Alternative sigma factor σH activates competence gene expression in Lactobacillus sakei

Area of Science:

• Microbiology
• Bacterial Genetics
• Gene Regulation

Background:

• Alternative sigma factors regulate adaptive responses in bacteria.
• Lactobacillus sakei, a meat-borne bacterium, possesses a σ(H)-like factor.
• The function of σ(H)-like factors in non-sporulating bacteria is poorly understood.

Purpose of the Study:

• To investigate the function of the σ(H) alternative sigma factor in Lactobacillus sakei.
• To explore the role of σ(H) in bacterial adaptation and gene expression.

Main Methods:

• Genome-wide transcriptomic profiling of Lactobacillus sakei 23 K with sigH overexpression.
• Quantitative PCR analysis to identify σ(H)-regulated genes.
• Bioinformatic analysis to assess gene function and conservation.

Main Results:

• Transcription of the sigH gene was largely unaffected by stationary phase entry.
• Twenty-five genes potentially regulated by σ(H) were identified.
• Over half of the identified genes are involved in DNA uptake and metabolism, suggesting a role in genetic competence.
• σ(H) overproduction did not lead to detectable genetic transformation.

Conclusions:

• σ(H) in L. sakei activates a state of genetic competence.
• This finding supports the hypothesis that σ(H)-like factors in non-sporulating Firmicutes share the function of promoting genetic competence.
• The results link σ(H) to DNA uptake machinery and metabolism in L. sakei, similar to ComX in streptococci.