AvL, Taste, and the Dis­cov­ery of Bac­te­ria

by Roberto

Be­fore ap­proach­ing mat­ters of taste, I'll ex­plain AvL. To many of our read­ers, the mean­ing of the acronym will be im­me­di­ately ap­par­ent. But to oth­ers, per­haps those newer to mi­cro­bi­ol­ogy, it may have no mean­ing at all. AvL is short for An­tonie van Leeuwen­hoek, con­sid­ered by many as the "fa­ther of mi­cro­bi­ol­ogy." I hope you will agree that the name is long enough to merit an acronym when ap­pear­ing re­peat­edly. At STC (mean­ing Small Things Con­sid­ered ;-)) we have paid homage to AvL nu­mer­ous times. See, as ex­am­ples, a trib­ute to him as nat­ural philoso­pher or Christoph's post de­scrib­ing him as the first to in­ves­ti­gate den­tal plaque with the aid of a mi­cro­scope. AvL was in­ter­ested in many and di­verse sub­jects and, when he was in­ter­ested in a sub­ject, he quickly put it un­der the mi­cro­scope.

AvL is, of course, rec­og­nized as the first to ob­serve in­di­vid­ual bac­te­ria. How did he come about this tow­er­ing dis­cov­ery? It was due to his in­ter­est in the sense of taste (in 1983, D. Bardell pub­lished a fun-to-read pa­per of this his­tory). On a let­ter to the Royal So­ci­ety dated 19 Oc­to­ber 1674 AvL wrotse: "Last win­ter while be­ing sickly and nearly un­able to taste, I ex­am­ined the ap­pear­ance of my tongue, which was very furred, in a mir­ror, and judged that my loss of tasted was caused by the thick skin on the tongue." While he did not find bac­te­ria through these ob­ser­va­tions, he did study ox tongues through the mi­cro­scope and de­scribed what we now know to be gus­ta­tory papil­lae as "very fine pointed pro­jec­tions" com­posed of "very small glob­ules." He con­cluded that the "thick skin" on his tongue in­ter­fered with the pro­jec­tions' abil­ity to sense taste dur­ing his ill­ness. He hy­poth­e­sized that when ex­posed to food these pro­jec­tions were stim­u­lated dif­fer­ently by tiny crys­tals of dif­fer­ent shapes present in the food. To in­ves­ti­gate this fur­ther, AvL de­cided to look at what shapes of crys­tals he might find in black pep­per which might ac­count for its strong taste. What he found was some­thing else, some­thing com­pletely un­fore­seen: bac­te­ria.

Fig. 1. Black Pep­per­corns. Source

AvL's ex­per­i­ment was sim­ple. He left pep­per­corns stand­ing in wa­ter for three weeks to ex­tract the strong fla­vor and ob­serve. He de­scribed his ober­va­tions in a let­ter to the Royal So­ci­ety dated 19 Oc­to­ber 1676. Alas! AvL did not dis­cover what ren­ders black pep­per spicy. In­stead, he saw more of his beloved "klei­jne dierken" (lit­tle an­i­mals, later trans­lated as an­i­mal­cules). But much to his sur­prise, he also saw or­gan­isms that were "in­cred­i­bly small,"  much smaller than the "klei­jne dierken." He es­ti­mated that one mil­lion of them would not amount to the size of a grain of sand. From this size de­scrip­tion we now sur­mise that AvL dis­cov­ered in­di­vid­ual bac­te­ria in this ex­per­i­ment. His later ob­ser­va­tions, par­tic­u­larly those in­volv­ing den­tal plaque, served as strong con­fir­ma­tion of the ex­is­tence of such in­cred­i­bly small or­gan­isms, our beloved bac­te­ria.

If you want more on AvL, on Mon­day Christoph will dis­cuss an­other "klei­jne dierken."

 

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