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Publications (10 of 21) Show all publications
Hallgren, J. & Jonas, K. (2024). Nutritional control of bacterial DNA replication. Current Opinion in Microbiology, 77, Article ID 102403.
Open this publication in new window or tab >>Nutritional control of bacterial DNA replication
2024 (English)In: Current Opinion in Microbiology, ISSN 1369-5274, E-ISSN 1879-0364, Vol. 77, article id 102403Article, review/survey (Refereed) Published
Abstract [en]

All cells must ensure precise regulation of DNA replication initiation in coordination with growth rate and in response to nutrient availability. According to a long-standing model, DNA replication initiation is tightly coupled to cell mass increase in bacteria. Despite controversies regarding this model, recent studies have provided additional support of this idea. The exact molecular mechanisms linking cell growth with DNA replication under different nutrient conditions remain elusive. However, recent studies in Caulobacter crescentus and Escherichia coli have provided insights into the regulation of DNA replication initiation in response to starvation. These mechanisms include the starvation-dependent regulation of DnaA abundance as well as mechanisms involving the small signaling molecule (p)ppGpp. In this review, we discuss these mechanisms in the context of previous findings. We highlight species-dependent similarities and differences and consider the precise growth conditions, in which the different mechanisms are active.

National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:su:diva-225394 (URN)10.1016/j.mib.2023.102403 (DOI)001128486600001 ()38035509 (PubMedID)2-s2.0-85178353545 (Scopus ID)
Available from: 2024-01-18 Created: 2024-01-18 Last updated: 2024-01-18Bibliographically approved
Hallgren, J., Koonce, K., Felletti, M., Mortier, J., Turco, E. & Jonas, K. (2023). Phosphate starvation decouples cell differentiation from DNA replication control in the dimorphic bacterium Caulobacter crescentus. PLOS Genetics, 19(11), Article ID e1010882.
Open this publication in new window or tab >>Phosphate starvation decouples cell differentiation from DNA replication control in the dimorphic bacterium Caulobacter crescentus
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2023 (English)In: PLOS Genetics, ISSN 1553-7390, E-ISSN 1553-7404, Vol. 19, no 11, article id e1010882Article in journal (Refereed) Published
Abstract [en]

Upon nutrient depletion, bacteria stop proliferating and undergo physiological and morphological changes to ensure their survival. Yet, how these processes are coordinated in response to distinct starvation conditions is poorly understood. Here we compare the cellular responses of Caulobacter crescentus to carbon (C), nitrogen (N) and phosphorus (P) starvation conditions. We find that DNA replication initiation and abundance of the replication initiator DnaA are, under all three starvation conditions, regulated by a common mechanism involving the inhibition of DnaA translation. By contrast, cell differentiation from a motile swarmer cell to a sessile stalked cell is regulated differently under the three starvation conditions. During C and N starvation, production of the signaling molecules (p)ppGpp is required to arrest cell development in the motile swarmer stage. By contrast, our data suggest that low (p)ppGpp levels under P starvation allow P-starved swarmer cells to differentiate into sessile stalked cells. Further, we show that limited DnaA availability, and consequently absence of DNA replication initiation, is the main reason that prevents P-starved stalked cells from completing the cell cycle. Together, our findings demonstrate that Ccrescentus decouples cell differentiation from DNA replication initiation under certain starvation conditions, two otherwise intimately coupled processes. We hypothesize that arresting the developmental program either as motile swarmer cells or as sessile stalked cells improves the chances of survival of Ccrescentus during the different starvation conditions.

National Category
Microbiology
Identifiers
urn:nbn:se:su:diva-227418 (URN)10.1371/journal.pgen.1010882 (DOI)001124341600006 ()38011258 (PubMedID)2-s2.0-85179583488 (Scopus ID)
Available from: 2024-03-14 Created: 2024-03-14 Last updated: 2024-03-14Bibliographically approved
Akar, R., Fink, M. J., Omnus, D. J. & Jonas, K. (2023). Regulation of the general stress response sigma factor σT by Lon-mediated proteolysis. Journal of Bacteriology, 205(11)
Open this publication in new window or tab >>Regulation of the general stress response sigma factor σT by Lon-mediated proteolysis
2023 (English)In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 205, no 11Article in journal (Refereed) Published
Abstract [en]

The Lon protease is widely conserved in both prokaryotic and eukaryotic organisms and fulfills important regulatory functions. Nevertheless, the number of identified Lon substrates is limited in most organisms, and the precise role of Lon in regulating these proteins is poorly understood. Here, we describe the α-proteobacterial general stress response sigma factor σT as a novel Lon substrate in Caulobacter crescentus. Based on previously published quantitative proteomics data, we find σT to be a promising putative Lon substrate and confirm a direct role of Lon in degrading σT. We show that Lon contributes to the downregulation of σT abundance under optimal conditions and during recovery from sucrose-induced osmotic stress. Furthermore, the presence of the Lon activity regulator LarA enhances Lon-mediated degradation of σT in vitro and reduces σT levels in vivo indicating a role of LarA in modulating Lon-mediated degradation of σT. Together, our results highlight the importance of Lon during the recovery phase following stress exposure by adjusting the concentrations of critical regulators of stress responses.

Keywords
regulated proteolysis, Lon protease, ECF sigma factor, general stress response, Caulobacter crescentus
National Category
Microbiology Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:su:diva-224280 (URN)10.1128/jb.00228-23 (DOI)001099059800001 ()37930077 (PubMedID)2-s2.0-85179426233 (Scopus ID)
Available from: 2023-12-18 Created: 2023-12-18 Last updated: 2024-01-15Bibliographically approved
Omnus, D. J., Fink, M. J., Kallazhi, A., Xandri Zaragoza, M., Leppert, A., Landreh, M. & Jonas, K. (2023). The heat shock protein LarA activates the Lon protease in response to proteotoxic stress. Nature Communications, 14, Article ID 7636.
Open this publication in new window or tab >>The heat shock protein LarA activates the Lon protease in response to proteotoxic stress
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2023 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 14, article id 7636Article in journal (Refereed) Published
Abstract [en]

The Lon protease is a highly conserved protein degradation machine that has critical regulatory and protein quality control functions in cells from the three domains of life. Here, we report the discovery of a α-proteobacterial heat shock protein, LarA, that functions as a dedicated Lon regulator. We show that LarA accumulates at the onset of proteotoxic stress and allosterically activates Lon-catalysed degradation of a large group of substrates through a five amino acid sequence at its C-terminus. Further, we find that high levels of LarA cause growth inhibition in a Lon-dependent manner and that Lon-mediated degradation of LarA itself ensures low LarA levels in the absence of stress. We suggest that the temporal LarA-dependent activation of Lon helps to meet an increased proteolysis demand in response to protein unfolding stress. Our study defines a regulatory interaction of a conserved protease with a heat shock protein, serving as a paradigm of how protease activity can be tuned under changing environmental conditions.

National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:su:diva-225405 (URN)10.1038/s41467-023-43385-x (DOI)001108433300006 ()37993443 (PubMedID)2-s2.0-85177684617 (Scopus ID)
Available from: 2024-01-17 Created: 2024-01-17 Last updated: 2024-01-17Bibliographically approved
Li, F., Cao, L., Bähre, H., Kim, S.-K., Schroeder, K., Jonas, K., . . . Römling, U. (2022). Patatin-like phospholipase CapV in Escherichia coli-morphological and physiological effects of one amino acid substitution. npj Biofilms and Microbiomes, 8(1), Article ID 39.
Open this publication in new window or tab >>Patatin-like phospholipase CapV in Escherichia coli-morphological and physiological effects of one amino acid substitution
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2022 (English)In: npj Biofilms and Microbiomes, E-ISSN 2055-5008, Vol. 8, no 1, article id 39Article in journal (Refereed) Published
Abstract [en]

In rod-shaped bacteria, morphological plasticity occurs in response to stress, which blocks cell division to promote filamentation. We demonstrate here that overexpression of the patatin-like phospholipase variant CapV(Q329R), but not CapV, causes pronounced sulA-independent pyridoxine-inhibited cell filamentation in the Escherichia coli K-12-derivative MG1655 associated with restriction of flagella production and swimming motility. Conserved amino acids in canonical patatin-like phospholipase A motifs, but not the nucleophilic serine, are required to mediate CapV(Q329R) phenotypes. Furthermore, CapV(Q329R) production substantially alters the lipidome and colony morphotype including rdar biofilm formation with modulation of the production of the biofilm activator CsgD, and affects additional bacterial traits such as the efficiency of phage infection and antimicrobial susceptibility. Moreover, genetically diverse commensal and pathogenic E. coli strains and Salmonella typhimurium responded with cell filamentation and modulation in colony morphotype formation to CapV(Q329R) expression. In conclusion, this work identifies the CapV variant CapV(Q329R) as a pleiotropic regulator, emphasizes a scaffold function for patatin-like phospholipases, and highlights the impact of the substitution of a single conserved amino acid for protein functionality and alteration of host physiology.

National Category
Biological Sciences Microbiology in the medical area
Identifiers
urn:nbn:se:su:diva-205215 (URN)10.1038/s41522-022-00294-z (DOI)000793878800001 ()35546554 (PubMedID)
Available from: 2022-06-07 Created: 2022-06-07 Last updated: 2022-06-07Bibliographically approved
Felletti, M., Romilly, C., Wagner, E. G. & Jonas, K. (2021). A nascent polypeptide sequence modulates DnaA translation elongation in response to nutrient availability. eLIFE, 10, Article ID e71611.
Open this publication in new window or tab >>A nascent polypeptide sequence modulates DnaA translation elongation in response to nutrient availability
2021 (English)In: eLIFE, E-ISSN 2050-084X, Vol. 10, article id e71611Article in journal (Refereed) Published
Abstract [en]

The ability to regulate DNA replication initiation in response to changing nutrient conditions is an important feature of most cell types. In bacteria, DNA replication is triggered by the initiator protein DnaA, which has long been suggested to respond to nutritional changes; nevertheless, the underlying mechanisms remain poorly understood. Here, we report a novel mechanism that adjusts DnaA synthesis in response to nutrient availability in Caulobacter crescentus. By performing a detailed biochemical and genetic analysis of the dnaA mRNA, we identified a sequence downstream of the dnaA start codon that inhibits DnaA translation elongation upon carbon exhaustion. Our data show that the corresponding peptide sequence, but not the mRNA secondary structure or the codon choice, is critical for this response, suggesting that specific amino acids in the growing DnaA nascent chain tune translational efficiency. Our study provides new insights into DnaA regulation and highlights the importance of translation elongation as a regulatory target. We propose that translation regulation by nascent chain sequences, like the one described, might constitute a general strategy for modulating the synthesis rate of specific proteins under changing conditions.

National Category
Biological Sciences
Identifiers
urn:nbn:se:su:diva-197866 (URN)10.7554/eLife.71611 (DOI)000696097100001 ()34524083 (PubMedID)
Available from: 2021-10-19 Created: 2021-10-19 Last updated: 2022-02-25Bibliographically approved
Wassing, G. M., Lidberg, K., Sigurlásdóttir, S., Frey, J., Schroeder, K., Ilehag, N., . . . Jonsson, A.-B. (2021). DNA Blocks the Lethal Effect of Human Beta-Defensin 2 Against Neisseria meningitidis. Frontiers in Microbiology, 12, Article ID 697232.
Open this publication in new window or tab >>DNA Blocks the Lethal Effect of Human Beta-Defensin 2 Against Neisseria meningitidis
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2021 (English)In: Frontiers in Microbiology, E-ISSN 1664-302X, Vol. 12, article id 697232Article in journal (Refereed) Published
Abstract [en]

Neisseria meningitidis is a gram-negative bacterium that often asymptomatically colonizes the human nasopharyngeal tract. These bacteria cross the epithelial barrier can cause life-threatening sepsis and/or meningitis. Antimicrobial peptides are one of the first lines of defense against invading bacterial pathogens. Human beta-defensin 2 (hBD2) is an antimicrobial peptide with broad antibacterial activity, although its mechanism of action is poorly understood. Here, we investigated the effect of hBD2 on N. meningitidis. We showed that hBD2 binds to and kills actively growing meningococcal cells. The lethal effect was evident after 2 h incubation with the peptide, which suggests a slow killing mechanism. Further, the membrane integrity was not changed during hBD2 treatment. Incubation with lethal doses of hBD2 decreased the presence of diplococci; the number and size of bacterial microcolonies/aggregates remained constant, indicating that planktonic bacteria may be more susceptible to the peptide. Meningococcal DNA bound hBD2 in mobility shift assays and inhibited the lethal effect of hBD2 in a dose-dependent manner both in suspension and biofilms, supporting the interaction between hBD2 and DNA. Taken together, the ability of meningococcal DNA to bind hBD2 opens the possibility that extracellular DNA due to bacterial lysis may be a means of N. meningitidis to evade immune defenses.

Keywords
Neisseria meningitidis, infection, hBD2, aggregation, eDNA
National Category
Biological Sciences
Identifiers
urn:nbn:se:su:diva-196515 (URN)10.3389/fmicb.2021.697232 (DOI)000673298600001 ()34276631 (PubMedID)
Available from: 2021-09-14 Created: 2021-09-14 Last updated: 2024-01-17Bibliographically approved
Schroeder, K., Heinrich, K., Neuwirth, I. & Jonas, K. (2021). The Chaperonin GroESL Facilitates Caulobacter crescentus Cell Division by Supporting the Functions of the Z-Ring Regulators FtsA and FzlA. mBio, 12(3), Article ID e03564-20.
Open this publication in new window or tab >>The Chaperonin GroESL Facilitates Caulobacter crescentus Cell Division by Supporting the Functions of the Z-Ring Regulators FtsA and FzlA
2021 (English)In: mBio, ISSN 2161-2129, E-ISSN 2150-7511, Vol. 12, no 3, article id e03564-20Article in journal (Refereed) Published
Abstract [en]

The highly conserved chaperonin GroESL performs a crucial role in protein folding; however, the essential cellular pathways that rely on this chaperone are underexplored. Loss of GroESL leads to severe septation defects in diverse bacteria, suggesting the folding function of GroESL may be integrated with the bacterial cell cycle at the point of cell division. Here, we describe new connections between GroESL and the bacterial cell cycle using the model organism Caulobacter crescentus. Using a proteomics approach, we identify candidate GroESL client proteins that become insoluble or are degraded specifically when GroESL folding is insufficient, revealing several essential proteins that participate in cell division and peptidoglycan biosynthesis. We demonstrate that other cell cycle events, such as DNA replication and chromosome segregation, are able to continue when GroESL folding is insuffi- cient. We further find that deficiency of two FtsZ-interacting proteins, the bacterial actin homologue FtsA and the constriction regulator FzlA, mediate the GroESL-dependent block in cell division. Our data show that sufficient GroESL is required to maintain normal dynamics of the FtsZ scaffold and divisome functionality in C. crescentus. In addition to supporting divisome function, we show that GroESL is required to maintain the flow of peptidoglycan precursors into the growing cell wall. Linking a chaperone to cell division may be a conserved way to coordinate environmental and internal cues that signal when it is safe to divide. IMPORTANCE All organisms depend on mechanisms that protect proteins from misfolding and aggregation. GroESL is a highly conserved molecular chaperone that functions to prevent protein aggregation in organisms ranging from bacteria to humans. Despite detailed biochemical understanding of GroESL function, the in vivo pathways that strictly depend on this chaperone remain poorly defined in most species. This study provides new insights into how GroESL is linked to the bacterial cell division machinery, a crucial target of current and future antimicrobial agents. We identify a functional interaction between GroESL and the cell division proteins FzlA and FtsA, which modulate Z-ring function. FtsA is a conserved bacterial actin homologue, suggesting that as in eukaryotes, some bacteria exhibit a connection between cytoskeletal actin proteins and chaperonins. Our work further defines how GroESL is integrated with cell wall synthesis and illustrates how highly conserved folding machines ensure the functioning of fundamental cellular processes during stress.

Keywords
FtsA, FzlA, GroEL, bacterial cell division, chaperonin, peptidoglycan, protein folding, actin-like proteins
National Category
Biological Sciences
Identifiers
urn:nbn:se:su:diva-195294 (URN)10.1128/mBio.03564-20 (DOI)000651433000004 ()
Available from: 2021-08-17 Created: 2021-08-17 Last updated: 2022-03-23Bibliographically approved
Omnus, D. J., Fink, M. J., Szwedo, K. & Jonas, K. (2021). The Lon protease temporally restricts polar cell differentiation events during the Caulobacter cell cycle. eLIFE, 10, Article ID e73875.
Open this publication in new window or tab >>The Lon protease temporally restricts polar cell differentiation events during the Caulobacter cell cycle
2021 (English)In: eLIFE, E-ISSN 2050-084X, Vol. 10, article id e73875Article in journal (Refereed) Published
Abstract [en]

The highly conserved protease Lon has important regulatory and protein quality control functions in cells from the three domains of life. Despite many years of research on Lon, only a few specific protein substrates are known in most organisms. Here, we used a quantitative proteomics approach to identify novel substrates of Lon in the dimorphic bacterium Caulobacter crescentus. We focused our study on proteins involved in polar cell differentiation and investigated the developmental regulator StaR and the flagella hook length regulator FliK as specific Lon substrates in detail. We show that Lon recognizes these proteins at their C-termini, and that Lon-dependent degradation ensures their temporally restricted accumulation in the cell cycle phase when their function is needed. Disruption of this precise temporal regulation of StaR and FliK levels in a Delta lon mutant contributes to defects in stalk biogenesis and motility, respectively, revealing a critical role of Lon in coordinating developmental processes with cell cycle progression. Our work underscores the importance of Lon in the regulation of complex temporally controlled processes by adjusting the concentrations of critical regulatory proteins. Furthermore, this study includes the first characterization of FliK in C. crescentus and uncovers a dual role of the C-terminal amino acids of FliK in protein function and degradation.

Keywords
Lon protease, proteolysis, cell differentiation, flagella, FliK, bacterial cell cycle, Other
National Category
Biological Sciences
Identifiers
urn:nbn:se:su:diva-198759 (URN)10.7554/eLife.73875 (DOI)000711524700001 ()34693909 (PubMedID)
Available from: 2021-11-17 Created: 2021-11-17 Last updated: 2023-02-07Bibliographically approved
Schroeder, K. & Jonas, K. (2021). The Protein Quality Control Network in Caulobacter crescentus. Frontiers in Molecular Biosciences, 8, Article ID 682967.
Open this publication in new window or tab >>The Protein Quality Control Network in Caulobacter crescentus
2021 (English)In: Frontiers in Molecular Biosciences, E-ISSN 2296-889X, Vol. 8, article id 682967Article, review/survey (Refereed) Published
Abstract [en]

The asymmetric life cycle of Caulobacter crescentus has provided a model in which to study how protein quality control (PQC) networks interface with cell cycle and developmental processes, and how the functions of these systems change during exposure to stress. As in most bacteria, the PQC network of Caulobacter contains highly conserved ATP-dependent chaperones and proteases as well as more specialized holdases. During growth in optimal conditions, these systems support a regulated circuit of protein synthesis and degradation that drives cell differentiation and cell cycle progression. When stress conditions threaten the proteome, most components of the Caulobacter proteostasis network are upregulated and switch to survival functions that prevent, revert, and remove protein damage, while simultaneously pausing the cell cycle in order to regain protein homeostasis. The specialized physiology of Caulobacter influences how it copes with proteotoxic stress, such as in the global management of damaged proteins during recovery as well as in cell type-specific stress responses. Our mini-review highlights the discoveries that have been made in how Caulobacter utilizes its PQC network for regulating its life cycle under optimal and proteotoxic stress conditions, and discusses open research questions in this model.

Keywords
protease, chaperone, holdase, protein quality control, cell cycle, bacterial development
National Category
Biological Sciences
Identifiers
urn:nbn:se:su:diva-193692 (URN)10.3389/fmolb.2021.682967 (DOI)000650019300001 ()33996917 (PubMedID)
Available from: 2021-06-13 Created: 2021-06-13 Last updated: 2022-02-25Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1469-4424

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