bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Clonal Complexes with an Unknown Animal Reservoir Dominate
Campylobacter jejuni
Isolates from River Water in New Zealand
Authors: Carter P. E. , McTavish S. M. , Brooks H. J. L. , Campbell D. , Collins-Emerson J. M. , Midwinter A. C. , French N. P. 
Published: August 2009

ABSTRACT

Campylobacter jejuni
is widely distributed in the environment, and river water has been shown to carry high levels of the organism. In this study, 244
C. jejuni
isolates from three river catchment areas in New Zealand were characterized using multilocus sequence typing. Forty-nine of the 88 sequence types identified were new. The most common sequence types identified were ST-2381 (30 isolates), ST-45 (25 isolates), and ST-1225 (23 isolates). The majority of the sequence types identified in the river water could be attributed to wild bird fecal contamination. Two novel clonal complexes (CC) were identified, namely, CC ST-2381 (11 sequence types, 46 isolates) and CC ST-3640 (6 sequence types, 12 isolates), in which all of the sequence types were new. CC ST-2381 was the largest complex identified among the isolates and was present in two of the three rivers. None of the sequence types associated with the novel complexes has been identified among human isolates. The ST-2381 complex is not related to complexes associated with cattle, sheep, or poultry. The source of the novel complexes has yet to be identified.
Impact of Alginate Overproduction on Attachment and Biofilm Architecture of a Supermucoid
Pseudomonas aeruginosa
Strain
Authors: Hay Iain D. , Gatland Kali , Campisano Andrea , Jordens J. Zoe , Rehm Bernd H. A. 
Published: August 2009

ABSTRACT

The supermucoid
Pseudomonas aeruginosa
strain PDO300Δ
alg8
(pBBR1MCS-5:
alg8
) showed strongly impaired attachment compared with the respective mucoid or nonmucoid strains and formed a thicker biofilm with large extended mushroom-like microcolonies. Alginate lyase treatment dissolved microcolonies. The data suggested that alginate overproduction impairs attachment but plays a structural role in microcolony formation.
Internalization of
Salmonella enterica
in Leaves Is Induced by Light and Involves Chemotaxis and Penetration through Open Stomata
Authors: Kroupitski Yulia , Golberg Dana , Belausov Eduard , Pinto Riky , Swartzberg Dvora , Granot David , Sela Shlomo 
Published: August 2009

ABSTRACT

Outbreaks of salmonellosis related to consumption of fresh produce have raised interest in
Salmonella-
plant interactions leading to plant colonization. Incubation of
gfp
-tagged
Salmonella enterica
with iceberg lettuce leaves in the light resulted in aggregation of bacteria near open stomata and invasion into the inner leaf tissue. In contrast, incubation in the dark resulted in a scattered attachment pattern and very poor stomatal internalization. Forcing stomatal opening in the dark by fusicoccin had no significant effect on
Salmonella
internalization. These results imply that the pathogen is attracted to nutrients produced de novo by photosynthetically active cells. Indeed, mutations affecting
Salmonella
motility and chemotaxis significantly inhibited bacterial internalization. These findings suggest a mechanistic account for entry of
Salmonella
into the plant's apoplast and imply that either
Salmonella
antigens are not well recognized by the stoma-based innate immunity or that this pathogen has evolved means to evade it. Internalization of leaves may provide a partial explanation for the failure of sanitizers to efficiently eradicate food-borne pathogens in leafy greens.
Symbiont Succession during Embryonic Development of the European Medicinal Leech,
Hirudo verbana
Authors: Rio Rita V. M. , Maltz Michele , McCormick Benjamin , Reiss Alexander , Graf Joerg 
Published: August 2009

ABSTRACT

The European medicinal leech,
Hirudo verbana
, harbors simple microbial communities in the digestive tract and bladder. The colonization history, infection frequency, and growth dynamics of symbionts through host embryogenesis are described using diagnostic PCR and quantitative PCR. Symbiont species displayed diversity in temporal establishment and proliferation through leech development.
Modeling of Spatially Referenced Environmental and Meteorological Factors Influencing the Probability ofListeriaSpecies Isolation from Natural Environments
Authors: Ivanek R. , Gröhn Y. T. , Wells M. T. , Lembo A. J. , Sauders B. D. , Wiedmann M. 
Published: August 2009

ABSTRACTMany pathogens have the ability to survive and multiply in abiotic environments, representing a possible reservoir and source of human and animal exposure. Our objective was to develop a methodological framework to study spatially explicit environmental and meteorological factors affecting the probability of pathogen isolation from a location. Isolation ofListeriaspp. from the natural environment was used as a model system. Logistic regression and classification tree methods were applied, and their predictive performances were compared. Analyses revealed that precipitation and occurrence of alternating freezing and thawing temperatures prior to sample collection, loam soil, water storage to a soil depth of 50 cm, slope gradient, and cardinal direction to the north are key predictors for isolation ofListeriaspp. from a spatial location. Different combinations of factors affected the probability of isolation ofListeriaspp. from the soil, vegetation, and water layers of a location, indicating that the three layers represent different ecological niches forListeriaspp. The predictive power of classification trees was comparable to that of logistic regression. However, the former were easier to interpret, making them more appealing for field applications. Our study demonstrates how the analysis of a pathogen's spatial distribution improves understanding of the predictors of the pathogen's presence in a particular location and could be used to propose novel control strategies to reduce human and animal environmental exposure.
Protein
O
-Mannosyltransferases B and C Support Hyphal Development and Differentiation in
Aspergillus nidulans
Authors: Goto Masatoshi , Harada Yuka , Oka Takuji , Matsumoto Sho , Takegawa Kaoru , Furukawa Kensuke 
Published: August 2009

ABSTRACT

Aspergillus nidulans
possesses three
pmt
genes encoding protein
O
-
d
-mannosyltransferases (Pmt). Previously, we reported that PmtA, a member of the PMT2 subfamily, is involved in the proper maintenance of fungal morphology and formation of conidia (T. Oka, T. Hamaguchi, Y. Sameshima, M. Goto, and K. Furukawa, Microbiology
150:
1973-1982, 2004). In the present paper, we describe the characterization of the
pmtA
paralogues
pmtB
and
pmtC
. PmtB and PmtC were classified as members of the PMT1 and PMT4 subfamilies, respectively. A
pmtB
disruptant showed wild-type (wt) colony formation at 30°C but slightly repressed growth at 42°C. Conidiation of the
pmtB
disruptant was reduced to approximately 50% of that of the wt strain; in addition, hyperbranching of hyphae indicated that PmtB is involved in polarity maintenance. A
pmtA
and
pmtB
double disruptant was viable but very slow growing, with morphological characteristics that were cumulative with respect to either single disruptant. Of the three single
pmt
mutants, the
pmtC
disruptant showed the highest growth repression; the hyphae were swollen and frequently branched, and the ability to form conidia under normal growth conditions was lost. Recovery from the aberrant hyphal structures occurred in the presence of osmotic stabilizer, implying that PmtC is responsible for the maintenance of cell wall integrity. Osmotic stabilization at 42°C further enabled the
pmtC
disruptant to form conidiophores and conidia, but they were abnormal and much fewer than those of the wt strain. Apart from the different, abnormal phenotypes, the three
pmt
disruptants exhibited differences in their sensitivities to antifungal reagents, mannosylation activities, and glycoprotein profiles, indicating that PmtA, PmtB, and PmtC perform unique functions during cell growth.
Flagellum-Mediated Biofilm Defense Mechanisms of
Pseudomonas aeruginosa
against Host-Derived Lactoferrin
Authors: Leid Jeff G. , Kerr Mathias , Selgado Candice , Johnson Chelsa , Moreno Gabriel , Smith Alyssa , Shirtliff Mark E. , O'Toole George A. , Cope Emily K. 
Published: August 2009

ABSTRACT

Chronic infection with the gram-negative organism
Pseudomonas aeruginosa
is a leading cause of morbidity and mortality in human patients, despite high doses of antibiotics used to treat the various diseases this organism causes. These infections are chronic because
P. aeruginosa
readily forms biofilms, which are inherently resistant to antibiotics as well as the host's immune system. Our laboratory has been investigating specific mutations in
P. aeruginosa
that regulate biofilm bacterial susceptibility to the host. To continue our investigation of the role of genetics in bacterial biofilm host resistance, we examined
P. aeruginosa
biofilms that lack the
flgK
gene. This mutant lacks flagella, which results in defects in early biofilm development (up to 36 h). For these experiments, the
flgK
-disrupted strain and the parental strain (PA14) were used in a modified version of the 96-well plate microtiter assay. Biofilms were challenged with freshly isolated human leukocytes for 4 to 6 h and viable bacteria enumerated by CFU. Subsequent to the challenge, both mononuclear cells (monocytes and lymphocytes) and neutrophils, along with tumor necrosis factor alpha (TNF-α), were required for optimal killing of the
flgK
biofilm bacteria. We identified a cytokine cross talk network between mononuclear cells and neutrophils that was essential to the production of lactoferrin and bacterial killing. Our data suggest that TNF-α is secreted from mononuclear cells, causing neutrophil activation, resulting in the secretion of bactericidal concentrations of lactoferrin. These results extend previous studies of the importance of lactoferrin in the innate immune defense against bacterial biofilms.
Powerful Induction of Divergent
tgs1-
Rv3131 Genes in
Mycobacterium tuberculosis
Is Mediated by DevR Interaction with a High-Affinity Site and an Adjacent Cryptic Low-Affinity Site
Authors: Chauhan Santosh , Tyagi Jaya Sivaswami 
Published: August 2009

ABSTRACT

DevR activates the transcription of ∼48 genes in response to hypoxia and other stresses and triggers metabolic downshift and dormancy development in
Mycobacterium tuberculosis. tgs1
and Rv3131 encode triacylglycerol synthase and a putative nitroreductase, respectively, and both are members of the DevR regulon. This study aimed to understand how a single putative DevR binding site identified previously could sustain powerful induction of divergent
tgs1-
Rv3131 genes. DNase I footprinting revealed that phosphorylated DevR in fact binds to two sites symmetrically located at −42.5 and −63.5 bp from transcription start points of both genes. DevR first bound to the high-affinity site, P, and cooperatively recruited another DevR molecule to the secondary low-affinity site, S, to activate
tgs1
-Rv3131 transcription by ∼210- and ∼110-fold, respectively. The presence of a single P site significantly reduced activation of
tgs1
expression and abolished Rv3131 activity, reinforcing the requirement of two binding sites for robust expression in both directions. P site inversion abolished
tgs1
but not Rv3131 transcription despite DevR occupancy at both sites. The lack of
tgs1
expression is most likely due to disruption of its −35 promoter element rather than inversion of the binding site per se. We conclude that (i) an overlap of a DevR binding site and −35 sequence is indispensable for promoter activation, (ii) DevR interaction with two binding sites is obligatory for synergistic activation of
tgs1
-Rv3131 promoters, and (iii) DevR interaction with binding sites of different affinities offers scope for temporal and differential expression of target genes.
The Role of PerR in O2-Affected Gene Expression ofClostridium acetobutylicum
Authors: Hillmann Falk , Döring Christina , Riebe Oliver , Ehrenreich Armin , Fischer Ralf-Jörg , Bahl Hubert 
Published: August 2009

ABSTRACTIn the strict anaerobeClostridium acetobutylicum, a PerR-homologous protein has recently been identified as being a key repressor of a reductive machinery for the scavenging of reactive oxygen species and molecular O2. In the absence of PerR, the full derepression of its regulon resulted in increased resistance to oxidative stress and nearly full tolerance of an aerobic environment. In the present study, the complementation of aBacillus subtilisPerR mutant confirmed that the homologous protein fromC. acetobutylicumacts as a functional peroxide sensor in vivo. Furthermore, we used a transcriptomic approach to analyze gene expression in the aerotolerant PerR mutant strain and compared it to the O2stimulon of wild-typeC. acetobutylicum. The genes encoding the components of the alternative detoxification system were PerR regulated. Only few other targets of direct PerR regulation were identified, including two highly expressed genes encoding enzymes that are putatively involved in the central energy metabolism. All of them were highly induced when wild-type cells were exposed to sublethal levels of O2. Under these conditions,C. acetobutylicumalso activated the repair and biogenesis of DNA and Fe-S clusters as well as the transcription of a gene encoding an unknown CO dehydrogenase-like enzyme. Surprisingly few genes were downregulated when exposed to O2, including those involved in butyrate formation. In summary, these results show that the defense of this strict anaerobe against oxidative stress is robust and by far not limited to the removal of O2and its reactive derivatives.
Integrative and Sequence Characteristics of a Novel Genetic Element, ICE
6013
, in
Staphylococcus aureus
Authors: Smyth Davida S. , Robinson D. Ashley 
Published: August 2009

ABSTRACT

A survey of chromosomal variation in the ST239 clonal group of methicillin-resistant
Staphylococcus aureus
(MRSA) revealed a novel genetic element, ICE
6013
. The element is 13,354 bp in length, excluding a 6,551-bp Tn
552
insertion. ICE
6013
is flanked by 3-bp direct repeats and is demarcated by 8-bp imperfect inverted repeats. The element was present in 6 of 15 genome-sequenced
S. aureus
strains, and it was detected using genetic markers in 19 of 44 diverse MRSA and methicillin-susceptible strains and in all 111 ST239 strains tested. Low integration site specificity was discerned. Multiple chromosomal copies and the presence of extrachromosomal circular forms of ICE
6013
were detected in various strains. The circular forms included 3-bp coupling sequences, located between the 8-bp ends of the element, that corresponded to the 3-bp direct repeats flanking the chromosomal forms. ICE
6013
is predicted to encode 15 open reading frames, including an IS
30
-like DDE transposase in place of a Tyr/Ser recombinase and homologs of gram-positive bacterial conjugation components. Further sequence analyses indicated that ICE
6013
is more closely related to ICE
Bs1
from
Bacillus subtilis
than to the only other potential integrative conjugative element known from
S. aureus
, Tn
5801
. Evidence of recombination between ICE
6013
elements is also presented. In summary, ICE
6013
is the first member of a new family of active, integrative genetic elements that are widely dispersed within
S. aureus
strains.
MrdH, a Novel Metal Resistance Determinant of
Pseudomonas putida
KT2440, Is Flanked by Metal-Inducible Mobile Genetic Elements
Authors: Haritha Adhikarla , Sagar Korripally Prem , Tiwari Anand , Kiranmayi Patnala , Rodrigue Agnes , Mohan Pamarthi Maruthi , Singh Surya Satyanarayana 
Published: August 2009

ABSTRACT

We report here the identification and characterization of
mrdH
, a novel chromosomal metal resistance determinant, located in the genomic island 55 of
Pseudomonas putida
KT2440. It encodes for MrdH, a predicted protein of ∼40 kDa with a chimeric domain organization derived from the RcnA and RND (for resistance-nodulation-cell division) metal efflux proteins. The metal resistance function of
mrdH
was identified by the ability to confer nickel resistance upon its complementation into
rcnA
mutant (a nickel- and cobalt-sensitive mutant) of
Escherichia coli
. However, the disruption of
mrdH
in
P. putida
resulted in an increased sensitivity to cadmium and zinc apart from nickel. Expression studies using quantitative reverse transcription-PCR showed the induction of
mrdH
by cadmium, nickel, zinc, and cobalt. In association with
mrdH
, we also identified a conserved hypothetical gene
mreA
whose encoded protein showed significant homology to NreA and NreA-like proteins. Expression of the
mreA
gene in
rcnA
mutant of
E. coli
enhanced its cadmium and nickel resistance. Transcriptional studies showed that both
mrdH
and
mreA
underwent parallel changes in gene expression. The mobile genetic elements Tn
4652
and IS
1246
, flanking
mrdH
and
mreA
were found to be induced by cadmium, nickel, and zinc, but not by cobalt. This study is the first report of a single-component metal efflux transporter,
mrdH
, showing chimeric domain organization, a broad substrate spectrum, and a location amid metal-inducible mobile genetic elements.
Identification of the [FeFe]-Hydrogenase Responsible for Hydrogen Generation inThermoanaerobacterium saccharolyticumand Demonstration of Increased Ethanol Yield via Hydrogenase Knockout
Authors: Shaw A. Joe , Hogsett David A. , Lynd Lee R. 
Published: August 2009

ABSTRACTThree putative hydrogenase enzyme systems inThermoanaerobacterium saccharolyticumwere investigated at the genetic, mRNA, enzymatic, and phenotypic levels. A four-gene operon containing two [FeFe]-hydrogenase genes, provisionally termedhfs(hydrogenase-Fe-S), was found to be the main enzymatic catalyst of hydrogen production.hfsB, perhaps the most interesting gene of the operon, contains an [FeFe]-hydrogenase and a PAS sensory domain and has several conserved homologues among clostridial saccharolytic, cellulolytic, and pathogenic bacteria. A second hydrogenase gene cluster,hyd, exhibited methyl viologen-linked hydrogenase enzymatic activity, buthydgene knockouts did not influence the hydrogen yield of cultures grown in closed-system batch fermentations. This result, combined with the observation thathydBcontains NAD(P)+ and FMN binding sites, suggests that thehydgenes are specific to the transfer of electrons from NAD(P)H to hydrogen ions. A third gene cluster, a putative [NiFe]-hydrogenase with homology to theechgenes, did not exhibit hydrogenase activity under any of the conditions tested. Deletion of thehfsandhydAgenes resulted in a loss of detectable methyl viologen-linked hydrogenase activity. Strains with a deletion of thehfsgenes exhibited a 95% reduction in hydrogen and acetic acid production. A strain withhfsandldhdeletions exhibited an increased ethanol yield from consumed carbohydrates and represents a new strategy for engineering increased ethanol yields inT. saccharolyticum.
Mutational Analysis ofBurkholderia thailandensisQuorum Sensing and Self-Aggregation
Authors: Chandler Josephine R. , Duerkop Breck A. , Hinz Aaron , West T. Eoin , Herman Jake P. , Churchill Mair E. A. , Skerrett Shawn J. , Greenberg E. Peter 
Published: August 2009

ABSTRACTAcyl-homoserine lactone (acyl-HSL) quorum-sensing signaling is common to manyProteobacteria. Acyl-HSLs are synthesized by the LuxI family of synthases, and the signal response is mediated by members of the LuxR family of transcriptional regulators.Burkholderia thailandensisis a member of a closely related cluster of three species, including the animal pathogensBurkholderia malleiandBurkholderia pseudomallei. Members of this group have similarluxIandluxRhomologs, and these genes contribute toB. pseudomalleiandB. malleivirulence.B. thailandensispossesses three pairs ofluxI-luxRhomologs. One of these pairs, BtaI2-BtaR2, has been shown to produce and respond to 3OHC10-HSL and to control the synthesis of an antibiotic. By using a markerless-exhange method, we constructed an assortment ofB. thailandensisquorum-sensing mutants, and we used these mutants to show that BtaI1 is responsible for C8-HSL production and BtaI3 is responsible for 3OHC8-HSL production. We also show that a strain incapable of acyl-HSL production is capable of growth on the same assortment of carbon and nitrogen sources as the wild type. Furthermore, this mutant shows no loss of virulence compared to the wild type in mice. However, the wild type self-aggregates in minimal medium, whereas the quorum-sensing mutant does not. The wild-type aggregation phenotype is recovered by addition of the BtaI1-R1 HSL signal C8-HSL. We propose that the key function of the BtaR1-BtaI1 quorum-sensing system is to cause cells to gather into aggregates once a sufficient population has been established.
A Unique β-1,2-Mannosyltransferase of
Thermotoga maritima
That Uses Di-
myo
-Inositol Phosphate as the Mannosyl Acceptor
Authors: Rodrigues Marta V. , Borges Nuno , Almeida Carla P. , Lamosa Pedro , Santos Helena 
Published: August 2009

ABSTRACT

In addition to di-
myo
-inositol-1,3′-phosphate (DIP), a compatible solute widespread in hyperthermophiles, the organic solute pool of
Thermotoga maritima
comprises 2-(
O
-β-
d-
mannosyl)-di-
myo
-inositol-1,3′-phosphate (MDIP) and 2-(
O
-β-
d-
mannosyl-1,2-
O
-β-
d-
mannosyl)-di-
myo
-inositol-1,3′-phosphate (MMDIP), two newly identified β-1,2-mannosides. In cells grown under heat stress, MDIP was the major solute, accounting for 43% of the total pool; MMDIP and DIP accumulated to similar levels, each corresponding to 11.5% of the total pool. The synthesis of MDIP involved the transfer of the mannosyl group from GDP-mannose to DIP in a single-step reaction catalyzed by MDIP synthase. This enzyme used MDIP as an acceptor of a second mannose residue, yielding the di-mannosylated compound. Minor amounts of the tri-mannosylated form were also detected. With a genomic approach, putative genes for MDIP synthase were identified in the genome of
T. maritima
, and the assignment was confirmed by functional expression in
Escherichia coli
. Genes with significant sequence identity were found only in the genomes of
Thermotoga
spp.,
Aquifex aeolicus
, and
Archaeoglobus profundus
. MDIP synthase of
T. maritima
had maximal activity at 95°C and apparent

K
m

values of 16 mM and 0.7 mM for DIP and GDP-mannose, respectively. The stereochemistry of MDIP was characterized by isotopic labeling and nuclear magnetic resonance (NMR): DIP selectively labeled with carbon 13 at position C1 of the
l-
inositol moiety was synthesized and used as a substrate for MDIP synthase. This β-1,2-mannosyltransferase is unrelated to known glycosyltransferases, and within the domain
Bacteria
, it is restricted to members of the two deepest lineages, i.e., the
Thermotogales
and the
Aquificales
. To our knowledge, this is the first β-1,2-mannosyltransferase characterized thus far.