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The function of Sufl, a well-studied substrate of the TatABC translocase in Eseherichia coli, is not known. It was earlier implicated in cell division, based on the finding that multiple copies of sufI suppressed the phenotypes of cells with mutations in flsI (fts123), which encodes a divisomal transpeptidase. Recently, sufI was identified as both a multicopy suppressor gene and a synthetic lethal mutant of ftsEX, which codes for a division-specific putative ABC transporter. In this study, we show that sufI is essential for the viability of E. coli cells subjected to various forms of stress, including oxidative stress and DNA damage. The sufI mutant also exhibits sulA-independent filamentation, indicating a role in cell division. The phenotypes of the sufI mutant are suppressed by factors that stabilize FtsZ ring assembly, such as increased expression of cell division proteins FtsQAZ or FtsN or the presence of the gain-of-function ftsA* (FtsA R286W) mutation, suggesting that SufI is a divisomal protein required during stress conditions. In support of this, multicopy sufI suppressed the divisional defects of mutants carrying the ftsA12, ftsQ1, or ftsK44 allele but not those of mutants earrying ftsZ84. Most of the division-defective mutants, in particular those carrying a [DELTA] flsEX or flsI23 allele, exhibited sensitivity to oxidative stress or DNA damage, and this sensitivity was also abolished by multiple copies of SufI. All of these data suggest that SufI is a division component involved in protecting or stabilizing the divisomal assembly under conditions of stress. Since sufI fulfils the requirements to be designated an fts gene, we propose that it be renamedflsP.

In Escherichia coli, at least 12 proteins, FtsZ, ZipA, FtsA, FtsE/X, FtsK, FtsQ, FtsL, FtsB, FtsW, FtsI, FtsN, and AmiC, are known to localize to the septal ring in an interdependent and sequential pathway to coordinate the septum formation at the midcell. The FtsEX complex is the latest recruit of this pathway, and unlike other division proteins, it is shown to be essential only on low-salt media. In this study, it is shown that flsEX null mutations are not only salt remedial but also osmoremedial, which suggests that FtsEX may not be involved in salt transport as previously thought. Increased coexpression of cell division proteins FtsQ-FtsA-FtsZ or FtsN alone restored the growth defects of flsEX mutants. flsEX deletion exacerbated the defects of most of the mutants affected in Z ring localization and septal assembly; however, the flsZ84 allele was a weak suppressor of flsEX. The viability of flsEX mutants in high-osmolarity conditions was shown to be dependent on the presence of a periplasmic protein, SufI, a substrate of twin-arginine translocase. In addition, SufI in multiple copies could substitute for the functions of FtsEX. Taken together, these results suggest that FtsE and FtsX are absolutely required for the process of cell division in conditions of low osmotic strength for the stability of the septal ring assembly and that, during high-osmolarity conditions, the FtsEX and SufI functions are redundant for this essential process.

Research reveals the consensus target site sequence for IS186 transposition/insertion by radiation in Escherichia coli B.

Research has been conducted on the uvrD gene in Escherichia coli. Results indicate that null mutations in uvrD are incompatible with lon.

Results show that uup locus is part of a complex operon located downstream of a conserved gene and mutations in this locus affect excisions and deletions of chromosomal tandem repeats. Data further reveal a differential response of mini-transposon 10 and transposon 10 to mutations.

Three Escherichia coli mutants with high frequency of Lac+ papillation (tex) exhibited mutated ssb genes which affected the N-terminal domain of SSB. The tex mutant strains exhibited tex alleles that were recessive to ssb+ and represent loss-of-function alleles based on the inverse relationship between ssb+ gene dosage and precise excision frequency. Furthermore, ssb and uup mutations in tex strains were additive with distinct pathways for the precise excision of the lacZ::Tn10dKan insertion.