Comparative composition, diversity, and abundance of oligosaccharides in early lactation milk from commercial dairy and beef cows.

Prebiotics are nondigestible dietary ingredients, usually oligosaccharides (OS), that provide a health benefit to the host by directly modulating the gut microbiota. Although there is some information describing OS content in dairy-source milk, no information is available to describe the OS content of beef-source milk. Given the different trait emphasis between dairy and beef for milk production and calf survivability, it is plausible that OS composition, diversity, and abundance differ between production types. The goal of this study was to compare OS in milk from commercial dairy and beef cows in early lactation. Early-lactation multiparous cows (5-12 d in milk) from 5 commercial Holstein dairy herds and 5 Angus or Angus hybrid beef herds were sampled once. Milk was obtained from each enrolled cow and frozen on the farm. Subsequently, each milk sample was assessed for total solids, pH, and OS content and relative abundance. Oligosaccharide diversity and abundance within and between samples was transformed through principal component analysis to reduce data complexity. Factors from principal component analysis were used to create similarity clusters, which were subsequently used in a multivariate logistic regression. In total, 30 OS were identified in early-lactation cow milk, including 21 distinct OS and 9 isomers with unique retention times. The majority of OS detected in the milk samples were present in all individual samples regardless of production type. Two clusters described distribution patterns of OS for the study sample; when median OS abundance was compared between the 2 clusters, we found that overall OS relative abundance was consistently greater in the cluster dominated by beef cows. For several of the structures, including those with known prebiotic effect, the difference in abundance was 2- to 4-fold greater in the beef-dominated cluster. Assuming that beef OS content in milk is the gold standard for cattle, it is likely that preweaning dairy calves are deprived of dietary-source OS. Although supplementing rations with OS is an approach to rectify this deficiency, understanding the health and productivity effects of improving OS abundance being fed to preweaning calves is a necessary next step before recommending supplementation. These studies should account for the observation that OS products are variable for both OS diversity and structural complexity, and some products may not be suitable as prebiotics

An endophytic <em>bacillus subtilis</em> strain protects grapevine against downy mildew by direct effect and defense stimulation

National audiencePlasmopara viticola, the causal agent of grapevine downy mildew, is one of the most devastating grape pathogen. Phytochemicals are generally used to control infections, but the appearance of resistant strains and the concern for possible adverse effects on environment and human health are increasing the search for alternative strategies. Biological control has received a great deal of attention as an alternative and promising measure to control different plant diseases. Many antagonistic microorganisms, including Bacillus spp., have been exploited against different pathogens. Bacillus spp. activity results from multiple modes of action including antibiosis, competition, and induction of the host systemic resistance. Bacillus production of the antibiotics lipopeptides, especially surfactin, iturin, and fengycin, is known as an efficient way to suppress diseases. We have isolated the Bacillus subtilis strain GLB191 and demonstrated it has a strong activity against grapevine downy mildew. Assays performed in greenhouses showed a reduction of more than 95 % of the leaf sporulating area. The bacterial activity results from both direct effect against the pathogen, and indirect effect via stimulation of the plant defenses. This strain indeed induces defense gene expression and defense reactions such as callose production. Mutants affected in lipopeptide production were obtained to further investigate the mode of action of this strain. The absence of production of the targeted lipopeptides was confirmed using high-performance thin-layer chromatography (HPTLC). Activity against downy mildew was lost for double mutants affected in both fengycin and surfactin, suggesting a key role of these two lipopeptides in the direct mode of action of Bacillus subtilis strain GLB191. This study shows that Bacillus subtilis strain GLB191 could be a potential biological agent to control grapevine downy mildew. It would be interesting to check activity against other grapevine diseases, especially Grapevine Trunk Diseases, and also against other crop pathogens

Surfactin and fengycin contribute to the protection of a Bacillus subtilis strain against grape downy mildew by both direct effect and defence stimulation

International audienceBacillus subtilis GLB191 (hereafter GLB191) is an efficient biological control agent against the biotrophic oomycete Plasmopara viticola, the causal agent of grapevine downy mildew. In this study, we show that GLB191 supernatant is also highly active against downy mildew and that the activity results from both direct effect against the pathogen and stimulation of the plant defences (induction of defence gene expression and callose production). High-performance thin-layer chromatography analysis revealed the presence of the cyclic lipopeptides fengycin and surfactin in the supernatant. Mutants affected in the production of fengycin and/or surfactin were thus obtained and allowed us to show that both surfactin and fengycin contribute to the double activity of GLB191 supernatant against downy mildew. Altogether, this study suggests that GLB191 supernatant could be used as a new biocontrol product against grapevine downy mildew