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Arginine catabolic mobile element encoded speG abrogates the unique hypersensitivity of Staphylococcus aureus to exogenous polyamines.
Mol Microbiol. 2011 Oct; 82(1):9-20
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22 Jun 2012
New Finding
DOI: 10.3410/f.717197862.792452914
This study challenges the dogma that polyamines are synthesized and required by all organisms; several bacteria were found to be either auxotrophic or exhibit polyamine-independent growth. Moreover, for species such as Staphylococcus aureus, polyamines were bactericidal at concentrations commonly encountered...Continue reading
This study challenges the dogma that polyamines are synthesized and required by all organisms; several bacteria were found to be either auxotrophic or exhibit polyamine-independent growth. Moreover, for species such as Staphylococcus aureus, polyamines were bactericidal at concentrations commonly encountered within the host environment. Interestingly, the community-associated methicillin-resistant strain USA-300 was found to be resistant to polyamine toxicity as a result of the SpeG spermine/spermidine acetyltransferase encoded within the strain-specific arginine catabolic mobile element (ACME). Thus, these findings provide insight into a mechanism that may be employed by the hypervirulent USA-300 strain to thrive within its host.
Disclosures
None declared
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Matthews R and Hondorp E: F1000Prime Recommendation of [Joshi GS et al., Mol Microbiol 2011, 82(1):9-20]. In F1000Prime, 22 Jun 2012; DOI: 10.3410/f.717197862.792452914. F1000Prime.com/717197862#eval792452914
F1000Prime Recommendations, Dissents and Comments for [Joshi GS et al., Mol Microbiol 2011, 82(1):9-20]. In F1000Prime, 26 May 2013; F1000Prime.com/717197862
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Polyamines, including spermine (Spm) and spermidine (Spd), are aliphatic cations that are reportedly synthesized by all living organisms. They exert pleiotropic effects on cells and are required for efficient nucleic acid and protein synthesis. Here, we report that the human pathogen Staphylococcus aureus lacks identifiable polyamine biosynthetic genes, and consequently produces no Spm/Spd or their precursor compounds putrescine and agmatine. Moreover, while supplementing defined medium with polyamines generally enhances bacterial growth, Spm and Spd exert bactericidal effects on S. aureus at physiological concentrations. Small colony variants specifically lacking menaquinone biosynthesis arose after prolonged Spm exposure and exhibited reduced polyamine sensitivity. However, other respiratory-defective mutants were no less susceptible to Spm implying menaquinone itself rather than general respiration is required for full Spm toxicity. Polyamine hypersensitivity distinguishes S. aureus from other bacteria and is exhibited by all tested strains save those belonging to the USA-300 group of community-associated methicillin-resistant S. aureus (CA-MRSA). We identified one gene within the USA-300-specific arginine catabolic mobile element (ACME) encoding a Spm/Spd N-acetyltransferase that is necessary and sufficient for polyamine resistance. S. aureus encounters significant polyamine levels during infection; however, the acquisition of ACME encoded speG allows USA-300 clones to circumvent polyamine hypersensitivity, a peculiar trait of S. aureus.
© 2011 Blackwell Publishing Ltd.
DOI: 10.1111/j.1365-2958.2011.07809.x
PMID: 21902734
