Influence of the maize silage to grass silage ratio and feed particle size of rations for ruminants on the community structure of ruminal Firmicutes in vitro.

AIMS: To investigate the effect of the forage source and feed particle size (FPS) in ruminant rations on the composition of the ruminal Firmicutes community in vitro. METHODS AND RESULTS: Three diets, varying in maize silage to grass silage ratio and FPS, were incubated in a rumen simulation system. Microbial samples were taken from the liquid fermenter effluents. Microbial community analysis was performed by 16S rRNA-based techniques. Clostridia-specific single-strand conformation polymorphism profiles revealed changes of the community structure in dependence on both factors tested. The coarse grass silage-containing diets seemed to enhance the occurrence of different Roseburia species. As detected by real-time quantitative PCR, Ruminococcus albus showed a higher abundance with decreasing FPS. A slightly lower proportion of Bacilli was found with increasing grass silage to maize silage ratio by fluorescence in situ hybridization (FISH). In contrast, a slightly higher proportion of bacterial species belonging to the Clostridium-clusters XIV a and b was detected by FISH with increasing grass silage contents in the diet. CONCLUSIONS: The ruminal Firmicutes community is affected by the choice of the forage source and FPS. SIGNIFICANCE AND IMPACT OF THE STUDY: This study supplies fundamental knowledge about the response of ruminal microbial communities to changing diets. Moreover, the data suggest a standardization of grinding of feeds for in vitro studies to facilitate the comparison of results of different laboratories.

Effect of the corn silage to grass silage ratio and feed particle size of diets for ruminants on the ruminal Bacteroides-Prevotella community in vitro.

This study examined whether different corn silage to grass silage ratios in ruminant rations and different grinding levels of the feed affect the composition of the ruminal Bacteroides-Prevotella community in vitro. Three diets, composed of 10% soybean meal as well as of different corn silage and grass silage proportions, were ground through 1mm or 4mm screened sieves and incubated in a semi-continuous rumen simulation system. On day 14 of the incubation microbes were harvested by centrifugation from the liquid effluent of fermenter vessels. Microbial DNA was extracted for single strand conformation polymorphism (SSCP) analysis of 16S rRNA genes followed by sequencing of single SSCP bands. Fluorescence in situ hybridization (FISH) and real-time quantitative (q) PCR were used to quantify differences in the relative abundance of Bacteroides-Prevotella and Prevotella bryantii. SSCP profiles revealed a significant influence of the forage source as well as of the feed particle size on the community structure of the Bacteroides-Prevotella group. Different, phylogenetically distinct, so far uncultured Prevotella species were detected by sequence analysis of several treatment-dependent occurring SSCP bands indicating different nutritional requirements of these organisms for growth. No quantitative differences in the occurrence of Bacteroides-Prevotella-related species were detected between diets by FISH with probe BAC303. However, real-time qPCR data revealed a higher abundance of P. bryantii with increasing grass silage to corn silage ratio, thus again indicating changes within the community composition of the Bacteroides-Prevotella group. As P. bryantii possesses high proteolytic activity its higher abundance may have been caused by the higher contents of crude protein in the grass silage containing diets. To conclude, results of this study show an influence of the forage source on the ruminal community of Bacteroides-Prevotella. Furthermore, they suggest an effect of the feed particle size on this bacterial group.

Aquatic hyphomycete communities as potential bioindicators for assessing anthropogenic stress.

With a profound knowledge of how physico-chemical parameters affect these communities, microbial communities could be used as indicators for environmental changes and for risk assessment studies. We studied aquatic hyphomycete communities in rivers and aquifers from sites shaped by intense mining activities (namely the "Mansfeld region") and chemical industry (cities of Halle and Bitterfeld) in Central Germany. Environmental stress factors such as high concentrations of heavy metals, sulphate, and nitrate as well as low concentrations of oxygen significantly reduced the diversity and biomass of hyphomycetes in the investigated samples. Redundancy analysis (RDA) indicates that variations in water chemistry cause a significant proportion of the change in fungal community structure (86.2%). Fungi were negatively correlated with high metal and nutrient concentrations. RDA also showed a strong influence of organic matter on individual species, with Anguillospora longissima (Sacc. et Syd.), Clavatospora longibrachiata (Ingold), Clavariopsis aquatica (De Wild), Flagellospora curvula (Ingold), Heliscus lugdunensis (Sacc. et Thérry), Tumularia aquatica (Ingold) and Lemonniera aquatica (De Wild) being most sensitive. We propose that aquatic hyphomycete communities can be used as sensitive and integrative indicators for freshwater quality.