Team:Hong Kong HKUST/pneumosensor/module two

Prof. Donald A. Morrison’s research lab in University of Illinois at Chicago published several papers on the competence for genetic transformation in Streptococcus pneumoniae which depends on quorum-sensing system to control many competence-specific genes acting in DNA uptake, processing, and integration. There is a link between this quorum-sensing system and the competence-specific genes, which is an alternative sigma factor ComX, σx. Expression of ComX allows transcription of many genes that are involved in transformation and specifically expressed during competence. These late genes share a conserved 8-bp sequence in their promoter regions, TACGAATA (combox) which is specifically induced by σx-containing RNA polymerase.

Combox promoters can be found on many different regions within the genomic DNA of Streptococcus Pneumoniae strains. The promoters were reported to have variants with different lengths and consensus sequences, but generally the range of variety has been kept small. Though much information about the combox promoter is readily available nowadays, its characterization of promoter activity, specificity, sequence, as well as the biomolecular mechanism can be greatly enhanced with further investigations and experiments.

Hence, we were interested in reproducing this gene circuit with all the associated genes and promoters to be combined into a single transcriptional unit. Despite the suggested susceptibility to leakage and other factors that may hinder or interrupt the mechanism, researches have reported that the pathway was highly specific to certain environmental conditions and stress, suggesting minimal or no leakage in the entire process.

Combox promoters have high specificity to σx for activation, so genes downstream the combox promoter will be translated only if σx are present. Hence, by using fluorescence protein as a reporting mechanism, this comX-combox system could be further utilized as a specific reporter device that could be used by iGEM communities.