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H HOFFMAN

Publications and source records attributed to H HOFFMAN.

At least 19 recordsLinked to original sources
PubMed1965

TIME-LAPSE PHOTOMICROGRAPHY OF CELL GROWTH AND DIVISION IN ESCHERICHIA COLI.

Hoffman, Heiner (New York University, New York, N.Y.), and Michael E. Frank. Time-lapse photomicrography of cell growth and division in Escherichia coli. J. Bacteriol. 89:212-216. 1965.-Photomicrographs at 15-sec intervals of cells growing at 37 C disclosed that in a cell with a generation time of 21.0 min the processes of furrowing, cross-wall formation, and cell separation are completed within 2.5 min after the division furrow first becomes clearly visible. Among a large number of cultivations examined, only a few cells late in one microculture at 43.5 C failed to separate once the cross wall was completed. Measurements of cell lengths during a 5-min period, extending from just before to just after division, showed that elongation of the cell is a discontinuous process, although the growth rate over the 5-min period is exponential. At the time of cell division, it appears that the synthesis of cell-wall material is diverted entirely into formation of the cross wall.

Cell Cycle↗
PubMed1965

SYNCHRONY OF DIVISION IN CLONAL MICROCOLONIES OF ESCHERICHIA COLI.

Hoffman, Heiner (New York University, New York, N.Y.), and Michael E. Frank. Synchrony of division in clonal microcolonies of Escherichia coli. J. Bacteriol. 89:513-517. 1965.-A common pattern of synchrony of division was found in 18 clonal microcolonies studied by means of time-lapse photomicrography. One of these is described in detail. Cell counts at 1-min intervals were carried into the 11th generation of a microcolony photographed for 5.25 hr. The counts indicated that an early synchrony of division occurred which apparently was gradually dissipated during the course of cultivation. However, when times of cell division for each generation were plotted, it became apparent that each generation conformed to a distribution curve which gradually changed in its characteristics from one generation to the next. The range of time during which the divisions occurred increased from 16 min in the 6th generation to at least 74 min in the 11th. Overlap between distribution curves increased from 3 min between the 7th and 8th generations, where it initially occurred, to at least 20 min between the 10th and 11th. Skewness of the distribution curve progressed from a negative value (-0.943) in the 5th generation to a positive value (+0.339) in the 10th. Genealogical identification of the first and last quarters of the cells to divide within a generation revealed, early in the course of cultivation, a cell subline which was dividing in a pattern of synchrony independent of the colony as a whole. The characteristics of this synchronous pattern, however, gradually progressed with each new generation toward those of the microcolony as a whole.

Cell Division↗
PubMed1964

"GERMINATION TUBE" GROWTH IN ESCHERICHIA COLI MICROCULTURES.

Hoffman, Heiner (New York University, New York, N.Y.), and Michael E. Frank. "Germination tube" growth in Escherichia coli microcultures. J. Bacteriol. 88:1151-1154. 1964.-Analysis of extensive time-lapse photomicrographic records of Escherichia coli microcultures uncovered two cases in which there occurred aberrant cell growth resembling a germination tube. Although previously observed by a number of investigators in gram-positive bacteria, the present observations appear to constitute the first time-lapse photomicrographic record concerning a gram-negative form. In the first case, with photographs taken at 15-sec intervals, the cell initially exhibited a clublike deformation, and the "germ tube" then issued from the club head. The "tube" had developed into a separate cell by the time the photographic record was concluded. In the second case, with the photographs taken at 1-min intervals over a longer period of time, the "germ tube" cell assumed a plastic dumbbell-like form after separation from its sister. It is suggested that the phenomenon results from a disturbance in cell-wall synthesis, while cytoplasmic growth continues unabated.

Cell Division↗
PubMed1963

CARS FOR SAFETY.

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Humans↗
PubMed1963

TEMPERATURE LIMITS, GENEALOGICAL ORIGIN, DEVELOPMENTAL COURSE, AND ULTIMATE FATE OF HEAT-INDUCED FILAMENTS IN ESCHERICHIA COLI MICROCULTURES.

Hoffman, Heiner (New York University, New York, N.Y.) and Michael E. Frank. Temperature limits, genealogical origin, developmental course, and ultimate fate of heat-induced filaments in Escherichia coli microcultures. J. Bacteriol. 85:1221-1234. 1963.-The heat induction of filaments in microcultures of Escherichia coli occurred through a wide range of temperature, with 43.5 C being the upper limit at which all cells continued to grow. The lower temperature limit was not determined, but filaments were obtained at room temperature in overnight cultivations. The evidence from genealogical histories, growth rates, and cell and filament lengths strongly suggested that the filaments are collections of morphologically undifferentiated, but quasi-independent cell units which continue to grow and multiply while retaining the capacity eventually to break off completely as normal, nonfilamented cells. Filaments which failed to give off a daughter by the end of the second generation after their inception lyse explosively. The evidence obtained contradicts the hypothesis that the mother cell of a clonal microcolony becomes a filament and eventually lyses, although the cell length patterns upon which this hypothesis is based were reproduced. A high degree of synchronization of division was obtained and maintained through the entire period of incubation, which in some cultivations extended into the tenth generation.

Cold Temperature↗
PubMed1963

TIME-LAPSE PHOTOMICROGRAPHY OF THE FORMATION OF A FREE SPHERICAL GRANULE IN AN ESCHERICHIA COLI CELL END.

Hoffman, Heiner (New York University, New York), and Michael E. Frank. Time-lapse photomicrography of the formation of a free spherical granule in an Escherichia coli cell end. J. Bacteriol. 86:1075-1078. 1963.-Only a single case of the formation of a free spherical granule at an Escherichia coli cell end was found among several thousand cells recorded by time-lapse photomicrography. The spherical end body apparently arose immediately upon or soon after binary fission, at the newly formed cell end. Several minutes elapsed between the appearance of the end body and its full separation, apparently by constriction, from the mother cell. The end body showed no cytological changes during a 51-min period of observation after its separation from the mother cell. A hypothesis concerning the nature of end bodies and the mechanisms underlying their production is presented.

Cytoplasmic Granules↗