Cellular Changes Accompanying the Swarming of Proteus Mirabilis: I. Observations of Living Cultures

Abstract

This paper reinvestigates the gross changes which follow the inoculation of Proteus mirabilis onto an agar plate. The sequence of development observed by earlier workers was confirmed: namely, the development of a primary colony at the site of inoculation, followed by alternating periods of swarming and consolidation. The paper"s main contribution is the demonstration, by means of time-lapse photography through the phase-contrast microscope, of the cellular changes which occur during the various stages—in particular, the differentiation of short rods into swarmers, the swarming process itself, the subsequent breakdown of the swarmers into progressively shorter units, and the multiplication of these rods. Of special note is the clear demonstration that most of the swarmers are normal viable cells.

Development of Flagella by Proteus mirabilis

“…There is no true phase of decline during the 48 hr of the experiment. The generation time of Proteus rnirabilis in this experiment was 40 min., a value which agrees fairly well with phase-contrast observations of division in living organisms (Hoeniger, 1964).…”

“…diameter Petri dish, thus giving an inoculum of approximately one bacterium/20 ,u2 of surface. Incubation was at 30°, this temperature having been found previously (Hoeniger, 1964) to be most suitable for following the morphological changes in living organisms by phase-contrast microscopy.…”

“…Previous studies (Hoeniger, 1964(Hoeniger, ,1965 were made with an inoculum of organisms which had passed through a tube of semi-solid agar, i.e. motility-tube cultures incubated for about 40 hr.…”

“…1 with morphological changes on the plates and in the organisms themselves, several points seem to emerge: the short lag phase encompasses the time during which the bacteria are known from phase-contrast studies (Hoeniger, 1964) to be enlarging prior to their first division; the latter half of the exponential phase corresponds to the period when most organisms differentiate into long motile filaments commonly called swarmers (see…”

“…This paper is one of a series, earlier papers having examined by phasecontrast microscopy the changes in living organisms (Hoeniger, 1964), and by ordinary microscopy the changes manifest in stained preparations (Hoeniger, 1965).…”