High‐throughput characterization of the influence of Streptococcus sanguinis genes on the interaction between Streptococcus sanguinis and Porphyromonas gingivalis.

<italic>Porphyromonas gingivalis</italic> is a keystone pathogen in periodontitis, and <italic>Streptococcus sanguinis</italic> is an abundant oral commensal bacterium associated with periodontal health. However, the interaction between <italic>P. gingivalis</italic> and <italic>S. sanguinis</italic> remains obscure. Here, we established a strategy for high‐throughput measurement of the cell number of <italic>P. gingivalis</italic> in the coculture with <italic>S. sanguinis</italic> by detecting the concentration of hydrogen sulfate. The interaction between <italic>P. gingivalis</italic> and over 2000 <italic>S. sanguinis</italic> single‐gene mutants was characterized using this strategy, and several interaction‐associated genes in <italic>S. sanguinis</italic> were determined by detecting more <italic>P. gingivalis</italic> cells in the coculture with matched <italic>S. sanguinis</italic> mutants. Three <italic>S. sanguinis</italic> interaction‐associated genes were predicted to be responsible for cysteine metabolism, and the supplementation of exogenous L‐cysteine promoted the cell number of <italic>P. gingivalis</italic> in the coculture with <italic>S. sanguinis</italic>. Thus, exogenous L‐cysteine and the compromised cysteine metabolism in <italic>S. sanguinis</italic> enhanced the growth of <italic>P. gingivalis</italic> in the existence of <italic>S. sanguinis</italic>. Additionally, the interaction between <italic>P. gingivalis</italic> and other <italic>Streptococcus</italic> spp. was examined, and <italic>S. pneumoniae</italic> was the only streptococci that had no inhibition on the cell number of <italic>P. gingivalis</italic>. In total, this study established a new strategy for high‐throughput screening of the interaction between <italic>Streptococcus</italic> and <italic>P. gingivalis</italic> and discovered a set of genes in <italic>S. sanguinis</italic> that impacted the interaction. The influence of exogenous L‐cysteine on the interaction between <italic>P. gingivalis</italic> and <italic>S. sanguinis</italic> in the oral cavity needs further investigation. [ABSTRACT FROM AUTHOR]