Flagellum-Mediated Mechanosensing and RflP Control Motility State of Pathogenic Escherichia coli

ABSTRACT Bacterial flagellar motility plays an important role in many processes that occur at surfaces or in hydrogels, including adhesion, biofilm formation, and bacterium-host interactions. Consequently, expression of flagellar genes, as well as genes involved in biofilm formation and virulence, can be regulated by the surface contact. In a few bacterial species, flagella themselves are known to serve as mechanosensors, where an increased load on flagella experienced during surface contact or swimming in viscous media controls gene expression. In this study, we show that gene regulation by motility-dependent mechanosensing is common among pathogenic Escherichia coli strains. This regulatory mechanism requires flagellar rotation, and it enables pathogenic E. coli to repress flagellar genes at low loads in liquid culture, while activating motility in porous medium (soft agar) or upon surface contact. It also controls several other cellular functions, including metabolism and signaling. The mechanosensing response in pathogenic E. coli depends on the negative regulator of motility, RflP (YdiV), which inhibits basal expression of flagellar genes in liquid. While no conditional inhibition of flagellar gene expression in liquid and therefore no upregulation in porous medium was observed in the wild-type commensal or laboratory strains of E. coli, mechanosensitive regulation could be recovered by overexpression of RflP in the laboratory strain. We hypothesize that this conditional activation of flagellar genes in pathogenic E. coli reflects adaptation to the dual role played by flagella and motility during infection. IMPORTANCE Flagella and motility are widespread virulence factors among pathogenic bacteria. Motility enhances the initial host colonization, but the flagellum is a major antigen targeted by the host immune system. Here, we demonstrate that pathogenic E. coli strains employ a mechanosensory function of the flagellar motor to activate flagellar expression under high loads, while repressing it in liquid culture. We hypothesize that this mechanism allows pathogenic E. coli to regulate its motility dependent on the stage of infection, activating flagellar expression upon initial contact with the host epithelium, when motility is beneficial, but reducing it within the host to delay the immune response.

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CsrA-Mediated Translational Activation of ymdA Expression in Escherichia coli

mBio ◽

10.1128/mbio.00849-20 ◽

2020 ◽

Vol 11 (5) ◽

Cited By ~ 1

Author(s):

Andrew Renda ◽

Stephanie Poly ◽

Ying-Jung Lai ◽

Archana Pannuri ◽

Helen Yakhnin ◽

...

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Binding Sites ◽

Biofilm Formation ◽

Central Component ◽

Content Type ◽

E Coli ◽

Ribosome Binding ◽

Activation Mechanisms ◽

Translational Activation

ABSTRACT The sequence-specific RNA-binding protein CsrA is the central component of the conserved global regulatory Csr system. In Escherichia coli, CsrA regulates many cellular processes, including biofilm formation, motility, carbon metabolism, iron homeostasis, and stress responses. Such regulation often involves translational repression by CsrA binding to an mRNA target, thereby inhibiting ribosome binding. While CsrA also extensively activates gene expression, no detailed mechanism for CsrA-mediated translational activation has been demonstrated. An integrated transcriptomic study identified ymdA as having the strongest CsrA-mediated activation across the E. coli transcriptome. Here, we determined that CsrA activates ymdA expression posttranscriptionally. Gel mobility shift, footprint, toeprint, and in vitro coupled transcription-translation assays identified two CsrA binding sites in the leader region of the ymdA transcript that are critical for translational activation. Reporter fusion assays confirmed that CsrA activates ymdA expression at the posttranscriptional level in vivo. Furthermore, loss of binding at either of the two CsrA binding sites abolished CsrA-dependent activation. mRNA half-life studies revealed that CsrA also contributes to stabilization of ymdA mRNA. RNA structure prediction revealed an RNA hairpin upstream of the ymdA start codon that sequesters the Shine-Dalgarno (SD) sequence, which would inhibit ribosome binding. This hairpin also contains one of the two critical CsrA binding sites, with the other site located just upstream. Our results demonstrate that bound CsrA destabilizes the SD-sequestering hairpin such that the ribosome can bind and initiate translation. Since YmdA represses biofilm formation, CsrA-mediated activation of ymdA expression may repress biofilm formation under certain conditions. IMPORTANCE The Csr system of E. coli controls gene expression and physiology on a global scale. CsrA protein, the central component of this system, represses translation initiation of numerous genes by binding to target transcripts, thereby competing with ribosome binding. Variations of this mechanism are so common that CsrA is sometimes called a translational repressor. Although CsrA-mediated activation mechanisms have been elucidated in which bound CsrA inhibits RNA degradation, no translation activation mechanism has been defined. Here, we demonstrate that CsrA binding to two sites in the 5′ untranslated leader of ymdA mRNA activates translation by destabilizing a structure that otherwise prevents ribosome binding. The extensive role of CsrA in activating gene expression suggests the common occurrence of similar activation mechanisms.

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PBP4 and PBP5 are involved in regulating exopolysaccharide synthesis during Escherichia coli biofilm formation

Microbiology ◽

10.1099/mic.0.001031 ◽

2021 ◽

Vol 167 (3) ◽

Author(s):

Sathi Mallick ◽

Shanti Kiran ◽

Tapas Kumar Maiti ◽

Anindya S. Ghosh

Keyword(s):

Escherichia Coli ◽

Biofilm Formation ◽

Type Species ◽

Pentose Phosphate ◽

Bacterial Cells ◽

Surface Adhesion ◽

Content Type ◽

Penicillin Binding Proteins ◽

E Coli ◽

Link Type

Escherichia coli low-molecular-mass (LMM) Penicillin-binding proteins (PBPs) help in hydrolysing the peptidoglycan fragments from their cell wall and recycling them back into the growing peptidoglycan matrix, in addition to their reported involvement in biofilm formation. Biofilms are external slime layers of extra-polymeric substances that sessile bacterial cells secrete to form a habitable niche for themselves. Here, we hypothesize the involvement of Escherichia coli LMM PBPs in regulating the nature of exopolysaccharides (EPS) prevailing in its extra-polymeric substances during biofilm formation. Therefore, this study includes the assessment of physiological characteristics of E. coli CS109 LMM PBP deletion mutants to address biofilm formation abilities, viability and surface adhesion. Finally, EPS from parent CS109 and its ΔPBP4 and ΔPBP5 mutants were purified and analysed for sugars present. Deletions of LMM PBP reduced biofilm formation, bacterial adhesion and their viability in biofilms. Deletions also diminished EPS production by ΔPBP4 and ΔPBP5 mutants, purification of which suggested an increased overall negative charge compared with their parent. Also, EPS analyses from both mutants revealed the appearance of an unusual sugar, xylose, that was absent in CS109. Accordingly, the reason for reduced biofilm formation in LMM PBP mutants may be speculated as the subsequent production of xylitol and a hindrance in the standard flow of the pentose phosphate pathway.

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Elucidation of Regulatory Modes for Five Two-Component Systems in Escherichia coli Reveals Novel Relationships

mSystems ◽

10.1128/msystems.00980-20 ◽

2020 ◽

Vol 5 (6) ◽

Author(s):

Kumari Sonal Choudhary ◽

Julia A. Kleinmanns ◽

Katherine Decker ◽

Anand V. Sastry ◽

Ye Gao ◽

...

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Target Gene ◽

Target Genes ◽

Rna Seq ◽

Content Type ◽

E Coli ◽

Component Systems ◽

Two Component ◽

Two Component Systems

ABSTRACT Escherichia coli uses two-component systems (TCSs) to respond to environmental signals. TCSs affect gene expression and are parts of E. coli’s global transcriptional regulatory network (TRN). Here, we identified the regulons of five TCSs in E. coli MG1655: BaeSR and CpxAR, which were stimulated by ethanol stress; KdpDE and PhoRB, induced by limiting potassium and phosphate, respectively; and ZraSR, stimulated by zinc. We analyzed RNA-seq data using independent component analysis (ICA). ChIP-exo data were used to validate condition-specific target gene binding sites. Based on these data, we do the following: (i) identify the target genes for each TCS; (ii) show how the target genes are transcribed in response to stimulus; and (iii) reveal novel relationships between TCSs, which indicate noncognate inducers for various response regulators, such as BaeR to iron starvation, CpxR to phosphate limitation, and PhoB and ZraR to cell envelope stress. Our understanding of the TRN in E. coli is thus notably expanded. IMPORTANCE E. coli is a common commensal microbe found in the human gut microenvironment; however, some strains cause diseases like diarrhea, urinary tract infections, and meningitis. E. coli’s two-component systems (TCSs) modulate target gene expression, especially related to virulence, pathogenesis, and antimicrobial peptides, in response to environmental stimuli. Thus, it is of utmost importance to understand the transcriptional regulation of TCSs to infer bacterial environmental adaptation and disease pathogenicity. Utilizing a combinatorial approach integrating RNA sequencing (RNA-seq), independent component analysis, chromatin immunoprecipitation coupled with exonuclease treatment (ChIP-exo), and data mining, we suggest five different modes of TCS transcriptional regulation. Our data further highlight noncognate inducers of TCSs, which emphasizes the cross-regulatory nature of TCSs in E. coli and suggests that TCSs may have a role beyond their cognate functionalities. In summary, these results can lead to an understanding of the metabolic capabilities of bacteria and correctly predict complex phenotype under diverse conditions, especially when further incorporated with genome-scale metabolic models.

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Bioinformatic and Molecular Analysis of Inverse Autotransporters from Escherichia coli

mSphere ◽

10.1128/msphere.00572-19 ◽

2019 ◽

Vol 4 (4) ◽

Cited By ~ 3

Author(s):

Kelvin G. K. Goh ◽

Danilo G. Moriel ◽

Steven J. Hancock ◽

Minh-Duy Phan ◽

Mark A. Schembri

Keyword(s):

Escherichia Coli ◽

Cell Surface ◽

Biofilm Formation ◽

Secretion System ◽

Content Type ◽

E Coli ◽

Wide Range ◽

Type V Secretion ◽

K 12 ◽

Type V

ABSTRACT Proteins secreted by the type V secretion system possess multiple functions, including the capacity to mediate adhesion, aggregation, and biolfilm formation. The type V secretion system can be divided into five subclasses, one of which is the type Ve system. Proteins of the type Ve secretion system are also referred to as inverse autotransporters (IATs). In this study, we performed an in silico analysis of 126 completely sequenced Escherichia coli genomes available in the NCBI database and identified several distinct IAT-encoding gene families whose distribution varied throughout the E. coli phylogeny. The genes included three characterized IATs (intimin, fdeC, and yeeJ) and four uncharacterized IATs (here named iatA, iatB, iatC, and iatD). The four iat genes were cloned from the completely sequenced environmental E. coli strain SMS-3-5 and characterized. Three of these IAT proteins (IatB, IatC, and IatD) were expressed at the cell surface and possessed the capacity to mediate biofilm formation in a recombinant E. coli K-12 strain. Further analysis of the iatB gene, which showed a unique association with extraintestinal E. coli strains, suggested that its regulation is controlled by the LeuO global regulator. Overall, this study provides new data describing the prevalence, sequence variation, domain structure, function, and regulation of IATs found in E. coli. IMPORTANCE Escherichia coli is one of the most prevalent facultative anaerobes of the human gut. E. coli normally exists as a harmless commensal but can also cause disease following the acquisition of genes that enhance its pathogenicity. Adhesion is an important first step in colonization of the host and is mediated by an array of cell surface components. In E. coli, these include a family of adhesins secreted by the type V secretion system. Here, we identified and characterized new proteins from an emerging subclass of the type V secretion system known as the inverse autotransporters (IATs). We found that IAT-encoding genes are present in a wide range of strains and showed that three novel IATs were localized on the E. coli cell surface and mediated biofilm formation. Overall, this study provides new insight into the prevalence, function, and regulation of IATs in E. coli.

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Differential Gene Expression of Three Mastitis-Causing Escherichia coli Strains Grown under Planktonic, Swimming, and Swarming Culture Conditions

mSystems ◽

10.1128/msystems.00064-16 ◽

2016 ◽

Vol 1 (4) ◽

Cited By ~ 8

Author(s):

John D. Lippolis ◽

Brian W. Brunelle ◽

Timothy A. Reinhardt ◽

Randy E. Sacco ◽

Tyler C. Thacker ◽

...

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Bacterial Motility ◽

Differentially Expressed ◽

Iron Regulation ◽

Content Type ◽

E Coli ◽

Different Types ◽

Compare Gene Expression ◽

Gene Expression Levels

ABSTRACT Bacteria can exhibit various types of motility. It is known that different types of motilities can be associated with virulence. In this work, we compare gene expression levels in bacteria that were grown under conditions that promoted three different types of E. coli motility. Better understanding of the mechanisms of how bacteria can cause an infection is an important first step to better diagnostics and therapeutics. Bacterial motility is thought to play an important role in virulence. We have previously shown that proficient bacterial swimming and swarming in vitro is correlated with the persistent intramammary infection phenotype observed in cattle. However, little is known about the gene regulation differences important for different motility phenotypes in Escherichia coli. In this work, three E. coli strains that cause persistent bovine mastitis infections were grown in three media that promote different types of motility (planktonic, swimming, and swarming). Using whole-transcriptome RNA sequencing, we identified a total of 935 genes (~21% of the total genome) that were differentially expressed in comparisons of the various motility-promoting conditions. We found that approximately 7% of the differentially expressed genes were associated with iron regulation. We show that motility assays using iron or iron chelators confirmed the importance of iron regulation to the observed motility phenotypes. Because of the observation that E. coli strains that cause persistent infections are more motile, we contend that better understanding of the genes that are differentially expressed due to the type of motility will yield important information about how bacteria can become established within a host. Elucidating the mechanisms that regulate bacterial motility may provide new approaches in the development of intervention strategies as well as facilitate the discovery of novel diagnostics and therapeutics. IMPORTANCE Bacteria can exhibit various types of motility. It is known that different types of motilities can be associated with virulence. In this work, we compare gene expression levels in bacteria that were grown under conditions that promoted three different types of E. coli motility. Better understanding of the mechanisms of how bacteria can cause an infection is an important first step to better diagnostics and therapeutics.

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In Vivo mRNA Profiling of Uropathogenic Escherichia coli from Diverse Phylogroups Reveals Common and Group-Specific Gene Expression Profiles

mBio ◽

10.1128/mbio.01075-14 ◽

2014 ◽

Vol 5 (4) ◽

Cited By ~ 39

Author(s):

Piotr Bielecki ◽

Uthayakumar Muthukumarasamy ◽

Denitsa Eckweiler ◽

Agata Bielecka ◽

Sarah Pohl ◽

...

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Expression Profiles ◽

Gene Expression Profiles ◽

Specific Gene ◽

Content Type ◽

E Coli ◽

Human Host ◽

Tract Infections

ABSTRACTmRNA profiling of pathogens during the course of human infections gives detailed information on the expression levels of relevant genes that drive pathogenicity and adaptation and at the same time allows for the delineation of phylogenetic relatedness of pathogens that cause specific diseases. In this study, we used mRNA sequencing to acquire information on the expression ofEscherichia colipathogenicity genes during urinary tract infections (UTI) in humans and to assign the UTI-associatedE. coliisolates to different phylogenetic groups. Whereas thein vivogene expression profiles of the majority of genes were conserved among 21E. colistrains in the urine of elderly patients suffering from an acute UTI, the specific gene expression profiles of the flexible genomes was diverse and reflected phylogenetic relationships. Furthermore, genes transcribedin vivorelative to laboratory media included well-described virulence factors, small regulatory RNAs, as well as genes not previously linked to bacterial virulence. Knowledge on relevant transcriptional responses that drive pathogenicity and adaptation of isolates to the human host might lead to the introduction of a virulence typing strategy into clinical microbiology, potentially facilitating management and prevention of the disease.IMPORTANCEUrinary tract infections (UTI) are very common; at least half of all women experience UTI, most of which are caused by pathogenicEscherichia colistrains. In this study, we applied massive parallel cDNA sequencing (RNA-seq) to provide unbiased, deep, and accurate insight into the nature and the dimension of the uropathogenicE. coligene expression profile during an acute UTI within the human host. This work was undertaken to identify key players in physiological adaptation processes and, hence, potential targets for new infection prevention and therapy interventions specifically aimed at sabotaging bacterial adaptation to the human host.

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Transcription of the Subtilase Cytotoxin Gene subAB1 in Shiga Toxin-Producing Escherichia coli Is Dependent on hfq and hns

Applied and Environmental Microbiology ◽

10.1128/aem.01281-19 ◽

2019 ◽

Vol 85 (20) ◽

Cited By ~ 2

Author(s):

Laura Heinisch ◽

Katharina Zoric ◽

Maike Krause ◽

Herbert Schmidt

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Shiga Toxin ◽

Promoter Activity ◽

Deletion Mutants ◽

Content Type ◽

E Coli ◽

Intensive Investigation ◽

Subtilase Cytotoxin

ABSTRACT Certain foodborne Shiga toxin-producing Escherichia coli (STEC) strains carry genes encoding the subtilase cytotoxin (SubAB). Although the mode of action of SubAB is under intensive investigation, information about the regulation of subAB gene expression is currently not available. In this study, we investigated the regulation of the chromosomal subAB1 gene in laboratory E. coli strain DH5α and STEC O113:H21 strain TS18/08 using a luciferase reporter gene assay. Special emphasis was given to the role of the global regulatory protein genes hfq and hns in subAB1 promoter activity. Subsequently, quantitative real-time PCR was performed to analyze the expression of Shiga toxin 2a (Stx2a), SubAB1, and cytolethal distending toxin V (Cdt-V) genes in STEC strain TS18/08 and its isogenic hfq and hns deletion mutants. The deletion of hfq led to a significant increase of up to 2-fold in subAB1 expression, especially in the late growth phase, in both strains. However, deletion of hns showed different effects on the promoter activity during the early and late exponential growth phases in both strains. Furthermore, upregulation of stx2a and cdt-V was demonstrated in hfq and hns deletion mutants in TS18/08. These data showed that the expression of subAB1, stx2a, and cdt-V is integrated in the regulatory network of global regulators Hfq and H-NS in Escherichia coli. IMPORTANCE Shiga toxin-producing Escherichia coli (STEC) strains are responsible for outbreaks of foodborne diseases, such as hemorrhagic colitis and the hemolytic uremic syndrome. The pathogenicity of those strains can be attributed to, among other factors, the production of toxins. Recently, the subtilase cytotoxin was detected in locus of enterocyte effacement (LEE)-negative STEC, and it was confirmed that it contributes to the cytotoxicity of those STEC strains. Although the mode of action of SubAB1 is under intensive investigation, the regulation of gene expression is currently not known. The global regulatory proteins H-NS and Hfq have impact on many cellular processes and have been described to regulate virulence factors as well. Here, we investigate the role of hns and hfq in expression of subAB1 as well as stx2a and cdt-V in an E. coli laboratory strain as well as in wild-type STEC strain TS18/08.

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The Catabolite Repressor Protein-Cyclic AMP Complex RegulatescsgDand Biofilm Formation in Uropathogenic Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.00652-16 ◽

2016 ◽

Vol 198 (24) ◽

pp. 3329-3334 ◽

Cited By ~ 20

Author(s):

David A. Hufnagel ◽

Margery L. Evans ◽

Sarah E. Greene ◽

Jerome S. Pinkner ◽

Scott J. Hultgren ◽

...

Keyword(s):

Escherichia Coli ◽

Extracellular Matrix ◽

Cyclic Amp ◽

Intergenic Region ◽

Biofilm Formation ◽

Cellulose Production ◽

Content Type ◽

E Coli ◽

Link Type ◽

K1 Capsule

ABSTRACTThe extracellular matrix protectsEscherichia colifrom immune cells, oxidative stress, predation, and other environmental stresses. Production of theE. coliextracellular matrix is regulated by transcription factors that are tuned to environmental conditions. The biofilm master regulator protein CsgD upregulates curli and cellulose, the two major polymers in the extracellular matrix of uropathogenicE. coli(UPEC) biofilms. We found that cyclic AMP (cAMP) regulates curli, cellulose, and UPEC biofilms throughcsgD. The alarmone cAMP is produced by adenylate cyclase (CyaA), and deletion ofcyaAresulted in reduced extracellular matrix production and biofilm formation. Thecataboliterepressorprotein (CRP) positively regulatedcsgDtranscription, leading to curli and cellulose production in the UPEC isolate, UTI89. Glucose, a known inhibitor of CyaA activity, blocked extracellular matrix formation when added to the growth medium. The mutant strains ΔcyaAand Δcrpdid not produce rugose biofilms, pellicles, curli, cellulose, or CsgD. Three putative CRP binding sites were identified within thecsgD-csgBintergenic region, and purified CRP could gel shift thecsgD-csgBintergenic region. Additionally, we found that CRP binded upstream ofkpsMT, which encodes machinery for K1 capsule production. Together our work shows that cAMP and CRP influenceE. colibiofilms through transcriptional regulation ofcsgD.IMPORTANCEThecataboliterepressorprotein (CRP)-cyclic AMP (cAMP) complex influences the transcription of ∼7% of genes on theEscherichia colichromosome (D. Zheng, C. Constantinidou, J. L. Hobman, and S. D. Minchin, Nucleic Acids Res 32:5874–5893, 2004,https://dx.doi.org/10.1093/nar/gkh908). Glucose inhibitsE. colibiofilm formation, and ΔcyaAand Δcrpmutants show impaired biofilm formation (D. W. Jackson, J.W. Simecka, and T. Romeo, J Bacteriol 184:3406–3410, 2002,https://dx.doi.org/10.1128/JB.184.12.3406-3410.2002). We determined that the cAMP-CRP complex regulates curli and cellulose production and the formation of rugose and pellicle biofilms throughcsgD. Additionally, we propose that cAMP may work as a signaling compound for uropathogenicE. coli(UPEC) to transition from the bladder lumen to inside epithelial cells for intracellular bacterial community formation through K1 capsule regulation.

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PVv3, a New Shuttle Vector for Gene Expression in Vibrio vulnificus

Applied and Environmental Microbiology ◽

10.1128/aem.03720-13 ◽

2013 ◽

Vol 80 (4) ◽

pp. 1477-1481 ◽

Cited By ~ 8

Author(s):

Karina Klevanskaa ◽

Nadja Bier ◽

Kerstin Stingl ◽

Eckhard Strauch ◽

Stefan Hertwig

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Green Fluorescent Protein ◽

Vibrio Parahaemolyticus ◽

Fluorescent Protein ◽

Vibrio Vulnificus ◽

Shuttle Vector ◽

Content Type ◽

E Coli ◽

Green Fluorescent

ABSTRACTAn efficient electroporation procedure forVibrio vulnificuswas designed using the new cloning vector pVv3 (3,107 bp). Transformation efficiencies up to 2 × 106transformants per μg DNA were achieved. The vector stably replicated in bothV. vulnificusandEscherichia coliand was also successfully introduced intoVibrio parahaemolyticusandVibrio cholerae. To demonstrate the suitability of the vector for molecular cloning, the green fluorescent protein (GFP) gene and thevvhBAhemolysin operon were inserted into the vector and functionally expressed inVibrioandE. coli.

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Pirated Siderophores Promote Sporulation in Bacillus subtilis

Applied and Environmental Microbiology ◽

10.1128/aem.03293-16 ◽

2017 ◽

Vol 83 (10) ◽

Cited By ~ 19

Author(s):

Gabrielle M. Grandchamp ◽

Lews Caro ◽

Elizabeth A. Shank

Keyword(s):

Gene Expression ◽

Escherichia Coli ◽

Bacillus Subtilis ◽

Iron Acquisition ◽

Microbial Interactions ◽

Mineral Nutrient ◽

Cell Physiology ◽

Content Type ◽

E Coli ◽

Esterase Gene

ABSTRACT In microbial communities, bacteria chemically and physically interact with one another. Some of these interactions are mediated by secreted specialized metabolites that act as either intraspecies or interspecies signals to alter gene expression and to change cell physiology. Bacillus subtilis is a well-characterized soil microbe that can differentiate into multiple cell types, including metabolically dormant endospores. We were interested in identifying microbial interactions that affected sporulation in B. subtilis. Using a fluorescent transcriptional reporter, we observed that coculturing B. subtilis with Escherichia coli promoted sporulation gene expression via a secreted metabolite. To identify the active compound, we screened the E. coli Keio Collection and identified the sporulation-accelerating cue as the siderophore enterobactin. B. subtilis has multiple iron acquisition systems that are used to take up the B. subtilis-produced siderophore bacillibactin, as well as to pirate exogenous siderophores such as enterobactin. While B. subtilis uses a single substrate binding protein (FeuA) to take up both bacillibactin and enterobactin, we discovered that it requires two distinct genes to sporulate in response to these siderophores (the esterase gene besA for bacillibactin and a putative esterase gene, ybbA, for enterobactin). In addition, we found that siderophores from a variety of other microbial species also promote sporulation in B. subtilis. Our results thus demonstrate that siderophores can act not only as bacterial iron acquisition systems but also as interspecies cues that alter cellular development and accelerate sporulation in B. subtilis. IMPORTANCE While much is known about the genetic regulation of Bacillus subtilis sporulation, little is understood about how other bacteria influence this process. This work describes an interaction between Escherichia coli and B. subtilis that accelerates sporulation in B. subtilis. The interaction is mediated by the E. coli siderophore enterobactin; we show that other species' siderophores also promote sporulation gene expression in B. subtilis. These results suggest that siderophores not only may supply bacteria with the mineral nutrient iron but also may play a role in bacterial interspecies signaling, providing a cue for sporulation. Siderophores are produced by many bacterial species and thus potentially play important roles in altering bacterial cell physiology in diverse environments.

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