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Publications (6 of 6) Show all publications
Urdaneta, V., Hernandez, S. B. & Casadesus, J. (2019). Mutational and non mutational adaptation of Salmonella enterica to the gall bladder. Scientific Reports, 9, Article ID 5203.
Open this publication in new window or tab >>Mutational and non mutational adaptation of Salmonella enterica to the gall bladder
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 5203Article in journal (Refereed) Published
Abstract [en]

During systemic infection of susceptible hosts, Salmonella enterica colonizes the gall bladder, which contains lethal concentrations of bile salts. Recovery of Salmonella cells from the gall bladder of infected mice yields two types of isolates: (i) bile-resistant mutants; (ii) isolates that survive lethal selection without mutation. Bile-resistant mutants are recovered at frequencies high enough to suggest that increased mutation rates may occur in the gall bladder, thus providing a tentative example of stress-induced mutation in a natural environment. However, most bile-resistant mutants characterized in this study show defects in traits that are relevant for Salmonella colonization of the animal host. Mutation may thus permit short-term adaptation to the gall bladder at the expense of losing fitness for transmission to new hosts. In contrast, non mutational adaptation may have evolved as a fitness-preserving strategy. Failure of RpoS(-) mutants to colonize the gall bladder supports the involvement of the general stress response in non mutational adaptation.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-162493 (URN)10.1038/s41598-019-41600-8 (DOI)000462298600090 ()30914708 (PubMedID)
Available from: 2019-08-22 Created: 2019-08-22 Last updated: 2019-08-22Bibliographically approved
Irazoki, O., Hernandez, S. B. & Cava, F. (2019). Peptidoglycan Muropeptides: Release, Perception, and Functions as Signaling Molecules. Frontiers in Microbiology, 10, Article ID 500.
Open this publication in new window or tab >>Peptidoglycan Muropeptides: Release, Perception, and Functions as Signaling Molecules
2019 (English)In: Frontiers in Microbiology, ISSN 1664-302X, E-ISSN 1664-302X, Vol. 10, article id 500Article, review/survey (Refereed) Published
Abstract [en]

Peptidoglycan (PG) is an essential molecule for the survival of bacteria, and thus, its biosynthesis and remodeling have always been in the spotlight when it comes to the development of antibiotics. The peptidoglycan polymer provides a protective function in bacteria, but at the same time is continuously subjected to editing activities that in some cases lead to the release of peptidoglycan fragments (i.e., muropeptides) to the environment. Several soluble muropeptides have been reported to work as signaling molecules. In this review, we summarize the mechanisms involved in muropeptide release (PG breakdown and PG recycling) and describe the known PG-receptor proteins responsible for PG sensing. Furthermore, we overview the role of muropeptides as signaling molecules, focusing on the microbial responses and their functions in the host beyond their immunostimulatory activity.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
peptidoglycan, PG cleaving enzymes, PG recycling, PG receptors, signaling functions, bacterial interactions
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-158090 (URN)10.3389/fmicb.2019.00500 (DOI)000462687700001 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationThe Kempe Foundations
Available from: 2019-04-15 Created: 2019-04-15 Last updated: 2019-04-15Bibliographically approved
Vanderlinde, E. M., Strozen, T. G., Hernandez, S. B., Cava, F. & Howard, S. P. (2017). Alterations in Peptidoglycan Cross-Linking Suppress the Secretin Assembly Defect Caused by Mutation of GspA in the Type II Secretion System. Journal of Bacteriology, 199(8), Article ID UNSP e00617-16.
Open this publication in new window or tab >>Alterations in Peptidoglycan Cross-Linking Suppress the Secretin Assembly Defect Caused by Mutation of GspA in the Type II Secretion System
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2017 (English)In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 199, no 8, article id UNSP e00617-16Article in journal (Refereed) Published
Abstract [en]

In Gram-negative bacteria, the peptidoglycan (PG) cell wall is a significant structural barrier for outer membrane protein assembly. In Aeromonas hydrophila, outer membrane multimerization of the type II secretion system (T2SS) secretin ExeD requires the function of the inner membrane assembly factor complex ExeAB. The putative mechanism of the complex involves the reorganization of PG and localization of ExeD, whereby ExeA functions by interacting with PG to form a site for secretin assembly and ExeB forms an interaction with ExeD. This mechanism led us to hypothesize that increasing the pore size of PG would circumvent the requirement for ExeA in the assembly of the ExeD secretin. Growth of A. hydrophila in 270 mM Gly reduced PG cross-links by approximately 30% and led to the suppression of secretin assembly defects in exeA strains and in those expressing ExeA mutants by enabling localization of the secretin in the outer membrane. We also established a heterologous ExeD assembly system in Escherichia coli and showed that ExeAB and ExeC are the only A. hydrophila proteins required for the assembly of the ExeD secretin in E. coli and that ExeAB-independent assembly of ExeD can occur upon overexpression of the D, D-carboxypeptidase PBP 5. These results support an assembly model in which, upon binding to PG, ExeA induces multimerization and pore formation in the sacculus, which enables ExeD monomers to interact with ExeB and assemble into a secretin that both is inserted in the outer membrane and crosses the PG layer to interact with the inner membrane platform of the T2SS. IMPORTANCE The PG layer imposes a strict structural impediment for the assembly of macromolecular structures that span the cell envelope and serve as virulence factors in Gram-negative species. This work revealed that by decreasing PG crosslinking by growth in Gly, the absolute requirement for the PG-binding activity of ExeA in the assembly of the ExeD secretin was alleviated in A. hydrophila. In a heterologous assembly model in E. coli, expression of the carboxypeptidase PBP 5 could relieve the requirement for ExeAB in the assembly of the ExeD secretin. These results provide some mechanistic details of the ExeAB assembly complex function, in which the PG-binding and oligomerization functions of ExeAB are used to create a pore in the PG that is required for secretin assembly.

National Category
Microbiology in the medical area
Identifiers
urn:nbn:se:umu:diva-134731 (URN)10.1128/JB.00617-16 (DOI)000399323500003 ()
Available from: 2017-05-11 Created: 2017-05-11 Last updated: 2018-06-09Bibliographically approved
Cuenca, M., Pfister, S. P., Buschor, S., Bayramova, F., Hernandez, S. B., Cava, F., . . . Hapfelmeier, S. (2016). D-Alanine-Controlled Transient Intestinal Mono-Colonization with Non-Laboratory-Adapted Commensal E. coli Strain HS. PLoS ONE, 11(3), Article ID e0151872.
Open this publication in new window or tab >>D-Alanine-Controlled Transient Intestinal Mono-Colonization with Non-Laboratory-Adapted Commensal E. coli Strain HS
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2016 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 3, article id e0151872Article in journal (Refereed) Published
Abstract [en]

Soon after birth the mammalian gut microbiota forms a permanent and collectively highly resilient consortium. There is currently no robust method for re-deriving an already microbially colonized individual again-germ-free. We previously developed the in vivo growth-incompetent E. coli K-12 strain HA107 that is auxotrophic for the peptidoglycan components D-alanine (D-Ala) and meso-diaminopimelic acid (Dap) and can be used to transiently associate germ-free animals with live bacteria, without permanent loss of germ-free status. Here we describe the translation of this experimental model from the laboratory-adapted E. coli K-12 prototype to the better gut-adapted commensal strain E. coli HS. In this genetic background it was necessary to complete the D-Ala auxotrophy phenotype by additional knockout of the hypothetical third alanine racemase metC. Cells of the resulting fully auxotrophic strain assembled a peptidoglycan cell wall of normal composition, as long as provided with D-Ala and Dap in the medium, but could not proliferate a single time after D-Ala/Dap removal. Yet, unsupplemented bacteria remained active and were able to complete their cell cycle with fully sustained motility until immediately before autolytic death. Also in vivo, the transiently colonizing bacteria retained their ability to stimulate a live-bacteria-specific intestinal Immunoglobulin (Ig) A response. Full D-Ala auxotrophy enabled rapid recovery to again-germ-free status. E. coli HS has emerged from human studies and genomic analyses as a paradigm of benign intestinal commensal E. coli strains. Its reversibly colonizing derivative may provide a versatile research tool for mucosal bacterial conditioning or compound delivery without permanent colonization.

National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-119279 (URN)10.1371/journal.pone.0151872 (DOI)000372697400052 ()27002976 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation, KAW 2012-0184Swedish Research Council, K201457X-22450-01-5
Available from: 2016-06-02 Created: 2016-04-15 Last updated: 2018-06-07Bibliographically approved
Hernández, S. B. & Cava, F. (2016). Environmental roles of microbial amino acid racemases. Environmental Microbiology, 18(6), 1673-1685
Open this publication in new window or tab >>Environmental roles of microbial amino acid racemases
2016 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 18, no 6, p. 1673-1685Article, review/survey (Refereed) Published
Abstract [en]

Enzymes catalysing the stereo-chemical inter-conversion of amino acids are known as amino acid racemases. In bacteria, these enzymes are fundamental to synthesize the D-Ala and D-Glu that are critical components of the peptidoglycan. In addition to this structural function in cell wall assembly, D-amino acids produced by microbial amino acid racemases have been described as relevant constituents in other prokaryotic structures (e.g. capsule, non-ribosomal peptides) and have been associated to growth fitness and to processes such as biofilm development, spore germination, and signalling. The recent discovery of broad spectrum racemases able to produce and release several D-amino acids to the environment suggests that these enzymes might have a great impact in microbial ecology. Consequently, new data on the biochemistry and regulation of racemases is key to understand the biological significance of D-enantiomers in nature, in particular their effect on microbial social networks. This review summarizes current knowledge on the environmental roles of bacterial racemases with an emphasis on the potential roles of the new broad spectrum enzymes in natural environments.

Place, publisher, year, edition, pages
Hoboken: Wiley-Blackwell, 2016
Keywords
racemases, bacteria, D-amino acids
National Category
Microbiology
Identifiers
urn:nbn:se:umu:diva-112374 (URN)10.1111/1462-2920.13072 (DOI)000380376700002 ()26419727 (PubMedID)2-s2.0-84976587398 (Scopus ID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2015-12-07 Created: 2015-12-07 Last updated: 2018-06-07Bibliographically approved
Alvarez, L., Hernandez, S. B., de Pedro, M. A. & Cava, F. (2016). Ultra-sensitive, high-resolution liquid chromatography methods for the high-throughput quantitative analysis of bacterial cell wall chemistry and structure. In: Hee-Jeon Hong (Ed.), Bacterial cell wall homeostasis: methods and protocols /edited by Hee-Jeon Hong (pp. 11-27). New York: Humana Press, 1440
Open this publication in new window or tab >>Ultra-sensitive, high-resolution liquid chromatography methods for the high-throughput quantitative analysis of bacterial cell wall chemistry and structure
2016 (English)In: Bacterial cell wall homeostasis: methods and protocols /edited by Hee-Jeon Hong / [ed] Hee-Jeon Hong, New York: Humana Press, 2016, Vol. 1440, p. 11-27Chapter in book (Refereed)
Abstract [en]

High-performance liquid chromatography (HPLC) analysis has been critical for determining the structural and chemical complexity of the cell wall. However this method is very time consuming in terms of sample preparation and chromatographic separation. Here we describe (1) optimized methods for peptidoglycan isolation from both Gram-negative and Gram-positive bacteria that dramatically reduce the sample preparation time, and (2) the application of the fast and highly efficient ultra-performance liquid chromatography (UPLC) technology to muropeptide separation and quantification. The advances in both analytical instrumentation and stationary-phase chemistry have allowed for evolved protocols which cut run time from hours (2-3 h) to minutes (10-20 min), and sample demands by at least one order of magnitude. Furthermore, development of methods based on organic solvents permits in-line mass spectrometry (MS) of the UPLC-resolved muropeptides. Application of these technologies to high-throughput analysis will expedite the better understanding of the cell wall biology.

Place, publisher, year, edition, pages
New York: Humana Press, 2016
Series
Methods in Molecular Biology, ISSN 1064-3745, E-ISSN 1940-6029 ; 1440
Keywords
Cell wall, HPLC, Muropeptide, Peptidoglycan, Reverse-phase liquid chromatography, UPLC
National Category
Microbiology Analytical Chemistry
Identifiers
urn:nbn:se:umu:diva-128371 (URN)10.1007/978-1-4939-3676-2_2 (DOI)27311661 (PubMedID)2-s2.0-84979988068 (Scopus ID)978-1-4939-3674-8 (ISBN)978-1-4939-3676-2 (ISBN)
Available from: 2016-12-02 Created: 2016-12-02 Last updated: 2018-06-09Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-8349-360x

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