Complex regulation of the sirtuin-dependent reversible lysine acetylation system of Salmonella enterica
October 12, 2015
The extensive involvement of the reversible lysine acylation (RLA) system in metabolism has attracted the attention of investigators interested in understanding the fundamentals of prokaryotic and eukaryotic cell function. Here the authors discuss the implications of recently reported work performed in the enteropathogen Salmonella enterica (mBio (2015) 6(4):e00891-15), which provided the first insights into the integration of the transcriptional regulation of genes encoding the RLA system with the acs gene encoding the central metabolic enzyme acetyl-CoA synthetase (Acs).
Starting with a degron: N-terminal formyl-methionine of nascent bacterial proteins contributes to their proteolytic control
October 4, 2015
In this article, the author comments on the study "Formyl-methionine as a degradation signal at the N-termini of bacterial proteins." by Piatkov et al. (Microbial Cell, 2015), discussing a novel N-terminal degradation signal (N-degron) that targets nascent proteins for degradation in Escherichia coli by a new branch of the bacterial N-end rule pathway, termed the fMet/N-end rule pathway
A bacterial volatile signal for biofilm formation
September 23, 2015
Bacteria constantly monitor the environment they reside in and respond to potential changes in the environment through a variety of signal sensing and transduction mechanisms in a timely fashion. In their recent study (Chen, et al. mBio (2015), 6: e00392-15), the authors demonstrated that the soil bacterium Bacillus subtilis uses acetic acid as a volatile signal to coordinate the timing of biofilm formation within physically separated cells in the community. They also showed that the bacterium possesses an intertwined gene network to produce, secrete, sense, and respond to acetic acid, in stimulating biofilm formation.
Elongation factor-P at the crossroads of the host-endosymbiont interface
September 23, 2015
Elongation factor P (EF-P) is an ancient bacterial translational factor that aids the ribosome in polymerizing oligo-prolines. EF-P structurally resembles tRNA and binds in-between the exit and peptidyl sites of the ribosome to accelerate the intrinsically slow reaction of peptidyl-prolyl bond formation. Recent studies have identified in separate organisms, two evolutionarily convergent EF-P post-translational modification systems (EPMS), split predominantly between gammaproteobacteria, and betaproteobacteria. Here, the authors highlight the recent discoveries made regarding EPMSs, with a focus on how these incomplete modification pathways shape or have been shaped by the endosymbiont-host relationship.
The great escape: Pseudomonas breaks out of the lung
September 23, 2015
The Gram-negative bacterium Pseudomonas aeruginosa is a major cause of hospital-acquired infections and the focus of much attention due to its resistance to many conventional antibiotics. This article discusses the potential mechanisms by which these processes occur as well as the novel techniques used to study ExoS function in vivo.
DNA damage checkpoint adaptation genes are required for division of cells harbouring eroded telomeres
September 21, 2015
In budding yeast, telomerase and the Cdc13p protein are two key players acting to ensure telomere stability. This article shows that while the capping process can be flexible, it takes a very specific genetic setup to allow a change from canonical capping to alternative capping.
The MAPKKKs Ste11 and Bck1 jointly transduce the high oxidative stress signal through the cell wall integrity MAP kinase pathway
September 6, 2015
Oxidative stress stimulates the Rho1 GTPase, which in turn induces the cell wall integrity (CWI) MAP kinase cascade. CWI activation promotes stress-responsive gene expression through activation of transcription factors (Rlm1, SBF) and nuclear release and subsequent destruction of the repressor cyclin C. This study reports that, in response to high hydrogen peroxide exposure, or in the presence of constitutively active Rho1, cyclin C still translocates to the cytoplasm and is degraded in cells lacking Bck1, the MAPKKK of the CWI pathway.
Feelin’ it: Differential oxidative stress sensing mediated by Cyclin C
September 6, 2015
Microbial cells that live exposed directly to their environmental milieu are faced with the challenge of adapting to the dynamic stress conditions that will inevitably be encountered. These stress conditions may vary over wide ranges and the most efficient responses would be tuned to produce a proportional buffering change. A mild stress would most efficiently be dealt with by a mild metabolic reprogramming that would prevent serious damage. A more severe environmental challenge would demand a more dramatic cellular compensatory response.
Formyl-methionine as a degradation signal at the N-termini of bacterial proteins
September 6, 2015
Varshavsky and colleagues solve a long-standing mystery in proteolysis! In bacteria, all nascent proteins bear the pretranslationally formed N-terminal formyl-methionine (fMet) residue. The fMet residue is cotranslationally deformylated by a ribosome-associated deformylase. The formylation of N-terminal Met in bacterial proteins is not strictly essential for either translation or cell viability. Moreover, protein synthesis by the cytosolic ribosomes of eukaryotes does not involve the formylation of N-terminal Met. What, then, is the main biological function of this metabolically costly, transient, and not strictly essential modification of N‑terminal Met, and why has Met formylation not been eliminated during bacterial evolution? One possibility is that the similarity of the formyl and acetyl groups, their identical locations in...
Peering into the ‘black box’ of pathogen recognition by cellular autophagy systems
August 22, 2015
Autophagy is an intracellular process that plays an important role in protecting eukaryotic cells and maintaining intracellular homeostasis. This review summarises the available evidence regarding the specific recognition of invading pathogens by which they are targeted into host autophagy pathways.