Imperial College London

ProfessorAlainFilloux

Faculty of Natural SciencesDepartment of Life Sciences

Visiting Professor
 
 
 
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Contact

 

+44 (0)20 7594 9651a.filloux Website CV

 
 
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Location

 

1.47Flowers buildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

236 results found

Eilers K, Hoong Yam JK, Liu X, Goh YF, To K-N, Paracuellos P, Morton R, Brizuela J, Hui Yong AM, Givskov M, Freibert S-A, Bange G, Rice SA, Steinchen W, Filloux Aet al., 2024, The dual GGDEF/EAL domain enzyme PA0285 is a Pseudomonas species housekeeping phosphodiesterase regulating early attachment and biofilm architecture, Journal of Biological Chemistry, Vol: 300, ISSN: 0021-9258

Bacterial lifestyles depend on conditions encountered during colonization. The transition between planktonic and biofilm growth is dependent on the intracellular second messenger c-di-GMP. High c-di-GMP levels driven by diguanylate cyclases (DGCs) activity favor biofilm formation, while low levels were maintained by phosphodiesterases (PDE) encourage planktonic lifestyle. The activity of these enzymes can be modulated by stimuli-sensing domains such as Per-ARNT-Sim (PAS). In Pseudomonas aeruginosa, more than 40 PDE/DGC are involved in c-di-GMP homeostasis, including 16 dual proteins possessing both canonical DGC and PDE motifs, that is, GGDEF and EAL, respectively. It was reported that deletion of the EAL/GGDEF dual enzyme PA0285, one of five c-di-GMP–related enzymes conserved across all Pseudomonas species, impacts biofilms. PA0285 is anchored in the membrane and carries two PAS domains. Here, we confirm that its role is conserved in various P. aeruginosa strains and in Pseudomonas putida. Deletion of PA0285 impacts the early stage of colonization, and RNA-seq analysis suggests that expression of cupA fimbrial genes is involved. We demonstrate that the C-terminal portion of PA0285 encompassing the GGDEF and EAL domains binds GTP and c-di-GMP, respectively, but only exhibits PDE activity in vitro. However, both GGDEF and EAL domains are important for PA0285 PDE activity in vivo. Complementation of the PA0285 mutant strain with a copy of the gene encoding the C-terminal GGDEF/EAL portion in trans was not as effective as complementation with the full-length gene. This suggests the N-terminal transmembrane and PAS domains influence the PDE activity in vivo, through modulating the protein conformation.

Journal article

Filloux A, 2024, Bacterial type VI secretion system helps prevent cheating in microbial communities, The ISME Journal: multidisciplinary journal of microbial ecology, Vol: 18, ISSN: 1751-7362

Journal article

Low H, Tassinari M, Filloux A, Rudzite Met al., 2023, Assembly mechanism of a Tad secretion system secretin-pilotin complex, Nature Communications, Vol: 14, ISSN: 2041-1723

The bacterial Tight adherence Secretion System (TadSS) assembles surface pili that drive cell adherence, biofilm formation and bacterial predation. The structure and mechanism of the TadSS is mostly unknown. This includes characterisation of the outer membrane secretin through which the pilus is channelled and recruitment of its pilotin. Here we investigate RcpA and TadD lipoprotein from Pseudomonas aeruginosa. Light microscopy reveals RcpA colocalising with TadD in P. aeruginosa and when heterologously expressed in Escherichia coli. We use cryogenic electron microscopy to determine how RcpA and TadD assemble a secretin channel with C13 and C14 symmetries. Despite low sequence homology, we show that TadD shares a similar fold to the type 4 pilus system pilotin PilF. We establish that the C-terminal four residues of RcpA bind TadD - an interaction essential for secretin formation. The binding mechanism between RcpA and TadD appears distinct from known secretin-pilotin pairings in other secretion systems.

Journal article

Teh WK, Ding Y, Gubellini F, Filloux A, Poyart C, Givskov M, Dramsi Set al., 2023, Characterization of TelE, a T7SS LXG effector exhibiting a conserved C-terminal glycine zipper motif required for toxicity, Microbiology Spectrum, Vol: 11, ISSN: 2165-0497

Streptococcus gallolyticus subsp. gallolyticus (SGG) is an opportunistic bacterial pathogen strongly associated with colorectal cancer. Here, through comparative genomics analysis, we demonstrated that the genetic locus encoding the type VIIb secretion system (T7SSb) machinery is uniquely present in SGG in two different arrangements. SGG UCN34 carrying the most prevalent T7SSb genetic arrangement was chosen as the reference strain. To identify the effectors secreted by this secretion system, we inactivated the essC gene encoding the motor of this machinery. A comparison of the proteins secreted by UCN34 wild type and its isogenic ΔessC mutant revealed six T7SSb effector proteins, including the expected WXG effector EsxA and three LXG-containing proteins. In this work, we characterized an LXG-family toxin named herein TelE promoting the loss of membrane integrity. Seven homologs of TelE harboring a conserved glycine zipper motif at the C terminus were identified in different SGG isolates. Scanning mutagenesis of this motif showed that the glycine residue at position 470 was crucial for TelE membrane destabilization activity. TelE activity was antagonized by a small protein TipE belonging to the DUF5085 family. Overall, we report herein a unique SGG T7SSb effector exhibiting a toxic activity against nonimmune bacteria.

Journal article

Kadeřábková N, Furniss RCD, Maslova E, Eisaiankhongi L, Bernal P, Filloux A, Landeta C, Gonzalez D, McCarthy RR, Mavridou DAIet al., 2023, Antibiotic potentiation and inhibition of cross-resistance in pathogens associated with cystic fibrosis., bioRxiv

Critical Gram-negative pathogens, like Pseudomonas, Stenotrophomonas and Burkholderia, have become resistant to most antibiotics. Complex resistance profiles together with synergistic interactions between these organisms increase the likelihood of treatment failure in distinct infection settings, for example in the lungs of cystic fibrosis patients. Here, we discover that cell envelope protein homeostasis pathways underpin both antibiotic resistance and cross-protection in CF-associated bacteria. We find that inhibition of oxidative protein folding inactivates multiple species-specific resistance proteins. Using this strategy, we sensitize multi-drug resistant Pseudomonas aeruginosa to β-lactam antibiotics and demonstrate promise of new treatment avenues for the recalcitrant pathogen Stenotrophomonas maltophilia. The same approach also inhibits cross-protection between resistant S. maltophilia and susceptible P. aeruginosa, allowing eradication of both commonly co-occurring CF-associated organisms. Our results provide the basis for the development of next-generation strategies that target antibiotic resistance, while also impairing specific interbacterial interactions that enhance the severity of polymicrobial infections.

Journal article

Rudzite M, Subramoni S, Endres RG, Filloux Aet al., 2023, Effectiveness of <i>Pseudomonas aeruginosa</i> type VI secretion system relies on toxin potency and type IV pili-dependent interaction, PLOS PATHOGENS, Vol: 19, ISSN: 1553-7366

Journal article

Bohning J, Dobbelstein AW, Sulkowski N, Eilers K, von Kugelgen A, Tarafder AK, Peak-Chew S-Y, Skehel M, Alva V, Filloux A, Bharat TAMet al., 2023, Architecture of the biofilm-associated archaic Chaperone-Usher pilus CupE from Pseudomonas aeruginosa, PLoS Pathogens, Vol: 19, ISSN: 1553-7366

Chaperone-Usher Pathway (CUP) pili are major adhesins in Gram-negative bacteria, mediating bacterial adherence to biotic and abiotic surfaces. While classical CUP pili have been extensively characterized, little is known about so-called archaic CUP pili, which are phylogenetically widespread and promote biofilm formation by several human pathogens. In this study, we present the electron cryomicroscopy structure of the archaic CupE pilus from the opportunistic human pathogen Pseudomonas aeruginosa. We show that CupE1 subunits within the pilus are arranged in a zigzag architecture, containing an N-terminal donor β-strand extending from each subunit into the next, where it is anchored by hydrophobic interactions, with comparatively weaker interactions at the rest of the inter-subunit interface. Imaging CupE pili on the surface of P. aeruginosa cells using electron cryotomography shows that CupE pili adopt variable curvatures in response to their environment, which might facilitate their role in promoting cellular attachment. Finally, bioinformatic analysis shows the widespread abundance of cupE genes in isolates of P. aeruginosa and the co-occurrence of cupE with other cup clusters, suggesting interdependence of cup pili in regulating bacterial adherence within biofilms. Taken together, our study provides insights into the architecture of archaic CUP pili, providing a structural basis for understanding their role in promoting cellular adhesion and biofilm formation in P. aeruginosa.

Journal article

Vilar Compte R, Evans L, Kotar A, Valentini M, Filloux A, Jamshidi S, Plavec J, Rahman KMet al., 2023, Identification and characterisation of G-quadruplex DNA-forming sequences in the Pseudomonas aeruginosa genome, RSC Chemical Biology, Vol: 4, Pages: 94-100, ISSN: 2633-0679

A number of Gram-negative bacteria such as Pseudomonas aeruginosa are becoming resistant to front-line antibiotics. Consequently, there is a pressing need to find alternative bio-molecular targets for the development of new drugs. Since non-canonical DNA structures such as guanine-quadruplexes (G4s) have been implicated in regulating transcription, we were interested in determining whether there are putative quadruplex-forming sequences (PQS) in the genome of Pseudomonas aeruginosa. Using bioinformatic tools, we screened 36 genes potentially relevant to drug resistance for the presence of PQS and 10 of these were selected for biophysical characterisation (i.e. circular dichroism and thermal difference UV/Vis spectroscopy). These studies showed that three of these G-rich sequences (linked to murE, ftsB and mexC genes) form stable guanine-quadruplexes which were studied by NMR spectroscopy; detailed analysis of one of the sequences (mexC) confirmed that it adopts a two-quartet antiparallel quadruplex structure in the presence of K+ ions. We also show by FRET melting assays that small molecules can stabilise these three new G4 DNA structures under physiological conditions. These initial results could be of future interest in the development of new antibiotics with alternative bio-molecular targets which in turn would help tackle antimicrobial resistance.

Journal article

Bernal P, Civantos C, Pacheco-Sanchez D, Quesada JM, Filloux A, Llamas MAet al., 2023, Transcriptional organization and regulation of the <i>Pseudomonas putida</i> K1 type VI secretion system gene cluster, MICROBIOLOGY-SGM, Vol: 169, ISSN: 1350-0872

Journal article

Fala AK, Alvarez-Ordonez A, Filloux A, Gahan CGM, Cotter PDet al., 2022, Quorum sensing in human gut and food microbiomes: significance and potential for therapeutic targeting, Frontiers in Microbiology, Vol: 13, ISSN: 1664-302X

Human gut and food microbiomes interact during digestion. The outcome of these interactions influences the taxonomical composition and functional capacity of the resident human gut microbiome, with potential consequential impacts on health and disease. Microbe-microbe interactions between the resident and introduced microbiomes, which likely influence host colonisation, are orchestrated by environmental conditions, elements of the food matrix, host-associated factors as well as social cues from other microorganisms. Quorum sensing is one example of a social cue that allows bacterial communities to regulate genetic expression based on their respective population density and has emerged as an attractive target for therapeutic intervention. By interfering with bacterial quorum sensing, for instance, enzymatic degradation of signalling molecules (quorum quenching) or the application of quorum sensing inhibitory compounds, it may be possible to modulate the microbial composition of communities of interest without incurring negative effects associated with traditional antimicrobial approaches. In this review, we summarise and critically discuss the literature relating to quorum sensing from the perspective of the interactions between the food and human gut microbiome, providing a general overview of the current understanding of the prevalence and influence of quorum sensing in this context, and assessing the potential for therapeutic targeting of quorum sensing mechanisms.

Journal article

Camara M, Filloux A, 2022, Supporting the strategic pillars of translational research in biofilms, NPJ BIOFILMS AND MICROBIOMES, Vol: 8

Journal article

Bullen NP, Sychantha D, Thang SS, Culviner PH, Rudzite M, Ahmad S, Shah VS, Filloux A, Prehna G, Whitney JCet al., 2022, An ADP-ribosyltransferase toxin kills bacterial cells by modifying structured non-coding RNAs, Molecular Cell, Vol: 82, Pages: 3484-3498.e11, ISSN: 1097-2765

ADP-ribosyltransferases (ARTs) were among the first identified bacterial virulence factors. Canonical ART toxins are delivered into host cells where they modify essential proteins, thereby inactivating cellular processes and promoting pathogenesis. Our understanding of ARTs has since expanded beyond protein-targeting toxins to include antibiotic inactivation and DNA damage repair. Here, we report the discovery of RhsP2 as an ART toxin delivered between competing bacteria by a type VI secretion system of Pseudomonas aeruginosa. A structure of RhsP2 reveals that it resembles protein-targeting ARTs such as diphtheria toxin. Remarkably, however, RhsP2 ADP-ribosylates 2'-hydroxyl groups of double-stranded RNA, and thus, its activity is highly promiscuous with identified cellular targets including the tRNA pool and the RNA-processing ribozyme, ribonuclease P. Consequently, cell death arises from the inhibition of translation and disruption of tRNA processing. Overall, our data demonstrate a previously undescribed mechanism of bacterial antagonism and uncover an unprecedented activity catalyzed by ART enzymes.

Journal article

Tortuel D, Tahrioui A, David A, Cambronel M, Nilly F, Clamens T, Maillot O, Barreau M, Feuilloley MGJ, Lesouhaitier O, Filloux A, Bouffartigues E, Cornelis P, Chevalier Set al., 2022, Pf4 Phage Variant Infection Reduces Virulence-Associated Traits in <i>Pseudomonas aeruginosa</i>, MICROBIOLOGY SPECTRUM, ISSN: 2165-0497

Journal article

Eilers K, Kuok Hoong Yam J, Morton R, Mei Hui Yong A, Brizuela J, Hadjicharalambous C, Liu X, Givskov M, Rice SA, Filloux Aet al., 2022, Phenotypic and integrated analysis of a comprehensive Pseudomonas aeruginosa PAO1 library of mutants lacking cyclic-di-GMP-related genes, Frontiers in Microbiology, Vol: 13, ISSN: 1664-302X

Pseudomonas aeruginosa is a Gram-negative bacterium that is able to survive and adapt in a multitude of niches as well as thrive within many different hosts. This versatility lies within its large genome of ca. 6 Mbp and a tight control in the expression of thousands of genes. Among the regulatory mechanisms widely spread in bacteria, cyclic-di-GMP signaling is one which influences all levels of control. c-di-GMP is made by diguanylate cyclases and degraded by phosphodiesterases, while the intracellular level of this molecule drives phenotypic responses. Signaling involves the modification of enzymes’ or proteins’ function upon c-di-GMP binding, including modifying the activity of regulators which in turn will impact the transcriptome. In P. aeruginosa, there are ca. 40 genes encoding putative DGCs or PDEs. The combined activity of those enzymes should reflect the overall c-di-GMP concentration, while specific phenotypic outputs could be correlated to a given set of dgc/pde. This notion of specificity has been addressed in several studies and different strains of P. aeruginosa. Here, we engineered a mutant library for the 41 individual dgc/pde genes in P. aeruginosa PAO1. In most cases, we observed a significant to slight variation in the global c-di-GMP pool of cells grown planktonically, while several mutants display a phenotypic impact on biofilm including initial attachment and maturation. If this observation of minor changes in c-di-GMP level correlating with significant phenotypic impact appears to be true, it further supports the idea of a local vs global c-di-GMP pool. In contrast, there was little to no effect on motility, which differs from previous studies. Our RNA-seq analysis indicated that all PAO1 dgc/pde genes were expressed in both planktonic and biofilm growth conditions and our work suggests that c-di-GMP networks need to be reconstructed for each strain separately and cannot be extrapolated from one to another.

Journal article

Filloux A, 2022, Bacterial protein secretion systems: Game of types, MICROBIOLOGY-SGM, Vol: 168, ISSN: 1350-0872

Journal article

Demmer J, Phillips B, Uhrig L, Filloux A, Allsopp L, Bublitz M, Meier Tet al., 2022, Structure of ATP synthase from ESKAPE pathogen Acinetobacter baumannii, Science Advances, Vol: 8, ISSN: 2375-2548

The global spread of multi-drug resistant Acinetobacter baumannii infections urgently calls for the identification of novel drug targets. We solved the cryo- electron microscopy structure of the F1Fo-ATP synthase from A. baumannii in three distinct conformational states. The nucleotide-converting F1 sub-complex reveals a specific self-inhibition mechanism, which supports a uni-directional ratchet mechanism to avoid wasteful ATP consumption. In the membrane-embedded Fo complex, the structure shows unique structural adaptations along both the entry and exit pathways of the proton-conducting a-subunit. These features, absent in mitochondrial ATP synthases, represent attractive targets for the development of next generation therapeutics that can act directly at the culmination of bioenergetics in this clinically relevant pathogen.

Journal article

Allsopp LP, Collins ACZ, Hawkins E, Wood TE, Filloux Aet al., 2022, RpoN/Sfa2-dependent activation of the Pseudomonas aeruginosa H2-T6SS and its cognate arsenal of antibacterial toxins., Nucleic Acids Research, Vol: 50, Pages: 227-243, ISSN: 0305-1048

Pseudomonas aeruginosa uses three type six secretion systems (H1-, H2- and H3-T6SS) to manipulate its environment, subvert host cells and for microbial competition. These T6SS machines are loaded with a variety of effectors/toxins, many being associated with a specific VgrG. How P. aeruginosa transcriptionally coordinates the main T6SS clusters and the multiple vgrG islands spread through the genome is unknown. Here we show an unprecedented level of control with RsmA repressing most known T6SS-related genes. Moreover, each of the H2- and H3-T6SS clusters encodes a sigma factor activator (SFA) protein called, Sfa2 and Sfa3, respectively. SFA proteins are enhancer binding proteins necessary for the sigma factor RpoN. Using a combination of RNA-seq, ChIP-seq and molecular biology approaches, we demonstrate that RpoN coordinates the T6SSs of P. aeruginosa by activating the H2-T6SS but repressing the H1- and H3-T6SS. Furthermore, RpoN and Sfa2 control the expression of the H2-T6SS-linked VgrGs and their effector arsenal to enable very effective interbacterial killing. Sfa2 is specific as Sfa3 from the H3-T6SS cannot complement loss of Sfa2. Our study further delineates the regulatory mechanisms that modulate the deployment of an arsenal of T6SS effectors likely enabling P. aeruginosa to adapt to a range of environmental conditions.

Journal article

Filloux A, Ramos JL, 2022, Preface, Advances in Experimental Medicine and Biology, Vol: 1386, Pages: v-x, ISSN: 0065-2598

Journal article

Filloux A, Ramos J-L, 2022, <i>Pseudomonas aeruginosa</i> Biology, Pathogenesis and Control Strategies Preface, PSEUDOMONAS AERUGINOSA, Editors: Filloux, Ramos, Publisher: SPRINGER INTERNATIONAL PUBLISHING AG, Pages: V-X, ISBN: 978-3-031-08490-4

Book chapter

Larrouy-Maumus G, Katy J, katheryn H, laurent D, markus K, Filloux A, Plesiat Pet al., 2021, Detection of colistin resistance in Pseudomonas aeruginosa using the MALDIxin test on the routine MALDI Biotyper Sirius mass spectrometer, Frontiers in Microbiology, Vol: 12, ISSN: 1664-302X

Colistin is frequently a last resort treatment for Pseudomonas aeruginosa infections caused by multidrug-resistant (MDR) and extensively drug resistant (XDR) strains, and detection of colistin resistance is essential for the management of infected patients. Therefore, we evaluated the recently developed MALDIxin test for the detection of colistin resistance in Pseudomonas aeruginosa clinical strains using the routine matrix-assisted laser desorption ionization (MALDI) Biotyper Sirius system. The test is based on the detection by mass spectrometry of modified lipid A by the addition of 4-amino-L-arabinose (L-ara4N) molecules on one or two phosphate groups, in strains resistant to colistin. Overproduction of L-Ara4N molecules is mainly due to the constitutive activation of the histidine kinase (PmrB) or the response regulator (PmrA) following an amino-acid substitution in clinical strains. The performance of the test was determined on a panel of 14 colistin-susceptible and 14 colistin-resistant Pseudomonas aeruginosa clinical strains, the reference strain PAO1 and positive control mutants PmrB (V28G), PmrB (D172), PhoQ (D240-247) and ParR (M59I). In comparison with the broth microdilution (BMD) method, all the susceptible strains (n=14) and 8/14 colistin-resistant strains were detected in less than 1 hour, directly on whole bacteria. The remaining resistant strains (n=6) were all detected after a short pre-exposure (4h) to colistin before sample preparation. Validation of the method on a larger panel of strains will be the next step before its use in diagnostics laboratories. Our data showed that the MALDIxin test offers rapid and efficient detection of colistin resistant Pseudomonas aeruginosa and is thus a valuable diagnostics tool to control the spread of these emerging resistant strains.

Journal article

Nolan LM, Cain AK, Clamens T, Furniss RCD, Manoli E, Sainz-Polo MA, Dougan G, Albesa-Jove D, Parkhill J, Mavridou DAI, Filloux Aet al., 2021, Identification of tse8 as a type VI secretion system toxin from pseudomonas aeruginosa that targets the bacterial transamidosome to inhibit protein synthesis in prey cells, Nature Microbiology, Vol: 6, Pages: 1199-+, ISSN: 2058-5276

The Type VI secretion system (T6SS) is a bacterial nanomachine that delivers toxic effectors to kill competitors or subvert some of their key functions. Here, we use transposon directed insertion–site sequencing to identify T6SS toxins associated with the H1-T6SS, one of the three T6SS machines found in Pseudomonas aeruginosa. This approach identified several putative toxin–immunity pairs, including Tse8–Tsi8. Full characterization of this protein pair demonstrated that Tse8 is delivered by the VgrG1a spike complex into prey cells where it targets the transamidosome, a multiprotein complex involved in protein synthesis in bacteria that lack either one, or both, of the asparagine and glutamine transfer RNA synthases. Biochemical characterization of the interactions between Tse8 and the transamidosome components GatA, GatB and GatC suggests that the presence of Tse8 alters the fine-tuned stoichiometry of the transamidosome complex, and in vivo assays demonstrate that Tse8 limits the ability of prey cells to synthesize proteins. These data expand the range of cellular components targeted by the T6SS by identifying a T6SS toxin affecting protein synthesis and validate the use of a transposon directed insertion site sequencing–based global genomics approach to expand the repertoire of T6SS toxins in T6SS-encoding bacteria.

Journal article

Demmer JK, Phillips BP, Uhrig OL, Filloux A, Allsopp LP, Bublitz M, Meier Tet al., 2021, Structure of ATP synthase from ESKAPE pathogen <i>Acinetobacter baumannii</i>

<jats:title>Abstract</jats:title><jats:p><jats:italic>Acinetobacter baumannii</jats:italic> is a clinically relevant pathogen which causes multi-drug resistant, hospital-acquired infections and is a top priority target for antibiotic development. <jats:italic>Cryo</jats:italic>-EM structures of the <jats:italic>A. baumannii</jats:italic> F<jats:sub>1</jats:sub>F<jats:sub>o</jats:sub>-ATP synthase in three conformational states reveal unique features, which represent attractive sites for the development of novel therapeutics.</jats:p><jats:sec><jats:title>One sentence summary</jats:title><jats:p>Structure of Acinetobacter baumannii ATP synthase</jats:p></jats:sec>

Working paper

Howard SA, Furniss RCD, Bonini D, Amin H, Paracuellos P, Zlotkin D, R D Costa T, Levy A, A I Mavridou D, Filloux Aet al., 2021, The breadth and molecular basis of Hcp-driven type six secretion system (T6SS) effector delivery, mBio, Vol: 12, Pages: 1-19, ISSN: 2150-7511

The type VI secretion system (T6SS) is a bacterial nanoscale weapon that delivers toxins into prey ranging from bacteria and fungi to animal hosts. The cytosolic contractile sheath of the system wraps around stacked hexameric rings of Hcp proteins, which form an inner tube. At the tip of this tube is a puncturing device comprising a trimeric VgrG topped by a monomeric PAAR protein. The number of toxins a single system delivers per firing event remains unknown, since effectors can be loaded on diverse sites of the T6SS apparatus, notably the inner tube and the puncturing device. Each VgrG or PAAR can bind one effector, and additional effector cargoes can be carried in the Hcp ring lumen. While many VgrG- and PAAR-bound toxins have been characterized, to date, very few Hcp-bound effectors are known. Here, we used 3 known Pseudomonas aeruginosa Hcp proteins (Hcp1 to -3), each of which associates with one of the three T6SSs in this organism (H1-T6SS, H2-T6SS, and H3-T6SS), to perform in vivo pulldown assays. We confirmed the known interactions of Hcp1 with Tse1 to -4, further copurified a Hcp1-Tse4 complex, and identified potential novel Hcp1-bound effectors. Moreover, we demonstrated that Hcp2 and Hcp3 can shuttle T6SS cargoes toxic to Escherichia coli. Finally, we used a Tse1-Bla chimera to probe the loading strategy for Hcp passengers and found that while large effectors can be loaded onto Hcp, the formed complex jams the system, abrogating T6SS function.

Journal article

Steinchen W, Ahmad S, Valentini M, Eilers K, Majkini M, Altegoer F, Lechner M, Filloux A, Whitney JC, Bange Get al., 2021, Dual role of a (p)ppGpp- and (p)ppApp-degrading enzyme in biofilm formation and interbacterial antagonism, Molecular Microbiology, Vol: 115, Pages: 1339-1356, ISSN: 0950-382X

The guanosine nucleotide‐based second messengers ppGpp and pppGpp (collectively: (p)ppGpp) enable adaptation of microorganisms to environmental changes and stress conditions. In contrast, the closely related adenosine nucleotides (p)ppApp are involved in type VI secretion system (T6SS)‐mediated killing during bacterial competition. Long RelA‐SpoT Homolog (RSH) enzymes regulate synthesis and degradation of (p)ppGpp (and potentially also (p)ppApp) through their synthetase and hydrolase domains, respectively. Small alarmone hydrolases (SAH) that consist of only a hydrolase domain are found in a variety of bacterial species, including the opportunistic human pathogen Pseudomonas aeruginosa. Here, we present the structure and mechanism of P. aeruginosa SAH showing that the enzyme promiscuously hydrolyses (p)ppGpp and (p)ppApp in a strictly manganese‐dependent manner. While being dispensable for P. aeruginosa growth or swimming, swarming, and twitching motilities, its enzymatic activity is required for biofilm formation. Moreover, (p)ppApp‐degradation by SAH provides protection against the T6SS (p)ppApp synthetase effector Tas1, suggesting that SAH enzymes can also serve as defense proteins during interbacterial competition.

Journal article

Bernal P, Furniss CD, Fecht S, Leung RCY, Spiga L, Mavridou DAI, Filloux ALAINet al., 2021, A novel stabilization mechanism for the type VI secretion system sheath, Proceedings of the National Academy of Sciences of USA, Vol: 118, ISSN: 0027-8424

The type VI secretion system (T6SS) is a phage-derived contractile nanomachine primarily involved in interbacterial competition. Its pivotal component, TssA, is indispensable for the assembly of the T6SS sheath structure, the contraction of which propels a payload of effector proteins into neighboring cells. Despite their key function, TssA proteins exhibit unexpected diversity and exist in two major forms, a short form (TssAS) and a long form (TssAL). While TssAL proteins interact with a partner, called TagA, to anchor the distal end of the extended sheath, the mechanism for the stabilization of TssAS-containing T6SSs remains unknown. Here we discover a class of structural components that interact with short TssA proteins and contribute to T6SS assembly by stabilizing the polymerizing sheath from the baseplate. We demonstrate that the presence of these components is important for full sheath extension and optimal firing. Moreover, we show that the pairing of each form of TssA with a different class of sheath stabilization proteins results in T6SS apparatuses that either reside in the cell for some time or fire immediately after sheath extension. We propose that this diversity in firing dynamics could contribute to the specialization of the T6SS to suit bacterial lifestyles in diverse environmental niches.

Journal article

Lossi NS, Manoli E, Foerster A, Dajani R, Pape T, Freemont P, Filloux Aet al., 2021, The HsiB1C1 (TssB-TssC) complex of the pseudomonas aeruginosa Type VI secretion system forms a bacteriophage tail sheathlike structure, Journal of Biological Chemistry, Vol: 288, Pages: 7536-7548, ISSN: 0021-9258

Protein secretion systems in Gram-negative bacteria evolved into a variety of molecular nanomachines. They are related to cell envelope complexes, which are involved in assembly of surface appendages or transport of solutes. They are classified as types, the most recent addition being the type VI secretion system (T6SS). The T6SS displays similarities to bacteriophage tail, which drives DNA injection into bacteria. The Hcp protein is related to the T4 bacteriophage tail tube protein gp19, whereas VgrG proteins structurally resemble the gp27/gp5 puncturing device of the phage. The tube and spike of the phage are pushed through the bacterial envelope upon contraction of a tail sheath composed of gp18. In Vibrio cholerae it was proposed that VipA and VipB assemble into a tail sheathlike structure. Here we confirm these previous data by showing that HsiB1 and HsiC1 of the Pseudomonas aeruginosa H1-T6SS assemble into tubules resulting from stacking of cogwheel-like structures showing predominantly 12-fold symmetry. The internal diameter of the cogwheels is ∼100 Å, which is large enough to accommodate an Hcp tube whose external diameter has been reported to be 85 Å. The N-terminal 212 residues of HsiC1 are sufficient to form a stable complex with HsiB1, but the C terminus of HsiC1 is essential for the formation of the tubelike structure. Bioinformatics analysis suggests that HsiC1 displays similarities to gp18-like proteins in its C-terminal region. In conclusion, we provide further structural and mechanistic insights into the T6SS and show that a phage sheathlike structure is likely to be a conserved element across all T6SSs.

Journal article

Brinkman FSL, Winsor GL, Done RE, Filloux A, Francis VI, Goldberg JB, Greenberg EP, Han K, Hancock REW, Haney CH, Haeussler S, Klockgether J, Lamont IL, Levesque RC, Lory S, Nikel PI, Porter SL, Scurlock MW, Schweizer HP, Tuemmler B, Wang M, Welch Met al., 2021, The Pseudomonas aeruginosa whole genome sequence: A 20th anniversary celebration, ADVANCES IN MICROBIAL PHYSIOLOGY, VOL 79, Vol: 79, Pages: 25-88, ISSN: 0065-2911

Journal article

Lin H-H, Filloux A, Lai E-M, 2020, Role of recipient susceptibility factors during contact-dependent interbacterial competition, Frontiers in Microbiology, Vol: 11, Pages: 1-15, ISSN: 1664-302X

Bacteria evolved multiple strategies to survive and develop optimal fitness in their ecological niche. They deployed protein secretion systems for robust and efficient delivery of antibacterial toxins into their target cells, therefore inhibiting their growth or killing them. To maximize antagonism, recipient factors on target cells can be recognized or hijacked to enhance the entry or toxicity of these toxins. To date, knowledge regarding recipient susceptibility (RS) factors and their mode of action is mostly originating from studies on the type Vb secretion system that is also known as the contact-dependent inhibition (CDI) system. Yet, recent studies on the type VI secretion system (T6SS), and the CDI by glycine-zipper protein (Cdz) system, also reported the emerging roles of RS factors in interbacterial competition. Here, we review these RS factors and their mechanistic impact in increasing susceptibility of recipient cells in response to CDI, T6SS, and Cdz. Past and future strategies for identifying novel RS factors are also discussed, which will help in understanding the interplay between attacker and prey upon secretion system-dependent competition. Understanding these mechanisms would also provide insights for developing novel antibacterial strategies to antagonize aggressive bacteria-killing pathogens.

Journal article

Sarah Wettstadt S, Lai E-M, Filloux AAM, 2020, Solving the puzzle: connecting a heterologous Agrobacterium tumefaciens T6SS effector to a Pseudomonas aeruginosa spike complex, Frontiers in Cellular and Infection Microbiology, Vol: 10, ISSN: 2235-2988

The type VI secretion system (T6SS) is a contractile injection apparatus that translocates a spike loaded with various effectors directly into eukaryotic and prokaryotic target cells. Such T6SS spike consists of a needle-shaped trimer of VgrG proteins topped by a conical and sharp PAAR protein that facilitates puncturing of the target membrane. T6SS-delivered effector proteins can be either fused to one of the two spike proteins or interact with either in a highly specific manner. In Agrobacterium tumefaciens the T6SS effector Tde1 is targeted to its cognate VgrG1 protein. Here, we attempted to use a VgrG shuttle to deliver a heterologous T6SS effector by directing Tde1 onto a T6SS spike in Pseudomonas aeruginosa. For this, we designed chimeras between VgrG1 from A. tumefaciens and VgrG1a from P. aeruginosa and showed that modification of the spike protein hampered T6SS functionality in the presence of the Tde1 effector complex. We provide evidence suggesting that Tde1 specifically binds to the VgrG spike in the heterologous environment and propose that there are additional requirements to allow proper effector delivery and translocation. Our work sheds light on complex aspects of the molecular mechanisms of T6SS delivery and highlights some limitations on how effectors can be translocated using this nanomachine.

Journal article

Larrouy-Maumus G, Dortet L, Filloux A, bonnin, le hello, bonnet, kostrzewaet al., 2020, Detection of colistin resistance in Salmonella enterica using MALDIxin test on the routine MALDI Biotyper Sirius mass spectrometer, Frontiers in Microbiology, Vol: 11, Pages: 1-6, ISSN: 1664-302X

Resistance to polymyxins in most Gram-negative bacteria arises from chemical modifications to the lipid A portion of their lipopolysaccharide (LPS) mediated by chromosomally-encoded mutations or the recently discovered plasmid-encoded mcr genes that have further complicated the landscape of colistin resistance. Currently, minimal inhibitory concentration (MIC) determination by broth microdilution, the gold standard for the detection of polymyxin resistance, is time consuming (24 hours) and challenging to perform in clinical and veterinatryveterinary laboratories. Here we present the use of the MALDIxin to detect colistin resistant Salmonella enterica using the MALDxin test on the routine matrix-assisted laser desorption ionization (MALDI) Biotyper Sirius system.

Journal article

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