CheY acetylation is required for ordinary adaptation time in Escherichia coli chemotaxis

Acetylation of Cyclic AMP Receptor Protein by Acetyl Phosphate Modulates Mycobacterial Virulence

The success of Mycobacterium tuberculosis (Mtb) as a pathogen is partly attributed to its ability to sense and respond to dynamic host microenvironments. The cyclic AMP (cAMP) receptor protein (CRP) is closely related to the pathogenicity of Mtb and plays an important role in this process. However, the molecular mechanisms guiding the autoregulation and downstream target genes of CRP while Mtb responds to its environment are not fully understood. Here, it is demonstrated that the acetylation of conserved lysine 193 (K193) within the C-terminal DNA-binding domain of CRP reduces its DNA-binding ability and inhibits transcriptional activity. The reversible acetylation status of CRP K193 was shown to significantly affect mycobacterial growth phenotype, alter the stress response, and regulate the expression of biologically relevant genes using a CRP K193 site-specific mutation. Notably, the acetylation level of K193 decreases under CRP-activating conditions, including the presence of cAMP, low pH, high temperature, and oxidative stress, suggesting that microenvironmental signals can directly regulate CRP K193 acetylation. Both cell- and murine-based infection assays confirmed that CRP K193 is critical to the regulation of Mtb virulence. Furthermore, the acetylation of CRP K193 was shown to be dependent on the intracellular metabolic intermediate acetyl phosphate (AcP), and deacetylation was mediated by NAD⁺-dependent deacetylases. These findings indicate that AcP-mediated acetylation of CRP K193 decreases CRP activity and negatively regulates the pathogenicity of Mtb. We believe that the underlying mechanisms of cross talk between transcription, posttranslational modifications, and metabolites are a common regulatory mechanism for pathogenic bacteria. IMPORTANCE Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, and the ability of Mtb to survive harsh host conditions has been the subject of intensive research. As a result, we explored the molecular mechanisms guiding downstream target genes of CRP when Mtb responds to its environment. Our study makes a contribution to the literature because we describe the role of acetylated K193 in regulating its binding affinity to target DNA and influencing the virulence of mycobacteria. We discovered that mycobacteria can regulate their pathogenicity through the reversible acetylation of CRP K193 and that this reversible acetylation is mediated by AcP and a NAD⁺-dependent deacetylase. The regulation of CRP_Mtb by posttranslational modifications, at the transcriptional level, and by metabolic intermediates contribute to a better understanding of its role in the survival and pathogenicity of mycobacteria.

Acetylome and Succinylome Profiling of Edwardsiella tarda Reveals Key Roles of Both Lysine Acylations in Bacterial Antibiotic Resistance

The antibiotic resistance of Edwardsiella tarda is becoming increasingly prevalent, and thus novel antimicrobial strategies are being sought. Lysine acylation has been demonstrated to play an important role in bacterial physiological functions, while its role in bacterial antibiotic resistance remains largely unclear. In this study, we investigated the lysine acetylation and succinylation profiles of E. tarda strain EIB202 using affinity antibody purification combined with LC-MS/MS. A total of 1511 lysine-acetylation sites were identified on 589 proteins, and 2346 lysine-succinylation sites were further identified on 692 proteins of this pathogen. Further bioinformatic analysis showed that both post-translational modifications (PTMs) were enriched in the tricarboxylic acid (TCA) cycle, pyruvate metabolism, biosynthesis, and carbon metabolism. In addition, 948 peptides of 437 proteins had overlapping associations with multiple metabolic pathways. Moreover, both acetylation and succinylation were found in many antimicrobial resistance (AMR) proteins, suggesting their potentially vital roles in antibiotic resistance. In general, our work provides insights into the acetylome and succinylome features responsible for the antibiotic resistance mechanism of E. tarda, and the results may facilitate future investigations into the pathogenesis of this bacterium.

Metacognition as a Consequence of Competing Evolutionary Time Scales

Evolution is full of coevolving systems characterized by complex spatio-temporal interactions that lead to intertwined processes of adaptation. Yet, how adaptation across multiple levels of temporal scales and biological complexity is achieved remains unclear. Here, we formalize how evolutionary multi-scale processing underlying adaptation constitutes a form of metacognition flowing from definitions of metaprocessing in machine learning. We show (1) how the evolution of metacognitive systems can be expected when fitness landscapes vary on multiple time scales, and (2) how multiple time scales emerge during coevolutionary processes of sufficiently complex interactions. After defining a metaprocessor as a regulator with local memory, we prove that metacognition is more energetically efficient than purely object-level cognition when selection operates at multiple timescales in evolution. Furthermore, we show that existing modeling approaches to coadaptation and coevolution—here active inference networks, predator–prey interactions, coupled genetic algorithms, and generative adversarial networks—lead to multiple emergent timescales underlying forms of metacognition. Lastly, we show how coarse-grained structures emerge naturally in any resource-limited system, providing sufficient evidence for metacognitive systems to be a prevalent and vital component of (co-)evolution. Therefore, multi-scale processing is a necessary requirement for many evolutionary scenarios, leading to de facto metacognitive evolutionary outcomes.

How Do Living Systems Create Meaning?

Meaning has traditionally been regarded as a problem for philosophers and psychologists. Advances in cognitive science since the early 1960s, however, broadened discussions of meaning, or more technically, the semantics of perceptions, representations, and/or actions, into biology and computer science. Here, we review the notion of “meaning” as it applies to living systems, and argue that the question of how living systems create meaning unifies the biological and cognitive sciences across both organizational and temporal scales.

Lysine acetylation of the housekeeping sigma factor enhances the activity of the RNA polymerase holoenzyme

Protein lysine acetylation, one of the most abundant post-translational modifications in eukaryotes, occurs in prokaryotes as well. Despite the evidence of lysine acetylation in bacterial RNA polymerases (RNAPs), its function remains unknown. We found that the housekeeping sigma factor (HrdB) was acetylated throughout the growth of an actinobacterium, Streptomyces venezuelae, and the acetylated HrdB was enriched in the RNAP holoenzyme complex. The lysine (K259) located between 1.2 and 2 regions of the sigma factor, was determined to be the acetylated residue of HrdB in vivo by LC–MS/MS analyses. Specifically, the label-free quantitative analysis revealed that the K259 residues of all the HrdB subunits were acetylated in the RNAP holoenzyme. Using mutations that mimic or block acetylation (K259Q and K259R), we found that K259 acetylation enhances the interaction of HrdB with the RNAP core enzyme as well as the binding activity of the RNAP holoenzyme to target promoters in vivo. Taken together, these findings provide a novel insight into an additional layer of modulation of bacterial RNAP activity.

Engineering protein production by rationally choosing a carbon and nitrogen source using E. coli BL21 acetate metabolism knockout strains

BACKGROUND

Escherichia coli (E. coli) is a bacteria that is widely employed in many industries for the production of high interest bio-products such as recombinant proteins. Nevertheless, the use of E. coli for recombinant protein production may entail some disadvantages such as acetate overflow. Acetate is accumulated under some culture conditions, involves a decrease in biomass and recombinant protein production, and its metabolism is related to protein lysine acetylation. Thereby, the carbon and nitrogen sources employed are relevant factors in cell host metabolism, and the study of the central metabolism of E. coli and its regulation is essential for optimizing the production of biomass and recombinant proteins. In this study, our aim was to find the most favourable conditions for carrying out recombinant protein production in E. coli BL21 using two different approaches, namely, manipulation of the culture media composition and the deletion of genes involved in acetate metabolism and Nε-lysine acetylation.

RESULTS

We evaluated protein overexpression in E. coli BL21 wt and five mutant strains involved in acetate metabolism (Δacs, ΔackA and Δpta) and lysine acetylation (ΔpatZ and ΔcobB) grown in minimal medium M9 (inorganic ammonium nitrogen source) and in complex TB7 medium (peptide-based nitrogen source) supplemented with glucose (PTS carbon source) or glycerol (non-PTS carbon source). We observed a dependence of recombinant protein production on acetate metabolism and the carbon and nitrogen source employed. The use of complex medium supplemented with glycerol as a carbon source entails an increase in protein production and an efficient use of resources, since is a sub-product of biodiesel synthesis. Furthermore, the deletion of the ackA gene results in a fivefold increase in protein production with respect to the wt strain and a reduction in acetate accumulation.

CONCLUSION

The results showed that the use of diverse carbon and nitrogen sources and acetate metabolism knockout strains can redirect E. coli carbon fluxes to different pathways and affect the final yield of the recombinant protein bioprocess. Thereby, we obtained a fivefold increase in protein production and an efficient use of the resources employing the most suitable strain and culture conditions.

Influence of Glucose Availability and CRP Acetylation on the Genome-Wide Transcriptional Response of Escherichia coli: Assessment by an Optimized Factorial Microarray Analysis

Background: While in eukaryotes acetylation/deacetylation regulation exerts multiple pleiotropic effects, in Escherichia coli it seems to be more limited and less known. Hence, we aimed to progress in the characterization of this regulation by dealing with three convergent aspects: the effector enzymes involved, the master regulator CRP, and the dependence on glucose availability.

Methods: The transcriptional response of E. coli BW25113 was analyzed across 14 relevant scenarios. These conditions arise when the wild type and four isogenic mutants (defective in deacetylase CobB, defective in N(ε)-lysine acetyl transferase PatZ, Q- and R-type mutants of protein CRP) are studied under three levels of glucose availability (glucose-limited chemostat and glucose-excess or glucose-exhausted in batch culture). The Q-type emulates a permanent stage of CRP^acetylated, whereas the R-type emulates a permanent stage of CRP^deacetylated. The data were analyzed by an optimized factorial microarray method (Q-GDEMAR).

Results: (a) By analyzing one mutant against the other, we were able to unravel the true genes that participate in the interaction between ΔcobB/ΔpatZ mutations and glucose availability; (b) Increasing stages of glucose limitation appear to be associated with the up-regulation of specific sets of target genes rather than with the loss of genes present when glucose is in excess; (c) Both CRP^deacetylated and CRP^acetylated produce extensive changes in specific subsets of genes, but their number and identity depend on the glucose availability; (d) In other sub-sets of genes, the transcriptional effect of CRP seems to be independent of its acetylation or deacetylation; (e) Some specific ontology functions can be associated with each of the different sets of genes detected herein.

Conclusions: CRP cannot be thought of only as an effector of catabolite repression, because it acts along all the glucose conditions tested (excess, limited, and exhausted), exerting both positive and negative effects through different sets of genes. Acetylation of CRP does not seem to be a binary form of regulation, as there is not a univocal relationship between its activation/inhibitory effect and its acetylation/deacetylation stage. All the combinatorial possibilities are observed. During the exponential growth phase, CRP also exerts a very significant transcriptional effect, mainly on flagellar assembly and chemotaxis (FDR = 7.2 × 10⁻⁴⁴).

Characterization of CobB kinetics and inhibition by nicotinamide

Lysine acetylation has emerged as a global protein regulation system in all domains of life. Sirtuins, or Sir2-like enzymes, are a family of histone deacetylases characterized by their employing NAD+ as a co-substrate. Sirtuins can deacetylate several acetylated proteins, but a consensus substrate recognition sequence has not yet been established. Product inhibition of many eukaryotic sirtuins by nicotinamide and its analogues has been studied in vitro due to their potential role as anticancer agents. In this work, the kinetics of CobB, the main Escherichia coli deacetylase, have been characterized. To our knowledge, this is the first kinetic characterization of a sirtuin employing a fully acetylated and natively folded protein as a substrate. CobB deacetylated several acetyl-CoA synthetase acetylated lysines with a single kinetic rate. In addition, in vitro nicotinamide inhibition of CobB has been characterized, and the intracellular nicotinamide concentrations have been determined under different growth conditions. The results suggest that nicotinamide can act as a CobB regulator in vivo. A nicotinamidase deletion strain was thus phenotypically characterized, and it behaved similarly to the ΔcobB strain. The results of this work demonstrate the potential regulatory role of the nicotinamide metabolite in vivo.