bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organization of the Electron Transfer Chain to Oxygen in the Obligate Human Pathogen
Neisseria gonorrhoeae
: Roles for Cytochromes
c
4
and
c
5
, but Not Cytochrome
c
2
, in Oxygen Reduction
Authors: Li Ying , Hopper Amanda , Overton Tim , Squire Derrick J. P. , Cole Jeffrey , Tovell Nicholas 
Published: February 2010

ABSTRACT

Although
Neisseria gonorrhoeae
is a prolific source of eight
c
-type cytochromes, little is known about how its electron transfer pathways to oxygen are organized. In this study, the roles in the respiratory chain to oxygen of cytochromes
c
2
,
c
4
, and
c
5
, encoded by the genes
cccA
,
cycA
, and
cycB
, respectively, have been investigated. Single mutations in genes for either cytochrome
c
4
or
c
5
resulted in an increased sensitivity to growth inhibition by excess oxygen and small decreases in the respiratory capacity of the parent, which were complemented by the chromosomal integration of an ectopic, isopropyl-β-
d
-thiogalactopyranoside (IPTG)-inducible copy of the
cycA
or
cycB
gene. In contrast, a
cccA
mutant reduced oxygen slightly more rapidly than the parent, suggesting that
cccA
is expressed but cytochrome
c
2
is not involved in electron transfer to cytochrome oxidase. The deletion of
cccA
increased the sensitivity of the
cycB
mutant to excess oxygen but decreased the sensitivity of the
cycA
mutant. Despite many attempts, a double mutant defective in both cytochromes
c
4
and
c
5
could not be isolated. However, a strain with the ectopically encoded, IPTG-inducible
cycB
gene with deletions in both
cycA
and
cycB
was constructed: the growth and survival of this strain were dependent upon the addition of IPTG, so gonococcal survival is dependent upon the synthesis of either cytochrome
c
4
or
c
5
. These results define the gonococcal electron transfer chain to oxygen in which cytochromes
c
4
and
c
5
, but not cytochrome
c
2
, provide alternative pathways for electron transfer from the cytochrome
bc
1
complex to the terminal oxidase cytochrome
cbb
3
.
Protecting against Antimicrobial Effectors in the Phagosome Allows SodCII To Contribute to Virulence in
Salmonella enterica
Serovar Typhimurium
Authors: Kim Byoungkwan , Richards Susan M. , Gunn John S. , Slauch James M. 
Published: February 2010

ABSTRACT

Salmonella enterica
serovar Typhimurium replicates in macrophages, where it is subjected to antimicrobial substances, including superoxide, antimicrobial peptides, and proteases. The bacterium produces two periplasmic superoxide dismutases, SodCI and SodCII. Although both are expressed during infection, only SodCI contributes to virulence in the mouse by combating phagocytic superoxide. The differential contribution to virulence is at least partially due to inherent differences in the SodCI and SodCII proteins that are independent of enzymatic activity. SodCII is protease sensitive, and like other periplasmic proteins, it is released by osmotic shock. In contrast, SodCI is protease resistant and is retained within the periplasm after osmotic shock, a phenomenon that we term “tethering.” We hypothesize that in the macrophage, antimicrobial peptides transiently disrupt the outer membrane. SodCII is released and/or phagocytic proteases gain access to the periplasm, and SodCII is degraded. SodCI is tethered within the periplasm and is protease resistant, thereby remaining to combat superoxide. Here we test aspects of this model. SodCII was released by the antimicrobial peptide polymyxin B or a mouse macrophage antimicrobial peptide (CRAMP), while SodCI remained tethered within the periplasm. A
Salmonella pmrA
constitutive mutant no longer released SodCII
in vitro
. Moreover, in the constitutive
pmrA
background, SodCII could contribute to survival of
Salmonella
during infection. SodCII also provided a virulence benefit in mice genetically defective in production of CRAMP. Thus, consistent with our model, protecting the outer membrane against antimicrobial peptides allows SodCII to contribute to virulence
in vivo
. These data also suggest direct
in vivo
cooperative interactions between macrophage antimicrobial effectors.
Polymyxin B Resistance in El Tor
Vibrio cholerae
Requires Lipid Acylation Catalyzed by MsbB
Authors: Matson Jyl S. , Yoo Hyun Ju , Hakansson Kristina , DiRita Victor J. 
Published: February 2010

ABSTRACT

Antimicrobial peptides are critical for innate antibacterial defense. Both Gram-negative and Gram-positive microbes have mechanisms to alter their surfaces and resist killing by antimicrobial peptides. In
Vibrio cholerae
, two natural epidemic biotypes, classical and El Tor, exhibit distinct phenotypes with respect to sensitivity to the peptide antibiotic polymyxin B: classical strains are sensitive and El Tor strains are relatively resistant. We carried out mutant screens of both biotypes, aiming to identify classical
V. cholerae
mutants resistant to polymyxin B and El Tor
V. cholerae
mutants sensitive to polymyxin B. Insertions in a gene annotated
msbB
(encoding a predicted lipid A secondary acyltransferase) answered both screens, implicating its activity in antimicrobial peptide resistance of
V. cholerae
. Analysis of a defined mutation in the El Tor biotype demonstrated that
msbB
is required for resistance to all antimicrobial peptides tested. Mutation of
msbB
in a classical strain resulted in reduced resistance to several antimicrobial peptides but in no significant change in resistance to polymyxin B.
msbB
mutants of both biotypes showed decreased colonization of infant mice, with a more pronounced defect observed for the El Tor mutant. Mass spectrometry analysis showed that lipid A of the
msbB
mutant for both biotypes was underacylated compared to lipid A of the wild-type isolates, confirming that MsbB is a functional acyltransferase in
V. cholerae
.
Cell Surface Xylanases of the Glycoside Hydrolase Family 10 Are Essential for Xylan Utilization byPaenibacillussp. W-61 as Generators of Xylo-Oligosaccharide Inducers for the Xylanase Genes
Authors: Fukuda Mutsumi , Watanabe Seiji , Yoshida Shigeki , Itoh Hiroya , Itoh Yoshifumi , Kamio Yoshiyuki , Kaneko Jun 
Published: February 2010

ABSTRACTPaenibacillussp. W-61 is capable of utilizing water-insoluble xylan for carbon and energy sources and has three xylanase genes,xyn1,xyn3, andxyn5. Xyn1, Xyn3, and Xyn5 are extracellular enzymes of the glycoside hydrolase (GH) families 11, 30, and 10, respectively. Xyn5 contains several domains including those of carbohydrate-binding modules (CBMs) similar to a surface-layer homologous (SLH) protein. This study focused on the role of Xyn5, localized on the cell surface, in water-insoluble xylan utilization. Electron microscopy using immunogold staining revealed Xyn5 clusters over the entire cell surface. Xyn5 was bound to cell wall fractions through its SLH domain. A Δxyn5mutant grew poorly and produced minimal amounts of Xyn1 and Xyn3 on water-insoluble xylan. A Xyn5 mutant lacking the SLH domain (Xyn5ΔSLH) grew poorly, secreting Xyn5ΔSLH into the medium and producing minimal Xyn1 and Xyn3 on water-insoluble xylan. A mutant with an intactxyn5produced Xyn5 on the cell surface, grew normally, and actively synthesized Xyn1 and Xyn3 on water-insoluble xylan. Quantitative reverse transcription-PCR showed that xylobiose, generated from water-insoluble xylan decomposition by Xyn5, is the most active inducer forxyn1andxyn3. Luciferase assays using a Xyn5-luciferase fusion protein suggested that xylotriose is the best inducer forxyn5. The cell surface Xyn5 appears to play two essential roles in water-insoluble xylan utilization: (i) generation of the xylo-oligosaccharide inducers of all thexyngenes from water-insoluble xylan and (ii) attachment of the cells to the substrate so that the generated inducers can be immediately taken up by cells to activate expression of thexynsystem.
Heterochronic Phosphorelay Gene Expression as a Source of Heterogeneity in
Bacillus subtilis
Spore Formation
Authors: de Jong Imke G. , Veening Jan-Willem , Kuipers Oscar P. 
Published: February 2010

ABSTRACT

In response to limiting nutrient sources and cell density signals,
Bacillus subtilis
can differentiate and form highly resistant endospores. Initiation of spore development is governed by the master regulator Spo0A, which is activated by phosphorylation via a multicomponent phosphorelay. Interestingly, only part of a clonal population will enter this developmental pathway, a phenomenon known as sporulation bistability or sporulation heterogeneity. How sporulation heterogeneity is established is largely unknown. To investigate the origins of sporulation heterogeneity, we constructed promoter-green fluorescent protein (GFP) fusions to the main phosphorelay genes and perturbed their expression levels. Using time-lapse fluorescence microscopy and flow cytometry, we showed that expression of the phosphorelay genes is distributed in a unimodal manner. However, single-cell trajectories revealed that phosphorelay gene expression is highly dynamic or “heterochronic” between individual cells and that stochasticity of phosphorelay gene transcription might be an important regulatory mechanism for sporulation heterogeneity. Furthermore, we showed that artificial induction or depletion of the phosphorelay phosphate flow results in loss of sporulation heterogeneity. Our data suggest that sporulation heterogeneity originates from highly dynamic and variable gene activity of the phosphorelay components, resulting in large cell-to-cell variability with regard to phosphate input into the system. These transcriptional and posttranslational differences in phosphorelay activity appear to be sufficient to generate a heterogeneous sporulation signal without the need of the positive-feedback loop established by the sigma factor SigH.
The Abi Proteins and Their Involvement in Bacteriocin Self-Immunity
Authors: Kjos Morten , Snipen Lars , Salehian Zhian , Nes Ingolf F. , Diep Dzung B. 
Published: February 2010

ABSTRACT

The Abi protein family consists of putative membrane-bound metalloproteases. While they are involved in membrane anchoring of proteins in eukaryotes, little is known about their function in prokaryotes. In some known bacteriocin loci, Abi genes have been found downstream of bacteriocin structural genes (e.g.,
pln
locus from
Lactobacillus plantarum
and
sag
locus from
Streptococcus pyogenes
), where they probably are involved in self-immunity. By modifying the profile hidden Markov model used to select Abi proteins in the Pfam protein family database, we show that this family is larger than presently recognized. Using bacteriocin-associated Abi genes as a means to search for novel bacteriocins in sequenced genomes, seven new bacteriocin-like loci were identified in Gram-positive bacteria. One such locus, from
Lactobacillus sakei
23K, was selected for further experimental study, and it was confirmed that the bacteriocin-like genes (
skkAB
) exhibited antimicrobial activity when expressed in a heterologous host and that the associated Abi gene (
skkI
) conferred immunity against the cognate bacteriocin. Similar investigation of the Abi gene
plnI
and the Abi-like gene
plnL
from
L. plantarum
also confirmed their involvement in immunity to their cognate bacteriocins (PlnEF and PlnJK, respectively). Interestingly, the immunity genes from these three systems conferred a high degree of cross-immunity against each other's bacteriocins, suggesting the recognition of a common receptor. Site-directed mutagenesis demonstrated that the conserved motifs constituting the putative proteolytic active site of the Abi proteins are essential for the immunity function of SkkI, and to our knowledge, this represents a new concept in self-immunity.
Strains of the East Asian (W/Beijing) Lineage ofMycobacterium tuberculosisAre DosS/DosT-DosR Two-Component Regulatory System Natural Mutants
Authors: Fallow Ashley , Domenech Pilar , Reed Michael B. 
Published: February 2010

ABSTRACTAs part of our ongoing efforts to uncover the phenotypic consequences of genetic variability among clinicalMycobacterium tuberculosisisolates, we previously reported that isolates of the “East Asian” or “W/Beijing” lineage constitutively overexpress the coordinately regulated transcriptional program known as the DosR regulon under standardin vitroconditions. This phenotype distinguishes the W/Beijing lineage from all otherM. tuberculosislineages, which normally induce expression of this regulon only once exposed to low oxygen or nitric oxide, both of which result in inhibition of bacterial respiration and replication. Transcription of the DosR regulon is controlled through a two-component regulatory system comprising the transcription factor DosR and two possible cognate histidine sensor kinases, DosS and DosT. Through sequence analysis of a carefully selected set of isolates representing each of the majorM. tuberculosislineages, we describe herein a naturally occurring frameshift mutation in the gene encoding the DosT sensor kinase for isolates of the most recently evolved W/Beijing sublineages. Intriguingly, the occurrence of the frameshift mutation correlates precisely with the appearance of the constitutive DosR regulon phenotype displayed by the same “modern” W/Beijing strains. However, complementation studies have revealed that the mutation indosTalone is not directly responsible for the constitutive DosR regulon phenotype. Our data serve to highlight the evolutionary pressure that exists among distinctM. tuberculosislineages to maintain tight control over DosR regulon expression.
Increase in Rhamnolipid Synthesis under Iron-Limiting Conditions Influences Surface Motility and Biofilm Formation in
Pseudomonas aeruginosa
Authors: Glick Rivka , Gilmour Christie , Tremblay Julien , Satanower Shirley , Avidan Ofir , Déziel Eric , Greenberg E. Peter , Poole Keith , Banin Ehud 
Published: February 2010

ABSTRACT

Iron is an essential element for life but also serves as an environmental signal for biofilm development in the opportunistic human pathogen
Pseudomonas aeruginosa
. Under iron-limiting conditions,
P. aeruginosa
displays enhanced twitching motility and forms flat unstructured biofilms. In this study, we present evidence suggesting that iron-regulated production of the biosurfactant rhamnolipid is important to facilitate the formation of flat unstructured biofilms. We show that under iron limitation the timing of rhamnolipid expression is shifted to the initial stages of biofilm formation (versus later in biofilm development under iron-replete conditions) and results in increased bacterial surface motility. In support of this observation, an
rhlAB
mutant defective in biosurfactant production showed less surface motility under iron-restricted conditions and developed structured biofilms similar to those developed by the wild type under iron-replete conditions. These results highlight the importance of biosurfactant production in determining the mature structure of
P. aeruginosa
biofilms under iron-limiting conditions.
Dual Control of
Sinorhizobium meliloti
RpoE2 Sigma Factor Activity by Two PhyR-Type Two-Component Response Regulators
Authors: Bastiat Bénédicte , Sauviac Laurent , Bruand Claude 
Published: February 2010

ABSTRACT

RpoE2 is an extracytoplasmic function (ECF) sigma factor involved in the general stress response of
Sinorhizobium meliloti
, the nitrogen-fixing symbiont of the legume plant alfalfa. RpoE2 orthologues are widely found among alphaproteobacteria, where they play various roles in stress resistance and/or host colonization. In this paper, we report a genetic and biochemical investigation of the mechanisms of signal transduction leading to
S. meliloti
RpoE2 activation in response to stress. We showed that RpoE2 activity is negatively controlled by two paralogous anti-sigma factors, RsiA1 (SMc01505) and RsiA2 (SMc04884), and that RpoE2 activation by stress requires two redundant paralogous PhyR-type response regulators, RsiB1 (SMc01504) and RsiB2 (SMc00794). RsiB1 and RsiB2 do not act at the level of
rpoE2
transcription but instead interact with the anti-sigma factors, and we therefore propose that they act as anti-anti-sigma factors to relieve RpoE2 inhibition in response to stress. This model closely resembles a recently proposed model of activation of RpoE2-like sigma factors in
Methylobacterium extorquens
and
Bradyrhizobium japonicum
, but the existence of two pairs of anti- and anti-anti-sigma factors in
S. meliloti
adds an unexpected level of complexity, which may allow the regulatory system to integrate multiple stimuli.
Fibril Morphology and Tendon Mechanical Properties in Patellar Tendinopathy
Authors: Kongsgaard Mads , Qvortrup Klaus , Larsen Jytte , Aagaard Per , Doessing Simon , Hansen Philip , Kjaer Michael , Magnusson S. Peter 
Published: February 2010

Background Patellar tendinopathy is characterized by pathologic abnormalities. Heavy slow resistance training (HSR) is effective in the management of patellar tendinopathy, but the underlying functional mechanisms remain elusive. Purpose To investigate fibril morphology and mechanical properties in patellar tendinopathy and the effect of HSR on these properties. Study Design Cohort study; Level of evidence, 2. Methods Eight male patients with patellar tendinopathy completed 12 weeks of HSR. Nine healthy subjects served as controls. Assessments were conducted at baseline and at 12 weeks. Patients assessed symptoms/function and maximal tendon pain during activity. Tendon biopsy samples were analyzed for fibril density, volume fraction, and mean fibril area. Tendon mechanical properties were assessed using force and ultrasonography samplings. Results Patients improved in symptoms/function (P = .02) and maximal tendon pain during activity (P = .008). Stiffness and modulus of control and tendinopathy tendons were similar at baseline. Stiffness remained unaffected in control tendons (3487 ± 392 to 3157 ± 327 N/mm, P = .57) but declined in tendinopathic tendons at 12 weeks (3185 ± 187 to 2701 ± 201 N/mm, P = .04). At baseline, fibril volume fraction was equal, fibril density smaller (P = .03), and mean fibril area tended to be higher in tendinopathy versus controls (P = .07). Fibril morphology remained unchanged in controls but fibril density increased (70% ± 18%, P = .02) and fibril mean area decreased (—26% ± 21%, P = .04) in tendinopathic tendons after HSR. Conclusion Fibril morphology is abnormal in tendinopathy, but tendon mechanical properties are not. Clinical improvements after HSR were associated with changes in fibril morphology toward normal fibril density and mean fibril area. Heavy slow resistance training improved the clinical outcome of patellar tendinopathy, and these improvements were associated with normalization of fibril morphology, most likely due to a production of new fibrils.
Increased prevalence of cardiovascular disease and risk biomarkers in patients with unknown type 2 diabetes visiting cardiology specialists: results from the DIASPORA study
Authors: Schöndorf Thomas , Lübben Georg , Karagiannis Efstrathios , Erdmann Erland , Forst Thomas , Pfützner Andreas 
Published: February 2010

Background: Patients with diabetes mellitus and IGT have a high risk for cardiovascular events. It is tempting to speculate that these patients are often first seen by cardiologists. Design: This cross-sectional study investigates the diabetes prevalence in cardiology care units and the correlated metabolic conditions as assessed by several circulating biomarkers. Methods: Patients aged 55 or older with suspected or overt coronary heart disease were eligible for trial participation. Fasting blood samples were drawn from patients to determine HOMA score, glycaemic and lipid profile, and several risk biomarkers. An OGTT was performed in patients without known diabetes. Results: We enrolled 530 patients (181 male, 349 female, mean age, 68±7 years) in this study from 22 German cardiology centres; 156 patients (29.4%) had known diabetes and OGTT revealed that 184 patients (34.7%) had no diabetes, 106 patients (20.0%) had IGT or IFG and 84 patients (15.9%) were newly diagnosed with diabetes. Increased cardiovascular risk as reflected by increased hsCRP, ICAM and MMP-9 values was observed in diabetes patients. A higher cardiovascular biomarkers risk profile was seen in the IGT/IFG cohort. Conclusions:This study confirms the observation that one third of patients of a cardiologic care unit suffer from impaired glucose regulation. Furthermore, the cardiology patients with previously unknown glucose homeostasis abnormalities had a higher prevalence of macrovacular disease and an impaired biomarker risk profile. This study underlines the importance of joint treatment efforts by cardiologists in concert with diabetologists for treatment of this patient group at high risk for cardiovascular events.
Perturbed hematopoiesis in the Tc1 mouse model of Down syndrome
Authors: Alford Kate A. , Slender Amy , Vanes Lesley , Li Zhe , Fisher Elizabeth M. C. , Nizetic Dean , Orkin Stuart H. , Roberts Irene , Tybulewicz Victor L. J. 
Published: February 2010

Abstract
Trisomy of human chromosome 21 (Hsa21) results in Down syndrome (DS), a disorder that affects many aspects of physiology, including hematopoiesis. DS children have greatly increased rates of acute lymphoblastic leukemia and acute megakaryoblastic leukemia (AMKL); DS newborns present with transient myeloproliferative disorder (TMD), a preleukemic form of AMKL. TMD and DS-AMKL almost always carry an acquired mutation in GATA1 resulting in exclusive synthesis of a truncated protein (GATA1s), suggesting that both trisomy 21 and GATA1 mutations are required for leukemogenesis. To gain further understanding of how Hsa21 contributes to hematopoietic abnormalities, we examined the Tc1 mouse model of DS, which carries an almost complete freely segregating copy of Hsa21, and is the most complete model of DS available. We show that although Tc1 mice do not develop leukemia, they have macrocytic anemia and increased extramedullary hematopoiesis. Introduction of GATA1s into Tc1 mice resulted in a synergistic increase in megakaryopoiesis, but did not result in leukemia or a TMD-like phenotype, demonstrating that GATA1s and trisomy of approximately 80% of Hsa21 perturb megakaryopoiesis but are insufficient to induce leukemia.
Molecular response to treatment redefines all prognostic factors in children and adolescents with B-cell precursor acute lymphoblastic leukemia: results in 3184 patients of the AIEOP-BFM ALL 2000 study
Authors: Conter Valentino , Bartram Claus R. , Valsecchi Maria Grazia , Schrauder André , Panzer-Grümayer Renate , Möricke Anja , Aricò Maurizio , Zimmermann Martin , Mann Georg , De Rossi Giulio , Stanulla Martin , Locatelli Franco , Basso Giuseppe , Niggli Felix , Barisone Elena , Henze Günter , Ludwig Wolf-Dieter , Haas Oskar A. , Cazzaniga Giovanni , Koehler Rolf , Silvestri Daniela , Bradtke Jutta , Parasole Rosanna , Beier Rita , van Dongen Jacques J. M. , Biondi Andrea , Schrappe Martin 
Published: February 2010

AbstractThe Associazione Italiana di Ematologia Oncologia Pediatrica and the Berlin-Frankfurt-Münster Acute Lymphoblastic Leukemia (AIEOP-BFM ALL 2000) study has for the first time introduced standardized quantitative assessment of minimal residual disease (MRD) based on immunoglobulin and T-cell receptor gene rearrangements as polymerase chain reaction targets (PCR-MRD), at 2 time points (TPs), to stratify patients in a large prospective study. Patients with precursor B (pB) ALL (n = 3184) were considered MRD standard risk (MRD-SR) if MRD was already negative at day 33 (analyzed by 2 markers, with a sensitivity of at least 10−4); MRD high risk (MRD-HR) if 10−3 or more at day 78 and MRD intermediate risk (MRD-IR): others. MRD-SR patients were 42% (1348): 5-year event-free survival (EFS, standard error) is 92.3% (0.9). Fifty-two percent (1647) were MRD-IR: EFS 77.6% (1.3). Six percent of patients (189) were MRD-HR: EFS 50.1% (4.1; P < .001). PCR-MRD discriminated prognosis even on top of white blood cell count, age, early response to prednisone, and genotype. MRD response detected by sensitive quantitative PCR at 2 predefined TPs is highly predictive for relapse in childhood pB-ALL. The study is registered at http://clinicaltrials.gov: NCT00430118 for BFM and NCT00613457 for AIEOP.