Intracellular Protective Functions and Therapeutical Potential of Trehalose.

Trehalose is a naturally occurring, non-reducing saccharide widely distributed in nature. Over the years, research on trehalose has revealed that this initially thought simple storage molecule is a multifunctional and multitasking compound protecting cells against various stress factors. This review presents data on the role of trehalose in maintaining cellular homeostasis under stress conditions and in the virulence of bacteria and fungi.

Influence of N-Lysine Acetylation on the Formation of Protein Aggregates and Antibiotic Persistence in .

Numerous studies indicate that reversible N-lysine acetylation in bacteria may play a key role in the regulation of metabolic processes, transcription and translation, biofilm formation, virulence, and drug resistance. Using appropriate mutant strains deficient in non-enzymatic acetylation and enzymatic acetylation or deacetylation pathways, we investigated the influence of protein acetylation on cell viability, protein aggregation, and persister formation in . Lysine acetylation was found to increase protein aggregation and cell viability under the late stationary phase.

Liquid-Liquid Phase Separation and Protective Protein Aggregates in Bacteria.

Liquid-liquid phase separation (LLPS) and the formation of membraneless organelles (MLOs) contribute to the spatiotemporal organization of various physiological processes in the cell. These phenomena have been studied and characterized mainly in eukaryotic cells. However, increasing evidence indicates that LLPS-driven protein condensation may also occur in prokaryotes.

New Strategies to Kill Metabolically-Dormant Cells Directly Bypassing the Need for Active Cellular Processes.

Antibiotic therapy failure is often caused by the presence of persister cells, which are metabolically-dormant bacteria capable of surviving exposure to antimicrobials. Under favorable conditions, persisters can resume growth leading to recurrent infections. Moreover, several studies have indicated that persisters may promote the evolution of antimicrobial resistance and facilitate the selection of specific resistant mutants; therefore, in light of the increasing numbers of multidrug-resistant infections worldwide, developing efficient strategies against dormant cells is of paramount importance.

Protein aggregation and glycation in Escherichia coli exposed to desiccation-rehydration stress.

In natural environments, bacteria often enter a state of anhydrobiosis due to water loss. Multiple studies have demonstrated that desiccation may lead to protein aggregation and glycation both in vivo and in vitro. However, the exact effects of water-loss-induced proteotoxic stress and the interplay between protein glycation and aggregation in bacteria remain elusive.

Antibiotic Heteroresistance in .

is one of the most common pathogens responsible for infections, including pneumonia, urinary tract infections, and bacteremias. The increasing prevalence of multidrug-resistant was recognized in 2017 by the World Health Organization as a critical public health threat. Heteroresistance, defined as the presence of a subpopulation of cells with a higher MIC than the dominant population, is a frequent phenotype in many pathogens.

Mechanisms Protecting against Multiple Stresses Triggered by the Host Immune Response, Antibiotics and Outside-Host Environment.

is considered one of the most persistent pathogens responsible for nosocomial infections. Due to the emergence of multidrug resistant strains, as well as high morbidity and mortality caused by this pathogen, was placed on the World Health Organization (WHO) drug-resistant bacteria and antimicrobial resistance research priority list. This review summarizes current studies on mechanisms that protect against multiple stresses caused by the host immune response, outside host environment, and antibiotic treatment.

New insight into the mechanisms protecting bacteria during desiccation.

Desiccation is a common stress that bacteria face in the natural environment, and thus, they have developed a variety of protective mechanisms to mitigate the damage caused by water loss. The formation of biofilms and the accumulation of trehalose and sporulation are well-known strategies used by bacteria to survive desiccation. Other mechanisms, including intrinsically disordered proteins and the anti-glycation defence, have been mainly studied in eukaryotic cells, and their role in bacteria remains unclear.

Trehalose protects Escherichia coli against carbon stress manifested by protein acetylation and aggregation.

The disaccharide trehalose is widely distributed in nature and can serve as a carbon reservoir, a signaling molecule for controlling glucose metabolism and a stress protectant. We demonstrated that in Escherichia coli ΔotsA cells, which are unable to synthesize trehalose, the aggregation of endogenous proteins during the stationary phase was increased in comparison to wild-type cells. The lack of trehalose synthesis boosted Nε-lysine acetylation of proteins, which in turn enhanced their hydrophobicity and aggregation.

Proteomic analysis of protein homeostasis and aggregation.

Protein homeostasis (proteostasis) refers to the ability of cells to preserve the correct balance between protein synthesis, folding and degradation. Proteostasis is essential for optimal cell growth and survival under stressful conditions. Various extracellular and intracellular stresses including heat shock, oxidative stress, proteasome malfunction, mutations and aging-related modifications can result in disturbed proteostasis manifested by enhanced misfolding and aggregation of proteins.

Physiologically distinct subpopulations formed in Escherichia coli cultures in response to heat shock.

Bacteria can form heterogeneous populations containing phenotypic variants of genetically identical cells. The heterogeneity of populations can be considered a bet-hedging strategy allowing adaptation to unknown environmental changes - at least some individual subpopulations or cells might be able to withstand future adverse conditions. Using Percoll gradient centrifugation, we demonstrated that in an Escherichia coli culture exposed to heat shock at 50 °C, two physiologically distinct subpopulations were formed.

Protein aggregation in Ehrlichia chaffeensis during infection of mammalian cells.

Ehrlichia chaffeensis is an obligatory intracellular pathogen transmitted through infected ticks to humans and other vertebrates. We investigated the extent of protein aggregation in E. chaffeensis during infection of canine macrophage cell line, DH82.

The effect of protein acetylation on the formation and processing of inclusion bodies and endogenous protein aggregates in Escherichia coli cells.

Background: Acetylation of lysine residues is a reversible post-translational modification conserved from bacteria to humans. Several recent studies have revealed hundreds of lysine-acetylated proteins in various bacteria; however, the physiological role of these modifications remains largely unknown. Since lysine acetylation changes the size and charge of proteins and thereby may affect their conformation, we assumed that lysine acetylation can stimulate aggregation of proteins, especially for overproduced recombinant proteins that form inclusion bodies.

Lack of intracellular trehalose affects formation of Escherichia coli persister cells.

Persisters are dormant antibiotic-tolerant cells that usually compose a small fraction of bacterial populations. In this work, we focused on the role of trehalose in persister formation. We found that the ΔotsA mutant, which is unable to synthesize trehalose, produced increased levels of persisters in the early stationary phase and under heat stress conditions.

The formation of persister cells in stationary-phase cultures of Escherichia coli is associated with the aggregation of endogenous proteins.

Persister cells (persisters) are transiently tolerant to antibiotics and usually constitute a small part of bacterial populations. Persisters remain dormant but are able to re-grow after antibiotic treatment. In this study we found that the frequency of persisters correlated to the level of protein aggregates accumulated in E.

Antibiotics promoting oxidative stress inhibit formation of Escherichia coli biofilm via indole signalling.

Recent studies have revealed that antibiotics can promote the formation of reactive oxygen species which contribute to cell death. In this study, we report that five different antibiotics known to stimulate production of reactive oxygen species inhibited growth of Escherichia coli biofilm. We demonstrated that supression of biofilm formation was mainly a consequence of the increase in the extracellular concentration of indole, a signal molecule which suppresses growth of bacterial biofilm.

IbpA the small heat shock protein from Escherichia coli forms fibrils in the absence of its cochaperone IbpB.

Small heat shock proteins (sHsps) associate with aggregated proteins, changing their physical properties in such a way that chaperone mediated disaggregation becomes much more efficient. In Escherichia coli two small Hsps, IbpA and IbpB, exist. They are 48% identical at the amino acid level, yet their roles in stabilisation of protein aggregates are quite distinct.

Small heat shock proteins and protein-misfolding diseases.

Small heat shock proteins (sHsps) are molecular chaperones ubiquitously distributed in numerous species, from bacteria to humans. A conserved C-terminal "alpha-crystallin" domain organized in a beta-sheet sandwich and oligomeric structure are common features of sHsps. sHsps protect cells against many kinds of stresses including heat shock, oxidative and osmotic stress.

Escherichia coli heat-shock proteins IbpA and IbpB affect biofilm formation by influencing the level of extracellular indole.

The development of Escherichia coli biofilm requires the differential expression of various genes implicated in cell signalling, stress responses, motility and the synthesis of structures responsible for cell attachment. The ibpAB operon is among the stress-response genes most induced during growth of the E. coli biofilm.

Role of Escherichia coli heat shock proteins IbpA and IbpB in protection of alcohol dehydrogenase AdhE against heat inactivation in the presence of oxygen.

Escherichia coli small heat shock proteins IbpA and IbpB are molecular chaperones that bind denatured proteins and facilitate their subsequent refolding by the ATP-dependent chaperones DnaK/DnaJ/GrpE and ClpB. In vivo, the lack of IbpA and IbpB proteins results in increased protein aggregation under severe heat stress or delayed removal of aggregated proteins at recovery temperatures. In this report we followed the appearance and removal of aggregated alcohol dehydrogenase, AdhE, in E.

Aggregation of Escherichia coli proteins during stationary phase depends on glucose and oxygen availability.

In natural environments, bacteria are often challenged by nutrient starvation and other stresses. As a consequence, cell growth is arrested and bacteria enter stationary phase. In this report, we demonstrate that during stationary phase, Escherichia coli cells accumulate aggregates of misfolded proteins and complexes of Dps (starvation-induced protein) with chromosomal DNA.

Escherichia coli heat-shock proteins IbpA/B are involved in resistance to oxidative stress induced by copper.

The small heat-shock proteins IbpA/B are molecular chaperones that bind denatured proteins and facilitate their subsequent refolding by the ATP-dependent chaperones DnaK, DnaJ, GrpE and ClpB. In this report, we demonstrate that IbpA/B participate in the defence against copper-induced stress under aerobic conditions. In the presence of oxygen, DeltaibpA/B cells exhibit increased sensitivity to copper ions and accumulate elevated amounts of oxidized proteins, while under oxygen depletion, the DeltaibpA/B mutation has no effect on copper tolerance.

The small heat shock protein IbpA of Escherichia coli cooperates with IbpB in stabilization of thermally aggregated proteins in a disaggregation competent state.

The small heat shock proteins are ubiquitous stress proteins proposed to increase cellular tolerance to heat shock conditions. We isolated IbpA, the Escherichia coli small heat shock protein, and tested its ability to keep thermally inactivated substrate proteins in a disaggregation competent state. We found that the presence of IbpA alone during substrate thermal inactivation only weakly influences the ability of the bi-chaperone Hsp70-Hsp100 system to disaggregate aggregated substrate.

Escherichia coli small heat shock proteins IbpA/B enhance activity of enzymes sequestered in inclusion bodies.

Escherichia coli small heat shock proteins, IbpA/B, function as molecular chaperones and protect misfolded proteins against irreversible aggregation. IbpA/B are induced during overproduction of recombinant proteins and bind to inclusion bodies in E. coli cells.

Aggregation of heat-shock-denatured, endogenous proteins and distribution of the IbpA/B and Fda marker-proteins in Escherichia coli WT and grpE280 cells.

Submission of wild-type Escherichia coli to heat shock causes an aggregation of cellular proteins. The aggregates (S fraction) are separable from membrane fractions by ultracentrifugation in a sucrose density gradient. In contrast, no protein aggregation was detectable in an E.