Morphology of Escherichia coli Exposed to Penicillin as Observed with the Electron Microscope

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Abstract
Cells of E. coli, strain 252 Univ. of Illinois stock culture collection, were grown on MacConkey''s agar (Difco) with 50 U./ml. of penicillin. Gram stains were made and suitable specimens prepd. for observation with a type B, RCA electron micro-scope. Spindle-shaped cells and elongated forms with fusiform swellings were shown to be highly granulated in older cells and homogeneously dense in young cells. Partially divided, short rods were shown both as granulated and dense cells. A photomicrograph of living cells of the same organism is presented for contrast with electron micrographs. Granulation of fusiform bodies is also evident in the latter prepn. but electron micrographs are far more satisfactory. Fusiform bodies were seen to arise by direct swelling of a portion of an elongated rod. Both normal cells and those with fusiform structures were found to be motile.