Microbial toxins

Toxins produced by organisms or living cells are virulence factors which encompass various groups of micro-molecules or proteins. Diseases caused by exposure to these toxins via inhalation, ingestion, touching, injection can bring about a severity scale of minor to deadly effects. Marine, environmental and microbial to name a few are part of the principal toxins groups.


Microbial toxins are produced by microorganisms such as bacteria and fungi. Bacterial toxins are putatively categorized into two major types: endotoxins and exotoxins. Endotoxins, lipopolysaccharides (LPS) of gram-negative bacterial cell wall, are released upon the death of bacteria mediated by host immune system. Their modes of actions entail disrupting the functional regulation of surrounding host cells and induce overproduction of cytokine. Exotoxins are protein in nature and released to the surrounding environment by living bacterium and also upon bacterial lysis. They are categorized into three main groups: 1st – superantigens (i.e. staphylococcal enterotoxin B); 2nd – exotoxins inflicting damage on host cell membrane (i.e. listeriolysin O); 3rd – exotoxins that interfere with the host cell function (i.e. AB toxin). Notwithstanding, bacterial toxins are currently being explored as potential therapeutic against cancer and microbial virulence.


Toxins naturally produced by mould (fungi) are referred as mycotoxins. These mycotoxins producing mould grow on various foodstuffs such as dried fruit, nuts, cereals, and spices. The growth of mould can occur pre- or post-harvest, within or on food kept under warm, damp and humid settings and during storage. To date, ≥ 300 mycotoxins have been identified, six of which (alflatoxins, ochratoxin A, patulin, fumonisins, zearalenone and nivalenol/deoxynivalenol) pose threat to the health of human and livestock. Mycotoxins are ubiquitous in food chain owing to mould infection of crops pre- and post-harvest. Exposure to mycotoxins can take place directly via consuming infected food or indirectly from animals that are nourished with contaminated ration (i.e. milk).



  1. BioLibretext. (2019). Toxins. Retrieved from https://bio.libretexts.org/Bookshelves/Microbiology/Book%3A_Microbiology_(Boundless)/14%3A_Pathogenicity/14.4%3A_Damaging_Host_Cells/14.4A%3A_Toxins
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  3. WHO. (2019) Mycotoxins. Retrieved from https://www.who.int/news-room/fact-sheets/detail/mycotoxins
  4. Alshannaq, A., & Yu, J. H. (2017). Occurrence, toxicity, and analysis of major mycotoxins in food. International journal of environmental research and public health, 14(6), 632.


Prepared by: Chain Yi Wei and Ong Hui Ling