Sharing my space with E. coli friends

Originally published 13 January 1986

I sing the prais­es of Escherichia coli, bean-shaped bac­teri­um, inhab­i­tant of the human intes­tine, best under­stood (as I shall soon reveal) of all God’s creatures.

Bac­te­ria are the most prim­i­tive forms of life on earth. E. coli is about as sim­ple as a crea­ture can be and still be alive. It is a pinch of pro­to­plasm in a mem­brane. It has a sin­gle chro­mo­some and a loop of DNA about as big as the dot on this let­ter i. By con­trast, the DNA in a human cell is a thou­sand times as long.

But E. coli moves. It feeds. It repro­duces. It rec­og­nizes and com­mu­ni­cates with its own kind. In a prim­i­tive sense, it can even remem­ber. It gets from here to there by wrig­gling its whip­like appendages; or screw­ing them, actu­al­ly, like pro­pellers. It has, such as it is, a life of its own.

E. coli is micro­scop­ic. A mil­lion of them laid end to end would make a line only as long as my arm. But there are enough of the bac­te­ria inside of me now to form a line that would stretch from Boston to San Fran­cis­co. A sig­nif­i­cant part of my body weight is not me at all, but my bur­geon­ing pop­u­la­tion of E. coli.

Ever the dinner guest

As house guests go, my E. coli are not unwel­come. They pro­duce, I am told, cer­tain use­ful vit­a­mins. They some­times devour oth­er micro-organ­isms that cause dis­ease. But most­ly they just go about their busi­ness, hap­pi­ly shar­ing my space, doing me very lit­tle good or harm. The tech­ni­cal term for our rela­tion­ship is com­men­sal: lit­er­al­ly, “eat­ing at the same table.”

E. coli is the most inten­sive­ly stud­ied of any liv­ing organ­ism. I checked a recent vol­ume of Bio­log­i­cal Abstracts, a jour­nal that index­es bio­log­i­cal research. There were five times more ref­er­ences to E. coli than to any oth­er species. This lit­tle bac­te­ria has no secrets. Its genes have been exhaus­tive­ly mapped. Its pro­teins have been cat­a­loged. It has been poked and probed in a thou­sand ways.

It is the sim­plic­i­ty of E. coli that makes it so attrac­tive to sci­ence. It has become the white rat of micro­bial research. It is hardy. It mul­ti­plies itself every twen­ty min­utes. Genet­ic researchers, espe­cial­ly, have found E. coli to be the ide­al sub­ject. It is pos­si­ble to snip lit­tle bits of gene from oth­er crea­tures and splice them into the DNA of E. coli, thus trick­ing the bac­te­ria into doing things it would oth­er­wise know noth­ing about. This new tech­nique is called recom­bi­nant DNA research.

E. col­i’s genes have been engi­neered in ways to cause the crea­ture to unwit­ting­ly man­u­fac­ture insulin, inter­fer­on, and human hor­mones, immense­ly valu­able sub­stances that are oth­er­wise extreme­ly dif­fi­cult to obtain. The human brain hor­mone somato­statin is a sub­stance that inhibits the secre­tion of the pitu­itary growth hor­mone. The researchers who first iso­lat­ed somato­statin need­ed a half-mil­lion sheep brains to col­lect 5 mil­ligrams of the sub­stance. A two-gal­lon cul­ture of E. coli can quick­ly pro­duce the same amount.

The dark side

The future of recom­bi­nant DNA research holds the promise of engi­neered cures for such genet­ic dis­eases as hemo­phil­ia and diabetes.

But there is a dark side to restruc­tur­ing genes. In the ear­ly days of genet­ic research it was feared that a dan­ger­ous vari­ant of re-engi­neered E. coli might escape from the lab and cause dis­ease among humans. Strin­gent mea­sures were tak­en to insure the con­tain­ment of the bac­te­ria. Nowa­days, most E. coli research employs a delib­er­ate­ly crip­pled strain of the bac­te­ria that can­not live except in the spe­cif­ic con­di­tions of the lab.

With the suc­cess of these genet­ic engi­neer­ing exper­i­ments, a new indus­try was born. It will not be long before there are fac­to­ries in which vast num­bers of genet­i­cal­ly altered E. coli labor like Per­due chick­ens to pro­duce use­ful prod­ucts for mankind: med­i­cines, insec­ti­cides, fer­til­iz­ers, and — if we are not watch­ful — weapons.

This new pow­er to tin­ker with the code of life rais­es stag­ger­ing eth­i­cal dilem­mas. Like all tech­nolo­gies, recom­bi­nant DNA research car­ries the pow­er for both good and evil. And I can’t help but feel a bac­teri­um-sized twinge of con­science about the cav­a­lier way we manip­u­late E. col­i’s genes. On the oth­er hand, bac­te­ria have sur­vived assort­ed ter­res­tri­al and cos­mic calami­ties for more than three bil­lion years; they will undoubt­ed­ly still be here when we are gone.

I sing the prais­es of Escherichia coli, best under­stood of my fel­low crea­tures, indus­tri­ous bac­teri­um, hardy sur­vivor, com­men­sal friend.