Selection of reference genes for real-time expression studies in Streptococcus agalactiae

Area of Science:

• Microbiology
• Molecular Biology

Background:

• Streptococcus agalactiae (GBS) causes severe neonatal infections.
• Quantitative real-time PCR (qRT-PCR) is vital for GBS gene expression studies.
• Validated reference genes are lacking for GBS qRT-PCR normalization.

Purpose of the Study:

• To systematically evaluate and validate the stability of 10 candidate reference genes in GBS.
• To identify optimal reference genes for qRT-PCR normalization under varying temperature conditions and strains.
• To provide a basis for reliable GBS gene expression analysis.

Main Methods:

• Analyzed 10 candidate reference genes (16SrRNA, glcK, glnA, groEL, gyrA, recA, rpoB, rpsL, sdhA, tkt).
• Used three GBS strains (O90R, NEM316, 2603V/R) at 37°C and 40°C.
• Calibrated transcript levels against bacterial counts (mRNA/gDNA) and used geNorm/NormFinder bioinformatic tools.

Main Results:

• Few genes were stable across all conditions; stability increased at logarithmic time points.
• At 37°C, recA and sdhA were simultaneously stable for all strains.
• recA demonstrated good stability at 40°C and across strains, consistent with bioinformatic analyses.

Conclusions:

• Reference gene expression fluctuates significantly with GBS strains and growth conditions.
• Careful validation of reference genes is essential for accurate qRT-PCR normalization in GBS.
• recA emerges as a promising candidate for normalizing GBS gene expression studies.