How E. coli Rose to Prominence – An Addendum

by Roberto
 

In an era of microbiology largely immersed in microbial diversity research, here at STC we still have a strong affection for the advances made investigating model bacteria; prime amongst these is E. coli. Thus, it is no surprise that we are fascinated by the history of E. coli research. Two prior posts immediately come to mind. The first was written by Memo Berkmen and Paul Riggs describing their detective work (How did E. coli get named K-12?). The second is my own "How E. coli Rose to Prominence," to which I am adding a fun detail today.

 

It is no exaggeration to state that most widely used E. coli strains are derivatives of either "K-12" or "B" (or hybrids thereof). The origin of the K-12 strain – though not why it is called so – was made clear in the post by Memo and Paul. It was a clinical isolate maintained at Stanford's Bacteriology Department.

 

In recent years, I did some limited research on the origin of E. coli B. Here's what I learned. Ellis and Delbrück, in the work leading to their landmark 1939 paper describing phage growth, used E. coli as the host. Why? Ellis, working in Morgan's lab at Caltech, obtained the E. coli host from lab mate Carl Lindegren. I used this anecdote as an example of serendipity in science in yet another post. Reading subsequent papers from the Phage Group and seeing that they routinely used E. coli B as the host, I assumed that strain was the one Delbrück had used with Ellis and afterwards insisted on everyone using. I was wrong!

 

Last month I participated in a KITP course/program on microbial evolution and, serendipitously (there's that word again!), had an enlightening conversation with Sergei Maslov. At one of the weekly cocktail hours, we began sharing stories on our mutual fascination with the history of E. coli. Given the focus of the program on evolution, it was not surprising that our conversation landed on E. coli B, a derivative of which was used in Lenski's world-famous Long Term Evolution Experiment (LTEE). I shared my story on how the "original" E. coli B must have come from Morgan's lab at Caltech. Sergei immediately corrected me: "Oh no, the E. coli B that Luria and Delbrück used goes back to Felix d'Herelle. Bill Studier has documented this very clearly. I'll send you the paper."  (And Sergei should know, himself having been involved in the work comparing the genomes of E. coli K-12 and E. coli B). I was thrilled! The strain used by the Phage Group, so important in the birth of molecular biology, could be traced to d'Herelle, one of the discoverers of phage! Once I received the paper from Sergei, I devoured it like a child does candy.

 

Fig. 1. Tracing the history of E. coli B and derived strain. Full legend in source. Frontispiece: E. coli B Ara⁺ and Ara^- colonies used in the long-term evolution experiment on an agar plate. Credit: Jeffrey Barrick. Adapted and modified from source.

While there is no substitute for reading the paper (I highly recommend you do so) here are what I consider key moments in the history of E. coli B. Around 1917 Felix d'Herelle, working at the Pasteur Institute in Paris, being intent on studying lytic activities from human feces, chose to use E. coli (first named Bacterium coli communis and then Bacillus coli). Subsequently, and largely due to their opposition to d'Herelle's interpretations, Jules Bordet (director of the Institute Pasteur in Brussels) and his student André Gratia (also working in Brussels), obtained the strain from d'Herelle. When Gratia moved to Rockefeller (1921-1923) to work on phage, he took the strain with him and distributed it widely. A couple of years after Gratia left, Jacques Bronfenbrenner arrived at Rockefeller and used that strain for subsequent phage work. It was Bronfenbrenner who then sent the strain to Luria. Luria in turn would share that strain with Delbrück and the rest of the Phage Group! From there, E. coli B spread widely among the community of molecular geneticists (Fig. 1. Click on it for legible size).

 

Those events show the trail of the strain from d'Herelle to the Phage Group. But why did it come to be called E. coli B? Bordet. Brussels. Bronfenbrenner. So many Bs to choose from! But, in the end the reason is much more pedestrian. From the start of his work with Ellis, Delbrück referred to phage as "P" and its host bacterium as "B." So, the "B" comes from bacterium! In fact, the strain that Luria obtained from Bronfenbrenner, originally referred to as E. coli PC (because it was susceptible to phage PC), was renamed E. coli B₃. To distinguish the various strains he used, Delbrück simply called them E. coli B₁ (from his work with Ellis), E. coli B₂ (from work done by himself), and E. coli B₃ (from work done with Luria). With time, the Phage Group used only E. coli B₃, dropping the "3" and called it simply E. coli B. The story is complete. (Yet, two questions remain in my mind: Why was E. coli B₁ in Morgan's lab, given that it was a Drosophila lab? More importantly, did it also come from d'Herelle? The answers to those questions are most likely lost in the past.)

 

In writing this post, I was reminded of the children's book "The Treasure" by Uri Shulevitz; I used to read it to my kids decades ago. The moral of the story, a reflection of a common theme in philosophy and literature, is that "sometimes one must travel far to discover what is near." In re-reading the STC post on how E. coli got its name K-12, I discovered how E. coli B got its name! The authors (Memo and Paul) had asked Bill Studier about the origin of the name to which he replied: "Delbrück had been in the habit of using B for Bacterium as the name for whatever bacterium he was using as host for whatever phage he was studying, referred to as P." All that was missing was the trail tracing it back to d'Herelle!

 

 

 

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