Characterization of broadly pleiotropic phenotypes caused by an hfq insertion mutation in Escherichia coli K‐12

Abstract

The region immediately downstream from the miaA tRNA modification gene at 94.8 min contains the hfq gene and the hflA region, which are important in the bacteriophage Q beta and lambda life cycles. The roles of these genes in bacteria remain largely unknown. We report here the characterization of two chromosomal hfq insertion mutations. An omega (omega) cassette insertion near the end of hfq resulted in phenotypes only slightly different from the parent, although transcript mapping demonstrated that the insertion was completely polar on hflX expression. In contrast, an equally polar omega cassette insertion near the beginning of hfq caused pronounced pleiotropic phenotypes, including decreased growth rates and yields, decreased negative supercoiling of plasmids in stationary phase, increased cell size, osmosensitivity, increased oxidation of carbon sources, increased sensitivity to ultraviolet light, and suppression of bgl activation by hns mutations. hfq::omega mutant phenotypes were distinct from those caused by omega insertions early in the miaA tRNA modification gene. On the other hand, both hfq insertions interfered with lambda phage plaque formation, probably by means of polarity at the hflA region. Together, these results show that hfq function plays a fundamental role in Escherichia coli physiology and that hfq and the hflA-region are in the amiB-mutL-miaA-hfq-hflX superoperon.

Involvement of HFq protein in the post-transcriptional regulation ofE. colibacterial cytoskeleton and cell division proteins

“…9 Our results with FtsZ showed that its expression in hfq -strains increased by ~15% in stationary phase (result not shown), which are in accordance with the result of Takada et al once the genetic background and growing conditions are taken into account. 8 This result suggested the involvement of at least one regulatory RNA.…”

Hfq Is Required for Optimal Nitrate Assimilation in the Cyanobacterium Anabaena sp. Strain PCC 7120

“…Inactivation of the hfq gene in diverse eubacteria caused pleiotropic physiological effects (32,33,46) and loss of virulence in pathogenic bacteria (9). However, no apparent phenotype emerged from an hfq knockout in Staphylococcus aureus (6).…”

Structure of Escherichia coli Hfq bound to polyriboadenylate RNA

“…H fq is a pleiotropic posttranscriptional regulator that is a member of the Sm/Lsm superfamily and found in many Gram-negative and Gram-positive bacteria (1)(2)(3). Hfq binds to AU-rich stretches near stem loop structures of small noncoding RNAs (sRNA) and their target mRNAs to facilitate the annealing of their trans-encoded complementary sequences and hence to effect message-specific translational regulation (4)(5)(6)(7)(8).…”