Summary Translation of mRNA lacking an in‐frame stop codon leads to ribosome arrest at the 3′ end transcript. In bacteria, tmRNA quality control system recycles these stalled ribosomes and tags incomplete nascent chains for degradation. Although ubiquitous in eubacteria, ssrA gene encoding is not essential viability Escherichia coli other model bacterial species. ArfA (YhdL) a mediator tmRNA‐independent rescue that E. Δ mutants. Here, we demonstrate synthesized from truncated therefore...

Clonally derived bacterial populations exhibit significant genotypic and phenotypic diversity that contribute to fitness in rapidly changing environments. Here, we show serial passage of Salmonella enterica serovar Typhimurium LT2 (StLT2) broth, or within a mouse host, results selection an evolved population inhibits the growth ancestral cells by direct contact. Cells each gain ability express deploy cryptic "orphan" toxin encoded rearrangement hotspot (rhs) locus. The Rhs orphan is gene...

Translational pausing can lead to cleavage of the A-site codon and facilitate recruitment transfer-messenger RNA (tmRNA) (SsrA) quality control system distressed ribosomes. We asked whether aminoacyl-tRNA binding site (A-site) mRNA occurs during regulatory translational using Escherichia coli SecM-mediated ribosome arrest as a model. find that SecM does not elicit efficient cleavage, but instead allows degradation downstream 3'-edge arrested ribosome. Characterization SecM-arrested ribosomes...

YezG binds to YeeF by pull down (View interaction)

Significance Contact-dependent growth inhibition (CDI) systems produce toxins that inhibit competing bacteria and immunity proteins protect against self-inhibition. The CDI toxin deployed by Escherichia coli 536 is a nuclease only cleaves transfer RNA (tRNA) molecules when bound to the biosynthetic enzyme O -acetylserine sulfhydrylase (CysK). Here, we present crystal structures of activated CysK/toxin binary complex neutralized CysK/toxin/immunity protein ternary complex. CysK significantly...

Bacteria deploy rearrangement hotspot (Rhs) proteins as toxic effectors against both prokaryotic and eukaryotic target cells. Rhs are characterized by YD-peptide repeats, which fold into a large β-cage structure that encapsulates the C-terminal toxin domain. Here, we show essential for type VI secretion system (T6SS) activity in Enterobacter cloacae (ECL). ECL rhs- mutants do not kill Escherichia coli bacteria defective T6SS-dependent export of hemolysin-coregulated protein (Hcp). The RhsA...

Significance Contact-dependent growth inhibition (CDI) systems enable cells to bind competing bacteria and deliver toxins that cleave nucleic acids or form membrane pores. Here, we characterize a CDI toxin specifically cleaves transfer RNA (tRNA), thereby blocking protein synthesis inhibiting bacterial growth. Remarkably, two highly conserved essential translation factors, EF-Ts EF-Tu, are critical for this toxic nuclease activity. The binds EF-Tu with high affinity only tRNA in complex the...

In Escherichia coli, translational arrest can elicit cleavage of codons within the ribosomal A site. This A-site mRNA is independent RelE, and has been proposed to be an endonucleolytic activity ribosome. Here, we show that 3'-->5' exonuclease RNase II plays important role in RelE-independent cleavage. Instead cleavage, pausing DeltaRNase cells produces transcripts are truncated +12 +28 nucleotides downstream codon. Deletions genes encoding polynucleotide phosphorylase (PNPase) R had little...

Type II toxin-antitoxin (TA) modules are thought to mediate stress-responses by temporarily suppressing protein synthesis while cells redirect transcription adapt environmental change. Here, we show that YoeB, a ribosome-dependent mRNase toxin, is activated in Escherichia coli grown at elevated temperatures. YoeB activation dependent on Lon protease, suggesting thermal stress promotes increased degradation of the YefM antitoxin. Though efficiently degraded response overproduction, find...

Contact-dependent growth inhibition (CDI) is a mode of inter-bacterial competition mediated by the CdiB/CdiA family two-partner secretion systems. CdiA binds to receptors on susceptible target bacteria, then delivers toxin domain derived from its C-terminus. Studies with Escherichia coli suggest existence multiple CDI growth-inhibition pathways, whereby different systems exploit distinct target-cell proteins deliver and activate toxins. Here, we explore pathway in Burkholderia using...

Contact-dependent growth inhibition (CDI) is a mechanism of inter-cellular competition in which Gram-negative bacteria exchange polymorphic toxins using type V secretion systems. Here, we present structures the CDI toxin from Escherichia coli NC101 ternary complex with its cognate immunity protein and elongation factor Tu (EF-Tu). The binds exclusively to domain 2 EF-Tu, partially overlapping site that interacts 3′-end aminoacyl-tRNA (aa-tRNA). exerts unique ribonuclease activity cleaves...

The maintenance of isomorphic life histories in algae has been difficult to explain when there is no difference between the ecological niche two adult phases. However, at level spores, physiological differences could exist reproduction and development tetraspores carpospores that influence composition both phases field interspecific competition. release, attachment (winter vs. beginning autumn) survival (seasonal), Gracilaria pacifica Abbott from Estero de Punta Banda, Baja California,...

In Escherichia coli, prolonged translational arrest allows mRNA degradation into the A site of stalled ribosomes. The enzyme that cleaves A-site codon is not known, but its activity requires RNase II to degrade downstream ribosome. This cleavage process thought function in translation quality control because ribosomes are recycled from truncated transcripts by tmRNA-SmpB "ribosome rescue" system. During rescue, tmRNA-encoded ssrA peptide added nascent chain, thereby targeting tagged protein...

Abstract Advanced glycation end-products (AGE) are a pervasive form of protein damage implicated in the pathogenesis neurodegenerative disease, atherosclerosis and diabetes mellitus. Glycation is typically mediated by reactive dicarbonyl compounds that accumulate all cells as toxic byproducts glucose metabolism. Here, we show AGE crosslinking harnessed to activate an antibacterial phospholipase effector deployed type VI secretion system Enterobacter cloacae . Endogenous methylglyoxal reacts...

The growth of microalgae in hypersaline conditions requires that cells accumulate osmoprotectants. In many instances, these are polyols. We isolated the diatom Nitzschia ovalis H. J. Arn. from saline and alkaline water body Mono Lake (CA, USA). This isolate can grow salinities ranging 5 to 120 parts per thousand (ppt) salt but normally at 90 ppt salinity. this report, we identified major polyol osmoprotectant as 1,4/2,5 cyclohexanetetrol by electron ionization‐mass spectrometry (EI–MS), 1 H,...

Type VI secretion systems (T6SSs) deliver cytotoxic effector proteins into target bacteria and eukaryotic host cells. Antibacterial effectors are invariably encoded with cognate immunity that protect the producing cell from self-intoxication. Here, we identify transposon insertions disrupt tli gene of Enterobacter cloacae induce autopermeabilization through unopposed activity Tle phospholipase effector. This hyperpermeability phenotype is T6SS dependent, indicating mutants intoxicated by...

Contact-dependent growth inhibition (CDI) is a wide-spread mechanism of inter-bacterial competition. CDI+ bacteria deliver CdiA-CT toxins into neighboring and produce specific immunity proteins that protect against self-intoxication. The toxin from uropathogenic Escherichia coli 536 latent tRNase only active when bound to the cysteine biosynthetic enzyme CysK. Remarkably, CysK:CdiA-CT binding interaction mimics 'cysteine synthase' complex CysK:CysE. C-terminal tails CysE each insert CysK...

Contact-dependent growth inhibition (CDI) is a common form of interbacterial competition in which cells use CdiA effectors to deliver toxic proteins into their neighbors. recognizes target bacteria through specific receptor molecules on the cell surface.

Type VI secretion systems (T6SS) deliver cytotoxic effector proteins into target bacteria and eukaryotic host cells. Antibacterial effectors are invariably encoded with cognate immunity that protect the producing cell from self-intoxication. Here, we identify transposon insertions disrupt tli gene of Enterobacter cloacae induce auto-permeabilization through unopposed activity Tle phospholipase effector. This hyper-permeability phenotype is T6SS-dependent, indicating mutants intoxicated by...