Background Porphyromonas gingivalis is part of the subgingival biofilm and a keystone species in the development of periodontitis. Interactions between P.gingivalis and other bacteria in biofilms have been shown to affect bacterial virulence. Helicobacter pylori also inhabits the subgingival biofilm, but the consequences of interactions there with P.gingivalis remain unknown. Here, we investigated how the pre-incubation of P.gingivalis with H.pylori affects P.gingivalis virulence. Methods We assayed P.gingivalis internalization by oral keratinocytes (OKs), hemagglutination and biofilm formation to identify alterations in virulence after pre-incubation with H. pylori . Also, we evaluated viability and migration of OKs infected with P. gingivalis, as well as the role of toll-like receptor 4 (TLR4). In addition, we quantified the mRNA of genes associated with P.gingivalis virulence. Results Pre-incubation of P.gingivalis with H.pylori enhanced P.gingivalis biofilm formation, bacterial internalization into OKs and hemagglutination. Infection with pre-incubated P.gingivalis increased OK migration in a manner dependent on the O-antigen and linked to increased expression of the gingipain RgpB. Also, OK TLR4 participates in these events, because upon TLR4 knock-down, pre-incubated P.gingivalis no longer stimulated OK migration. Discussion We provide here for the first time insight to the consequences of direct interaction between P.gingivalis and H.pylori. In doing so, we shed light on the mechanism by which H. pylori presence in the oral cavity increases the severity or progression of periodontitis.
Sheep and goat grazing diets on an annualMediterranean grassland containing tall wheatgrass (Thinopyrum ponticum (PODP.)). Cienc. Inv. Agr. 45(3):240-250. The development of mixed grazing systems is an interesting alternative for the utilization of rangelands with ecological and/ or economic limitations; therefore, the study of patterns and eating habits of different species in the same grazing area is important. A mixed grazing study was carried out on a Mediterranean grassland sown with Thinopyrum ponticum 30 years ago (Rinconada de Maipú, Chile 33º 28'S; 70º 51ʼ W) with the purpose of quantifying the botanical composition, dietary overlap and selectivity indexes of the main grass species consumed by goats and sheep. Trophic behavior was studied in seven young Suffolk Down rams, seven young Merino-Precoz rams and seven young Boer-Criollo bucks grazing together during three grassland phenological stages. During the grassland vegetative stage, diets were mainly composed of annual grasses and forbs. Perennial grasses dominated the animals' diets during the reproductive and dry grassland stages. The diversity of the goats' diets was higher than that of the sheep, demonstrating greater plasticity in their dietary habits. However, in this environment, both species behaved as generalist herbivores. The level of diet overlap between the sheep and goats was high, especially when grazing during the grassland reproductive and dry phenological stages, suggesting potential competition during lower forage quality stages.
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