Genomic compaction is an essential characteristic of living organisms. Nucleoid-associated proteins (NAPs) are a group of small proteins that play crucial roles in chromosome architecture and affect DNA replication, transcription, and recombination by imposing topological alterations in genomic DNA, thereby modulating global gene expression. EbfC/YbaB was first described as a DNA-binding protein of Borrelia burgdorferi that regulates the expression of surface lipoproteins with roles in virulence. Further studies indicated that this protein binds specifically and non-specifically to DNA and colocalises with nucleoids in this bacterium. The data showed that this protein binds to DNA as a homodimer, although it can form other organised structures. Crystallography analysis indicated that the protein possesses domains responsible for protein–protein interactions and forms a “tweezer” structure probably involved in DNA binding. Moreover, sequence analysis revealed conserved motifs that may be associated with dimerisation. Structural analysis also showed that the tridimensional structure of EbfC/YbaB is highly conserved within the bacterial domain. The DNA-binding activity was observed in different bacterial species, suggesting that this protein can protect DNA during stress conditions. These findings indicate that EbfC/YbaB is a broadly distributed NAP. Here, we present a review of the existing data on this NAP.

Porphyromonas gingivalis is an oral bacterium commonly associated with periodontitis. P. gingivalis synthesizes sphingolipids (SLs), and recently, we reported that P. gingivalis SLs packaged into outer membrane vesicles (OMVs) can regulate THP-1 macrophage inflammatory responses to P. gingivalis OMVs. The contribution that P. gingivalis SLs have on host-pathogen interactions remains poorly understood, especially in the context of OMVs. Here, we demonstrate that P. gingivalis SLs significantly reduce the uptake of OMVs isolated from SL-containing wild-type (WT) P. gingivalis compared to OMVs from an SL-null mutant P. gingivalis strain, and that the loss of SLs drives uptake of P. gingivalis OMVs via lipid rafts in THP-1 macrophages. Intriguingly, we found that the sensing of P. gingivalis OMVs via TLR2 and MyD88 is attenuated due to the presence of SLs. Lastly, transcriptomic analysis of THP-1 macrophages co-cultured with either WT or SL-null P. gingivalis OMVs for 2 h revealed an array of differentially expressed genes. Interestingly, at 2 h, WT P. gingivalis OMVs promoted an overall trend of gene downregulation in THP-1 macrophages when compared to unchallenged, whereas SL-null OMVs strongly promoted upregulated gene expression. These findings provide early-phase characterization of the role of SLs in initial host cellular responses to P. gingivalis OMVs and expand our knowledge of interactions between SL-containing P. gingivalis OMVs and the host.