Osteoblast integration of dental implant materials after challenge by sub-gingival pathogens: a co-culture study in vitro

Sub-gingival anaerobic pathogens can colonize an implant surface to compromise osseointegration of dental implants once the soft tissue seal around the neck of an implant is broken. In vitro evaluations of implant materials are usually done in monoculture studies involving either tissue integration or bacterial colonization. Co-culture models, in which tissue cells and bacteria battle simultaneously for estate on an implant surface, have been demonstrated to provide a better in vitro mimic of the clinical situation. Here we aim to compare the surface coverage by U2OS osteoblasts cells prior to and after challenge by two anaerobic sub-gingival pathogens in a co-culture model on differently modified titanium （Ti）, titanium-zirconium （TiZr） alloys and zirconia surfaces. Monoculture studies with either U2OS osteoblasts or bacteria were also carried out and indicated significant differences in biofilm formation between the implant materials, but interactions with U2OS osteoblasts were favourable on all materials. Adhering U2OS osteoblasts cells, however, were significantly more displaced from differently modified Ti surfaces by challenging sub-gingival pathogens than from TiZr alloys and zirconia variants. Combined with previous work employing a co-culture model consisting of human gingival fibroblasts and supra-gingival oral bacteria, results point to a different material selection to stimulate the formation of a soft tissue seal as compared to preservation of osseointegration under the unsterile conditions of the oral cavity.

Heterosis in root microbiota inhibits growth of soil-borne fungal pathogens in hybrid rice

In nature,plants are colonized by various microbes that play essential roles in their growth and health.Heterosis is a natural genetic phenomenon whereby first-generation hybrids exhibit superior phenotypic performance relative to their parents.It remains unclear whether this concept can be extended to the“hybridization”of microbiota from two parents in their descendants and what benefits the hybrid microbiota might convey.Here,we investigated the structure and function of the root microbiota from three hybrid rice varieties and their parents through amplicon sequencing analysis of bacterial 16S ribosomal DNA(rDNA)and fungal internal transcribed spacer(ITS)regions.We show that the bacterial and fungal root microbiota of the varieties are distinct from those of their parental lines and exhibit potential heterosis features in diversity and composition.Moreover,the root bacterial microbiota of hybrid variety LYP9 protects rice against soil-borne fungal pathogens.Systematic analysis of the protective capabilities of individual strains from a 30-member bacterial synthetic community derived from LYP9 roots indicated that community members have additive protective roles.Global transcription profiling analyses suggested that LYP9 root bacterial microbiota activate rice reactive oxygen species production and cell wall biogenesis,contributing to heterosis for protection.In addition,we demonstrate that the protection conferred by the LYP9 root microbiota is transferable to neighboring plants,potentially explaining the observed hybrid-mediated superior effects of mixed planting.Our findings suggest that some hybrids exhibit heterosis in their microbiota composition that promotes plant health,highlighting the potential for microbiota heterosis in breeding hybrid crops.