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The mitochondrial toxin produced by Streptomyces griseus strains isolated from an indoor environment is valinomycin
M A Andersson1, R Mikkola, R M Kroppenstedt
1Department of Applied Chemistry and Microbiology, FIN-00014 University of Helsinki, Finland. Maria.A.Andersson@helsinki.fi
Abstract:
Actinomycete isolates from indoor air and dust in water-damaged schools and children's day care centers were tested for toxicity by using boar spermatozoa as an indicator. Toxicity was detected in extracts of four strains which caused a loss of sperm motility, and the 50% effective concentrations (EC50) were 10 to 63 ng (dry weight) ml of extended boar semen-1. The four strains were identified as Streptomyces griseus strains by 16S ribosomal DNA and chemotaxonomic methods. The four S. griseus strains had similar effects on sperm cells, including loss of motility and swelling of mitochondria, but we observed no loss of plasma membrane integrity or depletion of cellular ATP. None of the effects was observed with sperm cells exposed to extracts of other indoor actinomycete isolates at concentrations of >/=5,000 to 72,000 ng ml-1. The toxin was purified from all four strains and was identified as a dodecadepsipeptide, and the fragmentation pattern obtained by tandem mass spectrometry was identical to that of valinomycin. Commercial valinomycin had effects in sperm cells that were identical to the effects of the four indoor isolates of S. griseus. The EC50 of purified toxin from the S. griseus strains were 1 to 3 ng ml of extended boar semen-1, and the EC50 of commercial valinomycin was 2 ng ml of extended boar semen-1. To our knowledge, this is the first report of the presence of ionophoric toxin producers in an indoor environment and the first report of valinomycin-producing strains identified as S. griseus.
Insights
Four Streptomyces griseus strains isolated from indoor environments produced the toxin valinomycin, which reduced sperm motility. This is the first report of ionophoric toxin producers in indoor settings.
Area of Science:
- Microbiology
- Environmental Health
- Toxicology
Background:
- Actinomycetes are common indoor microorganisms.
- Water-damaged buildings can harbor toxigenic microbes.
- Spermatozoa are sensitive indicators of cellular toxicity.
Purpose of the Study:
- To investigate the toxicity of actinomycete isolates from indoor air and dust.
- To identify the specific toxins produced by toxic strains.
- To assess the impact of these toxins on sperm cell function.
Main Methods:
- Isolation and identification of actinomycetes from indoor environments.
- Toxicity testing using boar spermatozoa motility assays.
- Purification and identification of the toxic compound using mass spectrometry.
- Comparison with commercial valinomycin.
Main Results:
- Four Streptomyces griseus strains exhibited toxicity, reducing sperm motility at low concentrations (EC50: 10-63 ng/ml).
- The toxic compound was identified as valinomycin.
- Valinomycin caused mitochondrial swelling but not plasma membrane damage or ATP depletion.
- Commercial valinomycin produced identical effects on sperm cells.
Conclusions:
- Indoor environments can harbor valinomycin-producing Streptomyces griseus.
- Valinomycin is a potent inhibitor of sperm motility.
- This study is the first to report ionophoric toxin producers in indoor environments.