Perilous Protista and Mycotoxic Molds

aflatoxin alert petri dishes
Aflatoxin Alert petri dishes.

Beauty is in the eye of the beholder, so it is said. It is also held that one man’s meat is another man’s poison. Part of our everyday lexicon, such aphorisms speak to the subjectivity of taste and individual predilection. However, some appetencies are less subjective, some foodstuffs are – at best – ‘an acquired taste.’ As a type of maggot-infested cheese, the Casu Marzu of Sardinia would be one example; Kale Pache (a stew made of boiled sheep’s head and trotters) would, conceivably, be another. And many are the diners who consider the less exotic but arguably more ubiquitous ingestible, mold, to be another example. But, mold can be a surprisingly interesting organism and one upon which – in terms of contamination – it might behoove us to focus. Take, for example, the excitement around a new type of mold, dubbed ‘the blob,’ which is currently on display at the Paris Zoological Garden, France. After all, ‘le blob’ (as it is actually not named but we like the sound of that anyhow) resembles little more than a random splat of yellow goo, has no mouth, not only survives when dissected but actually thrives, and has 720 sexes. Welcome to the world’s arguably most intriguing living splotch…

Taxonomically part of the Protista kingdom (neither plant nor animal nor fungus), the yellow goo is a Physarum polycephalum, a slime mold.

The branching structure of the organism is known as a plasmodium – a mass of multinucleate cytoplasm – that can grow to an area of several meters in search of its preferred food, bacteria. Molds in general have extensive filaments, termed hyphae, which travel across the surface of substrates, eventually covering them with a fuzzy coat or slimy film. Reproducing either sexually or asexually, they are easily transported via wind or water, and can range from utterly harmless to the cause of mild allergens, with some even identified as  carcinogens. Common symptoms of mold exposure include respiratory problems, throat irritation, sneezing, and sinus congestion, and the most commonly affected are those with existing allergies, compromised immune systems, or asthma.

More serious than a ticklish throat or sneezy nose, however, is the fact that some molds excrete mycotoxins, secondary metabolites that are categorized as belonging to one of four main classes: polyketides, terpenoids, shikimic acid derived compounds, and non-ribosomal peptides.

Of the more than four hundred metabolite varieties identified, the majority of studies focus on just a small handful – aflatoxins, ochratoxin A, Fusarium toxins, fumonisin, zearalenone, trichothecenes, and deoxynivalenol/nivalenol. The reason, according to the paper ‘Mycotoxins: The Hidden Danger in Foods’ (co-authored by Aycan Cinar and Elif Onbaşı) is simple: a concern for food safety and its impact upon the economy due to lost revenue. Focusing on the importance of the metabolites ‘in [the] food industry, preventive measures, and implementation of hazard analysis critical control point (HACCP) to control mycotoxin,’ the authors note that the chemicals are thought to be a natural defense system that protects mold colonies from predation by insects.(1) With ‘one quarter of [global] agricultural products […] reported to be contaminated with mycotoxins,’ the substances fall into a spectrum of different types: carcinogenic, mutagenic, teratogenic, hepatotoxic, nephrotoxic, immunosuppressive, and embryotoxic [with] cereals, grains, nuts, oilseeds, fruits, dried fruits, vegetables, cocoa and coffee beans, wine, beer, herbs, and spices [being] major mycotoxin vectors since they are consumed by a large mass of people.’(2)

So how do we test for these contaminants?

To date, the best resources we have are chromatographical analyses – techniques such as high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and thin-layer chromatography (TLC). Additionally, enzyme-linked immunosorbent assay (ELISA) – a plate-based assay technique that detects antigen binding – is another useful test, as are a variety of biosensor-based screens. However, the battlefield in the fight against mycotoxins is subject to shifting as their existence depends heavily upon environmental conditions, with temperature, pH levels, and water as regulating factors. All of this means, of course, that an ounce of initial prevention is better than a bushel of subsequent detection and cure, especially when the risks of potentially toxic exposure run anywhere from inhalation to dermal contact to ingestion.

But let us assume for a moment that preventative measures have failed and a food product tests positive for these metabolites, how do consumers protect themselves? Good question and the answer is threefold: do not inhale; glove up in their presence; and refuse the temptation to take a bite of them. But not so fast! According to an article in China Daily, when random checks in 2011 unearthed the contamination of products from the Mengniu Group, China’s dairy giant a surprising vector was identified. Aflatoxin, described by the World Health Organization (WHO) as a ‘first class carcinogen,’ was found in samples tested by the General Administration of Quality Supervision, Inspection and Quarantine and was traced back to the ingestion of contaminated feed by cattle.(3) Extremely virulent, aflatoxin can accumulate in the human body, is resistant to heat treatment including pasteurization, and is now understood to be transmissible not only through direct exposure but also via a third party – in this case, cows. And that is part of the reason why, for our purposes, ingestion is the most interesting route of transmission.

So far, this is a good primer on the organisms in general and, as intriguing as it is, Le Blob is not something we typically to see on food or unknowingly ingest. Unlike, for instance, Penicillium, Neurospora, and Aspergillus, P. polycephalum is certainly not out for your fast food meal, leaving that delicacy to other members of its large family. And, in an unconventional marketing campaign, one fast food giant is revealing exactly which kinds of mold are looking for a free lunch – especially if that meal comes at your expense. Like yeast, molds are eukaryotic organisms typically found in moist places that survive by using enzymes to breakdown organics such as plant and animal materials, performing – in the natural world – an important role. Decomposition of organic materials is, however, in direct conflict conflict with the mission of food manufacturers: where most retailers want an extended shelf life for products, molds want them to deteriorate. However, when we say ‘most’ retailers we are alluding to the new commercial by Burger King which offers a time-lapse view into the decay of one of their signature Whoppers. In a period of 34 days, the burger – bun, lettuce, pickles, tomato, onions, ketchup, mayo, and meat – undergoes a transition from fresh to mold-encased in a demonstration of natural spoilage. The aim of the ad is to show that Burger King’s Whoppers do not contain artificial preservatives that would otherwise eliminate the mold spores, thereby prolonging the life of the meal.

It must be acknowledged that this is a novel approach to generating an appetite for a food product and Burger King is certainly gambling on its slogan ‘The beauty of no artificial preservation’ being a success. However, other food manufacturers remain faithful to the traditional position when it comes to spoiled food, the mea culpa recall. In a couple of cases in recent years, applesauce manufacturer GoGo squeeZ recalled products due to the discovery of food residue in product pumps at its Traverse City, MI facility and for an issue involving mold growing in product pouches. Although that particular type occurs naturally on fruit and posed no risk to consumers, the company acknowledged that ‘mold is gross and unpleasant to look at or taste, and this is simply not the kind of experience we want you to have.’(4)

Additionally, in a more recent problem, Conagra Foods voluntarily recalled a variety of its Hunt’s Tomato Paste noting, according to the Food Poisoning Bulletin – a resource for food safety news, that contamination may have been introduced ‘when the final product [was] damaged after canning.’(5) And this year has already seen a recall of Good to Go Snack Bars, a product line of Riverside Natural Foods Ltd., based in Ontario, Canada. The Coconut Snack and Cinnamon Pecan Snack varieties of the bar were sold to consumers in the provinces of Saskatchewan, British Columbia, New Brunswick, Alberta, Ontario, and Quebec and have been recalled due to the potential for mold contamination. As of January 20th, 2020, however, there have been no reports of illness associated with the bars.

As discouraging as the situation may seem, let’s take a moment to consider the other side of the story. Beneficial strains of fungus and mold do exist and many of them have played an often under-rated but really rather significant role in some facets of human culture – the culinary arts being one such arena. Take, for example, the use of penicillium strains that are solely responsible for that singular gustatory pleasure: blue cheese. Legend has it that the forgotten lunch of a shepherd in the south of France underwent, over time, a mystical transformation from ordinary sheep’s milk cheese to what we now revere as as that dairy stinker, Roquefort. According to Food & Wine, ‘the damp limestone caves that dot southern France are filled with naturally occurring Penicillium roqueforti mold spores—a variety of mold that is in the same family as the one that the antibiotic Penicillin is made from.’(6) Moreover, unlike other species of mold ‘Penicillium roqueforti (and, just as commonly used, Penicillium glaucum) do not produce toxins by themselves and are not dangerous to humans.’(7) All of which is indeed fortunate for crafters of blue cheeses and those who love them.

The approach of using beneficial molds to create food products is an interesting one. In a process termed proteolysis, enzymes are produced that release amino acids to break down casein – the natural proteins precipitated from milk. The blue-gray veins and pockets so characteristic of Roquefort, Stilton, Danish Blue, and Gorgonzola trace where the amino acids are most active. In addition, Penicillium roqueforti also generates free fatty acids and the release of methyl ketone – a term known as lipolysis which accounts for the cheese’s look, taste, and aroma. And far from the damp limestone caves of southern France, today’s blue cheeses are created in controlled environments that cultivate beneficial molds while protecting against contamination by those spores which would harm us. But such spore variants do remain and, as we noted above, they can be hard to eliminate. Both in the kitchen and the cleanroom, surface spores cannot be killed using an isopropyl alcohol wipe alone but rather a dedicated sporicide must be used. When used on pre-cleaned surfaces, sodium hypochlorite, hydrogen peroxide, and hydrogen peroxide-peracetic acid blends are considered effective sporicidal agents, and conveniently pre-saturated wipes are available. 

But do not fear: slime molds are not about to take over the world. Unlike the eponymous red blob of the 1950s cult sci-fi movie with Steve McQueen, amoeboidal organisms are unlikely to evolve to the extent that they can attack and devour us. Unless, of course, you live in Phoenixville, PA, in which case you might want to reserve your place in the Downington Diner – refrigerated section…

Slime molds – intriguing or disgusting? Would you consider traveling to visit France’s newest tourist attraction? Let us know in the comments!


  2. ibid
  7. ibid

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