Sorry, Michigan, Guess Who They Named the Ring Rot Bacterium After?

And why it’s bad news for potatoes, but no problem for you.

Just as it has been for years, the most common last name in the US is Smith.

But although over 2.3 million Americans share it, apparently only 215 also have the first name Erwin.

And we’re fairly sure that few, if any, of today’s Erwin Smiths are likely to have the middle name Frink.

However, we do know that there has been at least one Erwin Frink Smith, a plant pathologist in the earliest days of the United States Department of Agriculture, who was born in 1854.

We’ll tell you a little of his story this week, partly as a way to introduce you to a new feature you can now see in uBiome Explorer.

It’s called Probiotics Explorer, and it enables you to investigate your level s of dozens of bacterial species that are all food- or probiotics-related.

Tireless work by our merry band of bioinformaticians (who may just have the greatest number of syllables in their job title of anyone at uBiome) is devoted to researching the microbes on which Probiotic Explorer focuses.

In the process, they uncover a wealth of fascinating detail.

So, the entirety of our post this week is devoted to just one minuscule microbe, originally isolated in 1910 by the aforementioned Erwin Frink Smith, in Grand Rapids, Michigan.

Clavibacter michiganensis, which gives even our bioinformaticians a run for their money syllable-wise, is found only infrequently in the human gut (apparently quite harmlessly) but is best known for being an important plant pathogen.

It causes canker in tomatoes and leads to a particularly damaging disease known as ring rot in potatoes.

Before we get too carried away with plant pathogens, though, let’s just dissect that whopper of a species name.

The genus Clavibacter comes from two Latin words: “clava” and “bacter,” each of which describes physical shape.

Bacter means rod, while clava suggests something shaped like a club or cudgel.

So pop any bacterium from the genus Clavibacter under an electron microscope, and you’ll see something that resembles Fred Flintstone’s club.

Actually, when we say “any bacterium,” Clavibacter is like a family with just one member: Clavibacter michiganensis.

In times gone by, other species were also classified in this genus but, as so often happens in microbiology, scientists reallocated them to other genera, leaving C. michiganensis as the only spoon in the drawer.

The name “michiganensis” may look complicated, but it simply means “from Michigan.”

So we’re dealing with a club-shaped microbe that was first formally recognised in Michigan.

This, however, doesn’t mean that it was born in the Wolverine State, simply that Erwin Smith isolated and named it there.

Ring rot, caused by a subspecies of C. michiganensis, was first seen in Germany in the late 1800s.

It’s a devastating disease, principally affecting potatoes, producing a kind of brown ring inside a potato, which is only visible when you slice it open.

Ring rot appeared in the US for the first time in the early 1930s, but it spread across the whole of the continental United States by the 1940s.

It can ruin whole potato crops, so is of huge economic consequence, and it can spread if farmers unknowingly buy infected seed potatoes or even if uncleaned commercial vehicles visit their farm.

One of Erwin Smith’s lasting scientific contributions was to prove that bacteria play a major role in causing plant disease, an idea that was largely ignored previously.

Such a leap of discovery would be pretty impressive for anyone, but it was particularly so for someone such as Smith, who had a fairly unconventional education.

Smith’s family owned a farm in Clinton County, Michigan, but the enterprise struggled and ultimately failed.

As a result, Smith was no longer needed to help agriculturally, so he entered High School at the age of 22 (fully bearded, apparently), and was still there five years later when he co-authored a book about the flora of Michigan.

These days, most students start college around the age of 18, but Smith didn’t begin University until he was a leisurely 31.

However, things accelerated pretty quickly thereafter, and after passing all his examinations remarkably swiftly, Smith was out the door with a Bachelor’s degree in Biology after mere year.

In addition to isolating C. michiganensis, Erwin Smith was also celebrated, in his position as Chief of Plant Pathology in the Bureau of Plant Industry, for hiring many female botanists at a time when it was highly unusual to do so.

Incidentally, the subspecies of C. michiganensis that causes ring rot is named sepidonicus, which comes from the Greek word “sepedon,” meaning rottenness, decay, or putrefaction, and from which we also get our words “septic” and “antiseptic.”

Thank goodness, eh? Somehow, keeping a tube of anti-putrefaction cream in your bathroom cabinet doesn’t sound that appetizing.

Finally, just to put your mind at ease, although C. michiganensis is indeed occasionally found in the human gut, the government of Ireland (a country where they know a thing or three about potatoes) reassures us that ring rot poses no risk to human health.

If you’ve already had a microbiome sample tested by uBiome using our Explorer kit, the good news is that you can retrospectively learn if it contained C. michiganensis (and dozens of other newly-added species) simply by signing into your account at No charge.

And if you haven’t used Explorer yet, why not check it out? Although we’ve devoted a whole newsletter to C. michiganensis, it’s only one of an absolute multitude that you can explore.

We think Erwin Smith would have been pretty amazed to see where his work led.

Click here to view your uBiome Probiotic results.

More reading

A Disease Cuts Corn Yields

Bacterial Ring Rot in Alaska Potato Crops

Bacterial Ring Rot of Potato

Bacterial Ring Rot of Potatoes


Clavibacter – Taxonomy Browser

Clavibacter michiganensis

Erwin Frink Smith

Erwin Frink Smith (book)

Goss’s Wilt

Goss’s Bacterial Wilt

Goss’s Wilt Found in Corn

Potato Ring Rot information sheet