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Prokaryotes contain cytoskeletal proteins such as the tubulin-like FtsZ, which forms the Z ring at the cell center for cytokinesis , and the actin-like MreB, which forms a helix along the long axis of the cell and is required for shape maintenance . Using time-lapse analysis of Escherichia coli cells expressing FtsZ-GFP, we found that FtsZ outside of the Z ring also localized in a helix-like pattern and moved very rapidly within this pattern. The movement occurred independently of the presence of Z rings and was most easily detectable in cells lacking Z rings. Moreover, we observed oscillation waves of FtsZ-GFP in the helix-like pattern, particularly in elongated cells, and the period of this oscillation was similar to that of the Min proteins. The MreB helix was not required for the rapid movement of FtsZ or the oscillation of MinD. The results suggest that FtsZ not only forms the Z ring but also is part of a highly dynamic, potentially helical cytoskeleton in bacterial cells. [Copyright &y& Elsevier]

The post-transcriptional processing of tRNAs decorates them with a number of modified bases important for their biological functions. Queuosine, found in the tRNAs with GUN anticodons (Asp, Asn, His, Tyr), is an extensively modified base whose biosynthetic pathway is still unclear. In this study, it was observed that the tRNA[sup Tyr] from Escherichia coli B105 (a B strain) migrated faster than that from E. coli CA274 (a K-12 strain) on acid urea gels. The organization of tRNA[sup Tyr] genes in E. coli B105 was found to be typical of the B strains. Subsequent analysis of tRNA[sup Tyr] and tRNA[sup His] from several strains of E. coli on acid urea gels, and modified base analysis of tRNA preparations enriched for tRNA[sup Tyr], showed that E. coli B105 lacked queuosine in its tRNAs. However, the lack of queuosine in tRNAs was not a common feature of all E. coli B strains. The tgt and queA genes in B105 were shown to be functional by their ability to complement tgt and queA mutant strains. These observations suggested a block at the step of the biosynthesis of preQ[sub 1] (or preQ[sub 0]) in the B105 strain. Interestingly, a multicopy vector harbouring a functional tgt gene was toxic to E. coli B105 but not to CA274. Also, in mixed cultures, E. coli B105 was readily competed out by the CA274 strain. The importance of these observations and this novel strain (E. coli B105) in unravelling the mechanism of preQ[sub 1] or preQ[sub 0] biosynthesis is discussed. [ABSTRACT FROM AUTHOR]

Examines the growth phenotypes of tRNA strains of Escherichia coli in the presence of the inhibitors of formyltetrahydrofolate biosynthesis. Application of the strains for analyzing initiation activities of the formylation-defective initiator tRNA; Significance of folate biosynthesis inhibitors in discerning the importance of the lack of rT modification; Analysis of the independent formylation.

Escherichia coli strains harbouring elongator tRNAs that insert amino acids in response to a termination codon during elongation have been generated for various applications. Additionally, it was shown that expression of an initiator tRNA containing a CUA anticodon from a multicopy plasmid in E. coli resulted in initiation from an amber codon. Even though the initiation-based system remedies toxicity-related drawbacks, its usefulness has remained limited for want of a strain with a chromosomally encoded initiator tRNA ‘suppressor’. E. coli K strains possess four initiator tRNA genes: the metZ, metW and metV genes, located at a single locus, encode tRNA1fMet, and a distantly located metY gene encodes a variant, tRNA2fMet. In this study, a stable strain of E. coli K-12 that affords efficient initiation from an amber initiation codon was isolated. Genetic analysis revealed that the metY gene in this strain acquired mutations to encode tRNA2fMet with a CUA anticodon (a U35A36 mutation). The acquisition of the mutations depended on the presence of a plasmid-borne copy of the mutant metY and recA+ host background. The mutations were observed when the plasmid-borne gene encoded tRNA2fMet (U35A36) with additional changes in the acceptor stem (G72; G72G73) but not in the anticodon stem (U29C30A31/U35A361/ψ39G40A41). The usefulness of this strain, and a possible role for multiple tRNA1fMet genes in E. coli in safeguarding their intactness, are discussed. [ABSTRACT FROM AUTHOR]