{"entity": "researcher", "timestamp": "2026-07-15T17:05:59.051Z", "family": "Jonas", "given": "Kristina", "initials": "K", "orcid": "0000-0002-1469-4424", "affiliations": ["Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden kristina.jonas@su.se."], "links": {"self": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26.json"}, "display": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26"}}, "publications": [{"entity": "publication", "iuid": "12010dd55a294967a7bec8f110ff6836", "links": {"self": {"href": "https://publications.scilifelab.se/publication/12010dd55a294967a7bec8f110ff6836.json"}, "display": {"href": "https://publications.scilifelab.se/publication/12010dd55a294967a7bec8f110ff6836"}}, "title": "Direct and indirect pathways linking the Lon protease to motility behaviors in the pathogen Pseudomonas aeruginosa.", "authors": [{"family": "Kallazhi", "given": "Aswathy", "initials": "A"}, {"family": "Rahman", "given": "Anamika", "initials": "A"}, {"family": "R\u00f6mling", "given": "Ute", "initials": "U"}, {"family": "Jonas", "given": "Kristina", "initials": "K", "orcid": "0000-0002-1469-4424", "researcher": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26.json"}}], "type": "journal article", "published": "2025-06-00", "journal": {"title": "PLoS Pathog.", "issn": "1553-7374", "volume": "21", "issue": "6", "pages": "e1013288", "issn-l": "1553-7366"}, "abstract": "The ATP-dependent cytoplasmic protease Lon has critical functions in protein quality control and cellular regulation in organisms across the three domains of life. In the opportunistic pathogen Pseudomonas aeruginosa, lon loss-of-function mutants exhibit multiple phenotypic defects in motility, virulence, antibiotic tolerance and biofilm formation. However, only a couple of native substrate proteins of Lon are described in P. aeruginosa until now and most of the phenotypes associated with Lon remain unexplained. Here, we searched for novel Lon substrates in P. aeruginosa by analyzing proteome-wide changes in protein levels and stabilities following lon overexpression. Our search yielded a large number of putative Lon substrates with diverse cellular functions, including metabolic enzymes, stress proteins and a significant fraction of motility-related proteins. In vitro degradation assays confirmed the metabolic protein SpeH, the heat shock protein IbpA as well as seven proteins involved in flagella- and type IV pilus-mediated motility as novel substrates of Lon. The new motility-associated substrates include both key regulators of motility (FliA, RpoN, AmrZ) as well as structural flagellar components (FliG, FliS and FlgE). Further, by isolating suppressor mutations bypassing the motility defect of lon- cells, we reveal that Lon-dependent degradation of the specific substrate SulA, a cell division inhibitor, is crucial for ensuring proper cell division and motility under optimal conditions. In sum, our work highlights Lon's regulatory role in degrading functional proteins involved in critical cellular processes and contributes to a better molecular understanding of the pathways underlying Pseudomonas pathogenicity.", "doi": "10.1371/journal.ppat.1013288", "pmid": "40561152", "labels": {"Global Proteomics and Proteogenomics": "Service"}, "xrefs": [{"db": "pmc", "key": "PMC12221181"}, {"db": "pii", "key": "PPATHOGENS-D-25-00035"}], "notes": [], "created": "2025-11-27T13:03:21.073Z", "modified": "2025-11-27T13:03:21.261Z"}, {"entity": "publication", "iuid": "533a5278db0a48f497051026722c4065", "links": {"self": {"href": "https://publications.scilifelab.se/publication/533a5278db0a48f497051026722c4065.json"}, "display": {"href": "https://publications.scilifelab.se/publication/533a5278db0a48f497051026722c4065"}}, "title": "Complete genome sequences of the prosthecate dimorphic bacteria Brevundimonas intermedia CB63T and Brevundimonas staleyi FWC43T.", "authors": [{"family": "Hallgren", "given": "Joel", "initials": "J", "orcid": "0000-0001-8602-8095", "researcher": {"href": "https://publications.scilifelab.se/researcher/883ec31492184c17a1e37d0bfdb73e75.json"}}, {"family": "Daneby", "given": "Fredrik", "initials": "F", "orcid": "0009-0005-2659-1771", "researcher": {"href": "https://publications.scilifelab.se/researcher/d0c49180b4af4e2d851b0586f69d2da0.json"}}, {"family": "Jonas", "given": "Kristina", "initials": "K", "orcid": "0000-0002-1469-4424", "researcher": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26.json"}}], "type": "journal article", "published": "2024-12-12", "journal": {"title": "Microbiol Resour Announc", "issn": "2576-098X", "volume": "13", "issue": "12", "pages": "e0105024", "issn-l": "2576-098X"}, "abstract": "Here, we report the complete genome sequences of the dimorphic prosthecate bacterial species type strains Brevundimonas intermedia CB63T and Brevundimonas staleyi FWC43T, isolated from pond water and wastewater, respectively. B. intermedia CB63T contains a chromosome of 3.60 Mb, and B. staleyi FWC43T contains a chromosome of 3.97 Mb and a 157-kb plasmid.", "doi": "10.1128/mra.01050-24", "pmid": "39565107", "labels": {"Bioinformatics Support for Computational Resources": "Service", "NGI Uppsala (Uppsala Genome Center)": "Service", "NGI Long read": "Service", "National Genomics Infrastructure": "Service"}, "xrefs": [{"db": "pmc", "key": "PMC11636228"}], "notes": [], "created": "2025-02-28T14:21:08.360Z", "modified": "2025-03-07T09:52:02.038Z"}, {"entity": "publication", "iuid": "7d95af839fa143759ce68c732ed930c2", "links": {"self": {"href": "https://publications.scilifelab.se/publication/7d95af839fa143759ce68c732ed930c2.json"}, "display": {"href": "https://publications.scilifelab.se/publication/7d95af839fa143759ce68c732ed930c2"}}, "title": "The heat shock protein LarA activates the Lon protease in response to proteotoxic stress.", "authors": [{"family": "Omnus", "given": "Deike J", "initials": "DJ", "orcid": "0000-0002-4091-4291", "researcher": {"href": "https://publications.scilifelab.se/researcher/4012e43cedf04b19be7a7edfa227aa8f.json"}}, {"family": "Fink", "given": "Matthias J", "initials": "MJ", "orcid": "0000-0002-4620-2009", "researcher": {"href": "https://publications.scilifelab.se/researcher/16ee1108730641498bcf0d38b116cb18.json"}}, {"family": "Kallazhi", "given": "Aswathy", "initials": "A", "orcid": "0009-0003-4585-2792", "researcher": {"href": "https://publications.scilifelab.se/researcher/df59bcc8d7524fdfaad0b6b43abe4e86.json"}}, {"family": "Xandri Zaragoza", "given": "Maria", "initials": "M"}, {"family": "Leppert", "given": "Axel", "initials": "A", "orcid": "0000-0001-6223-3350", "researcher": {"href": "https://publications.scilifelab.se/researcher/e89c2b7f8a294cfdae4848e96be7520b.json"}}, {"family": "Landreh", "given": "Michael", "initials": "M", "orcid": "0000-0002-7958-4074", "researcher": {"href": "https://publications.scilifelab.se/researcher/87494f4204c04be9bce5e9ddcdc92d8a.json"}}, {"family": "Jonas", "given": "Kristina", "initials": "K", "orcid": "0000-0002-1469-4424", "researcher": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26.json"}}], "type": "journal article", "published": "2023-11-22", "journal": {"title": "Nat Commun", "issn": "2041-1723", "volume": "14", "issue": "1", "pages": "7636", "issn-l": "2041-1723"}, "abstract": "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 \u03b1-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.", "doi": "10.1038/s41467-023-43385-x", "pmid": "37993443", "labels": {"Global Proteomics and Proteogenomics": "Service"}, "xrefs": [{"db": "pmc", "key": "PMC10665427"}, {"db": "pii", "key": "10.1038/s41467-023-43385-x"}], "notes": [], "created": "2023-11-29T12:37:38.523Z", "modified": "2023-11-29T12:37:38.620Z"}, {"entity": "publication", "iuid": "d56c0a51e3474595a4976d83d25ce974", "links": {"self": {"href": "https://publications.scilifelab.se/publication/d56c0a51e3474595a4976d83d25ce974.json"}, "display": {"href": "https://publications.scilifelab.se/publication/d56c0a51e3474595a4976d83d25ce974"}}, "title": "Regulation of the general stress response sigma factor \u03c3T by Lon-mediated proteolysis.", "authors": [{"family": "Akar", "given": "Roya", "initials": "R"}, {"family": "Fink", "given": "Matthias J", "initials": "MJ", "orcid": "0000-0002-4620-2009", "researcher": {"href": "https://publications.scilifelab.se/researcher/16ee1108730641498bcf0d38b116cb18.json"}}, {"family": "Omnus", "given": "Deike J", "initials": "DJ", "orcid": "0000-0002-4091-4291", "researcher": {"href": "https://publications.scilifelab.se/researcher/4012e43cedf04b19be7a7edfa227aa8f.json"}}, {"family": "Jonas", "given": "Kristina", "initials": "K", "orcid": "0000-0002-1469-4424", "researcher": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26.json"}}], "type": "journal article", "published": "2023-11-06", "journal": {"title": "J. Bacteriol.", "issn": "1098-5530", "volume": "205", "issue": "11", "pages": "e0022823", "issn-l": "0021-9193"}, "abstract": "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 \u03b1-proteobacterial general stress response sigma factor \u03c3T as a novel Lon substrate in Caulobacter crescentus. Based on previously published quantitative proteomics data, we find \u03c3T to be a promising putative Lon substrate and confirm a direct role of Lon in degrading \u03c3T. We show that Lon contributes to the downregulation of \u03c3T 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 \u03c3T in vitro and reduces \u03c3T levels in vivo indicating a role of LarA in modulating Lon-mediated degradation of \u03c3T. 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.IMPORTANCERegulated protein degradation is a critical process in all cell types, which contributes to the precise regulation of protein amounts in response to internal and external cues. In bacteria, protein degradation is carried out by ATP-dependent proteases. Although past work revealed detailed insights into the operation principles of these proteases, there is limited knowledge about the substrate proteins that are degraded by distinct proteases and the regulatory role of proteolysis in cellular processes. This study reveals a direct role of the conserved protease Lon in regulating \u03c3T, a transcriptional regulator of the general stress response in \u03b1-proteobacteria. Our work is significant as it underscores the importance of regulated proteolysis in modulating the levels of key regulatory proteins under changing conditions.", "doi": "10.1128/jb.00228-23", "pmid": "37930077", "labels": {"Global Proteomics and Proteogenomics": "Service"}, "xrefs": [{"db": "pmc", "key": "PMC10662116"}], "notes": [], "created": "2023-11-29T12:39:20.861Z", "modified": "2023-11-29T12:39:20.882Z"}, {"entity": "publication", "iuid": "c0722e8f133c4b4e8ade1bf3bb31bd95", "links": {"self": {"href": "https://publications.scilifelab.se/publication/c0722e8f133c4b4e8ade1bf3bb31bd95.json"}, "display": {"href": "https://publications.scilifelab.se/publication/c0722e8f133c4b4e8ade1bf3bb31bd95"}}, "title": "The Lon protease temporally restricts polar cell differentiation events during the Caulobacter cell cycle.", "authors": [{"family": "Omnus", "given": "Deike J", "initials": "DJ", "orcid": "0000-0002-4091-4291", "researcher": {"href": "https://publications.scilifelab.se/researcher/4012e43cedf04b19be7a7edfa227aa8f.json"}}, {"family": "Fink", "given": "Matthias J", "initials": "MJ", "orcid": "0000-0002-4620-2009", "researcher": {"href": "https://publications.scilifelab.se/researcher/16ee1108730641498bcf0d38b116cb18.json"}}, {"family": "Szwedo", "given": "Klaudia", "initials": "K"}, {"family": "Jonas", "given": "Kristina", "initials": "K", "orcid": "0000-0002-1469-4424", "researcher": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26.json"}}], "type": "journal article", "published": "2021-10-25", "journal": {"title": "Elife", "issn": "2050-084X", "volume": "10", "issn-l": "2050-084X"}, "abstract": "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 \u0394lon 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.", "doi": "10.7554/eLife.73875", "pmid": "34693909", "labels": {"Global Proteomics and Proteogenomics": "Service"}, "xrefs": [{"db": "pmc", "key": "PMC8545394"}, {"db": "pii", "key": "73875"}, {"db": "GEO", "key": "GSE68200"}], "notes": [], "created": "2021-12-10T06:59:51.791Z", "modified": "2022-11-25T11:59:34.337Z"}, {"entity": "publication", "iuid": "2ec7cb881a964cecb1c373c201c721d3", "links": {"self": {"href": "https://publications.scilifelab.se/publication/2ec7cb881a964cecb1c373c201c721d3.json"}, "display": {"href": "https://publications.scilifelab.se/publication/2ec7cb881a964cecb1c373c201c721d3"}}, "title": "Molecular Basis and Ecological Relevance of Caulobacter Cell Filamentation in Freshwater Habitats.", "authors": [{"family": "Heinrich", "given": "Kristina", "initials": "K"}, {"family": "Leslie", "given": "David J", "initials": "DJ"}, {"family": "Morlock", "given": "Michaela", "initials": "M"}, {"family": "Bertilsson", "given": "Stefan", "initials": "S", "orcid": "0000-0002-4265-1835", "researcher": {"href": "https://publications.scilifelab.se/researcher/2c17765c2a9f4383b5383138d11ae93f.json"}}, {"family": "Jonas", "given": "Kristina", "initials": "K", "orcid": "0000-0002-1469-4424", "researcher": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26.json"}}], "type": "journal article", "published": "2019-08-20", "journal": {"volume": "10", "issn": "2150-7511", "issue": "4", "pages": null, "title": "MBio", "issn-l": null}, "abstract": "All living cells are characterized by certain cell shapes and sizes. Many bacteria can change these properties depending on the growth conditions. The underlying mechanisms and the ecological relevance of changing cell shape and size remain unclear in most cases. One bacterium that undergoes extensive shape-shifting in response to changing growth conditions is the freshwater bacterium Caulobacter crescentus When incubated for an extended time in stationary phase, a subpopulation of C. crescentus forms viable filamentous cells with a helical shape. Here, we demonstrated that this stationary-phase-induced filamentation results from downregulation of most critical cell cycle regulators and a consequent block of DNA replication and cell division while cell growth and metabolism continue. Our data indicate that this response is triggered by a combination of three stresses caused by prolonged growth in complex medium, namely, the depletion of phosphate, alkaline pH, and an excess of ammonium. We found that these conditions are experienced in the summer months during algal blooms near the surface in freshwater lakes, a natural habitat of C. crescentus, suggesting that filamentous growth is a common response of C. crescentus to its environment. Finally, we demonstrate that when grown in a biofilm, the filamentous cells can reach beyond the surface of the biofilm and potentially access nutrients or release progeny. Altogether, our work highlights the ability of bacteria to alter their morphology and suggests how this behavior might enable adaptation to changing environments.IMPORTANCE Many bacteria drastically change their cell size and morphology in response to changing environmental conditions. Here, we demonstrate that the freshwater bacterium Caulobacter crescentus and related species transform into filamentous cells in response to conditions that commonly occur in their natural habitat as a result of algal blooms during the warm summer months. These filamentous cells may be better able to scavenge nutrients when they grow in biofilms and to escape from protist predation during planktonic growth. Our findings suggest that seasonal changes and variations in the microbial composition of the natural habitat can have profound impact on the cell biology of individual organisms. Furthermore, our work highlights that bacteria exist in morphological and physiological states in nature that can strongly differ from those commonly studied in the laboratory.", "doi": "10.1128/mBio.01557-19", "pmid": "31431551", "labels": {"Global Proteomics and Proteogenomics": "Service"}, "xrefs": [{"db": "pii", "key": "mBio.01557-19"}, {"db": "pmc", "key": "PMC6703425"}], "notes": [], "created": "2020-01-28T13:43:23.412Z", "modified": "2021-06-18T14:11:56.537Z"}, {"entity": "publication", "iuid": "1cb0377941b44b6f906dd35e4b1d6eee", "links": {"self": {"href": "https://publications.scilifelab.se/publication/1cb0377941b44b6f906dd35e4b1d6eee.json"}, "display": {"href": "https://publications.scilifelab.se/publication/1cb0377941b44b6f906dd35e4b1d6eee"}}, "title": "An essential regulatory function of the DnaK chaperone dictates the decision between proliferation and maintenance in Caulobacter crescentus.", "authors": [{"family": "Schramm", "given": "Frederic D", "initials": "FD", "orcid": "0000-0003-1858-7770", "researcher": {"href": "https://publications.scilifelab.se/researcher/3a56c58ad5de4950a837a7457e64a1e4.json"}}, {"family": "Heinrich", "given": "Kristina", "initials": "K"}, {"family": "Th\u00fcring", "given": "Marietta", "initials": "M"}, {"family": "Bernhardt", "given": "J\u00f6rg", "initials": "J"}, {"family": "Jonas", "given": "Kristina", "initials": "K", "orcid": "0000-0002-1469-4424", "researcher": {"href": "https://publications.scilifelab.se/researcher/3351b638c7904141b4ae20dd41929e26.json"}}], "type": "journal article", "published": "2017-12-00", "journal": {"volume": "13", "issn": "1553-7404", "issue": "12", "pages": "e1007148", "title": "PLoS Genet.", "issn-l": "1553-7390"}, "abstract": "Hsp70 chaperones are well known for their important functions in maintaining protein homeostasis during thermal stress conditions. In many bacteria the Hsp70 homolog DnaK is also required for growth in the absence of stress. The molecular reasons underlying Hsp70 essentiality remain in most cases unclear. Here, we demonstrate that DnaK is essential in the \u03b1-proteobacterium Caulobacter crescentus due to its regulatory function in gene expression. Using a suppressor screen we identified mutations that allow growth in the absence of DnaK. All mutations reduced the activity of the heat shock sigma factor \u03c332, demonstrating that the DnaK-dependent inactivation of \u03c332 is a growth requirement. While most mutations occurred in the rpoH gene encoding \u03c332, we also identified mutations affecting \u03c332 activity or stability in trans, providing important new insight into the regulatory mechanisms controlling \u03c332 activity. Most notably, we describe a mutation in the ATP dependent protease HslUV that induces rapid degradation of \u03c332, and a mutation leading to increased levels of the house keeping \u03c370 that outcompete \u03c332 for binding to the RNA polymerase. We demonstrate that \u03c332 inhibits growth and that its unrestrained activity leads to an extensive reprogramming of global gene expression, resulting in upregulation of repair and maintenance functions and downregulation of the growth-promoting functions of protein translation, DNA replication and certain metabolic processes. While this re-allocation from proliferative to maintenance functions could provide an advantage during heat stress, it leads to growth defects under favorable conditions. We conclude that Caulobacter has co-opted the DnaK chaperone system as an essential regulator of gene expression under conditions when its folding activity is dispensable.", "doi": "10.1371/journal.pgen.1007148", "pmid": "29281627", "labels": {"Global Proteomics and Proteogenomics": "Service"}, "xrefs": [{"db": "pii", "key": "PGENETICS-D-17-01799"}, {"db": "pmc", "key": "PMC5760092"}], "notes": [], "created": "2019-01-07T11:23:22.013Z", "modified": "2021-06-21T14:57:09.516Z"}]}