6,000 strains of bacteria are under one roof for the study of how they make us sick

In the winter of 1915, Pvt. Ernest Cable arrived at the No. 14 Stationary Hospital in Wimereux, France, in bad shape. The British soldiers stationed on the Western Front of World War I were being ravaged by a variety of microscopic enemies. For Cable, it was Shigella flexneri, the bacterium that causes dysentery.

A military bacteriologist named Lt. William Broughton-Alcock took a sample of S. flexneri from Cable's body after he died on March 13, 1915. It was likely kept alive in agar, sealed under paraffin wax, and was eventually renamed NCTC 1 when it became the very first specimen added to Britain's National Collection of Type Cultures, the oldest library of human bacterial pathogens in the world devoted to sharing strains with other scientists. The collection turned 100 this year.

Managed by Public Health England, the NCTC holds about 6,000 bacterial strains representing more than 900 species that can infect, sicken, maim and kill us. (Strains are genetic variants of a species.) Of the nearly 800 registered culture collections in 78 countries, it is one of only a few dedicated to clinically relevant bacteria — that is, to species that make us sick.

About half of the microorganisms in the world's culture collections are bacteria, dwarfing the number of viruses and fungi. Bacteria continue to outmaneuver our immune systems and antibiotics. We think of them as invaders in our world, but really, we live in theirs. "On any possible, reasonable or fair criterion," wrote Stephen Jay Gould, the evolutionary biologist, "bacteria are — and always have been — the dominant forms of life on Earth."

The collection supplies many of the world's clinical microbiologists with microbial strains of known origin. These scientists study how bacteria evolve; test safety protocols for infectious pathogens; develop vaccines, anticancer drugs and treatments for metabolic diseases; and study antimicrobial resistance.

Cable's killer, for instance, was brought back to life from its freeze-dried form by Kate Baker, a microbiologist at the University of Liverpool, and her colleagues, part of an effort to understand how S. flexneri has evolved. It still kills about 164,000 people every year, most of them children.

The team sequenced the NCTC 1's genome and then compared it with strains isolated in 1954, 1984 and 2002. Only 2% of the bacterium's genome had changed over the century, but those changes were associated with higher virulence, immune evasion and greater antimicrobial resistance.

"Their science can then be reproducible, because other people can study it," said Sarah Alexander, the collection's lead scientist and curator. "There may be new applications for those strains."

"From my perspective, it is one of the most important collections worldwide," said Jörg Overmann, director of the German Collection of Microorganisms and Cell Cultures, one of the world's largest and most diverse.

The collection opened in London in 1920 at the Lister Institute of Preventive Medicine. Its first 200 cultures — including Cable's — were deposited by Sir Frederick William Andrewes, a pathologist who studied dysentery throughout World War I.

The organization sent 2,000 strains to various institutions for free over the next year. The bacteria were delivered alive, teeming on a medium of agar and sealed with paraffin wax.

Safety protocols were not in place yet: In 1922, three NCTC researchers caught Tularemia, or rabbit fever, during an experiment in which they had rubbed the spleen of a guinea pig infected with Francisella tularensis on the scarified skin of a healthy guinea pig.

In the following decades, the collection moved back to London and raised its prices. Today it is a nonprofit that is self-supporting through the sale of strains, which usually cost between $85 and $375.

The NCTC holds many bacteria relevant to medical breakthroughs. Alexander Fleming, who discovered penicillin, deposited 16 strains into the collection between 1928 and 1948. Fleming sourced NCTC 4842, the bacterium Haemophilus influenzae, from his own nose. Betty Hobbs, a noted expert on food poisoning who identified Clostridium perfringens as the culprit behind many food-borne illnesses, deposited more than 20 related strains.

A subset of its holdings is the Murray Collection, assembled by Everitt George Dunne Murray in the first half of the 20th century from the stool, urine, blood, cerebrospinal fluid and other bodily products of sick people across the world. The sub-collection's 683 strains span the period when antibiotics entered into general use.

"It gives us this snapshot of an era for which we don't have much information but that is critical for understanding how we've got to the antimicrobial crisis that we're in today," Baker said.

The collection has also sequenced the genomes of about half the strains, making that data available publicly for genetic research.

They are shipped from a center outside London under strict protocols. Most bacteria are biosafety level 2 or 3, which means they can cause serious or lethal diseases but have a cure. Level 4, the deadliest, includes only viruses.

The collection is also growing. "We receive anywhere between 50 and 200 strains a year from all sorts of sources," microbiologist Jake Turnbull said.

Some are newly discovered, called type strains. Others are deposited from historical collections, or by scientists who retire or shift focus and want their strains to have a future.

New specimens are cultured on agar to make sure they are alive and uncontaminated, suspended in a sugar-rich cryoprotectant broth, freeze-dried at about minus 28 degrees Fahrenheit for three to four hours, plugged with sterilized cotton, flame sealed in an evacuated glass ampul and stored at 39 degrees. Not all specimens survive long-term storage.

"The process we use is very similar to the one developed in the 1930s," said Julie Russell, the head of culture collections at Public Health England.