonous cattle breeds, such as the Rendena (REN), have a lower prevalence of mastitis and other transition-related diseases. In this study, milk microbiota of 6 HF and 3 REN cows, all raised on the same farm under the same conditions, was compared. A special focus was placed on the transition period to define bacterial groups’ prevalence with a plausible effect on mammary gland health. Four time points (dry-off, 1 d, 7–10 d and 30 d after calving) were considered. Through 16S rRNA sequencing, we characterized the microbiota composition for 117 out of the 144 milk samples initially collected, keeping only the healthy quarters, in order to focus on physiological microbiome changes and avoid shifts due to suspected diseases. Microbial populations were very different in the two breeds along all the time points, with REN milk showing a significantly lower microbial biodiversity. The taxonomic profiles of both cosmopolitan and local breeds were dominated by Firmicutes, mostly represented by the Streptococcus genus, although in very different proportions (HF 27.5%, REN 68.6%). Large differences in HF and REN cows were, also, evident from the metabolic predictive analysis from microbiome data. Finally, only HF milk displayed significant changes in the microbial composition along the transition period, while REN maintained a more stable microbiota. In conclusion, in addition to the influence on the final characteristics of dairy products obtained from milk of the two breeds, differences in the milk microbiome might, also, have an impact on their mammary gland health.

Life in the gut: microbial responses to stress in the gastrointestinal tract

The complex physical and chemical conditions encountered in the gut present a range of physiological challenges to both the commensal microbiota and to pathogenic microorganisms attempting to colonise the gut. The innate immune system of the host, the host's diet and the microbial population present in the gut all contribute to the chemical complexity of the environment. The huge population of microorganisms in the gut also has a significant impact on the physicochemical properties of the gut environment. By focussing on some of the key physical and chemical stresses encountered by microorganisms in the gut, some of the molecular responses are described. Some promising new experimental approaches are outlined for studying the behaviour of microorganisms and their communities within the gut environment.