Abstract

Our previous studies showed that urea in acidic broth induced swarmer morphotypes in Proteus mirabilis, but the effects to other bacterial species remain unsolved. Here we report effects of urea on morphology and size distribution of urease-negativeEscherichia coli and Salmonella enterica serovar Abony grown in urea-containing broth. Statistical analysis indicated lognormal distribution of the cellular lengths below a threshold level, suggesting that the growth process of bacterial cells obeys some random multiplicative process below a threshold value, despite any other factors affecting the process above the threshold value, to produce elongated cells. In urea broth, the distribution shifted to larger size and enormously elongated cells appeared. Morphological studies in urea broth revealed that filamentous cells of E. coli and S. Abony, accompanied with incomplete chromosomal segregation without forming hyperflagellates were induced at logarithmic growth phase, unlike swarmer cells in P. mirabilis. Since cell division protein FtsZ (filamenting temperature-sensitive mutant Z) assembled round the chromosome segregated point and cells were divided into short rods after cell counts had reached to a threshold level, urea in broth was responsible for delay of chromosomal segregation.

Key words: Chromosomal segregation, enterobacteria, filamentous cells, urea.

Abbreviation

BSA, Bovine serum albumin; DAPI, 4’,6-diamidino-2-phenylindole; EDTA,ethylenediaminetetraacetic acid; FtsZ, filamenting temperature-sensitive mutant Z; P2,testing broth containing 2 g/L peptone; P2U, testing broth containing 2 g/L peptone and 25 g/L urea; P50, testing broth containing 50 g/L peptone; P50U, testing broth containing 50 g/L peptone and 25 g/L urea; PBS, phosphate buffered saline.