scholarly journals H2O2Production in Species of the Lactobacillus acidophilus Group: a Central Role for a Novel NADH-Dependent Flavin Reductase

2014 ◽  
Vol 80 (7) ◽  
pp. 2229-2239 ◽  
Author(s):  
Rosanne Hertzberger ◽  
Jos Arents ◽  
Henk L. Dekker ◽  
R. David Pridmore ◽  
Christof Gysler ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Lactobacillus Acidophilus ◽  
Nadh Oxidase ◽  
Reductase Activity ◽  
Bacterial Species ◽  
Flavin Mononucleotide ◽  
Flavin Reductase ◽  
Lactate Oxidase ◽  
Content Type

ABSTRACTHydrogen peroxide production is a well-known trait of many bacterial species associated with the human body. In the presence of oxygen, the probiotic lactic acid bacteriumLactobacillus johnsoniiNCC 533 excretes up to 1 mM H2O2, inducing growth stagnation and cell death. Disruption of genes commonly assumed to be involved in H2O2production (e.g., pyruvate oxidase, NADH oxidase, and lactate oxidase) did not affect this. Here we describe the purification of a novel NADH-dependent flavin reductase encoded by two highly similar genes (LJ_0548andLJ_0549) that are conserved in lactobacilli belonging to theLactobacillus acidophilusgroup. The genes are predicted to encode two 20-kDa proteins containing flavin mononucleotide (FMN) reductase conserved domains. Reductase activity requires FMN, flavin adenine dinucleotide (FAD), or riboflavin and is specific for NADH and not NADPH. TheKmfor FMN is 30 ± 8 μM, in accordance with its proposedin vivorole in H2O2production. Deletion of the encoding genes inL. johnsoniiled to a 40-fold reduction of hydrogen peroxide formation. H2O2production in this mutant could only be restored by intranscomplementation of both genes. Our work identifies a novel, conserved NADH-dependent flavin reductase that is prominently involved in H2O2production inL. johnsonii.

scholarly journals hfqPlays Important Roles in Virulence and Stress Adaptation in Cronobacter sakazakii ATCC 29544

2015 ◽  
Vol 83 (5) ◽  
pp. 2089-2098 ◽  
Author(s):  
Seongok Kim ◽  
Hyelyeon Hwang ◽  
Kwang-Pyo Kim ◽  
Hyunjin Yoon ◽  
Dong-Hyun Kang ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Bacterial Species ◽  
Soft Agar ◽  
Host Cells ◽  
Neonatal Meningitis ◽  
Animal Cells ◽  
Content Type ◽  
Flagellar Biosynthesis

Cronobacterspp. are opportunistic pathogens that cause neonatal meningitis and sepsis with high mortality in neonates. Despite the peril associated withCronobacterinfection, the mechanisms of pathogenesis are still being unraveled. Hfq, which is known as an RNA chaperone, participates in the interaction with bacterial small RNAs (sRNAs) to regulate posttranscriptionally the expression of various genes. Recent studies have demonstrated that Hfq contributes to the pathogenesis of numerous species of bacteria, and its roles are varied between bacterial species. Here, we tried to elucidate the role of Hfq inC. sakazakiivirulence. In the absence ofhfq,C. sakazakiiwas highly attenuated in disseminationin vivo, showed defects in invasion (3-fold) into animal cells and survival (103-fold) within host cells, and exhibited low resistance to hydrogen peroxide (102-fold). Remarkably, the loss ofhfqled to hypermotility on soft agar, which is contrary to what has been observed in other pathogenic bacteria. The hyperflagellated bacteria were likely to be attributable to the increased transcription of genes associated with flagellar biosynthesis in a strain lackinghfq. Together, these data strongly suggest thathfqplays important roles in the virulence ofC. sakazakiiby participating in the regulation of multiple genes.

scholarly journals Blakeslea trispora Photoreceptors: Identification and Functional Analysis

2020 ◽  
Vol 86 (8) ◽  
Author(s):  
Wei Luo ◽  
Chao Xue ◽  
Yuzheng Zhao ◽  
Huili Zhang ◽  
Zhiming Rao ◽  
...  
Keyword(s):  
Large Scale ◽  
Binding Domain ◽  
Site Directed Mutagenesis ◽  
Flavin Mononucleotide ◽  
Blakeslea Trispora ◽  
Scale Production ◽  
Bioinformatics Analyses ◽  
Content Type ◽  
Flavin Binding

ABSTRACT Blakeslea trispora is an industrial fungal species used for large-scale production of carotenoids. However, B. trispora light-regulated physiological processes, such as carotenoid biosynthesis and phototropism, are not fully understood. In this study, we isolated and characterized three photoreceptor genes, btwc-1a, btwc-1b, and btwc-1c, in B. trispora. Bioinformatics analyses of these genes and their protein sequences revealed that the functional domains (PAS/LOV [Per-ARNT-Sim/light-oxygen-voltage] domain and zinc finger structure) of the proteins have significant homology to those of other fungal blue-light regulator proteins expressed by Mucor circinelloides and Neurospora crassa. The photoreceptor proteins were synthesized by heterologous expression in Escherichia coli. The chromogenic groups consisting of flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) were detected to accompany BTWC-1 proteins by using high-performance liquid chromatography (HPLC) and fluorescence spectrometry, demonstrating that the proteins may be photosensitive. The absorbance changes of the purified BTWC-1 proteins seen under dark and light conditions indicated that they were light responsive and underwent a characteristic photocycle by light induction. Site-directed mutagenesis of the cysteine residual (Cys) in BTWC-1 did not affect the normal expression of the protein in E. coli but did lead to the loss of photocycle response, indicating that Cys represents a flavin-binding domain for photon detection. We then analyzed the functions of BTWC-1 proteins by complementing btwc-1a, btwc-1b, and btwc-1c into the counterpart knockout strains of M. circinelloides for each mcwc-1 gene. Transformation of the btwc-1a complement into mcwc-1a knockout strains restored the positive phototropism, while the addition of btwc-1c complement remedied the deficiency of carotene biosynthesis in the mcwc-1c knockout strains under conditions of illumination. These results indicate that btwc-1a and btwc-1c are involved in phototropism and light-inducible carotenogenesis. Thus, btwc-1 genes share a conserved flavin-binding domain and act as photoreceptors for control of different light transduction pathways in B. trispora. IMPORTANCE Studies have confirmed that light-regulated carotenogenesis is prevalent in filamentous fungi, especially in mucorales. However, few investigations have been done to understand photoinduced synthesis of carotenoids and related mechanisms in B. trispora, a well-known industrial microbial strains. In the present study, three photoreceptor genes in B. trispora were cloned, expressed, and characterized by bioinformatics and photoreception analyses, and then in vivo functional analyses of these genes were constructed in M. circinelloides. The results of this study will lead to a better understanding of photoreception and light-regulated carotenoid synthesis and other physiological responses in B. trispora.

scholarly journals Identification of the NADH-oxidase gene in Trichomonas vaginalis

2019 ◽  
Vol 119 (2) ◽  
pp. 683-686 ◽  
Author(s):  
Aline Lamien-Meda ◽  
David Leitsch
Keyword(s):  
Oxidase Activity ◽  
Trichomonas Vaginalis ◽  
Nadh Oxidase ◽  
Flavin Mononucleotide ◽  
Flavin Reductase ◽  
Oxidase Gene ◽  
Reading Frame ◽  
Sexually Transmitted ◽  
Cell Extracts ◽  
Nadh Oxidase Activity

AbstractThe microaerophilic human parasite Trichomonas vaginalis causes infections in the urogenital tract and is one of the most often sexually transmitted pathogens worldwide. Due to its anaerobic metabolism, it has to quickly remove intracellular oxygen in order to avoid deactivation of essential metabolic enzymes such as oxygen-sensitive pyruvate:ferredoxin oxidoreductase (PFOR). Two major enzyme activities which are responsible for the removal, i.e. reduction, of molecular oxygen have been identified in T. vaginalis flavin reductase, formerly designated NADPH oxidase, which indirectly reduces oxygen to hydrogen peroxide via flavin mononucleotide (FMN), and NADH oxidase which reduces oxygen to water. Flavin reductase has been identified and characterized at the gene level as well as enzymatically, but NADH oxidase has so far only been characterized enzymatically with enzyme isolated from T. vaginalis cell extracts. In this study, we identified NADH oxidase by mass spectrometry after isolation of the enzyme from gel bands positively staining for NADH oxidase activity. In strain C1 (ATCC 30001) which is known to lack NADH oxidase activity completely, the NADH oxidase gene has a deletion at position 1540 of the open reading frame leading to a frame shift and, as a consequence, to premature termination of the encoded polypeptide.

scholarly journals Screening and Evaluation of New Hydroxymethylfurfural Oxidases for Furandicarboxylic Acid Production

2020 ◽  
Vol 86 (16) ◽  
Author(s):  
Mario Viñambres ◽  
Marta Espada ◽  
Angel T. Martínez ◽  
Ana Serrano
Keyword(s):  
Hydrogen Peroxide ◽  
Heterologous Expression ◽  
Half Life ◽  
Enzyme Stability ◽  
Bacterial Species ◽  
Building Blocks ◽  
Enzymatic Production ◽  
Content Type ◽  
Furandicarboxylic Acid ◽  
Total Turnover

ABSTRACT The enzymatic production of 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethylfurfural (HMF) has gained interest in recent years, as FDCA is a renewable precursor of poly(ethylene-2,5-furandicarboxylate) (PEF). 5-Hydroxymethylfurfural oxidases (HMFOs) form a flavoenzyme family with genes annotated in a dozen bacterial species but only one enzyme purified and characterized to date (after heterologous expression of a Methylovorus sp. HMFO gene). This oxidase acts on both furfuryl alcohols and aldehydes and, therefore, is able to catalyze the conversion of HMF into FDCA through 2,5-diformylfuran (DFF) and 2,5-formylfurancarboxylic acid (FFCA), with only the need of oxygen as a cosubstrate. To enlarge the repertoire of HMFO enzymes available, genetic databases were screened for putative HMFO genes, followed by heterologous expression in Escherichia coli. After unsuccessful trials with other bacterial HMFO genes, HMFOs from two Pseudomonas species were produced as active soluble enzymes, purified, and characterized. The Methylovorus sp. enzyme was also produced and purified in parallel for comparison. Enzyme stability against temperature, pH, and hydrogen peroxide, three key aspects for application, were evaluated (together with optimal conditions for activity), revealing differences between the three HMFOs. Also, the kinetic parameters for HMF, DFF, and FFCA oxidation were determined, the new HMFOs having higher efficiencies for the oxidation of FFCA, which constitutes the bottleneck in the enzymatic route for FDCA production. These results were used to set up the best conditions for FDCA production by each enzyme, attaining a compromise between optimal activity and half-life under different conditions of operation. IMPORTANCE HMFO is the only enzyme described to date that can catalyze by itself the three consecutive oxidation steps to produce FDCA from HMF. Unfortunately, only one HMFO enzyme is currently available for biotechnological application. This availability is enlarged here by the identification, heterologous production, purification, and characterization of two new HMFOs, one from Pseudomonas nitroreducens and one from an unidentified Pseudomonas species. Compared to the previously known Methylovorus HMFO, the new enzyme from P. nitroreducens exhibits better performance for FDCA production in wider pH and temperature ranges, with higher tolerance for the hydrogen peroxide formed, longer half-life during oxidation, and higher yield and total turnover numbers in long-term conversions under optimized conditions. All these features are relevant properties for the industrial production of FDCA. In summary, gene screening and heterologous expression can facilitate the selection and improvement of HMFO enzymes as biocatalysts for the enzymatic synthesis of renewable building blocks in the production of bioplastics.

scholarly journals In Vivo Fitness Adaptations of Colistin-Resistant Acinetobacter baumannii Isolates to Oxidative Stress

2016 ◽  
Vol 61 (3) ◽  
Author(s):  
Crystal L. Jones ◽  
Shweta S. Singh ◽  
Yonas Alamneh ◽  
Leila G. Casella ◽  
Robert K. Ernst ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Acinetobacter Baumannii ◽  
Catalase Activity ◽  
Content Type ◽  
Increased Susceptibility

ABSTRACT The loss of fitness in colistin-resistant (CR) Acinetobacter baumannii was investigated using longitudinal isolates from the same patient. Early CR isolates were outcompeted by late CR isolates for growth in broth and survival in the lungs of mice. Fitness loss was associated with an increased susceptibility to oxidative stress since early CR strains had reduced in vitro survival in the presence of hydrogen peroxide and decreased catalase activity compared to that of late CR and colistin-susceptible (CS) strains.

scholarly journals Hydrogen Peroxide Production from Glycerol Metabolism Is Dispensable for Virulence of Mycoplasma gallisepticum in the Tracheas of Chickens

2014 ◽  
Vol 82 (12) ◽  
pp. 4915-4920 ◽  
Author(s):  
S. M. Szczepanek ◽  
M. Boccaccio ◽  
K. Pflaum ◽  
X. Liao ◽  
S. J. Geary
Keyword(s):  
Hydrogen Peroxide ◽  
Mycoplasma Gallisepticum ◽  
Eukaryotic Cells ◽  
Glycerol Metabolism ◽  
Content Type ◽  
Avian Pathogen ◽  
Mucosal Thickness ◽  
Transposon Mutants ◽  
Utilization Pathway

ABSTRACTHydrogen peroxide (H2O2) is a by-product of glycerol metabolism in mycoplasmas and has been shown to cause cytotoxicity for cocultured eukaryotic cells. There appears to be selective pressure for mycoplasmas to retain the genes needed for glycerol metabolism. This has generated interest and speculation as to their function during infection. However, the actual effects of glycerol metabolism and H2O2production on virulencein vivohave never been assessed in anyMycoplasmaspecies. To this end, we determined that the wild-type (WT) Rlowstrain of the avian pathogenMycoplasma gallisepticumis capable of producing H2O2when grown in glycerol and is cytotoxic to eukaryotic cells in culture. Transposon mutants with mutations in the genes present in the glycerol transport and utilization pathway, namely,glpO,glpK, andglpF, were identified. All mutants assessed were incapable of producing H2O2and were not cytotoxic when grown in glycerol. We also determined that vaccine strains ts-11 and 6/85 produce little to no H2O2when grown in glycerol, while the naturally attenuated F strain does produce H2O2. Chickens were infected with one of twoglpOmutants, aglpKmutant, Rlow, or growth medium, and tracheal mucosal thickness and lesion scores were assessed. Interestingly, allglpmutants were reproducibly virulent in the respiratory tracts of the chickens. Thus, there appears to be no link between glycerol metabolism/H2O2production/cytotoxicity and virulence for thisMycoplasmaspecies in its natural host. However, it is possible that glycerol metabolism is required byM. gallisepticumin a niche that we have yet to study.

scholarly journals LuxG Is a Functioning Flavin Reductase for Bacterial Luminescence

2007 ◽  
Vol 190 (5) ◽  
pp. 1531-1538 ◽  
Author(s):  
Sarayut Nijvipakul ◽  
Janewit Wongratana ◽  
Chutintorn Suadee ◽  
Barrie Entsch ◽  
David P. Ballou ◽  
...  
Keyword(s):  
Gene Knockout ◽  
Biochemical Properties ◽  
Flavin Mononucleotide ◽  
Flavin Reductase ◽  
Knockout Mutant ◽  
Prosthetic Group ◽  
Bacterial Luminescence ◽  
Luminous Bacteria

ABSTRACT The luxG gene is part of the lux operon of marine luminous bacteria. luxG has been proposed to be a flavin reductase that supplies reduced flavin mononucleotide (FMN) for bacterial luminescence. However, this role has never been established because the gene product has not been successfully expressed and characterized. In this study, luxG from Photobacterium leiognathi TH1 was cloned and expressed in Escherichia coli in both native and C-terminal His6-tagged forms. Sequence analysis indicates that the protein consists of 237 amino acids, corresponding to a subunit molecular mass of 26.3 kDa. Both expressed forms of LuxG were purified to homogeneity, and their biochemical properties were characterized. Purified LuxG is homodimeric and has no bound prosthetic group. The enzyme can catalyze oxidation of NADH in the presence of free flavin, indicating that it can function as a flavin reductase in luminous bacteria. NADPH can also be used as a reducing substrate for the LuxG reaction, but with much less efficiency than NADH. With NADH and FMN as substrates, a Lineweaver-Burk plot revealed a series of convergent lines characteristic of a ternary-complex kinetic model. From steady-state kinetics data at 4°C pH 8.0, Km for NADH, Km for FMN, and k cat were calculated to be 15.1 μM, 2.7 μM, and 1.7 s−1, respectively. Coupled assays between LuxG and luciferases from P. leiognathi TH1 and Vibrio campbellii also showed that LuxG could supply FMNH− for light emission in vitro. A luxG gene knockout mutant of P. leiognathi TH1 exhibited a much dimmer luminescent phenotype compared to the native P. leiognathi TH1, implying that LuxG is the most significant source of FMNH− for the luminescence reaction in vivo.

scholarly journals Evidence that Oxidative Stress InducesspxA2Transcription in Bacillus anthracis Sterne through a Mechanism Requiring SpxA1 and Positive Autoregulation

2016 ◽  
Vol 198 (21) ◽  
pp. 2902-2913 ◽  
Author(s):  
Skye Barendt ◽  
Cierra Birch ◽  
Lea Mbengi ◽  
Peter Zuber
Keyword(s):  
Oxidative Stress ◽  
Bacillus Anthracis ◽  
Transcription Initiation ◽  
Bacterial Species ◽  
Negative Control ◽  
Mobility Shift ◽  
Content Type ◽  
Oxidative Protein Damage

ABSTRACTBacillus anthracispossesses two paralogs of the transcriptional regulator, Spx. SpxA1 and SpxA2 interact with RNA polymerase (RNAP) to activate the transcription of genes implicated in the prevention and alleviation of oxidative protein damage. ThespxA2gene is highly upregulated in infected macrophages, but how this is achieved is unknown. Previous studies have shown that thespxA2gene was under negative control by the Rrf2 family repressor protein, SaiR, whose activity is sensitive to oxidative stress. These studies also suggested thatspxA2was under positive autoregulation. In the present study, we show byin vivoandin vitroanalyses thatspxA2is under direct autoregulation but is also dependent on the SpxA1 paralogous protein. The deletion of eitherspxA1orspxA2reduced the diamide-inducible expression of anspxA2-lacZconstruct.In vitrotranscription reactions using purifiedB. anthracisRNAP showed that SpxA1 and SpxA2 protein stimulates transcription from a DNA fragment containing thespxA2promoter. Ectopically positionedspxA2-lacZfusion requires both SpxA1 and SpxA2 for expression, but the requirement for SpxA1 is partially overcome whensaiRis deleted. Electrophoretic mobility shift assays showed that SpxA1 and SpxA2 enhance the affinity of RNAP forspxA2promoter DNA and that this activity is sensitive to reductant. We hypothesize that the previously observed upregulation ofspxA2in the oxidative environment of the macrophage is at least partly due to SpxA1-mediated SaiR repressor inactivation and the positive autoregulation ofspxA2transcription.IMPORTANCERegulators of transcription initiation are known to govern the expression of genes required for virulence in pathogenic bacterial species. Members of the Spx family of transcription factors function in control of genes required for virulence and viability in low-GC Gram-positive bacteria. InBacillus anthracis, thespxA2gene is highly induced in infected macrophages, which suggests an important role in the control of virulence gene expression during the anthrax disease state. We provide evidence that elevated concentrations of oxidized, active SpxA2 result from an autoregulatory positive-feedback loop drivingspxA2transcription.

scholarly journals Quorum Sensing in Pseudomonas savastanoi pv. savastanoi and Erwinia toletana: Role in Virulence and Interspecies Interactions in the Olive Knot

2018 ◽  
Vol 84 (18) ◽  
Author(s):  
Eloy Caballo-Ponce ◽  
Xianfa Meng ◽  
Gordana Uzelac ◽  
Nigel Halliday ◽  
Miguel Cámara ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Bacterial Species ◽  
Interspecies Interaction ◽  
Interspecies Interactions ◽  
In Planta ◽  
Content Type ◽  
Aggressive Disease ◽  
Olive Knot Disease ◽  
Stable Community

ABSTRACT The olive knot disease (Olea europea L.) is caused by the bacterium Pseudomonas savastanoi pv. savastanoi. P. savastanoi pv. savastanoi in the olive knot undergoes interspecies interactions with the harmless endophyte Erwinia toletana; P. savastanoi pv. savastanoi and E. toletana colocalize and form a stable community, resulting in a more aggressive disease. P. savastanoi pv. savastanoi and E. toletana produce the same type of the N-acylhomoserine lactone (AHL) quorum sensing (QS) signal, and they share AHLs in planta. In this work, we have further studied the AHL QS systems of P. savastanoi pv. savastanoi and E. toletana in order to determine possible molecular mechanism(s) involved in this bacterial interspecies interaction/cooperation. The AHL QS regulons of P. savastanoi pv. savastanoi and E. toletana were determined, allowing the identification of several QS-regulated genes. Surprisingly, the P. savastanoi pv. savastanoi QS regulon consisted of only a few loci whereas in E. toletana many putative metabolic genes were regulated by QS, among which are several involved in carbohydrate metabolism. One of these loci was the aldolase-encoding gene garL, which was found to be essential for both colocalization of P. savastanoi pv. savastanoi and E. toletana cells inside olive knots as well as knot development. This study further highlighted that pathogens can cooperate with commensal members of the plant microbiome. IMPORTANCE This is a report on studies of the quorum sensing (QS) systems of the olive knot pathogen Pseudomonas savastanoi pv. savastanoi and olive knot cooperator Erwinia toletana. These two bacterial species form a stable community in the olive knot, share QS signals, and cooperate, resulting in a more aggressive disease. In this work we further studied the QS systems by determining their regulons as well as by studying QS-regulated genes which might play a role in this cooperation. This represents a unique in vivo interspecies bacterial virulence model and highlights the importance of bacterial interspecies interaction in disease.

scholarly journals csrR, a Paralog and Direct Target of CsrA, Promotes Legionella pneumophila Resilience in Water

mBio ◽  
2015 ◽  
Vol 6 (3) ◽  
Author(s):  
Zachary D. Abbott ◽  
Helen Yakhnin ◽  
Paul Babitzke ◽  
Michele S. Swanson
Keyword(s):  
Legionella Pneumophila ◽  
Tap Water ◽  
Bacterial Species ◽  
Regulatory Protein ◽  
Opportunistic Pathogen ◽  
Water Systems ◽  
Phenotypic Analysis ◽  
Term Survival ◽  
Content Type

ABSTRACTCritical to microbial versatility is the capacity to express the cohort of genes that increase fitness in different environments.Legionella pneumophilaoccupies extensive ecological space that includes diverse protists, pond water, engineered water systems, and mammalian lung macrophages. One mechanism that equips this opportunistic pathogen to adapt to fluctuating conditions is a switch between replicative and transmissive cell types that is controlled by the broadly conserved regulatory protein CsrA. A striking feature of the legionellae surveyed is that each of 14 strains encodes 4 to 7csrA-like genes, candidate regulators of distinct fitness traits. Here we focus on the onecsrAparalog (lpg1593) that, like the canonicalcsrA, is conserved in all 14 strains surveyed. Phenotypic analysis revealed that long-term survival in tap water is promoted by thelpg1593locus, which we namecsrR(for “CsrA-similar protein forresilience”). As predicted by its GGA motif,csrRmRNA was bound directly by the canonical CsrA protein, as judged by electromobility shift and RNA-footprinting assays. Furthermore, CsrA repressed translation ofcsrRmRNAin vivo, as determined by analysis ofcsrR-gfpreporters,csrRmRNA stability in the presence and absence ofcsrAexpression, and mutation of the CsrA binding site identified on thecsrRmRNA. Thus, CsrA not only governs the transition from replication to transmission but also represses translation of its paralogcsrRwhen nutrients are available. We propose that, during prolonged starvation, relief of CsrA repression permits CsrR protein to coordinateL. pneumophila's switch to a cell type that is resilient in water supplies.IMPORTANCEPersistence ofL. pneumophilain water systems is a public health risk, and yet there is little understanding of the genetic determinants that equip this opportunistic pathogen to adapt to and survive in natural or engineered water systems. A potent regulator of this pathogen's intracellular life cycle is CsrA, a protein widely distributed among bacterial species that is understood quite well. Our finding that every sequencedL. pneumophilastrain carries severalcsrAparalogs—including two common to all isolates—indicates that the legionellae exploit CsrA regulatory switches for multiple purposes. Our discovery that one paralog, CsrR, is a target of CsrA that enhances survival in water is an important step toward understanding colonization of the engineered environment by pathogenicL. pneumophila.

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