The Peptide Toxin Amylosin of Bacillus amyloliquefaciens from Moisture-Damaged Buildings Is Immunotoxic, Induces Potassium Efflux from Mammalian Cells, and Has Antimicrobial Activity

Stiina Rasimus-Sahari*, Vera V. Teplova, Maria A. Andersson, Raimo Mikkola, Palvi Kankkunen, Sampsa Matikainen, Carl G. Gahmberg, Leif C. Andersson, Mirja Salkinoja-Salonen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

10 Citations (Scopus)

Abstract

Amylosin, a heat-stable channel-forming non-ribosomally synthesized peptide toxin produced by strains of Bacillus amyloliquefaciens isolated from moisture-damaged buildings, is shown in this paper to have immunotoxic and cytotoxic effects on human cells as well as antagonistic effects on microbes. Human macrophages exposed to 50 ng of amylosin ml(-1) secreted high levels of cytokines interleukin-1 beta (IL-1 beta) and IL-18 within 2 h, indicating activation of the NLRP3 inflammasome, an integral part of the innate immune system. At the same exposure level, expression of IL-1 beta and IL-18 mRNA increased. Amylosin caused dose-dependent potassium ion efflux from all tested mammalian cells (human monocytes and keratinocytes and porcine sperm cells) at 1 to 2 mu M exposure. Amylosin also inhibited the motility of porcine sperm cells and depolarized the mitochondria of human keratinocytes. Amylosin may thus trigger the activation of the NLRP3 inflammasome and subsequently cytokine release by causing potassium efflux from exposed cells. The results of this study indicate that exposure to amylosin activates the innate immune system, which could offer an explanation for the inflammatory symptoms experienced by occupants of moisture-damaged buildings. In addition, the amylosin-producing B. amyloliquefaciens inhibited the growth of both prokaryotic and eukaryotic indoor microbes, and purified amylosin also had an antimicrobial effect. These antimicrobial effects could make amylosin producers dominant and therefore significant causal agents of health problems in some moisture-damaged sites.

Original languageEnglish
Pages (from-to)2939-2949
Number of pages11
JournalApplied and Environmental Microbiology
Volume81
Issue number8
DOIs
Publication statusPublished - Apr 2015
MoE publication typeA1 Journal article-refereed

Keywords

  • SECONDARY METABOLITES
  • NLRP3 INFLAMMASOME
  • HUMAN MACROPHAGES
  • INNATE IMMUNITY
  • EMETIC TOXIN
  • CEREULIDE
  • BACTERIAL
  • STRAINS
  • DISEASE
  • K+

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