Biology subjects

Rocha, E. P. C.

Publications and source records attributed to Rocha, E. P. C..

At least 19 recordsLinked to original sources

bioRxiv2026

Unveiling a missing component of the atypical type IV secretion system required for natural transformation of Helicobacter pylori

Exchange of genetic information by natural transformation shapes bacterial evolution. In Helicobacter pylori it is thought to drive its unusually high recombination rate, which has a crucial role in the evolution of virulence and the propagation of antibiotics resistance genes. While in most cases uptake of the incoming DNA into the periplasm is mediated by type IV pili, in H. pylori this initial step of natural transformation requires ComB, a unique competence-specific type IV secretion system (T4SS). The mechanisms by which ComB mediates DNA uptake are still poorly understood, since T4SS are usually involved in an opposite process of DNA export. Here, we identify a gene (hp1421) that is absolutely required for uptake of the transforming DNA into the periplasm, although distant from the comB operons. We show that hp1421 codes for a hexameric ATPase from the VirB11 family. HP1421 is present in the cytoplasm and interacts with ComB4, another ATPase of the T4SS inner membrane subcomplex. The structural modelling and functional analysis of HP1421 and its interaction with ComB4 indicate that HP1421 is a missing component of the ComB inner-membrane subcomplex that we propose to name ComB11. Phylogenetic analyses show that comB11 is a H. pylori core gene and suggest that the competence-dedicated ComB T4SS was a recent acquisition within Helicobacteraceae. Hence, co-option of the T4SS for DNA transformation requires nearly all the proteins that were previously essential for DNA conjugation. Author SummaryThe capacity of bacteria to exchange genetic information contributes in the case of pathogens to the spreading of antibiotic resistance and virulence factors. For Helicobacter pylori, a Gram-negative pathogen that colonises about half of the world population and is at the origin of diseases such as ulcers and gastric cancers, natural transformation is the major mechanism of horizontal gene transfer. However, H. pylori uses a very unusual system to capture and internalise the foreign DNA. Indeed, a Type 4 secretion system mediates this process. Here, we identify a so far missing and essential component of the T4SS, coded by a gene distant from the operon coding the other subunits. Through a combination of structural modelling, biochemical and microscopy approaches we show that this ATPase is an indispensable part of the ComB T4SS. Our study provides new insights into the mechanism by which the peculiar ComB T4SS works backwards to allow the passage of the tDNA from the bacterial environment into the periplasm.

microbiology↗

bioRxiv2026

Rapid modular evolution of antiviral repertoires in P2 phages and their P4 satellites: shuttling, swapping and mixing

Interactions between bacteria, bacteriophages, and their satellites are shaped by a myriad of defence and counter-defence mechanisms. Here, we identified and characterized the defence hotspots of thousands of P2-like phages and P4-like satellites to elucidate the origins and evolutionary dynamics of defence systems. Both P4 and P2 encode a broad diversity of recognizable defence systems. Defences are a substantial, yet likely underestimated, share of the elements pangenomes, as shown by novel antiviral functions discovered in P4 loci lacking known defence genes. Defence loci are very rapidly swapped, without pseudogenization, suggesting defences are replaced before becoming non-adaptive. This intense local recombination melds components of distinct systems into novel functional chimeras. Systems swap so rapidly that many elements with identical core genes have completely different defences. Surprisingly, despite P4 and P2s concomitant replication and packaging, they almost never exchange defence genes. In contrast, near identical defence systems can be found in distinct types of MGEs and in cryptic chromosomal locations. Our findings highlight P4 and P2 as mobile platforms driving the modular diversification of bacterial antiviral repertoires. Hence, bacterial defences change quickly by phage and satellite turnover, and by the quick swap of defences within these elements.

microbiology↗

bioRxiv2026

Genomic Islands as minimal hitchers of conjugative elements

Bacterial chromosomes contain Genomic Islands carrying genes involved in virulence, mutualism, and resistance to antibiotics that are transferred horizontally. Some of them conjugate autonomously (Integrative Conjugative Elements, ICEs), while others use relaxases to hitch on the formers conjugation machinery (Integrative Mobilizable Elements, IMEs). Yet, the mobility mechanism of most Genomic Islands remains elusive. Here, we explore the hypothesis that many carry origins of transfer (oriTs) by conjugation. Since very few known oriTs were found in ICEs and IMEs, we identified 52 novel families of oriTs that cover most integrative elements in 6 major nosocomial species. Most of these oriTs are specific to integrative elements, suggesting a clear split in the targets of hitchers of conjugative elements between plasmids and integrative elements. Among 7,363 Genomic Islands, we discovered more than 1,500 IMEs carrying an oriT and lacking relaxases and MPF systems. These elements, coined iOriTs, form diverse large ancient families that can be found in different species. These hitchers are genetically unrelated to the putative helpers, beyond the similarity at the oriT sequence, and often outnumber them. They include well-known pathogenicity islands, for which the mechanisms of mobility remained unknown. Unlike plasmids, iOriTs have few antibiotic resistance genes, but high density of virulence factors. Like plasmids, the vicinity of oriTs concentrates defense and counter-defense systems potentially favoring Genomic Islands dissemination. Hence, iOriTs are frequent integrative mobile genetic elements that evolved to transfer horizontally by hitching on other elements while contributing to bacterial genetic adaptation.

microbiology↗

bioRxiv2026

Interplay between mobile genetic elements drives a fusion-deletion life cycle of plasmids to fuel antimicrobial resistance

Plasmids are key drivers of bacterial adaptation, yet the mechanisms that generate their diversity remain poorly understood. Here, we show that mobile genetic elements (MGEs) orchestrate a fusion-deletion life cycle that repeatedly remodels plasmids during evolution in Staphylococcus aureus. Large-scale genomic analyses reveal that multireplicon plasmids are widespread and strongly enriched in transposases. Using experimental assays, we demonstrate that rare MGE-mediated fusion events, via homologous recombination or transposition, combine distinct plasmids into single multireplicon elements, expanding gene content and transfer potential. Antibiotic pressure selectively enriches these fused plasmids, rescuing bacterial populations under stress, whereas opposing selective forces, including phage predation, favour deletion derivatives that preserve essential functions and phage transmissibility. This cyclical process generates dynamic plasmid repertoires with conserved backbones and diverse accessory modules. We propose that MGE-driven fusion-deletion cycles represent a general principle of plasmid evolution, explaining the rapid emergence and persistence of multidrug-resistant plasmids across bacterial pathogens.

microbiology↗

bioRxiv2025

Serotype swapping in Klebsiella spp. by plug-and-play

Understanding how complex, multi-gene systems evolve and function across genetic backgrounds is a central question in molecular evolution. While such systems often impose costs through epistatic interactions, some may behave as modular, "plug-and-play" units that retain function with minimal disruption. We used the polysaccharide capsule locus of Klebsiella pneumoniae, a highly exchangeable and fast-evolving locus, as a model. We genetically engineered capsule exchanges (swaps) across diverse genetic backgrounds and combined transcriptomics, fitness assays, and evolution experiments, to show that capsule exchange has negligible effects on global expression and only marginal fitness costs, regardless of serotype. Adaptation to capsule-costly environments consistently reduced capsule production, regardless of serotype, revealing shared adaptive trajectories rather than serotype-specific pathways. Moreover, serotype-specific traits involved in bacterial virulence, such as biofilm formation and hypermucoviscosity, were conserved across genetic backgrounds. This reveals that capsule swapping can directly shape host-pathogen interactions and influence within-patient evolution. Our findings provide strong evidence that capsule loci display plug-and-play dynamics: they are transferable, functional across contexts, and minimally disruptive to the host genome. This allows capsules to be seamlessly swapped, and help explain the evolutionary success, ecological versatility, and pervasive exchangeability of capsules in K. pneumoniae.

evolutionary biology↗

bioRxiv2025

Efficient detection and typing of phage-plasmids

Phage-plasmids are temperate phages that replicate as plasmids during lysogeny. Despite their high diversity, they carry genes similar to phages and plasmids. This leads to gene exchanges, and to the formation of hybrid or defective elements, which limits accurate detection of phage-plasmids. To address this challenge, we present tyPPing, an easy-to-use method that efficiently detects and types phage-plasmids with high accuracy. It searches for distinct frequencies and sets of conserved proteins to separate phage-plasmids from plasmids and phages. tyPPings strength comes from both its precise predictions and its ability to systematically type phage-plasmids, including the assignment of confidence levels. We tested tyPPing on current databases and a collection of incomplete (draft) genomes. While predictions rely on the quality of assemblies, we detected high-quality phage-plasmids and experimentally proved them to be functional. Compared to other classification methods, tyPPing is designed to detect distinct types of phage-plasmids, and surpasses other tools in terms of sensitivity and scalability. Phage-plasmids are highly diverse, making the systematic identification of new types a difficult task. By combining tyPPing with other tools, however, we show a valuable foundation for addressing this challenge.

genomics↗

bioRxiv2025

Capsular specificity in temperate phages of Klebsiella pneumoniae is driven by diverse receptor-binding enzymes

In bacteriophages infecting Klebsiella pneumoniae, capsule specificity is a major determinant of host range due to the presence of capsule-specific depolymerases. Yet for temperate phages, the genetic and functional basis of this specificity remains less well understood. Depolymerases appear unexpectedly rare in prophage genomes, raising unresolved questions about which prophage genes mediate capsule tropism, whether this apparent scarcity reflects biological or ecological differences versus annotation limits, and whether prophage-encoded receptor-binding proteins (RBPs) are functionally active. To address these questions, we analysed 3,900 Klebsiella genomes from diverse ecological niches to identify prophage-encoded proteins mediating capsule tropism. We conducted a genome-wide association study (GWAS) correlating prophage protein clusters (from 8,105 prophages) with confidently assigned bacterial K-loci. GWAS identified high-confidence predictors for 16 out of 35 most diverse K-loci, of which 14 were receptor-binding proteins (RBPs) belonging to classical depolymerases (n = 6), SGNH hydrolases which deacetylate polysaccharides (n = 6), and structurally novel RBPs (n = 2). Overall, we predicted K-locus specificity for 26 putative depolymerases, of which 12 were deemed as strong predictions against 10 K-loci. In parallel, we attempted recombinant production of 50 putative depolymerases selected from 469 candidate proteins identified in prophages from a representative subset of 99 bacterial isolates, together with an additional 10 depolymerases selected based on GWAS predictions. All recombinant proteins were tested against a Klebsiella reference panel of 119 K-types. Of the 50 manually chosen putative depolymerases, 34 failed to yield detectable recombinant expression, a pattern unlikely to be explained by degraded or defective prophages. Of the 14 active enzymes, 5 targeted a K-locus different from that of their bacterial host, and enzyme specificity could not always be reliably inferred from sequence similarity or structural homology. Comparison of GWAS predictions with experimental validation results revealed that 10 of the 12 strongest GWAS predictors were confirmed experimentally, while 2 produced soluble protein but showed no detectable activity against the tested K-types. Together, these results highlight the intrinsic difficulty of predicting activity and capsule specificity of prophage-encoded RBPs from genomic information alone. Finally, analysis of 4,598 high-completeness prophages revealed that SGNH-domain hydrolases are among the most prevalent enzymatic domains in prophage RBPs. Two SGNH-domain RBPs identified by GWAS were experimentally confirmed as active esterases, supporting capsule deacetylation as a widespread alternative to polysaccharide depolymerisation in temperate phages. Our findings reveal that Klebsiella prophages encode structurally diverse RBPs, suggesting temperate phages may rely not only on depolymerisation but also on capsule modification--such as deacetylation--for infection. This also implies that capsule diversity in K. pneumoniae may be substantially underestimated, with implications for phage specificity, competition and vaccine design.

microbiology↗

bioRxiv2025

Impact of natural transformation on the acquisition of novel genes in bacteria

Natural transformation is the only process of gene exchange under the exclusive control of the recipient bacteria. It has often been considered as a source of novel genes but quantitative assessments of this claim are lacking. To investigate the potential role of natural transformation in gene acquisition, we analysed a large collection of genomes of Acinetobacter baumannii (Ab) and Legionella pneumophila (Lp) for which transformation rates were experimentally determined. Natural transformation rates are weakly correlated with genome size. But they are negatively associated with gene flow in both species. This might result from a negative balance between transformations ability to cure the chromosome from mobile genetic elements (MGEs), resulting in gene loss, and its facilitation of gene acquisition. By focusing on the latter, we found that transformation was significantly associated with small gene acquisition events while MGEs-driven gene acquisition tend to be associated with larger ones. Events of gene gain by transformation were spread more evenly in the chromosome than MGEs encoding the ability to integrate autonomously. We estimated the contribution of natural transformation to gene gains by comparing recombination-driven gene acquisition rates between transformable and non-transformable strains. Natural transformation may have caused the acquisition of up to 6.4% (Ab) and 1.1% (Lp) of the novel genes. This low contribution of natural transformation to the acquisition of novel genes implies that most novel genes must have been acquired by other means. Interestingly, the ones potentially acquired by transformation include almost 15% of the recently acquired antibiotic resistance genes in A. baumannii. Hence, natural transformation may drive the acquisition of relatively few novel genes but these may have a high fitness impact.

genomics↗

bioRxiv2025

Persistent virulent phages exist in bacterial isolates

Despite the immense diversity of tailed bacteriophages, they are traditionally classified as either virulent or temperate, with only the latter thought capable of long-term persistence in bacterial cells through lysogeny. Virulent phages, characterized by their obligatory lytic cycle, are assumed to lack the ability to persist within bacterial colonies, and their infection is expected to decimate the host population under in-vitro conditions. Consequently, when bacterial isolates are cultured for sequencing, the resulting assemblies are not expected to contain virulent phage genomes. To test this assumption on a large scale, we analyzed over 267,000 publicly available Escherichia assemblies. Surprisingly, we identified 373 genomes corresponding to virulent phages within the bacterial genomes. These viral genomes are associated with specific phage groups and especially with jumbo phages with very large genomes (>200 kb). Chimallin was a core gene in two of these jumbo phage clusters, the major protein used by some jumbo phages to form a protective phage nucleus during infection. We found multiple lines of evidence suggesting that these virulent phage genomes in bacterial assemblies arise from persistent infections rather than contamination. Supporting this, we experimentally demonstrated the coexistence of non-temperate jumbo phages with their bacterial hosts. In a targeted follow-up search for three clades of persistent jumbo phages, we identified 285 additional jumbo phage genomes in bacterial taxa beyond Escherichia, highlighting that there are many more undiscovered persistent phages in bacterial assemblies. Our findings challenge the traditional virulent-temperate dichotomy, highlighting the overlooked diversity and prevalence of non-canonical phage lifestyles.

microbiology↗

bioRxiv2024

Plasmid-chromosome transcriptional crosstalk in multidrug resistant clinical enterobacteria

Conjugative plasmids promote the dissemination and evolution of antimicrobial resistance in bacterial pathogens. However, plasmid acquisition can produce physiological alterations in the bacterial host, leading to potential fitness costs that determine the clinical success of bacteria-plasmid associations. In this study, we used a transcriptomic approach to characterize the interactions between a globally disseminated carbapenem resistance plasmid, pOXA-48, and a diverse collection of multidrug resistant clinical enterobacteria. Although pOXA-48 produced mostly strain-specific transcriptional alterations, it also led to the common overexpression of a small chromosomal operon present in Klebsiella spp. and Citrobacter freundii strains. This operon included two genes coding for a pirin and an isochorismatase family proteins (pfp and ifp), and showed evidence of horizontal mobilization across Proteobacteria species. Combining genetic engineering, transcriptomics, and CRISPRi gene silencing, we showed that a pOXA-48-encoded LysR regulator is responsible for the plasmid-chromosome crosstalk. Crucially, the operon overexpression produced a fitness benefit in a pOXA-48-carrying K. pneumoniae clinical strain, suggesting that this crosstalk promotes the dissemination of carbapenem resistance in clinical settings.

microbiology↗

bioRxiv2024

The spread of antibiotic resistance is driven by plasmids amongst the fastest evolving and of broadest host range

Microorganisms endure novel challenges for which other microorganisms in other biomes may have already evolved solutions. This is the case of nosocomial bacteria under antibiotic therapy because antibiotics are of ancient natural origin and resistances to them have previously emerged in environmental bacteria. In such cases, the rate of adaptation crucially depends on the acquisition of genes by horizontal transfer of plasmids from distantly related bacteria in different biomes. We hypothesized that such processes should be driven by plasmids amongst the most mobile and evolvable. We confirmed these predictions by showing that plasmid families encoding antibiotic resistance are very mobile, have broad host ranges, while showing higher rates of homologous recombination and faster turnover of gene repertoires than the other plasmids. These characteristics remain outstanding when we remove resistance plasmids from our dataset, suggesting that antibiotic resistance genes are preferentially acquired and carried by plasmid families that are intrinsically very mobile and plastic. Evolvability and mobility facilitate the transfer of antibiotic resistance, and presumably of other phenotypes, across distant taxonomic groups and biomes. Hence, plasmid families, and possibly those of other mobile genetic elements, have differentiated and predictable roles in the spread of novel traits.

evolutionary biology↗

bioRxiv2024

A mechanistic step in the genesis of secondary chromosomes from plasmids

Bacterial genomes contain a plethora of secondary replicons of divergent size. Circular replicons must carry a system for resolving dimeric forms, resulting from recombination between sister copies. These systems use site-specific recombinases. Among these, the XerCD recombinase resolves dimers of chromosomes and certain plasmids using different controls. We have analyzed the dimer resolution functions in enterobacterial secondary replicons and show that, in addition to the main chromosomes, XerCD is preferentially used by small plasmids and by the largest secondary replicons, megaplasmids and secondary chromosomes. Indeed, all replicons longer than 250 kb host an active XerCD recombination site. These sites, in contrast to those of small plasmids, use the same control as chromosomes, coupled to cell division by the FtsK protein. We conclude that a chromosome-like mode of dimer resolution is mandatory for the faithful inheritance of large plasmids and chromids, its acquisition being a prerequisite for the genesis of secondary chromosomes from plasmids.

microbiology↗

bioRxiv2024

YraN is a helicase-associated nuclease fostering extended recombination events by natural transformation

Natural transformation is a widespread mechanism driving genetic exchanges in bacteria. It proceeds by the capture and internalization of exogenous DNA in linear single strands, ultimately integrated in the genome by homologous recombination. It is unknown how the RecA-directed D-loop intermediate of this dedicated recombination pathway is processed. We report that resolution of the transformation D-loop depends on two endonucleases of opposing phylogenetic distribution in bacteria. One is YraN, which has co-evolved and interacts with the ComM helicase, known to extend DNA recombination at the transformation D-loop. The other is CoiA, which is restricted to the Bacillota. CoiA is shown to be a resolvase of the transformation D-loop, extended by the RadA helicase in these species. We demonstrate that both YraN and CoiA act synergistically with their cognate helicases. These findings reveal that bacteria have evolved two helicase/nuclease pairs for the maturation and recombination extension of the transformation D-loop.

microbiology↗

bioRxiv2024

Reference-free Structural Variant Detection inMicrobiomes via Long-read Coassembly Graphs

Bacterial genome dynamics are vital for understanding the mechanisms underlying microbial adaptation, growth, and their broader impact on host phenotype. Structural variants (SVs), genomic alterations of 10 base pairs or more, play a pivotal role in driving evolutionary processes and maintaining genomic heterogeneity within bacterial populations. While SV detection in isolate genomes is relatively straightforward, metagenomes present broader challenges due to absence of clear reference genomes and presence of mixed strains. In response, our proposed method rhea, forgoes reference genomes and metagenome-assembled genomes (MAGs) by encompassing a single metagenome coassembly graph constructed from all samples in a series. The log fold change in graph coverage between subsequent samples is then calculated to call SVs that are thriving or declining throughout the series. We show rhea to outperform existing methods for SV and horizontal gene transfer (HGT) detection in two simulated mock metagenomes, which is particularly noticeable as the simulated reads diverge from reference genomes and an increase in strain diversity is incorporated. We additionally demonstrate use cases for rhea on series metagenomic data of environmental and fermented food microbiomes to detect specific sequence alterations between subsequent time and temperature samples, suggesting host advantage. Our innovative approach leverages raw read patterns rather than references or MAGs to include all sequencing reads in analysis, and thus provide versatility in studying SVs across diverse and poorly characterized microbial communities for more comprehensive insights into microbial genome dynamics.

bioinformatics↗

bioRxiv2024

Identification of novel origins of transfer across bacterial plasmids

Conjugative plasmids are important drivers of bacterial evolution, but most plasmids lack genes for conjugation. It is currently not known if the latter can transfer because origins of transfer by conjugation (oriT), which would allow their mobilization by conjugative plasmids, are poorly known. Here, we identify and characterize occurrences of known oriT families across thousands of plasmids confirming that most conjugative and mobilizable plasmids still lack identifiable families of oriTs. They reveal clear patterns in terms of intergenic position, distance to the relaxases, and MOB-type association. This allowed to develop a computational method to discover novel oriTs. As a proof of concept, we identify 21 novel oriTs from the nosocomial pathogens Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii, some of them responsible for the mobility of critical antimicrobial resistance genes. These 21 oriT families share key characteristics of the others and fill most of the missing diversity of oriTs in relaxase-encoding plasmids both in terms of frequency and phylogeny. We confirmed experimentally the function of six of them. The ability to identify novel oriTs paves the way to explore conjugation across bacterial plasmids, notably among the majority lacking conjugation-related genes.

microbiology↗

bioRxiv2023

Intragenomic conflicts with plasmids and chromosomal mobile genetic elements drive the evolution of natural transformation within species

Natural transformation is the only mechanism of genetic exchange controlled by the recipient bacteria. We quantified its rates in 1282 strains of the human pathogens Legionella pneumophila (Lp) and Acinetobacter baumannii (Ab) and found that transformation rates evolve by large quick changes as a jump process across six orders of magnitude. Close to half of the strains are non-transformable in standard conditions. Transitions to non-transformability were frequent and recent, suggesting that they are deleterious and subsequently purged by natural selection. Accordingly, we find that transformation decreases genetic linkage in both species, which often accelerates adaptation. Intragenomic conflicts with chromosomal mobile genetic elements (MGEs) and plasmids could explain these transitions and a GWAS confirmed systematic negative associations between transformation and MGEs: plasmids and other conjugative elements in Lp, prophages in Ab, and transposable elements in both. In accordance with the modulation of transformation rates by genetic conflicts, transformable strains have fewer MGEs. Defense systems against the latter are associated with lower transformation except the adaptive CRISPR-Cas systems which show the inverse trend. The two species have different lifestyles and gene repertoires, but they exhibit very similar trends in terms of variation of transformation rates and its determinants, suggesting that genetic conflicts could drive the evolution of natural transformation in many bacteria.

genomics↗

bioRxiv2023

Phage-plasmids promote genetic exchanges between phages and plasmids and create novel ones.

Phages and plasmids have key roles in bacterial evolution and are usually very different. Yet, they must recombine, since they sometimes carry nearly identical accessory genes. Phage-plasmids are both plasmids and phages and we found they connect them by being at their interface in the network of gene repertoire relatedness. We searched for recombining genes in all three types of elements and found that phage-plasmid exchange rates are between those of plasmids (highest) and phages (lowest). Phage-plasmids drive gene flow between phages and plasmids, including that of antibiotic resistances and defense systems. Genetic exchanges and gene inactivation resulted in P1-like phage-plasmids turning into integrative prophages or just plasmids. The latter acquired conjugation-related functions thereby transitioning from viral to conjugation-driven horizontal transfer. Phage-plasmids have thus a key role in spreading traits across mobile genetic elements and their hosts, while facilitating conversions of one type of element into another.

genomics↗

bioRxiv2023

Emergence of novel non-aggregative variants under negative frequency-dependent selection in Klebsiella variicola

Klebsiella variicola is an emergent human pathogen causing diverse infections, including in the urinary tract. However, little is known about the evolution and maintenance of genetic diversity in this species, the molecular mechanisms and their population dynamics. Here, we characterized the emergence of a novel rdar-like morphotype which is contingent both on the genetic background and the environment. We show that mutations in either the nitrogen assimilation control gene (nac) or the type III fimbriae regulator, mrkH, suffice to generate rdar-like colonies. These morphotypes are primarily selected for the reduced inter-cellular aggregation as a result of loss-of-function yielding reduced fimbriae expression. Additionally, these clones also display increased growth rate and reduced biofilm formation. Direct competitions between rdar and wild type clone show that mutations in mrkH provide large fitness advantages. In artificial urine, the morphotype is under strong negative frequency-dependent selection and is able to socially exploit wild type strains. An exhaustive search for mrkH mutants in public databases revealed that ca 8% of natural isolates analysed had truncated MrkH proteins many of which were due to insertions of IS elements, including a reported clinical isolate with rdar morphology. These strains were all isolated from human, mostly from urine. The decreased aggregation of these mutants could have important clinical implications as such clones could better disperse within the host allowing colonisation of other body sites and leading to systemic infections. One-sentence SummaryReport of the emergence of a novel non-aggregative colony morphology in K. variicola and the first example of social exploitation in the Klebsiella genus.

microbiology↗