Bile Salts Mediate In Vitro Activation of the Vibrio cholerae ToxR Virulence Regulon
Vibrio cholerae virulence is regulated by the ToxR regulon in response to unknown intestinal cues. In the 1980s, in vitro virulence-activating conditions, called AKI conditions, were developed. While AKI conditions facilitated virulence studies in the laboratory, the virulence-inducing cues remained unknown. Bina et al. (e00441-21) demonstrate that bile salts present in AKI medium are critical for virulence activation. They further show that the ToxR regulon was preferentially activated by bile salts that predominate in the proximal intestine, suggesting that specific bile salts may function as spatial cues that modulate V. cholerae virulence in the human gastrointestinal tract.
Neutrophil Modulation of the Composition of the Oral Microbiota
Using a combination of a knockout mouse model lacking the neutrophil receptor CXCR2, which is essential for the recruitment of these cells into the periodontal tissues, and microbial transfer into gnotobiotic germ-free mice, Hashim et al. (e00309-21) demonstrate the role of neutrophils in shaping the qualitative and quantitative composition of the oral microbiota and, through this, the progression of periodontal disease in the form of periodontal bone destruction. This study demonstrates the inherent flexibility of the oral microbiome under the influence of host genetic factors—a bidirectional interaction that can play a significant role in the development of disease.