Crohn's disease is characterized by increased permeability of the intestinal mucosal barriers and an abnormal or dysregulated immune response to specific and/or commensal bacteria arising from the intestinal lumen. To determine the types of bacteria that are transgressing the mucosal barrier and colonizing the intestinal submucosal tissues, we performed 16S rRNA gene microbiota sequencing of the submucosal and mucosal tissues at the advancing disease margin in ileal Crohn's disease. Microbial populations were compared between mucosa and submucosa and non-inflammatory bowel disease (non-IBD) controls, as well as to microbial populations previously found at the centre of the disease lesion. There was no significant increase in bacteria within the submucosa of non-IBD controls at any taxonomic level when compared to the corresponding superjacent mucosa, indicating an effective mucosal barrier within the non-IBD population. In contrast, there was a statistically significant increase in 13 bacterial families and 16 bacterial genera within the submucosa at the advancing disease margin in Crohn's disease when compared to the superjacent mucosa. Major increases within the submucosa included bacteria of the Families Sphingomonadaceae, Alicyclobacillaceae, Methylobacteriaceae, Pseudomonadaceae and Prevotellaceae. Data suggest that the primary site of bacterial translocation across the mucosal barrier occurs at the margin between diseased and normal tissue, the advancing disease margin. The heterogeneity of the bacterial populations penetrating the mucosal barrier and colonizing the submucosal intestinal tissues and, therefore, contributing to the inflammatory processes, suggests that bacterial translocation is secondary to a primary event leading to a breakdown of the mucosal barrier.
Natural transformation is the main means of horizontal genetic exchange in the obligate human pathogen Neisseria gonorrhoeae and drives the spread of antibiotic resistance and virulence determinants. Transformation can be divided into four steps: (1) DNA binding, (2) DNA uptake, (3) DNA processing and (4) DNA recombination into the chromosome. The DNA processing enzyme DprA has been shown to shuttle incoming ssDNA to the recombination enzyme RecA during transformation in Bacillus subtilis and Streptococcus pneumoniae. Here, we investigate the role of DprA during transformation in N. gonorrhoeae. Inactivation of dprA completely abrogated transformation of gyrB1-encoding DNA, which confers nalidixic acid resistance. The presence of the DNA uptake sequence enhances DNA uptake and transformation by binding to the minor pilus protein ComP. Loss of transformation in the dprA null mutants was independent of the DNA uptake sequence. DprA mutants exhibited increased RecA-dependent pilin variation suggesting that DprA affects pilin variation. Unlike the exquisite UV sensitivity of a recA mutant, inactivation of dprA did not affect survival following UV irradiation. These results demonstrate that DprA has a conserved function during transformation, and reveal additional effects of DprA in N. gonorrhoeae during pilin variation.