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.
Highlights
Bacterial shapes differ among various genera, and it is a characteristic feature of some bacteria to grow and multiply in filaments, clusters or chains
We report effects of urea on morphology and size distribution of urease-negative Escherichia coli and Salmonella enterica serovar Abony grown in urea-containing broth
Since cell division protein filamenting temperature-sensitive mutant Z (FtsZ) 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
Summary
Bacterial shapes differ among various genera, and it is a characteristic feature of some bacteria to grow and multiply in filaments, clusters or chains. All these morphological properties are of value in the identification and classification of bacterial strains, though a particular species may show variations of shape and size according to environments including nutrient conditions. Bacterial cells grown in rich nutrient medium are Abbreviations: 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. Several antibacterial reagents blocking FtsZ, the tubulin homologue that forms cytokinetic Z ring (Löwe and Amos, 1998) are known to yield filamentous cells (Beuria et al, 2005; Jaiswal et al, 2007; Wang et al, 2003)
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