3 research outputs found
Defense Against Cannibalism: The SdpI Family of Bacterial Immunity/Signal Transduction Proteins
The SdpI family consists of putative bacterial toxin immunity and signal transduction proteins. One member of the family in Bacillus subtilis, SdpI, provides immunity to cells from cannibalism in times of nutrient limitation. SdpI family members are transmembrane proteins with 3, 4, 5, 6, 7, 8, or 12 putative transmembrane α-helical segments (TMSs). These varied topologies appear to be genuine rather than artifacts due to sequencing or annotation errors. The basic and most frequently occurring element of the SdpI family has 6 TMSs. Homologues of all topological types were aligned to determine the homologous TMSs and loop regions, and the positive-inside rule was used to determine sidedness. The two most conserved motifs were identified between TMSs 1 and 2 and TMSs 4 and 5 of the 6 TMS proteins. These showed significant sequence similarity, leading us to suggest that the primordial precursor of these proteins was a 3 TMSâencoding genetic element that underwent intragenic duplication. Various deletional and fusional events, as well as intragenic duplications and inversions, may have yielded SdpI homologues with topologies of varying numbers and positions of TMSs. We propose a specific evolutionary pathway that could have given rise to these distantly related bacterial immunity proteins. We further show that genes encoding SdpI homologues often appear in operons with genes for homologues of SdpR, SdpIâs autorepressor. Our analyses allow us to propose structureâfunction relationships that may be applicable to most family members
Defense against cannibalism : the SdpI family of bacterial immunity/signal transduction proteins
The SdpI family consists of putative bacterial toxin immunity and signal transduction proteins. One member of the family in Bacillus subtilis, SdpI, provides immunity to cells from cannibalism in times of nutrient limitation. SdpI family members are transmembrane proteins with 3, 4, 5, 6, 7, 8 or 12 putative transmembrane [alpha]-helical segments (TMSs). These varied topologies appear to be genuine rather than artifactual due to sequencing or annotation errors. Bioinformatic methods were used to show that the basic and most frequently occurring element of the SdpI family has 6 TMSs. Homologues of all topological types were aligned to determine the homologous TMSs and loop regions, and the Positive-Inside Rule was used to determine sidedness. The two most conserved motifs were identified between TMSs 1 and 2 and TMSs 4 and 5 of the 6 TMS proteins. These showed significant sequence similarity, leading us to suggest that the primordial precursor of these proteins was a 3 TMS-encoding genetic element that underwent intragenic duplication. Various fusional, insertional and deletion events, as well as intragenic duplications and inversions, are proposed to have yielded SdpI homologues with topologies of varying numbers of TMSs. We propose a specific evolutionary pathway that could have given rise to these distantly related bacterial immunity proteins. Our analyses allow us to propose structure-function relationships that may be applicable to most or all family member
Genomische VariabilitĂ€t in der Kontrolle des SignalmolekĂŒles c-di-GMP und dessen Rolle in PathogenizitĂ€t und Biofilmbildung von kommensalen und pathogenen Escherichia coli
Cyclic-di-GMP is a second messenger molecule found ubiquitously throughout the
bacterial kingdom. It is the driving force behind the regulation of processes
including biofilm formation, bacterial adherence, cell-cell signaling,
differentiation, motility, and virulence. Its cellular level is modulated by
two sets of proteins: diguanylate cyclases (DGCs) synthesize and
phosphodiesterases (PDEs) degrade c-di-GMP. DGCs are characterized by the
presence of the GGDEF domain and PDEs are identified by the EAL domain. In the
K-12 strains Escherichia coli W3110 and MG1655, 29 different GGDEF/EAL domain-
containing proteins have been identified. However, little is known about how
that list may differ between strains of E. coli, particularly comparing
pathogenic and commensal strains. This study presents a systematic comparison
of the complement of putative DGC and PDE proteins as well as genes associated
with biofilm formation, among 61 strains of E. coli including
enterohemorrhagic (EHEC), uropathogenic (UPEC), enteroaggregative (EAEC),
enteropathogenic (EPEC) and enterotoxigenic (ETEC) as well as commensal
strains. It has been found that some groups of pathogenic E. coli possess
potentially novel DGC and PDE genes, whereas other common DGCs and PDEs are
absent. 8 GGDEF/EAL domain-containing genes were found to be universally
conserved among the 61 E. coli strains analyzed. Four novel putative PDEs
(PdeT, PdeX, PdeY and PdeZ) and two novel DGCs (DgcX and DgcY) were
discovered. A large number of strains, including E. coli K-12 strains, contain
a large 5â deletion in the DGC gene yneF, implying that this gene is not
expressed in these strains. Two variants of the PDE gene yahA have been
detected, one of which contains an upstream insertion of an aidA-I adhesin-
like gene resulting in the alteration of the 5â end encoding the LuxR-like
N-terminal domain in the DNA-binding motif. The ycgG gene was also found in
two variants, one full version encoding its transmembrane domain containing a
CSS motif and a shortened version encoding only the EAL domain uncoupled from
the transmembrane sensory domain. csg genes were almost universally conserved
among the analyzed strains and encode proteins for amyloid curli fiber
production and export and the biofilm regulator CsgD, essential for the
production of two biofilm matrix components: curli fibers and cellulose. The
novel dgcX gene has been found in a total of nine strains and was conserved
among all EAECs of the O104:H4 serotype: 55989, HUSEC041, LB226692,
2011C-3493, 2009EL-2050 and 2009EL-2071. The three additional strains
containing the dgcX gene were two ETECs: E24377A and ETEC H10407, and one
commensal strain SE11. In 2011 nearly 4000 persons in Germany were infected by
a Shiga toxin (Stx)-producing Escherichia coli O104:H4, with more than 20% of
patients developing hemolytic uremic syndrome (HUS). The outbreak strain is
genetically most similar to an EAEC but has acquired a Stx carrying phage from
EHEC (Mellmann et al., 2011) and contains the novel dgcX gene. This outbreak
led to the DgcX protein being chosen for further characterization of
regulation and function as well as focus on the outbreak strain and its
special characteristics with respect to DGC/PDE genes and genes associated
with biofilm formation. DgcX has been found to be the most highly expressed
DGC of all of the others studied so far in E. coli. It is expressed at both
28°C and 37°C and throughout the E. coliâs growth cycle. The outbreak strain
was shown to produce thick biofilms (Al Safadi et al., 2012) and this work
shows that it contains two novel DGCs (one of them highly active and atypical
of many E. coli), expressing the biofilm regulator CsgD and amyloid curli
fibers at 37°C but is cellulose-negative. The outbreak strains high incidence
of HUS and adherence may be due to its high production of c-di-GMP and curli
fiber, while at the same time not being able to produce cellulose. Curli
fibers cause a strong proinflammatory response (TĂŒkel et al., 2005, 2009)
while cellulose has been shown to counteract this. Thus the strong
proinflammatory response triggered by an infection by the outbreak strain may
be the result of high curli production without cellulose and may facilitate
the systemic absorption of the shiga-toxin by the body and transport through
the bloodstream to the kidneys, which can lead to hemorrhagic diarrhea and
HUS. This study will contribute to elucidating the complex regulatory network
of c-di-GMP as well as shed light upon which DGCs and PDEs may be
indispensable for c-di-GMP regulation in E. coli and which may be linked to
virulence. It brings attention to the outbreak strain and its unique ensemble
of properties that may be linked to its increased virulence.Zyklisches di-Guanosinemonophosphat (c-di-GMP) ist ein sekundÀrer Botenstoff,
der im gesamten Bakterienreich anzutreffen ist. Er ist die treibende Kraft
hinter der Regulation verschiedener Prozesse, einschlieĂlich Biofilmbildung,
bakterieller AdhÀrenz, Zell-Zell-Kommunikation, Differenzierung, MotilitÀt und
Virulenz. Der zellulÀre c-di-GMP Spiegel wird durch zwei SÀtze von Proteinen
moduliert: Diguanylate Cyclasen (DGCs) synthetisieren und Phosphodiesterasen
(PDEs) degradieren c-di-GMP. DGCs werden durch die Anwesenheit der GGDEF- und
PDEs durch die der EAL-DomÀne identifiziert. In den K-12 StÀmmen von
Escherichia coli W3110 und MG1655 wurden 29 verschiedene Gene fĂŒr GGDEF/EAL-
DomĂ€nen enthaltende Proteine annotiert, allerdings ist nur wenig darĂŒber
bekannt wie sich diese Liste zwischen pathogenen und kommensalen E. coli
StÀmmen unterscheidet. Diese Studie prÀsentiert einen systematischen Vergleich
zwischen den prognostizierten Genen in insgesamt 61 StÀmmen von E. Coli,
einschlieĂlich enterohĂ€morrhagischen (EHEC), uropathogenen (UPEC),
enteroaggregative (EAG), enteropathogenen (EPEC) und enterotoxigene (ETEC)
sowie kommensalen StĂ€mmen, die fĂŒr DGC und PDE Proteine sowie fĂŒr Proteine
codieren, die mit der Biofilmbildung assoziiert werden. Es wurde gezeigt, dass
einige Gruppen von pathogenen E. coli potentiell neuartige DGC und PDE-Gene
besitzen, wÀhrend andere DGCs und PDEs tatsÀchlich fehlen. So wurden sechs
neue mutmaĂliche Gene entdeckt, vier fĂŒr PDEs (PdeT, PdeX, PdeY und PdeZ) und
zwei fĂŒr DGCs (DgcX und DgcY). Dagegen enthalten eine groĂe Anzahl an StĂ€mmen,
einschlieĂlich der E. coli K-12 StĂ€mme, eine lange 5â Deletion im DGC Gen
yneF, was impliziert, dass dieses Gen in diesen StÀmmen nicht exprimiert wird.
Die allgemeine âGrundausttattungâ umfasst 8 Gene, die fĂŒr GGDEF- und/oder EAL-
DomÀnenproteine codieren und unter allen hier untersuchten 61 E. coli StÀmmen
konserviert sind. Desweiteren wurden jeweils zwei Varianten der PDE Gene yahA
und ycgG gefunden. Bei ersterem gibt es aufgrund einer stromaufwÀrts
vorliegenden Insertion eines Gens fĂŒr ein AidA-I-AdhĂ€sin-Ă€hnliches Protein
eine VerĂ€nderung der 5â-Sequenz, welche fĂŒr das LuxR-Ă€hnliche N-terminale DNA-
Bindemotif in YahA codiert. Im Falle von ycgG findet man eine Vollversion
inklusive der fĂŒr die TransmembrandomĂ€ne mit CSS-Motif codierenden Sequenzen
sowie eine verkĂŒrzte Version, die lediglich fĂŒr die cytoplasmatische EAL
DomĂ€ne codiert. Die csg Gene sind fast universell in allen fĂŒr diese Studie
herangezogenen StĂ€mmen konserviert und codieren fĂŒr Proteine, die an der
Produktion und Export der amyloiden Curlifasern beteiligt sind, darunter auch
der Biofilmregulator CsgD, der ebenfalls fĂŒr die Produktion der
Biofilmmatrixkomponente Cellulose essentiell ist. Im Jahr 2011 wurden fast
4000 Personen in Deutschland von einem Shiga-Toxin (Stx) produzierenden
Escherichia coli O104:H4 infiziert, wobei mehr als 20% der Patienten
hÀmolytisch-urÀmisches Syndrom (HUS) entwickelten. Der Ausbruchsstamm ist
einem EAEC genetisch am Àhnlichsten, hat aber einen das Stx Gen tragenden
Phagen aus EHEC erworben (Mellmann et al., 2011). Er enthĂ€lt auĂerdem das fĂŒr
die neuartige Diguanylatcyclase DgcX codierende Gen, welches in allen sechs
untersuchten EAEC O104:H4 konserviert sowie in zwei ETECs, E24377A und ETEC
H10407, und dem kommensalen Stamm SE11 zu finden ist. Aufgrund diese Ausbruchs
wurde das DgcX Protein zur weiteren Charakterisierung der Regulation und
Funktion ausgewÀhlt sowie der Fokus auf den Ausbruchsstamm und seine
besonderen Eigenschaften bezĂŒglich DGC/PDE-Gene und mit Biofilm assoziierten
Gene gesetzt. DgcX wurde als die am höchsten exprimierte DGC von allen anderen
bisher in E. coli untersuchten identifiziert. Es wird sowohl bei 28°C als auch
37°C exprimiert, und dies wÀhrend des gesamten Wachstumszyklus in E. coli. Der
Ausbruchsstamm produziert besonders starke Biofilme (Al Safadi et al., 2012)
und diese Arbeit zeigt, dass er mit zwei neuartigen DGCs ausgestattet, jedoch
Cellulose-negativ ist. Der Ausbruchsstamm exprimiert den Biofilmregulator CsgD
und amyloide Curlifasern bei 37°C. Die hohe Inzidenz von HUS und Adherenz des
Ausbruchsstammes könnte auf seine hohen c-di-GMP- und starken
Curlifasersynthese bei gleichzeitiger Defizienz in der Zelluloseproduktion
zurĂŒckzufĂŒhren sein. Curli Fasern bewirken eine starke proinflammatorische
Reaktion (TĂŒkel et al., 2005, 2009), wĂ€hrend Zellulose dieser entgegenwirkt.
So ist die starke proinflammatorische Reaktion ausgelöst durch eine Infektion
mit dem Ausbruchsstamm vermutlich das Ergebnis der hohen Curli Produktion ohne
Zellulose und könnte die systemische Absorption des Shiga-Toxins vom Körper
und den Transport durch den Blutstrom zu den Nieren ermöglichen, was
schlieĂlich zu hĂ€morrhagischen Durchfall und HUS fĂŒhrt. Diese Studie trĂ€gt zu
der AufklÀrung des komplexen Regulationsnetzwerk von c-di-GMP bei und schafft
einen Einblick welche DGCs und PDEs fĂŒr c-di-GMP Regulation in E. coli
unverzichtbar sein könnten. Es lenkt die Aufmerksamkeit auf den Ausbruchsstamm
und sein einzigartiges Ensemble von Eigenschaften, die vermutlich in
Zusammenhang mit seiner erhöhten Virulenz stehen