Microbiological, virological, bacteriological, immunological, medical, epidemiological, historical, anecdotal

Tag: yeast

Viruses can be RE-activated by light?

When you’re always looking at old sources, you run the risk of condescending to the experts of the past, who believed scientifically plausible things that now seem obviously wrong. More than once I’ve been ready to point out some amusing practice of the distant past, only to find out that it’s a perfectly valid fact that I (having no medical or physiological training) had never heard of.

One example is “vicarious menstruation”. Is it possible that menstruation could manifest as a nosebleed, or sores in the mouth (sometimes called “herpes”)? Or as a pair of ulcers on the legs, as D.H. Galloway of Roswell, New Mexico reported in 1913? Isn’t it more likely that these stories are exaggerated, or are coincidental? But yes, some combination of hormone levels and blood pressure creates that phenomenon in some women.


Another one is “activated milk”, which contained a substance called “viosterol” that was in high demand for preventing rickets in children. Activated milk? Activated by what?

Ultraviolet light, it turns out. Did this work? Well, UV light turns cholesterol into vitamin D3 when our own bodies are exposed to the sun, and it turns the fungal (yeast) equivalent, ergosterol, into vitamin D2. Cows could be fed UV-activated yeast to make them produce “activated milk”, or activated yeast extract could be directly added to milk. Either of these was a way of “activating” milk that probably worked. Exposure of normal milk to UV light seems like it would be a waste of time.

Whether its benefits were exaggerated or not, activation of milk and other foods was extremely popular, as described in Michael Holick’s great historical review in Public Health Reports, called “The Vitamin D Deficiency Pandemic: a Forgotten Hormone Important for Health”. The drug and food industries fought over whether companies like Fleischmann’s Yeast could claim their products were the equivalent of vitamin D supplements. Here’s a contemporary excerpt from Cartels: Challenge to a Free World, Wendell Berge’s 1944 classic of vaguely paranoid economics.


And all the way into the 21st century, there’s heated debate over whether vitamin D2 (the vitamin D in most supplements) is an appropriate substitute for our own vitamin D3.

* * *

So anyway, here’s another real thing that looked weird and debunkable at first glance.

In virology papers from the fifties and sixties, there are many mentions of something called “photoreactivation”. This started with 1949 work by future Nobel laureate Renato Dulbecco, done in the Indiana University laboratory of future Nobel and National Book Award laureate Salvador Luria. In 1950 Dulbecco summarized the story.

Kelner (1949), working with conidia of Streptomyces griseus, discovered that light belonging to the visible range is capable of reactivating biological material that has been rendered inactive by ultraviolet radiation (UV). Shortly after Kelner’s discovery was known, a similar phenomenon in bacteriophages (bacterial viruses) was observed by accident. Plates of nutrient agar containing UV-inactivated phage and sensitive bacteria had been left for several hours on a table illuminated by a fluorescent lamp. After incubation it was noticed that the number of plaques was higher on these plates than on similar plates incubated in darkness. A short report of this phenomenon of “photoreactivation” (PHTR) has already been published (Dulbecco, 1950).

We’ve been using UV light, gamma rays, and chemical agents like nitrogen mustard to make “killed” versions of viruses, safe for use in vaccines. And now it’s possible that visible light could then re-activate these menaces? Should vaccines be stored in the dark?

Beyond  bacteriophages, many other viruses were found to be capable of photoreativation. A sample:

  • 1955: “Of the three viruses we studied earlier, tomato bushy stunt and the Rothamsted tobacco necrosis virus showed the phenomenon of photoreactivation, and tobacco mosaic virus did not … Of the six viruses that did [in this study], potato X showed it much the most strongly, tomato bushy stunt and a tobacco necrosis virus the least; cabbage black ringspot, cucumber mosaic and tobacco ringspot were intermediate.”
  • 1958: “Thirty minutes of illumination at 300-380 f.c. gave substantial photo-reactivation [of] potato virus X”
  • 1961: Tobacco mosaic virus particles can’t be photoreactivated, but RNA preparations from the virus can.
  • 1967: “Photoreactivation of UV-irradiated blue-green algal virus LPP-1”
  • 1967: “By contrast, photoreactivation of the irradiated [tobacco necrosis virus] was observed in French bean and tobacco, but not in Chenopodium.”
  • 1968: Pseudorabies virus can be photoreactivated in chick embryo cultures, but not in rabbit kidney cells.

In the last of those quotes, it’s becoming clear that viruses don’t photoreactivate on their own. They photoreactivate inside cells. You can use UV light to damage the DNA (or RNA) of a virus so it can’t multiply. But it may still infect cells if the protein coat is intact. Then once the viral DNA (or RNA) is inside the cell, the cell’s DNA repair mechanisms can go to work. One of these is photolyase, found in plants, bacteria, fungi, and some animals, but not mammals. Blue light activates this enzyme to reverse the DNA damage caused by UV light (specifically, covalently-linked pyrimidine dimers).

So instead of thinking of photoreactivation as something that happens to certain viruses, we should think of it as something that happens in certain types of cells, to viral DNA as well as cellular DNA.

By 1958, Dr. John Jagger (who does not have a Wikipedia page, though his wife, also a scientist, does) was already able to write a fantastic review of photoreactivation in general (not just viruses and bacteria), saying:

Photoreactivation seems to be possible whether the UV damage occurs in the liquid or the solid state. However, the reactivation seems to require not only the liquid state, but a rather complex environment, similar to that within a living cell.

It doesn’t quite require a living cell, but it requires “cellular material”. A cellular extract still contains the photolyase enzyme.

* * *

You’ll notice that the above examples are almost all plant viruses. This is partially because plants were a very convenient system for virology in the era before cell lines, but it also has to do with the importance of light in plant biology. Dependent on the sun, they need to be able to counteract the negative aspects of ultraviolet light.

But it’s also clear that photoreactivation takes place in insects and fish.

The data show that fish cells have an efficient photoreactivation system at wavelength > 304 nm that reverses cytotoxicity and dimer formation after exposure to filtered sunlamp irradiation of a shorter wavelength (lambda > 290 nm). Shorter wavelengths in UVB (> 304 nm) are more effective in photoreversal than longer ones (> 320 nm). As a consequence, 50-85% of dimers induced by these wavelengths in fish are photoreactivated while they are being formed. A major cytotoxicological lesion is the cyclobutane pyrimidine dimers. Cultured human fibroblasts do not possess such a repair system.

What about that paper above, in which chicken embryo cells enable pseudorabies virus (a herpesvirus) to reactivate? That looks weird, to me at least. Shouldn’t chickens, being warm-blooded animals, be grouped with mammals rather than fish? But chickens aren’t mammals. This table, from Photoreactivating-enzyme activity in metazoa [Cook JS, McGrath JR [1967] PNAS 58(4):1359-1365] sums it up.


Mammals have other DNA repair mechanisms, but we lack photolyase. Which as it turns out, makes us kind of weird.

No, don’t do that either.

I don’t want to spend all my time poking fun with the benefit of hindsight, but here’s another thing that looks truly ridiculous. A lot of thought has gone into it, as well as careful planning of the procedure… but really.

From the New England Medical Monthly, volume 24 (1905), pages 220-223:


Yes, he suggests that yeast can be … not necessarily the cause of this embarrassing condition … but the cure!

What comes to mind here are the words of Andy Zaltzman in episode 76 of The Bugle podcast, upon hearing about Dr. Henry Heimlich’s plan to cure people of AIDS by infecting them with malaria.

“Now, I’m not a scientist, John, but that sounds like quite a bad idea. Without wanting to use the term ‘obvious crackpot,’ there is something about fighting a major disease by giving yourself another major disease that just doesn’t feel quite right. Treating AIDS with malaria, John, to me, is along the lines of dealing with losing your favorite socks by chainsawing your feet off.”

That isn’t quite fair; it makes sense that one infectious organism could be used to fight off another. In the case of malaria, by inducing a fever that may enhance the immune response against viruses that don’t normally induce fevers.

But this is just not going to work, any more than Saccharomyces could cure typhoid back in 1891. Neisseria gonorrhoeae is not just a superficial growth on the surface of the mucous membranes — it grows inside cells. And this treatment is supposedly happening in patients with “chronic” gonorrhea, which has already spread to the cervix and quite possibly other organs outside the reproductive system? That makes it an even worse idea.

Just as the phrase “fight fire with fire” does not apply to actual fires, we should not try to fight vaginitis with more vaginitis.

Yeast vs. Typhoid: Requiem

In 1891, a flurry of medical interest followed the experiments of Auguste de Bavay, a 35-year-old Belgian chemist and yeast expert, who had moved to Melbourne, Australia in 1884 and quickly revolutionized the colony’s primitive brewing industry.

Dr. J. W. “Springy” Springthorpe was the Vice President of the British Medical Association, Victorian Branch (“Victorian” as in “Victoria, Australia”, thus this was basically the Melbourne Medical Association). To publicize a new use for his beloved Saccharomyces yeast, Monsieur de Bavay (he is universally referred to as “Monsieur de Bavay” in these articles) wrote a speech that was read by Dr. Springthorpe at the June 1891 meeting of the Victorian Branch.

In 1891 M. de Bavay was working for the Victoria Parade Brewery, makers of fine ales.

In 1891 M. de Bavay was working for the Victoria Parade Brewery, makers of fine ales.

Earlier, M. de Bavay had become aware of an interesting sample of fluid, consisting of chyle (fat-rich lymph from the lymphatics that drain the intestines) from someone with a chest injury.

Some time last year, Dr. Cox introduced Dr. O’Hara to me, and submitted for analysis a milky-looking fluid, which they believed to be possessed of antiseptic and deodorising properties, this fluid having escaped from the thoracic duct through an ulceration.

There’s no indication of why Drs. Cox and O’Hara believed this, but M. de Bavay found that they might have been right. The fluid contained no culturable organism, except for a Saccharomyces yeast that he assumed was a contamination from his brewery work. Which it probably was, so the original fluid is irrelevant for what follows. But then…

Some six months afterwards, however, I examined these flasks again. To my surprise, though in every instance I had sown considerable quantities of the chyle, no bacteria had made their appearance in either medium. … To further test the power of these saccharomyces to resist the growth of bacteria, I mixed some germs of putrefaction with them. The result was, that the saccharomyces developed very rapidly, whilst it was difficult to find traces of the germs of putrefaction. Some of these saccharomyces added to matter undergoing putrefaction, and very foul smelling, removed the offensive odour in a very short time.

* * *

There’s no need to go through all of M. de Bavay’s results, which are presented in the June 1891 issue of the Australian Medical Journal, pages 351-360 (available at Google Books here). A synopsis was syndicated in various other publications (e.g the Montreal Medical Journal (1890), pages 631-632). The main points are as follows (I don’t know how much of this is true):

  • Typhoid bacilli (what we now call Salmonella Typhi) produce more of their toxin under alkaline conditions. Toxicity was measured by taking bacterial cultures, heating them to kill the bacteria, and injecting them into guinea pigs.
  • Under these conditions, most of the toxin precipitates into a solid, instead of remaining dissolved.
  • Yeast produce acid as they grow.
  • Acid is good, because it makes the typhoid toxin stay soluble, thus poisoning the bacteria themselves. This is similar to the way yeast eventually produce so much alcohol that the yeast themselves get poisoned.
  • Also, typhoid toxin that stays in solution in the gut might have an additional benefit: activating the immune system to attack typhoid bacteria.
    “Pasteur, Roux, Chantemesse, Vidal, Martin, Hankin, Salomon, Charrin, Ruffer, and others, have proved that immunity can be given to animals by injecting the soluble products of the life of the microbe. This is precisely the effect I claim for yeast, when its acid renders soluble the poison of typhoid and allows of its absorption. Consequently, the yeast is not the direct cause of the cure, but the means of bringing about an automatic vaccination of the tissues with the produce of the growth of the typhoid bacilli.”
  • It’s perfectly safe to feed people large amounts of yeast, with regular food or by itself.
  • Adding sugar makes the yeast work better. Particularly maltose, as found in barley.
  • Dr. Matthew Barclay Thomson of the Alfred Hospital has “given a clinical trial to the cure thus recommended.” He’ll be presenting the results soon.

* * *

At the next month’s meeting, there was considerable discussion of this, followed by Dr. Barclay Thomson’s presentation of his clinical results, all taking up pages 402-407 of the July Australian Medical Journal (found in the same 1891 pdf file linked above). And here’s the electrifying conclusion:


Well, that sounds good!

And yet, I don’t see any further work on this would-be cure. It sounds vaguely plausible, particularly from the probiotic perspective, in a world without antibiotics. Dr. Barclay Thomson also says:

The striking difference between [the various drugs that have been used to attempt to destroy the germs] and the saccharomyces is the power the latter has of reproducing itself, in its passage through the intestines.

And another doctor points out in the discussion that during typhoid, evidence from the feces suggests that the normal bacteria have effectively been outcompeted and replaced by the typhoid bacteria. Maybe something else could outcompete typhoid! But it was not to be.

* * *

The Australian and New Zealand media certainly took note of these investigations. In fact, before his presentation to the medical society, M. de Bavay attracted attention from ordinary doctors and patients.

February 27, 1891: “A physician” interviewed for the Melbourne Argus expresses extreme distaste for the whole idea and suggests that the idea of yeast as an antibacterial agent was debunked 50 years ago.

March 18, 1891: The Argus reports the death of a patient being treated by Dr. Springthorpe with M. de Bavay’s fungal concoctions. However, this is not proof that the treatment is worthless.

July 4, 1891: A correspondent writes the Melbourne Age with evidence that yeast is useful for typhoid and other fevers. Apparently Edmund Cartwright, inventor of the power loom that so enraged the Luddites, had been a medical student. Cartwright wrote in his memoirs that when he was practicing in the benighted village of Brampton, Derbyshire, he gave yeast to a boy whose typhoid responded to no other treatment, and it worked great, especially for something that was affordable to the impoverished townsfolk of Brampton.

Of course, this would have been around 1775, so if it hadn’t spread into popular use over the ensuing century, it probably didn’t work. But it’s always good to give something a second try, when it can be improved by new scientific methods!

Most Nourishing

Disillusioned by his failure to cure typhoid, M. de Bavay left Victoria Parade and turned corporate, helping Foster’s accelerate mass production of its watery lager.