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Published on: February 7, 2013
Involvement of Heme in Colony Spreading of Staphylococcus aureus
Chao-Chin Liu1, Mei-Hui Lin1,2,3
1Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
Abstract:
Staphylococcus aureus spreads rapidly on the surface of soft agar medium. The spreading depends on the synthesis of biosurfactants, i.e., phenol soluble modulins (PSMs), which facilitate colony spreading of S. aureus. Our earlier study demonstrated that water accumulates in a colony is important to modulate colony spreading of S. aureus. The current study screened a transposon-based mutant library of S. aureus HG001 and obtained four non-spreading mutants with mutations in hemY and ctaA, which are involved in heme synthesis. The spreading ability of these mutants was restored when the mutants are transformed with a plasmid encoding hemY or ctaA, respectively. HemY mutants, which do not synthesize heme B, were able to spread on agar medium supplemented with hemin, a heme B derivative. By contrast, hemin supplementation did not rescue the spreading of the ctaA mutant, which lacks heme B and heme A, indicating that heme A is also critical for colony spreading. Moreover, mutations in hemY and ctaA had little effect on PSMs production but affect ATP production and water accumulation in the colony. In conclusion, this study sheds light on the role of heme synthesis and energy production in the regulation of S. aureus colony spreading, which is important for understanding the movement mechanisms of bacteria lacking a motor apparatus.
Insights
Staphylococcus aureus colony spreading relies on heme synthesis, impacting energy and water levels. Mutations in heme synthesis genes hemY and ctaA disrupt spreading, highlighting heme
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Biochemistry
Background:
- Staphylococcus aureus exhibits rapid colony spreading on soft agar, facilitated by biosurfactants like phenol soluble modulins (PSMs).
- Previous research indicated that water accumulation within colonies is crucial for modulating S. aureus spreading.
- Understanding the regulatory mechanisms of bacterial motility, especially in non-motorized bacteria, is essential.
Purpose of the Study:
- To investigate the role of heme synthesis in regulating Staphylococcus aureus colony spreading.
- To identify specific genes involved in heme synthesis that affect bacterial motility.
- To elucidate the relationship between heme synthesis, energy production, and water accumulation in S. aureus spreading.
Main Methods:
- Screening of a transposon-based mutant library of S. aureus HG001.
- Identification of non-spreading mutants with defects in heme synthesis genes (hemY and ctaA).
- Complementation studies using plasmids encoding hemY or ctaA to restore spreading ability.
- Analysis of the effects of hemin supplementation on mutant spreading.
- Assessment of PSMs production, ATP production, and water accumulation in wild-type and mutant strains.
Main Results:
- Four non-spreading S. aureus mutants were identified with mutations in hemY and ctaA, genes involved in heme synthesis.
- Complementation with functional hemY or ctaA restored the spreading ability of the respective mutants.
- hemY mutants could spread on hemin-supplemented agar, while ctaA mutants could not, indicating heme A's critical role.
- Mutations in hemY and ctaA minimally affected PSMs production but significantly impacted ATP production and water accumulation within colonies.
Conclusions:
- Heme synthesis, specifically involving heme A, is critical for Staphylococcus aureus colony spreading on soft agar.
- Energy production (ATP) and water accumulation are key factors regulated by heme synthesis that influence bacterial spreading.
- This study provides insights into the non-motorized movement mechanisms of bacteria, linking metabolic pathways to colony motility.
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