bluuebunny/crossref_metadata_2025_split huggingface dataset:
Versatile Metabolic Adaptations ofRalstonia eutrophaH16 to a Loss of PdhL, the E3 Component of the Pyruvate Dehydrogenase Complex
Authors: Raberg Matthias , Bechmann Jan , Brandt Ulrike , Schlüter Jonas , Uischner Bianca , Voigt Birgit , Hecker Michael , Steinbüchel Alexander 
Published: February 2011

ABSTRACTA previous study reported that the Tn5-induced poly(3-hydroxybutyric acid) (PHB)-leaky mutantRalstonia eutrophaH1482 showed a reduced PHB synthesis rate and significantly lower dihydrolipoamide dehydrogenase (DHLDH) activity than the wild-typeR. eutrophaH16 but similar growth behavior. Insertion of Tn5was localized in thepdhLgene encoding the DHLDH (E3 component) of the pyruvate dehydrogenase complex (PDHC). Taking advantage of the available genome sequence ofR. eutrophaH16, observations were verified and further detailed analyses and experiments were done.In silicogenome analysis revealed thatR. eutrophapossesses all five known types of 2-oxoacid multienzyme complexes and five DHLDH-coding genes. Of these DHLDHs, only PdhL harbors an amino-terminal lipoyl domain. Furthermore, insertion of Tn5inpdhLof mutant H1482 disrupted the carboxy-terminal dimerization domain, thereby causing synthesis of a truncated PdhL lacking this essential region, obviously leading to an inactive enzyme. The defined ΔpdhLdeletion mutant ofR. eutrophaexhibited the same phenotype as the Tn5mutant H1482; this excludes polar effects as the cause of the phenotype of the Tn5mutant H1482. However, insertion of Tn5or deletion ofpdhLdecreases DHLDH activity, probably negatively affecting PDHC activity, causing the mutant phenotype. Moreover, complementation experiments showed that different plasmid-encoded E3 components ofR. eutrophaH16 or of other bacteria, likeBurkholderia cepacia, were able to restore the wild-type phenotype at least partially. Interestingly, the E3 component ofB. cepaciapossesses an amino-terminal lipoyl domain, like the wild-type H16. A comparison of the proteomes of the wild-type H16 and of the mutant H1482 revealed striking differences and allowed us to reconstruct at least partially the impressive adaptations ofR. eutrophaH1482 to the loss of PdhL on the cellular level.
Altering the Composition of Caseicins A and B as a Means of Determining the Contribution of Specific Residues to Antimicrobial Activity
Authors: Norberg Sarah , O'Connor Paula M. , Stanton Catherine , Ross R. Paul , Hill Colin , Fitzgerald Gerald F. , Cotter Paul D. 
Published: February 2011

ABSTRACT

Caseicin A (IKHQGLPQE) and caseicin B (VLNENLLR) are antimicrobial peptides generated through the bacterial fermentation of sodium caseinate, and on the basis of this and previous studies, they are active against many Gram-negative pathogens (
Cronobacter sakazakii
,
Cronobacter muytjensii
,
Salmonella enterica
serovar Typhimurium,
Escherichia coli
,
Klebsiella pneumoniae
, and
Pseudomonas fluorescens
) as well as the Gram-positive organism
Staphylococcus aureus
. Here we describe further studies with the aim of establishing the importance of specific (charged and nonpolar aliphatic) residues within the caseicin peptides and the effects that they have on the bacteria listed above. In order to achieve our objective, we created four derivatives of each caseicin (A1 to A4 and B1 to B4) in which specific residues were altered, and results obtained with these derivatives were compared to wild-type caseicin activity. Although conversion of cationic residues to alanine in caseicins B1 (R8A change), A1 (K2A), A2 (H3A), and A3 (K2A-H3A) generally resulted in their activity against microbial targets being reduced or unaltered,
C. sakazakii
DPC6440 was unusual in that it displayed enhanced sensitivity to three peptides (caseicins A1, A3, and B2) in which positively charged residues had been eliminated. While the replacement of leucine with alanine in selected variants (B3 and B4) resulted in reduced activity against a number of strains of
Cronobacter
and, in some cases,
S.
Typhimurium, these changes enhanced the activities of these peptides against DPC6440 and a number of
S. aureus
strains. It is thus apparent that the importance of specific residues within the caseicin peptides is dependent on the strain being targeted.
Significant Shift in Median Guinea Pig Infectious Dose Shown by an Outbreak-AssociatedListeria monocytogenesEpidemic Clone Strain and a Strain Carrying a Premature Stop Codon Mutation ininlA
Authors: Van Stelten A. , Simpson J. M. , Chen Y. , Scott V. N. , Whiting R. C. , Ross W. H. , Nightingale K. K. 
Published: February 2011

ABSTRACTListeria monocytogenescontains (i) epidemic clone (EC) strains, which have been linked to the majority of listeriosis outbreaks worldwide and are overrepresented among sporadic cases in the United States, and (ii) strains commonly isolated from ready-to-eat foods that carry a mutation leading to a premature stop codon (PMSC) ininlA, which encodes the key virulence factor internalin A (InlA). Internalin A binds certain isoforms of the cellular receptor E-cadherin to facilitate crossing the intestinal barrier during the initial stages of anL. monocytogenesinfection. Juvenile guinea pigs, which express the human isoform of E-cadherin that binds InlA, were intragastrically challenged with a range of doses of (i) an EC strain associated with a listeriosis outbreak or (ii) a strain carrying a PMSC mutation ininlA. Recovery ofL. monocytogenesfrom tissues (i.e., liver, spleen, mesenteric lymph nodes, and ileum) was used to develop strain-specific dose-response curves on the basis of individual and combined organ data. Modeling of individual and combined organ data revealed an approximate 1.2 to 1.3 log10increase in the median infectious dose for the strain carrying a PMSC ininlArelative to that for the EC strain. Inclusion of the strain parameter significantly improved the goodness of fit for individual and combined organ models, indicating a significant shift in median infectious dose for guinea pigs challenged with aninlAPMSC strain compared to that for guinea pigs challenged with an EC strain. Results from this work provide evidence that theL. monocytogenesdose-response relationship is strain specific and will provide critical data for enhancement of current risk assessments and development of future risk assessments.
Phylogeny of Replication Initiator Protein TrfA Reveals a Highly Divergent Clade of Incompatibility Group P1 Plasmids
Authors: Stenger Drake C. , Lee Min Woo 
Published: February 2011

ABSTRACT

Incompatibility group P1 (IncP-1) plasmid diversity was evaluated based on replication initiator protein (TrfA) phylogeny. A new and highly divergent clade was identified. Replication assays indicated that TrfA of recently discovered IncP-1 plasmids from
Xylella fastidiosa
and
Verminephrobacter eiseniae
initiated plasmid replication using cognate or heterologous origins of replication.
Efficient Generation of Unmarked Deletions in
Legionella pneumophila
Authors: Bryan Andrew , Harada Kaoru , Swanson Michele S. 
Published: February 2011

ABSTRACT

Unmarked gene deletions facilitate studies of
Legionella pneumophila
multicomponent processes, such as motility and exonuclease activity. For this purpose,
FRT
-flanked alleles constructed in
Escherichia coli
using λ-Red recombinase were transferred to
L. pneumophila
by natural transformation. Resistance cassettes were then efficiently excised using the Flp site-specific recombinase encoded on a plasmid that is readily lost.
Shuttle Vector System for
Methanococcus maripaludis
with Improved Transformation Efficiency
Authors: Walters Alison D. , Smith Sarah E. , Chong James P. J. 
Published: February 2011

ABSTRACT

We have identified an open reading frame and DNA element that are sufficient to maintain shuttle vectors in
Methanococcus maripaludis
. Strain S0001, containing ORF1 from pURB500 integrated into the
M. maripaludis
genome, supports a significantly smaller shuttle vector, pAW42, and a 7,000-fold increase in transformation efficiency for pURB500-based vectors.
Proximity-Dependent Inhibition in
Escherichia coli
Isolates from Cattle
Authors: Sawant Ashish A. , Casavant N. Carol , Call Douglas R. , Besser Thomas E. 
Published: February 2011

ABSTRACT

We describe a novel proximity-dependent inhibition phenotype of
Escherichia coli
that is expressed when strains are cocultured in defined minimal media. When cocultures of “inhibitor” and “target” strains approached a transition between logarithmic and stationary growth, target strain populations rapidly declined >4 log CFU per ml over a 2-h period. Inhibited strains were not affected by exposure to conditioned media from inhibitor and target strain cocultures or when the inhibitor and target strains were incubated in shared media but physically separated by a 0.4-μm-pore-size membrane. There was no evidence of lytic phage or extracellular bacteriocin involvement, unless the latter was only present at effective concentrations within immediate proximity of the inhibited cells. The inhibitory activity observed in this study was effective against a diversity of
E. coli
strains, including enterohemorrhagic
E. coli
serotype O157:H7, enterotoxigenic
E. coli
expressing F5 (K99) and F4 (K88) fimbriae, multidrug-resistant
E. coli
, and commensal
E. coli.
The decline in counts of target strains in coculture averaged 4.8 log CFU/ml (95% confidence interval, 4.0 to 5.5) compared to their monoculture counts. Coculture of two inhibitor strains showed mutual immunity to inhibition. These results suggest that proximity-dependent inhibition can be used by bacteria to gain a numerical advantage when populations are entering stationary phase, thus setting the stage for a competitive advantage when growth conditions improve.
Traffic of Chitin Synthase 1 (CHS-1) to the Spitzenkörper and Developing Septa in Hyphae of Neurospora crassa: Actin Dependence and Evidence of Distinct Microvesicle Populations
Authors: Sánchez-León Eddy , Verdín Jorge , Freitag Michael , Roberson Robert W. , Bartnicki-Garcia Salomon , Riquelme Meritxell 
Published: February 2011

ABSTRACT

We describe the subcellular location of chitin synthase 1 (CHS-1), one of seven chitin synthases in
Neurospora crassa
. Laser scanning confocal microscopy of growing hyphae showed CHS-1–green fluorescent protein (GFP) localized conspicuously in regions of active wall synthesis, namely, the core of the Spitzenkörper (Spk), the apical cell surface, and developing septa. It was also present in numerous fine particles throughout the cytoplasm plus some large vacuoles in distal hyphal regions. Although the same general subcellular distribution was observed previously for CHS-3 and CHS-6, they did not fully colocalize. Dual labeling showed that the three different chitin synthases were contained in different vesicular compartments, suggesting the existence of a different subpopulation of chitosomes for each CHS. CHS-1–GFP persisted in the Spk during hyphal elongation but disappeared from the septum after its development was completed. Wide-field fluorescence microscopy and total internal reflection fluorescence microscopy revealed subapical clouds of particles, suggestive of chitosomes moving continuously toward the Spk. Benomyl had no effect on CHS-1–GFP localization, indicating that microtubules are not strictly required for CHS trafficking to the hyphal apex. Conversely, actin inhibitors caused severe mislocalization of CHS-1–GFP, indicating that actin plays a major role in the orderly traffic and localization of CHS-1 at the apex.
Immunolocalization of an Alternative Respiratory Chain in Antonospora (Paranosema) locustae Spores: Mitosomes Retain Their Role in Microsporidial Energy Metabolism
Authors: Dolgikh Viacheslav V. , Senderskiy Igor V. , Pavlova Olga A. , Naumov Anton M. , Beznoussenko Galina V. 
Published: February 2011

ABSTRACT

Microsporidia are a group of fungus-related intracellular parasites with severely reduced metabolic machinery. They lack canonical mitochondria, a Krebs cycle, and a respiratory chain but possess genes encoding glycolysis enzymes, a glycerol phosphate shuttle, and ATP/ADP carriers to import host ATP. The recent finding of alternative oxidase genes in two clades suggests that microsporidial mitosomes may retain an alternative respiratory pathway. We expressed the fragments of mitochondrial chaperone Hsp70 (mitHsp70), mitochondrial glycerol-3-phosphate dehydrogenase (mitG3PDH), and alternative oxidase (AOX) from the microsporidium
Antonospora (Paranosema) locustae
in
Escherichia coli.
Immunoblotting with antibodies against recombinant polypeptides demonstrated specific accumulation of both metabolic enzymes in
A. locustae
spores. At the same time comparable amounts of mitochondrial Hsp70 were found in spores and in stages of intracellular development as well. Immunoelectron microscopy of ultrathin cryosections of spores confirmed mitosomal localization of the studied proteins. Small amounts of enzymes of an alternative respiratory chain in merogonial and early sporogonial stages, alongside their accumulation in mature spores, suggest conspicuous changes in components and functions of mitosomes during the life cycle of microsporidia and the important role of these organelles in parasite energy metabolism, at least at the final stages of sporogenesis.
Lactate Dehydrogenase A Promotes Communication between Carbohydrate Catabolism and Virulence inBacillus cereus
Authors: Laouami Sabrina , Messaoudi Kahina , Alberto François , Clavel Thierry , Duport Catherine 
Published: February 2011

ABSTRACTThe diarrheal potential of aBacillus cereusstrain is essentially dictated by the amount of secreted nonhemolytic enterotoxin (Nhe). Expression of genes encoding Nhe is regulated by several factors, including the metabolic state of the cells. To identify metabolic sensors that could promote communication between central metabolism andnheexpression, we compared four strains of theB. cereusgroup in terms of metabolic andnheexpression capacities. We performed growth performance measurements, metabolite analysis, and mRNA measurements of strains F4430/73, F4810/72, F837/76, and PA cultured under anoxic and fully oxic conditions. The results showed that expression levels ofnheandldhA, which encodes lactate dehydrogenase A (LdhA), were correlated in both aerobically and anaerobically grown cells. We examined the role of LdhA in the F4430/73 strain by constructing anldhAmutant. TheldhAmutation was more deleterious to anaerobically grown cells than to aerobically grown cells, causing growth limitation and strong deregulation of key fermentative genes. More importantly, theldhAmutation downregulated enterotoxin gene expression under both anaerobiosis and aerobiosis, with a more pronounced effect under anaerobiosis. Therefore, LdhA was found to exert a major control on both fermentative growth and enterotoxin expression, and it is concluded that there is a direct link between fermentative metabolism and virulence inB. cereus. The data presented also provide evidence that LdhA-dependent regulation of enterotoxin gene expression is oxygen independent. This study is the first report to describe a role of a fermentative enzyme in virulence inB. cereus.
An Experimentally Validated Genome-Scale Metabolic Reconstruction of
Klebsiella pneumoniae
MGH 78578,
i
YL1228
Authors: Liao Yu-Chieh , Huang Tzu-Wen , Chen Feng-Chi , Charusanti Pep , Hong Jay S. J. , Chang Hwan-You , Tsai Shih-Feng , Palsson Bernhard O. , Hsiung Chao A. 
Published: February 2011

ABSTRACT

Klebsiella pneumoniae
is a Gram-negative bacterium of the family
Enterobacteriaceae
that possesses diverse metabolic capabilities: many strains are leading causes of hospital-acquired infections that are often refractory to multiple antibiotics, yet other strains are metabolically engineered and used for production of commercially valuable chemicals. To study its metabolism, we constructed a genome-scale metabolic model (
i
YL1228) for strain MGH 78578, experimentally determined its biomass composition, experimentally determined its ability to grow on a broad range of carbon, nitrogen, phosphorus and sulfur sources, and assessed the ability of the model to accurately simulate growth versus no growth on these substrates. The model contains 1,228 genes encoding 1,188 enzymes that catalyze 1,970 reactions and accurately simulates growth on 84% of the substrates tested. Furthermore, quantitative comparison of growth rates between the model and experimental data for nine of the substrates also showed good agreement. The genome-scale metabolic reconstruction for
K. pneumoniae
presented here thus provides an experimentally validated
in silico
platform for further studies of this important industrial and biomedical organism.
Mycobacterium tuberculosis
Can Utilize Heme as an Iron Source
Authors: Jones Christopher M. , Niederweis Michael 
Published: February 2011

ABSTRACT

Most iron in mammals is found within the heme prosthetic group. Consequently, many bacterial pathogens possess heme acquisition systems to utilize iron from the host. Here, we demonstrate that
Mycobacterium tuberculosis
can utilize heme as an iron source, suggesting that
M. tuberculosis
possesses a yet-unknown heme acquisition system.
Protection ofBacillus subtilisagainst Cold Stress via Compatible-Solute Acquisition
Authors: Hoffmann Tamara , Bremer Erhard 
Published: February 2011

ABSTRACTAccumulation of compatible solutes is a strategy widely employed by bacteria to achieve cellular protection against high osmolarity. These compounds are also used in some microorganisms as thermostress protectants. We found thatBacillus subtilisuses the compatible solute glycine betaine as an effective cold stress protectant. Glycine betaine strongly stimulated growth at 15°C and permitted cell proliferation at the growth-inhibiting temperature of 13°C. Initial uptake of glycine betaine at 15°C was low but led eventually to the buildup of an intracellular pool whose size was double that found in cells grown at 35°C. Each of the three glycine betaine transporters (OpuA, OpuC, and OpuD) contributed to glycine betaine accumulation in the cold. Protection against cold stress was also accomplished when glycine betaine was synthesized from its precursor choline. Growth of a mutant defective in the osmoadaptive biosynthesis for the compatible solute proline was not impaired at low temperature (15°C). In addition to glycine betaine, the compatible solutes and osmoprotectantsl-carnitine, crotonobetaine, butyrobetaine, homobetaine, dimethylsulfonioactetate, and proline betaine all served as cold stress protectants as well and were accumulated via known Opu transport systems. In contrast, the compatible solutes and osmoprotectants choline-O-sulfate, ectoine, proline, and glutamate were not cold protective. Our data highlight an underappreciated facet of the acclimatization ofB. subtilisto cold environments and allow a comparison of the characteristics of compatible solutes with respect to their osmotic, heat, and cold stress-protective properties forB. subtiliscells.
Effects of Modified Phycobilin Biosynthesis in the CyanobacteriumSynechococcussp. Strain PCC 7002
Authors: Alvey Richard M. , Biswas Avijit , Schluchter Wendy M. , Bryant Donald A. 
Published: February 2011

ABSTRACTThe pathway for phycocyanobilin biosynthesis inSynechococcussp. strain PCC 7002 comprises two enzymes: heme oxygenase and phycocyanobilin synthase (PcyA). The phycobilin content of cells can be modified by overexpressing genes encoding alternative enzymes for biliverdin reduction. Overexpression of thepebABand HY2 genes, encoding alternative ferredoxin-dependent biliverdin reductases, caused unique effects due to the overproduction of phycoerythrobilin and phytochromobilin, respectively. Colonies overexpressingpebABbecame reddish brown and visually resembled strains that naturally produce phycoerythrin. This was almost exclusively due to the replacement of phycocyanobilin by phycoerythrobilin on the phycocyanin α-subunit. This phenotype was unstable, and such strains rapidly reverted to the wild-type appearance, presumably due to strong selective pressure to inactivatepebABexpression. Overproduction of phytochromobilin, synthesized by theArabidopsis thalianaHY2 product, was tolerated much better. Cells overexpressing HY2 were only slightly less pigmented and blue-green than the wild type. Although thepcyAgene could not be inactivated in the wild type,pcyAwas easily inactivated when cells expressed HY2. These results indicate that phytochromobilin can functionally substitute for phycocyanobilin inSynechococcussp. strain PCC 7002. Although functional phycobilisomes were assembled in this strain, the overall phycobiliprotein content of cells was lower, the efficiency of energy transfer by these phycobilisomes was lower than for wild-type phycobilisomes, and the absorption cross-section of the cells was reduced relative to that of the wild type because of an increased spectral overlap of the modified phycobiliproteins with chlorophylla. As a result, the strain producing phycobiliproteins carrying phytochromobilin grew much more slowly at low light intensity.
Poisoning hospitalisations among reproductive-aged women in the USA, 1998–2006
Authors: Cox Shanna , Kuo Cassie , Jamieson Denise J , Kourtis Athena P , McPheeters Melissa L , Meikle Susan F , Posner Samuel F 
Published: February 2011

ObjectiveTo describe poisoning hospitalisations among reproductive-aged women from 1998 to 2006.Methods1998–2006 data from the Nationwide Inpatient Sample of the Healthcare Cost and Utilisation Project were used to identify hospitalisations for poisonings among US women aged 15–44 years. Differences in hospitalisation characteristics were compared by intent using χ2statistics. Trends in poisoning hospitalisation rates were calculated overall and by subgroup.ResultsThere were approximately 636 000 poisoning hospitalisations in women aged 15–44 years during 1998–2006. Hospitalisations for intentionally self-inflicted poisonings had a higher proportion of women aged 15–24 years and privately insured women than did unintentional poisonings (p<0.001). Poisoning hospitalisations in rural areas and those that resulted in death were more likely to be of undetermined intent than those for which intent was specified (p<0.001). Co-diagnoses of substance abuse (34.5%) or mental disorders (66.5%) were high. The rate of poisoning hospitalisations overall and unintentional poisoning hospitalisations increased 6% and 22%, respectively, during this period (p<0.001). The most frequently diagnosed poisoning agent was acetaminophen. Poisonings attributable to acetaminophen, opioids, central nervous system stimulants and benzodiazepines increased, while poisonings attributable to antidepressants decreased (p<0.05).ConclusionsThe increase in unintentional poisoning hospitalisations among women aged 15–44 years and the changing profile of poisoning agents should inform the healthcare community's poisoning prevention strategies. Poisoning prevention strategies should include a component to address substance abuse and mental health disorders among reproductive-age women.