scholarly journals Capsule Production and Glucose Metabolism Dictate Fitness duringSerratia marcescensBacteremia

mBio ◽  
2017 ◽  
Vol 8 (3) ◽  
Author(s):  
Mark T. Anderson ◽  
Lindsay A. Mitchell ◽  
Lili Zhao ◽  
Harry L. T. Mobley
Keyword(s):  
Glucose Metabolism ◽  
Serratia Marcescens ◽  
Opportunistic Infections ◽  
Opportunistic Pathogen ◽  
Extracellular Polysaccharides ◽  
Mammalian Host ◽  
Wild Type ◽  
Transposon Insertion ◽  
Capsule Production ◽  
Tract Infections

ABSTRACTSerratia marcescensis an opportunistic pathogen that causes a range of human infections, including bacteremia, keratitis, wound infections, and urinary tract infections. Compared to other members of theEnterobacteriaceaefamily, the genetic factors that facilitateSerratiaproliferation within the mammalian host are less well defined. Anin vivoscreen of transposon insertion mutants identified 212S. marcescensfitness genes that contribute to bacterial survival in a murine model of bloodstream infection. Among those identified, 11 genes were located within an 18-gene cluster encoding predicted extracellular polysaccharide biosynthesis proteins. A mutation in thewzxgene contained within this locus conferred a loss of fitness in competition infections with the wild-type strain and a reduction in extracellular uronic acids correlating with capsule loss. A second gene,pgm, encoding a phosphoglucomutase exhibited similar capsule-deficient phenotypes, linking central glucose metabolism with capsule production and fitness ofSerratiaduring mammalian infection. Further evidence of the importance of central metabolism was obtained with apfkAglycolytic mutant that demonstrated reduced replication in human serum and during murine infection. An MgtB magnesium transporter homolog was also among the fitness factors identified, and anS. marcescens mgtBmutant exhibited decreased growth in defined medium containing low concentrations of magnesium and was outcompeted ~10-fold by wild-type bacteria in mice. Together, these newly identified genes provide a more complete understanding of the specific requirements forS. marcescenssurvival in the mammalian host and provide a framework for further investigation of the means by whichS. marcescenscauses opportunistic infections.IMPORTANCESerratia marcescensis a remarkably prolific organism that replicates in diverse environments, including as an opportunistic pathogen in human bacteremia. The genetic requirements forS. marcescenssurvival in the mammalian bloodstream were defined in this work by transposon insertion sequencing. In total, 212 genes that contribute to bacterial fitness were identified. When sorted via biological function, two of the major fitness categories identified herein were genes encoding capsule polysaccharide biogenesis functions and genes involved in glucose utilization. Further investigation determined that certain glucose metabolism fitness genes are also important for the generation of extracellular polysaccharides. Together, these results identify critical biological processes that allowS. marcescensto colonize the mammalian bloodstream.

scholarly journals Complete Genome Sequence of Serratia marcescens Myophage MyoSmar

2019 ◽  
Vol 8 (38) ◽  
Author(s):  
Savannah Cooper ◽  
Quang Nguyen ◽  
Heather Newkirk ◽  
Mei Liu ◽  
Jesse Cahill ◽  
...  
Keyword(s):  
Serratia Marcescens ◽  
Digestive Tract ◽  
Genome Sequence ◽  
Complete Genome Sequence ◽  
Complete Genome ◽  
Opportunistic Pathogen ◽  
Content Type ◽  
Tract Infections

Serratia marcescens is an opportunistic pathogen that causes respiratory, urinary, and digestive tract infections in humans. Here, we describe the annotation of Serratia marcescens myophage MyoSmar. The 68,745-bp genome encodes 105 predicted proteins and is most similar to the genomes of Pseudomonas PB1-like viruses.

scholarly journals Cysteine Biosynthesis Controls Serratia marcescens Phospholipase Activity

2017 ◽  
Vol 199 (16) ◽  
Author(s):  
Mark T. Anderson ◽  
Lindsay A. Mitchell ◽  
Harry L. T. Mobley
Keyword(s):  
Serratia Marcescens ◽  
Gene Transcription ◽  
Extracellular Enzymes ◽  
Opportunistic Infections ◽  
Cysteine Biosynthesis ◽  
Phospholipase Activity ◽  
Gene Encoding ◽  
Content Type ◽  
Transposon Insertion ◽  
The Many

ABSTRACT Serratia marcescens causes health care-associated opportunistic infections that can be difficult to treat due to a high incidence of antibiotic resistance. One of the many secreted proteins of S. marcescens is the PhlA phospholipase enzyme. Genes involved in the production and secretion of PhlA were identified by screening a transposon insertion library for phospholipase-deficient mutants on phosphatidylcholine-containing medium. Mutations were identified in four genes (cyaA, crp, fliJ, and fliP) that are involved in the flagellum-dependent PhlA secretion pathway. An additional phospholipase-deficient isolate harbored a transposon insertion in the cysE gene encoding a predicted serine O-acetyltransferase required for cysteine biosynthesis. The cysE requirement for extracellular phospholipase activity was confirmed using a fluorogenic phospholipase substrate. Phospholipase activity was restored to the cysE mutant by the addition of exogenous l-cysteine or O-acetylserine to the culture medium and by genetic complementation. Additionally, phlA transcript levels were decreased 6-fold in bacteria lacking cysE and were restored with added cysteine, indicating a role for cysteine-dependent transcriptional regulation of S. marcescens phospholipase activity. S. marcescens cysE mutants also exhibited a defect in swarming motility that was correlated with reduced levels of flhD and fliA flagellar regulator gene transcription. Together, these findings suggest a model in which cysteine is required for the regulation of both extracellular phospholipase activity and surface motility in S. marcescens. IMPORTANCE Serratia marcescens is known to secrete multiple extracellular enzymes, but PhlA is unusual in that this protein is thought to be exported by the flagellar transport apparatus. In this study, we demonstrate that both extracellular phospholipase activity and flagellar function are dependent on the cysteine biosynthesis pathway. Furthermore, a disruption of cysteine biosynthesis results in decreased phlA and flagellar gene transcription, which can be restored by supplying bacteria with exogenous cysteine. These results identify a previously unrecognized role for CysE and cysteine in the secretion of S. marcescens phospholipase and in bacterial motility.

scholarly journals Genomic dissection of the bacterial population underlying Klebsiella pneumoniae infections in hospital patients: insights into an opportunistic pathogen

2021 ◽  
Author(s):  
Claire L Gorrie ◽  
Mirjana Mirceta ◽  
Ryan R Wick ◽  
Louise M Judd ◽  
Margaret M C Lam ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Opportunistic Infections ◽  
Carbapenem Resistance ◽  
Opportunistic Pathogen ◽  
Nosocomial Transmission ◽  
Virulence Plasmid ◽  
Diagnostic Laboratory ◽  
Hospitalised Patients ◽  
Wide Range ◽  
Tract Infections

Klebsiella pneumoniae is a major cause of opportunistic healthcare-associated infections, which are increasingly complicated by the presence of extended-spectrum beta-lactamases (ESBLs) and carbapenem resistance. We conducted a year-long prospective surveillance study of K. pneumoniae clinical isolates identified in a hospital microbiological diagnostic laboratory. Disease burden was two-thirds urinary tract infections (UTI; associated with female sex and age), followed by pneumonia (15%), wound (10%) and disseminated infections/sepsis (10%). Whole-genome sequencing (WGS) revealed a diverse pathogen population, including other species within the K. pneumoniae complex (18%). Several infections were caused by K. variicola/K. pneumoniae species hybrids, one of which showed evidence of nosocomial transmission, indicating fitness to transmit and cause disease despite a lack of acquired antimicrobial resistance (AMR). A wide range of AMR phenotypes were observed and, in most cases, corresponding mechanisms were identified in the genomes, mainly in the form of plasmid-borne genes. ESBLs were correlated with presence of other acquired AMR genes (median 10). Bacterial genomic features associated with nosocomial onset of disease were ESBL genes (OR 2.34, p=0.015) and rhamnose-positive capsules (OR 3.12, p<0.001). Virulence plasmid-encoded features (aerobactin, hypermucoidy) were rare (<3%), and mostly present in community-onset cases. WGS-confirmed nosocomial transmission was rare (10% of cases) but strongly associated with ESBLs (OR 21, p<1x10-11). We estimate 28% risk of onward nosocomial transmission for ESBL-positive strains vs 1.7% for ESBL-negative strains. These data indicate the underlying burden of K. pneumoniae disease in hospitalised patients is due largely to opportunistic infections with diverse strains. However, we also identified several successful lineages that were overrepresented but not due to nosocomial transmission. These lineages were associated with ESBL, yersiniabactin, mannose+ K loci and rhamnose- K loci; most are also common in public clinical genome collections, suggesting enhanced propensity for colonisation and spread in the human population.

scholarly journals INSIGHTS INTO THE VIRULENCE FACTORS OF ACINETOBACTER BAUMANNII AND THEIR ROLES IN PERSISTENCE AND INFECTIOUS PROCESS

2021 ◽  
Vol 80 (2) ◽  
pp. 141-150
Author(s):  
Al Shaikhli Nawfal Haitham ◽  
Irina Gheorghe ◽  
Andreea Gheorghe
Keyword(s):  
Acinetobacter Baumannii ◽  
Virulence Factors ◽  
Iron Acquisition ◽  
Opportunistic Pathogen ◽  
Bioinformatic Analysis ◽  
Infection Process ◽  
Virulence Markers ◽  
Capsule Production ◽  
Tract Infections ◽  
Biofilm Development

Acinetobacter baumannii is a Gram-negative opportunistic pathogen, which is responsible for a significant and ever-increasing number of health care associated severe infections (such as pneumonia, sepsis, meningitis, wound and urinary tract infections), mainly in severely ill patients. With only a limited number of “traditional” virulence factors, the mechanisms underlying the success of this opportunistic and nosocomial pathogen remain of great interest. With the advent of whole genome sequencing and bioinformatic analysis, some virulence features, including motility, iron-acquisition systems, biofilm development, capsule production, porins, and enzymes, among others have been described. The main purpose of this minireview was to present an update on the main virulence markers of A. baumannii strains and their role in the persistence, infection process and modulation of host immune response.

scholarly journals A Serratia marcescens OxyR Homolog Mediates Surface Attachment and Biofilm Formation

2007 ◽  
Vol 189 (20) ◽  
pp. 7262-7272 ◽  
Author(s):  
Robert M. Q. Shanks ◽  
Nicholas A. Stella ◽  
Eric J. Kalivoda ◽  
Megan R. Doe ◽  
Dawn M. O'Dee ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Serratia Marcescens ◽  
Biofilm Formation ◽  
Bacterial Species ◽  
Opportunistic Pathogen ◽  
Type I ◽  
Multicopy Plasmid ◽  
Wild Type ◽  
Resistance Mutations ◽  
In The Wild

ABSTRACT OxyR is a conserved bacterial transcription factor with a regulatory role in oxidative stress response. From a genetic screen for genes that modulate biofilm formation in the opportunistic pathogen Serratia marcescens, mutations in an oxyR homolog and predicted fimbria structural genes were identified. S. marcescens oxyR mutants were severely impaired in biofilm formation, in contrast to the hyperbiofilm phenotype exhibited by oxyR mutants of Escherichia coli and Burkholderia pseudomallei. Further analysis revealed that OxyR plays a role in the primary attachment of cells to a surface. Similar to what is observed in other bacterial species, S. marcescens OxyR is required for oxidative stress resistance. Mutations in oxyR and type I fimbrial genes resulted in severe defects in fimbria-associated phenotypes, revealing roles in cell-cell and cell-biotic surface interactions. Transmission electron microscopy revealed the absence of fimbria-like surface structures on an OxyR-deficient strain and an enhanced fimbrial phenotype in strains bearing oxyR on a multicopy plasmid. The hyperfimbriated phenotype conferred by the multicopy oxyR plasmid was absent in a type I fimbrial mutant background. Real-time reverse transcriptase PCR indicated an absence of transcripts from a fimbrial operon in an oxyR mutant that were present in the wild type and a complemented oxyR mutant strain. Lastly, chromosomal Plac -mediated expression of fimABCD was sufficient to restore wild-type levels of yeast agglutination and biofilm formation to an oxyR mutant. Together, these data support a model in which OxyR contributes to early stages of S. marcescens biofilm formation by influencing fimbrial gene expression.

scholarly journals The Serratia marcescens Siderophore Serratiochelin Is Necessary for Full Virulence during Bloodstream Infection

2020 ◽  
Vol 88 (8) ◽  
Author(s):  
Danelle R. Weakland ◽  
Sara N. Smith ◽  
Bailey Bell ◽  
Ashootosh Tripathi ◽  
Harry L. T. Mobley
Keyword(s):  
Serratia Marcescens ◽  
Bloodstream Infection ◽  
Iron Acquisition ◽  
Gene Clusters ◽  
Clinical Isolates ◽  
Wild Type ◽  
Serratia Plymuthica ◽  
Content Type ◽  
Cas Assay ◽  
Essential Nutrient

ABSTRACT Serratia marcescens is a bacterium frequently found in the environment, but over the last several decades it has evolved into a concerning clinical pathogen, causing fatal bacteremia. To establish such infections, pathogens require specific nutrients; one very limited but essential nutrient is iron. We sought to characterize the iron acquisition systems in S. marcescens isolate UMH9, which was recovered from a clinical bloodstream infection. Using RNA sequencing (RNA-seq), we identified two predicted siderophore gene clusters (cbs and sch) that were regulated by iron. Mutants were constructed to delete each iron acquisition locus individually and in conjunction, generating both single and double mutants for the putative siderophore systems. Mutants lacking the sch gene cluster lost their iron-chelating ability as quantified by the chrome azurol S (CAS) assay, whereas the cbs mutant retained wild-type activity. Mass spectrometry-based analysis identified the chelating siderophore to be serratiochelin, a siderophore previously identified in Serratia plymuthica. Serratiochelin-producing mutants also displayed a decreased growth rate under iron-limited conditions created by dipyridyl added to LB medium. Additionally, mutants lacking serratiochelin were significantly outcompeted during cochallenge with wild-type UMH9 in the kidneys and spleen after inoculation via the tail vein in a bacteremia mouse model. This result was further confirmed by an independent challenge, suggesting that serratiochelin is required for full S. marcescens pathogenesis in the bloodstream. Nine other clinical isolates have at least 90% protein identity to the UMH9 serratiochelin system; therefore, our results are broadly applicable to emerging clinical isolates of S. marcescens causing bacteremia.

scholarly journals Mab_3083c Is a Homologue of RNase J and Plays a Role in Colony Morphotype, Aggregation, and Sliding Motility of Mycobacterium abscessus

2021 ◽  
Vol 9 (4) ◽  
pp. 676
Author(s):  
Ting-Yu Liu ◽  
Sheng-Hui Tsai ◽  
Jenn-Wei Chen ◽  
Yu-Ching Wang ◽  
Shiau-Ting Hu ◽  
...  
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Opportunistic Pathogen ◽  
Mycobacterium Abscessus ◽  
Colony Morphology ◽  
Clinical Strain ◽  
Immunocompromised Patients ◽  
Clinical Infection ◽  
Wild Type ◽  
Sliding Motility

Mycobacterium abscessus is an opportunistic pathogen causing human diseases, especially in immunocompromised patients. M. abscessus strains with a rough morphotype are more virulent than those with a smooth morphotype. Morphotype switch may occur during a clinical infection. To investigate the genes involved in colony morphotype switching, we performed transposon mutagenesis in a rough clinical strain of M. abscessus. A morphotype switching mutant (smooth) named mab_3083c::Tn was obtained. This mutant was found to have a lower aggregative ability and a higher sliding motility than the wild type strain. However, its glycopeptidolipid (GPL) content remained the same as those of the wild type. Complementation of the mutant with a functional mab_3083c gene reverted its morphotype back to rough, indicating that mab_3083c is associated with colony morphology of M. abscessus. Bioinformatic analyses showed that mab_3083c has a 75.4% identity in amino acid sequence with the well-characterized ribonuclease J (RNase J) of M. smegmatis (RNase JMsmeg). Complementation of the mutant with the RNase J gene of M. smegmatis also switched its colony morphology from smooth back to rough. These results suggest that Mab_3083c is a homologue of RNase J and involved in regulating M. abscessus colony morphotype switching.

scholarly journals Mutational analysis of genes implicated in LPS and capsular polysaccharide biosynthesis in the opportunistic pathogen Bacteroides fragilis

Microbiology ◽  
2009 ◽  
Vol 155 (4) ◽  
pp. 1039-1049 ◽  
Author(s):  
Sheila Patrick ◽  
Simon Houston ◽  
Zubin Thacker ◽  
Garry W. Blakely
Keyword(s):  
Capsular Polysaccharide ◽  
Mutational Analysis ◽  
Bacteroides Fragilis ◽  
Gene Clusters ◽  
Opportunistic Pathogen ◽  
Extracellular Polysaccharides ◽  
Phase Variable ◽  
Multiple Gene ◽  
Polysaccharide Biosynthesis ◽  
Group 1

The obligate anaerobe Bacteroides fragilis is a normal resident of the human gastrointestinal tract. The clinically derived B. fragilis strain NCTC 9343 produces an extensive array of extracellular polysaccharides (EPS), including antigenically distinct large, small and micro- capsules. The genome of NCTC 9343 encodes multiple gene clusters potentially involved in the biosynthesis of EPS, eight of which are implicated in production of the antigenically variable micro-capsule. We have developed a rapid and robust method for generating marked and markerless deletions, together with efficient electroporation using unmodified plasmid DNA to enable complementation of mutations. We show that deletion of a putative wzz homologue prevents production of high-molecular-mass polysaccharides (HMMPS), which form the micro-capsule. This observation suggests that micro-capsule HMMPS constitute the distal component of LPS in B. fragilis. The long chain length of this polysaccharide is strikingly different from classical enteric O-antigen, which consists of short-chain polysaccharides. We also demonstrate that deletion of a putative wbaP homologue prevents expression of the phase-variable large capsule and that expression can be restored by complementation. This suggests that synthesis of the large capsule is mechanistically equivalent to production of Escherichia coli group 1 and 4 capsules.

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