scholarly journals Genetics and Physiology of Acetate Metabolism by the Pta-Ack Pathway of Streptococcus mutans

2015 ◽  
Vol 81 (15) ◽  
pp. 5015-5025 ◽  
Author(s):  
Jeong Nam Kim ◽  
Sang-Joon Ahn ◽  
Robert A. Burne
Keyword(s):  
Streptococcus Mutans ◽  
Wild Type Strain ◽  
Acetate Metabolism ◽  
Global Changes ◽  
Acetyl Phosphate ◽  
Wild Type ◽  
Aerobic Conditions ◽  
Content Type ◽  
Atp Pool ◽  
Complex Regulation

ABSTRACTIn the dental caries pathogenStreptococcus mutans, phosphotransacetylase (Pta) catalyzes the conversion of acetyl coenzyme A (acetyl-CoA) to acetyl phosphate (AcP), which can be converted to acetate by acetate kinase (Ack), with the concomitant generation of ATP. A ΔackAmutant displayed enhanced accumulation of AcP under aerobic conditions, whereas little or no AcP was observed in the Δptaor ΔptaΔackAmutant. The Δptaand ΔptaΔackAmutants also had diminished ATP pools compared to the size of the ATP pool for the parental or ΔackAstrain. Surprisingly, when exposed to oxidative stress, the ΔptaΔackAstrain appeared to regain the capacity to produce AcP, with a concurrent increase in the size of the ATP pool compared to that for the parental strain. The ΔackAand ΔptaΔackAmutants exhibited enhanced (p)ppGpp accumulation, whereas the strain lacking Pta produced less (p)ppGpp than the wild-type strain. The ΔackAand ΔptaΔackAmutants displayed global changes in gene expression, as assessed by microarrays. All strains lacking Pta, which had defects in AcP production under aerobic conditions, were impaired in their abilities to form biofilms when glucose was the growth carbohydrate. Collectively, these data demonstrate the complex regulation of the Pta-Ack pathway and critical roles for these enzymes in processes that appear to be essential for the persistence and pathogenesis ofS. mutans.

scholarly journals Introduction of Glyoxylate Bypass Increases Hydrogen Gas Yield from Acetate and L-Glutamate inRhodobacter sphaeroides

2018 ◽  
Vol 85 (2) ◽  
Author(s):  
Tetsu Shimizu ◽  
Haruhiko Teramoto ◽  
Masayuki Inui
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Rhodobacter Capsulatus ◽  
Coenzyme A ◽  
Hydrogen Gas ◽  
Acetate Metabolism ◽  
Clear Understanding ◽  
Wild Type ◽  
Glyoxylate Bypass ◽  
Content Type

ABSTRACTRhodobacter sphaeroidesproduces hydrogen gas (H2) from organic compounds via nitrogenase under anaerobic-light conditions in the presence of poor nitrogen sources, such asl-glutamate.R. sphaeroidesutilizes the ethylmalonyl-coenzyme A (EMC) pathway for acetate assimilation, but its H2yield from acetate in the presence ofl-glutamate has been reported to be low. In this study, the deletion ofccrencoding crotonyl-coenzyme A (crotonyl-CoA) carboxylase/reductase, a key enzyme for the EMC pathway inR. sphaeroides, revealed that the EMC pathway is essential for H2production from acetate andl-glutamate but not for growth and acetate consumption in the presence ofl-glutamate. We introduced a plasmid expressingaceBAfromRhodobacter capsulatusencoding two key enzymes for the glyoxylate bypass intoR. sphaeroides, which resulted in a 64% increase in H2production. However, compared with the wild-type strain expressing heterologousaceBAgenes, the strain withaceBAintroduced in the genetic background of an EMC pathway-disrupted mutant showed a lower H2yield. These results indicate that a combination of the endogenous EMC pathway and a heterologously expressed glyoxylate bypass is beneficial for H2production. In addition, introduction of the glyoxylate bypass into a polyhydroxybutyrate (PHB) biosynthesis-disrupted mutant resulted in a delay in growth along with H2production, although its H2yield was comparable to that of the wild-type strain expressing heterologousaceBAgenes. These results suggest that PHB production is important for fitness to the culture during H2production from acetate andl-glutamate when both acetate-assimilating pathways are present.IMPORTANCEAs an alternative to fossil fuel, H2is a promising renewable energy source. Although photofermentative H2production from acetate is key to developing an efficient process of biohydrogen production from biomass-derived sugars, H2yields from acetate andl-glutamate byR. sphaeroideshave been reported to be low. In this study, we observed that in addition to the endogenous EMC pathway, heterologous expression of the glyoxylate bypass inR. sphaeroidesmarkedly increased H2yields from acetate andl-glutamate. Therefore, this study provides a novel strategy for improving H2yields from acetate in the presence ofl-glutamate and contributes to a clear understanding of acetate metabolism inR. sphaeroidesduring photofermentative H2production.

scholarly journals A Novel CO-Responsive Transcriptional Regulator and Enhanced H2Production by an Engineered Thermococcus onnurineus NA1 Strain

2014 ◽  
Vol 81 (5) ◽  
pp. 1708-1714 ◽  
Author(s):  
Min-Sik Kim ◽  
Ae Ran Choi ◽  
Seong Hyuk Lee ◽  
Hae-Chang Jung ◽  
Seung Seob Bae ◽  
...  
Keyword(s):  
Production Rate ◽  
Gene Cluster ◽  
Type Strain ◽  
Wild Type Strain ◽  
Regulatory System ◽  
Transcriptional Regulator ◽  
Bioreactor Culture ◽  
Wild Type ◽  
Content Type ◽  
Transcriptional Regulatory

ABSTRACTGenome analysis revealed the existence of a putative transcriptional regulatory system governing CO metabolism inThermococcus onnurineusNA1, a carboxydotrophic hydrogenogenic archaeon. The regulatory system is composed of CorQ with a 4-vinyl reductase domain and CorR with a DNA-binding domain of the LysR-type transcriptional regulator family in close proximity to the CO dehydrogenase (CODH) gene cluster. Homologous genes of the CorQR pair were also found in the genomes ofThermococcusspecies and “CandidatusKorarchaeum cryptofilum” OPF8. In-frame deletion of eithercorQorcorRcaused a severe impairment in CO-dependent growth and H2production. WhencorQandcorRdeletion mutants were complemented by introducing thecorQRgenes under the control of a strong promoter, the mRNA and protein levels of the CODH gene were significantly increased in a ΔCorR strain complemented with integratedcorQR(ΔCorR/corQR↑) compared with those in the wild-type strain. In addition, the ΔCorR/corQR↑strain exhibited a much higher H2production rate (5.8-fold) than the wild-type strain in a bioreactor culture. The H2production rate (191.9 mmol liter−1h−1) and the specific H2production rate (249.6 mmol g−1h−1) of this strain were extremely high compared with those of CO-dependent H2-producing prokaryotes reported so far. These results suggest that thecorQRgenes encode a positive regulatory protein pair for the expression of a CODH gene cluster. The study also illustrates that manipulation of the transcriptional regulatory system can improve biological H2production.

scholarly journals Activation of 2,4-Diaminoquinazoline in Mycobacterium tuberculosis by Rv3161c, a Putative Dioxygenase

2018 ◽  
Vol 63 (1) ◽  
Author(s):  
Eduard Melief ◽  
Shilah A. Bonnett ◽  
Edison S. Zuniga ◽  
Tanya Parish
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Type A ◽  
Wild Type ◽  
Metabolite Analysis ◽  
Content Type ◽  
Data Support ◽  
In The Wild

ABSTRACT The diaminoquinazoline series has good potency against Mycobacterium tuberculosis. Resistant isolates have mutations in Rv3161c, a putative dioxygenase. We carried out metabolite analysis on a wild-type strain and an Rv3161c mutant strain after exposure to a diaminoquinazoline. The parental compound was found in intracellular extracts from the mutant but not the wild type. A metabolite consistent with a monohydroxylated form was identified in the wild type. These data support the hypothesis that Rv3161c metabolizes diaminoquinazolines in M. tuberculosis.

scholarly journals Ionophore activity of sarcotoxin I, a bactericidal protein of Sarcophaga peregrina

1985 ◽  
Vol 229 (2) ◽  
pp. 453-458 ◽  
Author(s):  
M Okada ◽  
S Natori
Keyword(s):  
Escherichia Coli ◽  
Oxidative Phosphorylation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Bactericidal Effect ◽  
Proton Gradient ◽  
Wild Type ◽  
Atp Pool

When Escherichia coli was treated with sarcotoxin I, a potent bactericidal protein of Sarcophaga peregrina (fleshfly), K+ inside of the cells leaked out rapidly and the ATP pool of the cells rapidly decreased. These results suggested that the bactericidal effect of sarcotoxin I was due to its ionophore activity, and that it blocked the generation of ATP by inhibiting formation of the proton gradient essential for oxidative phosphorylation. This was confirmed by use of an uncA mutant, which was much less susceptible than the wild-type strain to sarcotoxin I under fixed ionic conditions.

scholarly journals The Riemerella anatipestiferAS87_01735Gene Encodes Nicotinamidase PncA, an Important Virulence Factor

2016 ◽  
Vol 82 (19) ◽  
pp. 5815-5823 ◽  
Author(s):  
Xiaolan Wang ◽  
Beibei Liu ◽  
Yafeng Dou ◽  
Hongjie Fan ◽  
Shaohui Wang ◽  
...  
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Vaccine Candidate ◽  
Wild Type ◽  
Salvage Pathway ◽  
Effective Protection ◽  
Domestic Ducks ◽  
Content Type ◽  
Key Enzyme ◽  
Important Virulence Factor

ABSTRACTRiemerella anatipestiferis a major bacterial pathogen that causes septicemic and exudative diseases in domestic ducks. In our previous study, we found that deletion of theAS87_01735gene significantly decreased the bacterial virulence ofR. anatipestiferstrain Yb2 (mutant RA625). TheAS87_01735gene was predicted to encode a nicotinamidase (PncA), a key enzyme that catalyzes the conversion of nicotinamide to nicotinic acid, which is an important reaction in the NAD+salvage pathway. In this study, theAS87_01735gene was expressed and identified as the PncA-encoding gene, using an enzymatic assay. Western blot analysis demonstrated thatR. anatipestiferPncA was localized to the cytoplasm. The mutant strain RA625 (named Yb2ΔpncAin this study) showed a similar growth rate but decreased NAD+quantities in both the exponential and stationary phases in tryptic soy broth culture, compared with the wild-type strain Yb2. In addition, Yb2ΔpncA-infected ducks showed much lower bacterial loads in their blood, and no visible histological changes were observed in the heart, liver, and spleen. Furthermore, Yb2ΔpncAimmunization of ducks conferred effective protection against challenge with the virulent wild-type strain Yb2. Our results suggest that theR. anatipestiferAS87_01735gene encodes PncA, which is an important virulence factor, and that the Yb2ΔpncAmutant can be used as a novel live vaccine candidate.IMPORTANCERiemerella anatipestiferis reported worldwide as a cause of septicemic and exudative diseases of domestic ducks. ThepncAgene encodes a nicotinamidase (PncA), a key enzyme that catalyzes the conversion of nicotinamide to nicotinic acid, which is an important reaction in the NAD+salvage pathway. In this study, we identified and characterized thepncA-homologous geneAS87_01735inR. anatipestiferstrain Yb2.R. anatipestiferPncA is a cytoplasmic protein that possesses similar PncA activity, compared with other organisms. Generation of thepncAmutant Yb2ΔpncAled to a decrease in the NAD+content, which was associated with decreased capacity for invasion and attenuated virulence in ducks. Furthermore, Yb2ΔpncAimmunization of ducks conferred effective protection against challenge with the virulent wild-type strain Yb2. Altogether, these results suggest that PncA contributes to the virulence ofR. anatipestiferand that the Yb2ΔpncAmutant can be used as a novel live vaccine candidate.

scholarly journals Influence of Chemotaxis and Swimming Patterns on the Virulence of the Coral PathogenVibrio coralliilyticus

2018 ◽  
Vol 200 (15) ◽  
Author(s):  
Blake Ushijima ◽  
Claudia C. Häse
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Bacterial Colonization ◽  
Valuable Insight ◽  
Wild Type ◽  
Coral Mucus ◽  
Content Type ◽  
Swimming Pattern ◽  
Vibrio Coralliilyticus ◽  
Insight Into

ABSTRACTChemotaxis, the directed movement toward or away from a chemical signal, can be essential to bacterial pathogens for locating hosts or avoiding hostile environments. The coral pathogenVibrio coralliilyticuschemotaxes toward coral mucus; however, chemotaxis has not been experimentally demonstrated to be important for virulence. To further examine this, in-frame mutations were constructed in genes predicted to be important forV. coralliilyticuschemotaxis. MostVibriogenomes contain multiple homologs of various chemotaxis-related genes, and two paralogs of each forcheB,cheR, andcheAwere identified. Based on single mutant analyses, the paralogscheB2,cheR2, andcheA1were essential for chemotaxis in laboratory assays. As predicted, the ΔcheA1and ΔcheR2strains had a smooth-swimming pattern, while the ΔcheB2strain displayed a zigzag pattern when observed under light microscopy. However, these mutants, unlike the parent strain, were unable to chemotax toward the known attractants coral mucus, dimethylsulfoniopropionate, andN-acetyl-d-glucosamine. The ΔcheB2strain and an aflagellate ΔfliG1strain were avirulent to coral, while the ΔcheA1and ΔcheR2strains were hypervirulent (90 to 100% infection within 14 h on average) compared to the wild-type strain (66% infection within 36 h on average). Additionally, the ΔcheA1and ΔcheR2strains appeared to better colonize coral fragments than the wild-type strain. These results suggest that although chemotaxis may be involved with infection (the ΔcheB2strain was avirulent), a smooth-swimming phenotype is important for bacterial colonization and infection. This study provides valuable insight into understandingV. coralliilyticuspathogenesis and how this pathogen may be transmitted between hosts.IMPORTANCECorals are responsible for creating the immense structures that are essential to reef ecosystems; unfortunately, pathogens like the bacteriumVibrio coralliilyticuscan cause fatal infections of reef-building coral species. However, compared to related human pathogens, the mechanisms by whichV. coralliilyticusinitiates infections and locates new coral hosts are poorly understood. This study investigated the effects of chemotaxis, the directional swimming in response to chemical signals, and bacterial swimming patterns on infection of the coralMontipora capitata. Infection experiments with different mutant strains suggested that a smooth-swimming pattern resulted in hypervirulence. These results demonstrate that the role of chemotaxis in coral infection may not be as straightforward as previously hypothesized and provide valuable insight intoV. coralliilyticuspathogenesis.

scholarly journals Loss of Ethanolamine Utilization in Enterococcus faecalis Increases Gastrointestinal Tract Colonization

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Karan Gautam Kaval ◽  
Kavindra V. Singh ◽  
Melissa R. Cruz ◽  
Sruti DebRoy ◽  
Wade C. Winkler ◽  
...  
Keyword(s):  
Enterococcus Faecalis ◽  
Opposite Effect ◽  
Wild Type Strain ◽  
Food Poisoning ◽  
Wild Type ◽  
Gi Tract ◽  
Human Gut ◽  
Content Type ◽  
Serovar Typhimurium ◽  
High Concentrations

ABSTRACT Enterococcus faecalis is paradoxically a dangerous nosocomial pathogen and a normal constituent of the human gut microbiome, an environment rich in ethanolamine. E. faecalis carries the eut (ethanolamine utilization) genes, which enable the catabolism of ethanolamine (EA) as a valuable source of carbon and/or nitrogen. EA catabolism was previously shown to contribute to the colonization and growth of enteric pathogens, such as Salmonella enterica serovar Typhimurium and enterohemorrhagic Escherichia coli (EHEC), in the gut environment. We tested the ability of eut mutants of E. faecalis to colonize the gut using a murine model of gastrointestinal (GI) tract competition and report the surprising observation that these mutants outcompete the wild-type strain. IMPORTANCE Some bacteria that are normal, harmless colonizers of the human body can cause disease in immunocompromised patients, particularly those that have been heavily treated with antibiotics. Therefore, it is important to understand the factors that promote or negate these organisms’ ability to colonize. Previously, ethanolamine, found in high concentrations in the GI tract, was shown to promote the colonization and growth of bacteria associated with food poisoning. Here, we report the surprising, opposite effect of ethanolamine utilization on the commensal colonizer E. faecalis , namely, that loss of this metabolic capacity made it a better colonizer.

Identification of Crp as a novel regulator of the Std fimbrial expression in Salmonella

Microbiology ◽  
2021 ◽  
Author(s):  
Karine Dufresne ◽  
France Daigle
Keyword(s):  
Wild Type Strain ◽  
Distal Region ◽  
Transcriptional Factor ◽  
Major Influence ◽  
Wild Type ◽  
Content Type ◽  
Link Type ◽  
Serovar Typhimurium ◽  
Metabolic Regulators

The Salmonella enterica serovar Typhi genome contains 14 putative fimbrial systems. The Std fimbriae belong to the chaperone-usher family and its regulation has not been investigated in S. Typhi. Several regulators of Std were previously identified in the closely related serovar Typhimurium. We hypothesize that regulators of S. Typhimurium may be shared with S. Typhi, but that several other regulators remain to be discovered. Here, we describe the role of more than 50 different candidate regulators on std expression. Three types of regulators were investigated: known regulators in S. Typhimurium, in silico predicted regulators and virulence/metabolic regulators. Expression of std was determined in the regulator mutants and compared with the wild-type strain. Overall, 21 regulator mutations affect std promoter expression. The role of Crp, a newly identified factor for std expression, was further investigated. Crp acted as an activator of std expression on a distal region of the std promoter region. Together, our results demonstrate the major influence of Crp as a novel transcriptional factor on std promoter expression and later production of Std fimbriae in Salmonella .

scholarly journals The Ser/Thr Kinase PrkC Participates in Cell Wall Homeostasis and Antimicrobial Resistance inClostridium difficile

2019 ◽  
Vol 87 (8) ◽  
Author(s):  
Elodie Cuenot ◽  
Transito Garcia-Garcia ◽  
Thibaut Douche ◽  
Olivier Gorgette ◽  
Pascal Courtin ◽  
...  
Keyword(s):  
Cell Wall ◽  
Type Strain ◽  
Wild Type Strain ◽  
Cell Envelope ◽  
Wild Type ◽  
Hamster Model ◽  
Content Type ◽  
Physiological Processes ◽  
Signal Transduction Networks ◽  
Mean Size

ABSTRACTClostridium difficileis the leading cause of antibiotic-associated diarrhea in adults. During infection,C. difficilemust detect the host environment and induce an appropriate survival strategy. Signal transduction networks involving serine/threonine kinases (STKs) play key roles in adaptation, as they regulate numerous physiological processes. PrkC ofC. difficileis an STK with two PASTA domains. We showed that PrkC is membrane associated and is found at the septum. We observed that deletion ofprkCaffects cell morphology with an increase in mean size, cell length heterogeneity, and presence of abnormal septa. A ΔprkCmutant was able to sporulate and germinate but was less motile and formed more biofilm than the wild-type strain. Moreover, a ΔprkCmutant was more sensitive to antimicrobial compounds that target the cell envelope, such as the secondary bile salt deoxycholate, cephalosporins, cationic antimicrobial peptides, and lysozyme. This increased susceptibility was not associated with differences in peptidoglycan or polysaccharide II composition. However, the ΔprkCmutant had less peptidoglycan and released more polysaccharide II into the supernatant. A proteomic analysis showed that the majority ofC. difficileproteins associated with the cell wall were less abundant in the ΔprkCmutant than the wild-type strain. Finally, in a hamster model of infection, the ΔprkCmutant had a colonization delay that did not significantly affect overall virulence.

scholarly journals Selective Pressure for Biofilm Formation in Bacillus subtilis: Differential Effect of Mutations in the Master Regulator SinR on Bistability

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Jan Kampf ◽  
Jan Gerwig ◽  
Kerstin Kruse ◽  
Robert Cleverley ◽  
Miriam Dormeyer ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bacillus Subtilis ◽  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Selective Pressure ◽  
Wild Type ◽  
Master Regulator ◽  
Form Complex ◽  
Content Type

ABSTRACT Biofilm formation by Bacillus subtilis requires the expression of genes encoding enzymes for extracellular polysaccharide synthesis and for an amyloid-like protein. The master regulator SinR represses all the corresponding genes, and repression of these key biofilm genes is lifted when SinR interacts with its cognate antagonist proteins. The YmdB phosphodiesterase is a recently discovered factor that is involved in the control of SinR activity: cells lacking YmdB exhibit hyperactive SinR and are unable to relieve the repression of the biofilm genes. In this study, we have examined the dynamics of gene expression patterns in wild-type and ymdB mutant cells by microfluidic analysis coupled to time-lapse microscopy. Our results confirm the bistable expression pattern for motility and biofilm genes in the wild-type strain and the loss of biofilm gene expression in the mutant. Moreover, we demonstrated dynamic behavior in subpopulations of the wild-type strain that is characterized by switches in sets of the expressed genes. In order to gain further insights into the role of YmdB, we isolated a set of spontaneous suppressor mutants derived from ymdB mutants that had regained the ability to form complex colonies and biofilms. Interestingly, all of the mutations affected SinR. In some mutants, large genomic regions encompassing sinR were deleted, whereas others had alleles encoding SinR variants. Functional and biochemical studies with these SinR variants revealed how these proteins allowed biofilm gene expression in the ymdB mutant strains. IMPORTANCE Many bacteria are able to choose between two mutually exclusive lifestyles: biofilm formation and motility. In the model bacterium Bacillus subtilis, this choice is made by each individual cell rather than at the population level. The transcriptional repressor SinR is the master regulator in this decision-making process. The regulation of SinR activity involves complex control of its own expression and of its interaction with antagonist proteins. We show that the YmdB phosphodiesterase is required to allow the expression of SinR-repressed genes in a subpopulation of cells and that such subpopulations can switch between different SinR activity states. Suppressor analyses revealed that ymdB mutants readily acquire mutations affecting SinR, thus restoring biofilm formation. These findings suggest that B. subtilis cells experience selective pressure to form the extracellular matrix that is characteristic of biofilms and that YmdB is required for the homeostasis of SinR and/or its antagonists.

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