HtrA‐mediated selective degradation of DNA uptake apparatus accelerates termination of pneumococcal transformation

Abstract

Summary Natural transformation mediates horizontal gene transfer, and thereby promotes exchange of antibiotic resistance and virulence traits among bacteria. Streptococcus pneumoniae, the first known transformable bacterium, rapidly activates and then terminates the transformation state, but it is unclear how the bacterium accomplishes this rapid turn‐around at the protein level. This work determined the transcriptomic and proteomic dynamics during the window of pneumococcal transformation. RNA sequencing revealed a nearly uniform temporal pattern of rapid transcriptional activation and subsequent shutdown for the genes encoding transformation proteins. In contrast, mass spectrometry analysis showed that the majority of transformation proteins were substantially preserved beyond the window of transformation. However, ComEA and ComEC, major components of the DNA uptake apparatus for transformation, were completely degraded at the end of transformation. Further mutagenesis screening revealed that the membrane‐associated serine protease HtrA mediates selective degradation of ComEA and ComEC, strongly suggesting that breakdown of the DNA uptake apparatus by HtrA is an important mechanism for termination of pneumococcal transformation. Finally, our mutagenesis analysis showed that HtrA inhibits natural transformation of Streptococcus mitis and Streptococcus gordonii. Together, this work has revealed that HtrA regulates the level and duration of natural transformation in multiple streptococcal species.

Regulation of pneumococcal epigenetic and colony phases by multiple two-component regulatory systems

“…TCS05 (CiaR/H) and TCS12 (ComE/D) represent the best-characterized pneumococcal TCSs. TCS05 inhibits the competence state [18][19][20][21], and promotes pneumococcal resistance to certain antibiotics and other stressful conditions [20,[22][23][24]. TCS12 activates the genes associated with the competence state and natural transformation [25][26][27].…”

“…RNA sequencing (RNA-seq) was carried out as described with minor modifications [19]. Specifically, pneumococci were cultured on catalase-TSA plates for 17 hrs (a time for the routine colony photographing) before colonies on multiple plates were collected in pre-chilled Ringer's solution and pooled as described for genomic DNA purification.…”

Unbiased homeologous recombination during pneumococcal transformation allows for multiple chromosomal integration events

“…The competent transformation state in S. pneumoniae is transient as DprA interacts with phosphorylated ComE to inhibit its activity (Mirouze et al, 2013). In addition, several key Com proteins are rapidly turned over after their synthesis, leading to a window of DNA uptake of approximately 15 min (Liu et al, 2019;Tomasz, 1966;Weng et al, 2013).…”

Direct Visualization of Horizontal Gene Transfer by Transformation in Live Pneumococcal Cells Using Microfluidics

“…Importantly, synthetic CSP externally added into pneumococcal cultures efficiently induces competence in a broad range of conditions and culture media [ 6 ]. It triggers the transcriptional activation of a global regulon comprising approximately 100 genes [ 7 , 8 , 9 , 10 ]. This regulon is made of two classes of genes with distinct temporal expression profiles defined as ‘early’ and ‘late’ com genes.…”