1
|
Abstract
![]()
The class II lanthipeptide
mersacidin, a ribosomally synthesized
and post-translationally modified peptide (RiPP), displays unique
intramolecular structures, including a very small lanthionine ring.
When applied in the growing field of RiPP engineering, these can add
unique features to new-to-nature compounds with novel properties.
Recently, a heterologous expression system for mersacidin in Escherichia coli was developed to add its modification
enzymes to the RiPP engineering toolbox and further explore mersacidin
biosynthesis and leader-processing. The dedicated mersacidin transporter
and leader protease MrsT was shown to cleave the leader peptide only
partially upon export, transporting GDMEAA-mersacidin out of the cell.
The extracellular Bacillus amyloliquefaciens protease AprE was shown to release active mersacidin in a second
leader-processing step after transport. The conserved LanT cleavage
site in the mersacidin leader is present in many other class II lanthipeptides.
In contrast to mersacidin, the leader of these peptides is fully processed
in one step. This difference with mersacidin leader-processing raises
fundamentally interesting questions about the specifics of mersacidin
modification and processing, which is also crucial for its application
in RiPP engineering. Here, mutational studies of the mersacidin leader–core
interface were performed to answer these questions. Results showed
the GDMEAA sequence is crucial for both mersacidin modification and
leader processing, revealing a unique leader layout in which a LanM
recognition site is positioned downstream of the conserved leader-protease
LanT cleavage site. Moreover, by identifying residues and regions
that are crucial for mersacidin-type modifications, the wider application
of mersacidin modifications in RiPP engineering has been enabled.
Collapse
Affiliation(s)
- Jakob H. Viel
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Oscar P. Kuipers
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| |
Collapse
|
2
|
Viel JH, van Tilburg AY, Kuipers OP. Characterization of Leader Processing Shows That Partially Processed Mersacidin Is Activated by AprE After Export. Front Microbiol 2021; 12:765659. [PMID: 34777321 PMCID: PMC8581636 DOI: 10.3389/fmicb.2021.765659] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 10/05/2021] [Indexed: 11/26/2022] Open
Abstract
The ribosomally synthesized and post-translationally modified peptide mersacidin is a class II lanthipeptide with good activity against Gram-positive bacteria. The intramolecular lanthionine rings, that give mersacidin its stability and antimicrobial activity, are specific structures with potential applications in synthetic biology. To add the mersacidin modification enzymes to the synthetic biology toolbox, a heterologous expression system for mersacidin in Escherichia coli has recently been developed. While this system was able to produce fully modified mersacidin precursor peptide that could be activated by Bacillus amyloliquefaciens supernatant and showed that mersacidin was activated in an additional proteolytic step after transportation out of the cell, it lacked a mechanism for clean and straightforward leader processing. Here, the protease responsible for activating mersacidin was identified and heterologously produced in E. coli, improving the previously reported heterologous expression system. By screening multiple proteases, the stringency of proteolytic activity directly next to a very small lanthionine ring is demonstrated, and the full two-step proteolytic activation of mersacidin was elucidated. Additionally, the effect of partial leader processing on diffusion and antimicrobial activity is assessed, shedding light on the function of two-step leader processing.
Collapse
Affiliation(s)
- Jakob H Viel
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| | - Amanda Y van Tilburg
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| | - Oscar P Kuipers
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| |
Collapse
|
3
|
Abstract
A large number of antimicrobial peptides depend on intramolecular disulfide bonds for their biological activity. However, the relative instability of disulfide bonds has limited the potential of some of these peptides to be developed into therapeutics. Conversely, peptides containing intramolecular (methyl)lanthionine-based bonds, lanthipeptides, are highly stable under a broader range of biological and physical conditions. Here, the class-II lanthipeptide synthetase CinM, from the cinnamycin gene cluster, was employed to create methyllanthionine stabilized analogues of disulfide-bond-containing antimicrobial peptides. The resulting analogues were subsequently modified in vitro by adding lipid tails of variable lengths through chemical addition. Finally, the created compounds were characterized by MIC tests against several relevant pathogens, killing assays, membrane permeability assays, and hemolysis assays. It was found that CinM could successfully install methyllanthionine bonds at the intended positions of the analogues and that the lipidated macrocyclic core peptides have bactericidal activity against tested Gram-positive and Gram-negative pathogenic bacteria. Additionally, fluorescence microscopy assays revealed that the lipidated compounds disrupt the bacterial membrane and lyse bacterial cells, hinting toward a potential mode of action. Notably, the semisynthesized macrocyclic lipo-lanthipeptides show low hemolytic activity. These results show that the methods developed here extend the toolbox for novel antimicrobial development and might enable the further development of novel compounds with killing activity against relevant pathogenic bacteria.
Collapse
Affiliation(s)
- Xinghong Zhao
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen 9747 AG, The Netherlands
| | - Yanli Xu
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen 9747 AG, The Netherlands
| | - Jakob H. Viel
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen 9747 AG, The Netherlands
| | - Oscar P. Kuipers
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen 9747 AG, The Netherlands
| |
Collapse
|
4
|
Abstract
![]()
The lanthipeptide
mersacidin is a ribosomally synthesized and post-translationally
modified peptide (RiPP) produced by Bacillus amyloliquefaciens. It has antimicrobial activity against a range of Gram-positive
bacteria, including methicillin-resistant Staphylococcus aureus, giving it potential therapeutic relevance. The structure and bioactivity
of mersacidin are derived from a unique combination of lanthionine
ring structures, which makes mersacidin also interesting from a lantibiotic-engineering
point of view. Until now, mersacidin and its derivatives have exclusively
been produced in Bacillus strains and purified from
the supernatant in their bioactive form. However, to fully exploit
its potential in lanthipeptide-engineering, mersacidin would have
to be expressed in a standardized expression system and obtained in
its inactive prepeptide form. In such a system, the mersacidin biosynthetic
enzymes could be employed to create novel peptides, enhanced by the
recent advancements in RiPP engineering, while the leader peptide
prevents activity against the expression host. This system would however
need a means of postpurification in vitro leader
processing to activate the obtained precursor peptides. While mersacidin’s
native leader processing mechanism has not been confirmed, the bifunctional
transporter MrsT and extracellular Bacillus proteases
have been suggested to be responsible. Here, a modular system is presented
for the heterologous expression of mersacidin in Escherichia
coli, which was successfully used to produce and purify inactive
premersacidin. The purified product was used to determine the cleavage
site of MrsT. Additionally, it was concluded from antimicrobial activity
tests that in a second processing step mersacidin is activated by
specific extracellular proteases from Bacillus amyloliquefaciens.
Collapse
Affiliation(s)
- Jakob H. Viel
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Ate H. Jaarsma
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Oscar P. Kuipers
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| |
Collapse
|
5
|
de Vries RH, Viel JH, Kuipers OP, Roelfes G. Rapid and Selective Chemical Editing of Ribosomally Synthesized and Post-Translationally Modified Peptides (RiPPs) via Cu II -Catalyzed β-Borylation of Dehydroamino Acids. Angew Chem Int Ed Engl 2021; 60:3946-3950. [PMID: 33185967 PMCID: PMC7898795 DOI: 10.1002/anie.202011460] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Indexed: 12/22/2022]
Abstract
We report the fast and selective chemical editing of ribosomally synthesized and post-translationally modified peptides (RiPPs) by β-borylation of dehydroalanine (Dha) residues. The thiopeptide thiostrepton was modified efficiently using CuII -catalysis under mild conditions and 1D/2D NMR of the purified product showed site-selective borylation of the terminal Dha residues. Using similar conditions, the thiopeptide nosiheptide, lanthipeptide nisin Z, and protein SUMO_G98Dha were also modified efficiently. Borylated thiostrepton showed an up to 84-fold increase in water solubility, and minimum inhibitory concentration (MIC) assays showed that antimicrobial activity was maintained in thiostrepton and nosiheptide. The introduced boronic-acid functionalities were shown to be valuable handles for chemical mutagenesis and in a reversible click reaction with triols for the pH-controlled labeling of RiPPs.
Collapse
Affiliation(s)
- Reinder H. de Vries
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
| | - Jakob H. Viel
- Department of Molecular GeneticsGroningen Biomolecular Sciences and Biotechnology InstituteUniversity of GroningenNijenborgh 79747AGGroningenThe Netherlands
| | - Oscar P. Kuipers
- Department of Molecular GeneticsGroningen Biomolecular Sciences and Biotechnology InstituteUniversity of GroningenNijenborgh 79747AGGroningenThe Netherlands
| | - Gerard Roelfes
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
| |
Collapse
|
6
|
Montalbán-López M, Scott TA, Ramesh S, Rahman IR, van Heel AJ, Viel JH, Bandarian V, Dittmann E, Genilloud O, Goto Y, Grande Burgos MJ, Hill C, Kim S, Koehnke J, Latham JA, Link AJ, Martínez B, Nair SK, Nicolet Y, Rebuffat S, Sahl HG, Sareen D, Schmidt EW, Schmitt L, Severinov K, Süssmuth RD, Truman AW, Wang H, Weng JK, van Wezel GP, Zhang Q, Zhong J, Piel J, Mitchell DA, Kuipers OP, van der Donk WA. New developments in RiPP discovery, enzymology and engineering. Nat Prod Rep 2021; 38:130-239. [PMID: 32935693 PMCID: PMC7864896 DOI: 10.1039/d0np00027b] [Citation(s) in RCA: 362] [Impact Index Per Article: 120.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Covering: up to June 2020Ribosomally-synthesized and post-translationally modified peptides (RiPPs) are a large group of natural products. A community-driven review in 2013 described the emerging commonalities in the biosynthesis of RiPPs and the opportunities they offered for bioengineering and genome mining. Since then, the field has seen tremendous advances in understanding of the mechanisms by which nature assembles these compounds, in engineering their biosynthetic machinery for a wide range of applications, and in the discovery of entirely new RiPP families using bioinformatic tools developed specifically for this compound class. The First International Conference on RiPPs was held in 2019, and the meeting participants assembled the current review describing new developments since 2013. The review discusses the new classes of RiPPs that have been discovered, the advances in our understanding of the installation of both primary and secondary post-translational modifications, and the mechanisms by which the enzymes recognize the leader peptides in their substrates. In addition, genome mining tools used for RiPP discovery are discussed as well as various strategies for RiPP engineering. An outlook section presents directions for future research.
Collapse
|
7
|
Vries RH, Viel JH, Kuipers OP, Roelfes G. Rapid and Selective Chemical Editing of Ribosomally Synthesized and Post‐Translationally Modified Peptides (RiPPs) via Cu
II
‐Catalyzed β‐Borylation of Dehydroamino Acids. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202011460] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Reinder H. Vries
- Stratingh Institute for Chemistry University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Jakob H. Viel
- Department of Molecular Genetics Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen Nijenborgh 7 9747 AG Groningen The Netherlands
| | - Oscar P. Kuipers
- Department of Molecular Genetics Groningen Biomolecular Sciences and Biotechnology Institute University of Groningen Nijenborgh 7 9747 AG Groningen The Netherlands
| | - Gerard Roelfes
- Stratingh Institute for Chemistry University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
| |
Collapse
|
8
|
Deng J, Viel JH, Kubyshkin V, Budisa N, Kuipers OP. Conjugation of Synthetic Polyproline Moietes to Lipid II Binding Fragments of Nisin Yields Active and Stable Antimicrobials. Front Microbiol 2020; 11:575334. [PMID: 33329435 PMCID: PMC7715017 DOI: 10.3389/fmicb.2020.575334] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 10/30/2020] [Indexed: 12/26/2022] Open
Abstract
Coupling functional moieties to lantibiotics offers exciting opportunities to produce novel derivatives with desirable properties enabling new functions and applications. Here, five different synthetic hydrophobic polyproline peptides were conjugated to either nisin AB (the first two rings of nisin) or nisin ABC (the first three rings of nisin) by using click chemistry. The antimicrobial activity of nisin ABC + O6K3 against Enterococcus faecium decreased 8-fold compared to full-length nisin, but its activity was 16-fold better than nisin ABC, suggesting that modifying nisin ABC is a promising strategy to generate semi-synthetic nisin hybrids. In addition, the resulting nisin hybrids are not prone to degradation at the C-terminus, which has been observed for nisin as it can be degraded by nisinase or other proteolytic enzymes. This methodology allows for getting more insight into the possibility of creating semi-synthetic nisin hybrids that maintain antimicrobial activity, in particular when synthetic and non-proteinaceous moieties are used. The success of this approach in creating viable nisin hybrids encourages further exploring the use of different modules, e.g., glycans, lipids, active peptide moieties, and other antimicrobial moieties.
Collapse
Affiliation(s)
- Jingjing Deng
- Department of Molecular Genetics, University of Groningen, Groningen, Netherlands
| | - Jakob H Viel
- Department of Molecular Genetics, University of Groningen, Groningen, Netherlands
| | - Vladimir Kubyshkin
- Institute of Chemistry, Technical University of Berlin, Berlin, Germany.,Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada
| | - Nediljko Budisa
- Institute of Chemistry, Technical University of Berlin, Berlin, Germany.,Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada
| | - Oscar P Kuipers
- Department of Molecular Genetics, University of Groningen, Groningen, Netherlands
| |
Collapse
|
9
|
Deng J, Viel JH, Chen J, Kuipers OP. Synthesis and Characterization of Heterodimers and Fluorescent Nisin Species by Incorporation of Methionine Analogues and Subsequent Click Chemistry. ACS Synth Biol 2020; 9:2525-2536. [PMID: 32786360 PMCID: PMC7507115 DOI: 10.1021/acssynbio.0c00308] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
![]()
Noncanonical
amino acids form a highly diverse pool of building
blocks that can render unique physicochemical properties to peptides
and proteins. Here, four methionine analogues with unsaturated and
varying side chain lengths were successfully incorporated at four
different positions in nisin in Lactococcus lactis through force feeding. This approach allows for residue-specific
incorporation of methionine analogues into nisin to expand their structural
diversity and alter their activity profiles. Moreover, the insertion
of methionine analogues with biorthogonal chemical reactivity, e.g.,
azidohomoalanine and homopropargylglycine, provides the opportunity
for chemical coupling to functional moieties and fluorescent probes
as well as for intermolecular coupling of nisin variants. All resulting
nisin conjugates retained antimicrobial activity, which substantiates
the potential of this method as a tool to further study its localization
and mode of action.
Collapse
Affiliation(s)
- Jingjing Deng
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Jakob H. Viel
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Jingqi Chen
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Oscar P. Kuipers
- Department of Molecular Genetics, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| |
Collapse
|
10
|
de Vries RH, Viel JH, Oudshoorn R, Kuipers OP, Roelfes G. Selective Modification of Ribosomally Synthesized and Post-Translationally Modified Peptides (RiPPs) through Diels-Alder Cycloadditions on Dehydroalanine Residues. Chemistry 2019; 25:12698-12702. [PMID: 31361053 PMCID: PMC6790694 DOI: 10.1002/chem.201902907] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 07/29/2019] [Indexed: 11/08/2022]
Abstract
We report the late‐stage chemical modification of ribosomally synthesized and post‐translationally modified peptides (RIPPs) by Diels–Alder cycloadditions to naturally occurring dehydroalanines. The tail region of the thiopeptide thiostrepton could be modified selectively and efficiently under microwave heating and transition‐metal‐free conditions. The Diels–Alder adducts were isolated and the different site‐ and endo/exo isomers were identified by 1D/2D 1H NMR. Via efficient modification of the thiopeptide nosiheptide and the lanthipeptide nisin Z the generality of the method was established. Minimum inhibitory concentration (MIC) assays of the purified thiostrepton Diels–Alder products against thiostrepton‐susceptible strains displayed high activities comparable to that of native thiostrepton. These Diels–Alder products were also subjected successfully to inverse‐electron‐demand Diels–Alder reactions with a variety of functionalized tetrazines, demonstrating the utility of this method for labeling of RiPPs.
Collapse
Affiliation(s)
- Reinder H de Vries
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
| | - Jakob H Viel
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands
| | - Ruben Oudshoorn
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
| | - Oscar P Kuipers
- Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands
| | - Gerard Roelfes
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands
| |
Collapse
|
11
|
van Heel AJ, de Jong A, Song C, Viel JH, Kok J, Kuipers OP. BAGEL4: a user-friendly web server to thoroughly mine RiPPs and bacteriocins. Nucleic Acids Res 2019; 46:W278-W281. [PMID: 29788290 PMCID: PMC6030817 DOI: 10.1093/nar/gky383] [Citation(s) in RCA: 464] [Impact Index Per Article: 92.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 05/17/2018] [Indexed: 11/21/2022] Open
Abstract
Interest in secondary metabolites such as RiPPs (ribosomally synthesized and posttranslationally modified peptides) is increasing worldwide. To facilitate the research in this field we have updated our mining web server. BAGEL4 is faster than its predecessor and is now fully independent from ORF-calling. Gene clusters of interest are discovered using the core-peptide database and/or through HMM motifs that are present in associated context genes. The databases used for mining have been updated and extended with literature references and links to UniProt and NCBI. Additionally, we have included automated promoter and terminator prediction and the option to upload RNA expression data, which can be displayed along with the identified clusters. Further improvements include the annotation of the context genes, which is now based on a fast blast against the prokaryote part of the UniRef90 database, and the improved web-BLAST feature that dynamically loads structural data such as internal cross-linking from UniProt. Overall BAGEL4 provides the user with more information through a user-friendly web-interface which simplifies data evaluation. BAGEL4 is freely accessible at http://bagel4.molgenrug.nl.
Collapse
Affiliation(s)
- Auke J van Heel
- Molecular Genetics, GBB, University of Groningen, Groningen, 9747AG, the Netherlands
| | - Anne de Jong
- Molecular Genetics, GBB, University of Groningen, Groningen, 9747AG, the Netherlands
| | - Chunxu Song
- Molecular Genetics, GBB, University of Groningen, Groningen, 9747AG, the Netherlands
| | - Jakob H Viel
- Molecular Genetics, GBB, University of Groningen, Groningen, 9747AG, the Netherlands
| | - Jan Kok
- Molecular Genetics, GBB, University of Groningen, Groningen, 9747AG, the Netherlands
| | - Oscar P Kuipers
- Molecular Genetics, GBB, University of Groningen, Groningen, 9747AG, the Netherlands
| |
Collapse
|
12
|
Bartholomae M, Buivydas A, Viel JH, Montalbán-López M, Kuipers OP. Major gene-regulatory mechanisms operating in ribosomally synthesized and post-translationally modified peptide (RiPP) biosynthesis. Mol Microbiol 2017; 106:186-206. [DOI: 10.1111/mmi.13764] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 08/02/2017] [Accepted: 08/03/2017] [Indexed: 02/06/2023]
Affiliation(s)
- Maike Bartholomae
- Department of Molecular Genetics; University of Groningen, Nijenborgh 7; 9747AG Groningen The Netherlands
| | - Andrius Buivydas
- Department of Molecular Genetics; University of Groningen, Nijenborgh 7; 9747AG Groningen The Netherlands
| | - Jakob H. Viel
- Department of Molecular Genetics; University of Groningen, Nijenborgh 7; 9747AG Groningen The Netherlands
| | - Manuel Montalbán-López
- Department of Microbiology; University of Granada, C. Fuentenueva s/n; 18071 Granada Spain
| | - Oscar P. Kuipers
- Department of Molecular Genetics; University of Groningen, Nijenborgh 7; 9747AG Groningen The Netherlands
| |
Collapse
|