bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genotypic Characterization and Prevalence of Virulence Factors among Canadian
Escherichia coli
O157:H7 Strains
Authors: Ziebell Kim , Steele Marina , Zhang Yongxiang , Benson Andrew , Taboada Eduardo N. , Laing Chad , McEwen Scott , Ciebin Bruce , Johnson Roger , Gannon Victor 
Published: May 2008

ABSTRACT

In this study, the association between genotypic and selected phenotypic characteristics was examined in a collection of Canadian
Escherichia coli
O157:H7 strains isolated from humans and cattle in the provinces of Alberta, Ontario, Saskatchewan, and Quebec. In a subset of 69 strains selected on the basis of specific phage types (PTs), a strong correlation between the lineage-specific polymorphism assay (LSPA6) genotype and PT was observed with all strains of PTs 4, 14, 21, 31, 33, and 87 belonging to the LSPA6 lineage I (LSPA6-LI) genotype, while those of PTs 23, 45, 67, and 74 belonged to LSPA6 lineage II (LSPA6-LII) genotypes. This correlation was maintained when additional strains of each PT were tested.
E. coli
O157:H7 strains with the LSPA6-LI genotype were much more common in the collection than were the LSPA6-LII or lineage I/II (LSPA6-LI/II)-related genotypes (82.6, 11.2, and 5.8%, respectively). Of the strains tested, proportionately more LSPA6-LI than LSPA6-LII genotype strains were isolated from humans (52.7% versus 19.7%) than from cattle (47.8% versus 80.2%). In addition, 96.7% of the LSPA6-LII strains carried the
stx
2c
variant gene, while only 50.0% of LSPA6-LI/II and 2.7% of LSPA6-LI strains carried this gene. LSPA6-LII strains were also significantly more likely to possess the colicin D gene,
cda
(50.8% versus 23.2%), and have combined resistance to streptomycin, sulfisoxazole, and tetracycline (72.1% versus 0.9%) than were LSPA6-LI strains. The LSPA6 genotype- and PT-related characteristics identified may be important markers of specific ecotypes of
E. coli
O157:H7 that have unique epidemiological and virulence characteristics.
A Monoclonal Antibody toHistoplasma capsulatumAlters the Intracellular Fate of the Fungus in Murine Macrophages
Authors: Shi Li , Albuquerque Priscila C. , Lazar-Molnar Eszter , Wang Xintao , Santambrogio Laura , Gácser Attila , Nosanchuk Joshua D. 
Published: May 2008

ABSTRACTMonoclonal antibodies (MAbs) to a cell surface histone onHistoplasma capsulatummodify murine infection and decrease the growth ofH. capsulatumwithin macrophages. Without the MAbs,H. capsulatumsurvives within macrophages by modifying the intraphagosomal environment. In the present study, we aimed to analyze the affects of a MAb on macrophage phagosomes. Using transmission electron and fluorescence microscopy, we showed that phagosome activation and maturation are significantly greater whenH. capsulatumyeast are opsonized with MAb. The MAb reduced the ability of the organism to regulate the phagosomal pH. Additionally, increased antigen processing and reduced negative costimulation occur in macrophages that phagocytose yeast cells opsonized with MAb, resulting in more-efficient T-cell activation. The MAb alters the intracellular fate ofH. capsulatumby affecting the ability of the fungus to regulate the milieu of the phagosome.
Histone Acetyltransferase Inhibitor Anacardic Acid Causes Changes in Global Gene Expression during In Vitro
Plasmodium falciparum
Development
Authors: Cui Long , Miao Jun , Furuya Tetsuya , Fan Qi , Li Xinyi , Rathod Pradipsinh K. , Su Xin-zhuan , Cui Liwang 
Published: May 2008

ABSTRACT

To better understand the role of histone lysine acetylation in transcription in
Plasmodium falciparum
, we sought to attenuate histone acetyltransferase (HAT) activity using anacardic acid (AA). We showed that AA reversibly and noncompetitively inhibited the HAT activity of recombinant PfGCN5. To a lesser extent, AA inhibited the PfGCN5 activity in parasite nuclear extracts but did not affect histone deacetylase activity. AA blocked the growth of both chloroquine-sensitive and -resistant strains, with a 50% inhibitory concentration of ∼30 μM. Treatment of the parasites with 20 μM of AA for 12 h had no obvious effect on parasite growth or gross morphology but induced hypoacetylation of histone H3 at K9 and K14, but not H4 at K5, K8, K12, and K16, suggesting inhibition of the PfGCN5 HAT. Microarray analysis showed that this AA treatment resulted in twofold or greater change in the expression of 271 (∼5%) parasite genes in late trophozoites, among which 207 genes were downregulated. Cluster analysis of gene expression indicated that AA mostly downregulated active genes, and this gene pool significantly overlapped with that enriched for H3K9 acetylation. We further demonstrated by chromatin immunoprecipitation and real-time PCR that AA treatment reduced acetylation near the putative promoters of a set of downregulated genes. This study suggests that the parasiticidal effect of AA is at least partially associated with its inhibition of PfGCN5 HAT, resulting in the disturbance of the transcription program in the parasites.
TransgenicLeishmaniaModel for Delta-Aminolevulinate-Inducible Monospecific Uroporphyria: Cytolytic Phototoxicity Initiated by Singlet Oxygen-Mediated Inactivation of Proteins and Its Ablation by Endosomal Mobilization of Cytosolic Uroporphyrin
Authors: Dutta Sujoy , Kolli Bala Krishna , Tang Aihua , Sassa Shigeru , Chang Kwang-Poo 
Published: May 2008

ABSTRACTInherent deficiencies ofLeishmaniain heme biosynthesis were genetically complemented for delta-aminolevulinate-inducible biosynthesis and accumulation of light-excitable uroporphyrin. The phototoxic flagellar immobilization and cytolysis phenotypes and porphyrin mobilization noted previously were further analyzed biochemically and cytologically to delineate the mechanism of phototoxicity and detoxification in this monoporphyric model. Under optimal conditions of induction for approximately 3 days, cells remained viable but became increasingly uroporphyric, peaking at ≥90% of the population by approximately day 2; thereafter, a small population of less porphyric or aporphyric cells emerged. On exposure to light, the flagella of porphyric cells were immobilized in milliseconds, and singlet oxygen became detectable in their lysates. Both photosensitive phenotypes increased proportionally with the cellular uroporphyric levels and were susceptible to inhibition by azide, but not byd-mannitol. Brief irradiation of the uroporphyric cells produced no appreciable protein degradation but inactivated cytosolic neomycin phosphotransferase and significantly bleached cytosolic green fluorescent protein, which was azide reversible. These cells were irreparably photodamaged, as indicated by their subsequent loss of membrane permeability and viability. This is the first in situ demonstration that early inactivation of functional proteins by singlet oxygen initiates the cytolytic phototoxicity in uroporphyria. Detoxification appears to involve endocytic/exocytic mobilization of uroporphyrin from cytosol to “porphyrinosomes” for its eventual extracellular expulsion. This is proposed as the sole mechanism of detoxification, since it is attributable to the reversion of porphyric to aporphyric cells during uroporphyrinogenesis and repeated cycles of this event plus photolysis selected no resistant mutants, only aporphyric clones of the parental phenotypes. Further characterization of the transport system for uroporphyrin in this model is expected to benefit not only our understanding of the cellular mechanism for disposal of toxic soluble wastes but also potentially the effective management of human uroporphyria and the use of uroporphyricLeishmaniafor vaccine/drug delivery.
The Membrane-Bound Transcriptional Regulator CadC Is Activated by Proteolytic Cleavage in Response to Acid Stress
Authors: Lee Yong Heon , Kim Ji Hye , Bang Iel Soo , Park Yong Keun 
Published: May 2008

ABSTRACT

Proteolytic processes often participate in signal transduction across bacterial membranes. In
Salmonella enterica
serovar Typhimurium, the transcriptional regulator CadC activates genes of lysine decarboxylase system in response to external acidification and exogenous lysine. However, the signaling mechanism of CadC activation remains unexplored. We report here that CadC is located on the inner membrane under normal growth conditions but rapidly cleaved under acid stress conditions, leading to the induction of target gene transcription. As full-length CadC is degraded, the N-terminal fragment containing the DNA-binding domain accumulates in the inner membrane. Moreover, we show that C-terminal truncations of CadC abolish its degradation, resulting in complete loss of activator function. Together, these observations suggest that site-specific proteolysis at the periplasmic domain of CadC generates a biologically active form of N-terminal DNA-binding domain to promote target gene activation.
The Evolution of Class 1 Integrons and the Rise of Antibiotic Resistance
Authors: Gillings Michael , Boucher Yan , Labbate Maurizio , Holmes Andrew , Krishnan Samyuktha , Holley Marita , Stokes H. W. 
Published: May 2008

ABSTRACTClass 1 integrons are central players in the worldwide problem of antibiotic resistance, because they can capture and express diverse resistance genes. In addition, they are often embedded in promiscuous plasmids and transposons, facilitating their lateral transfer into a wide range of pathogens. Understanding the origin of these elements is important for the practical control of antibiotic resistance and for exploring how lateral gene transfer can seriously impact on, and be impacted by, human activities. We now show that class 1 integrons can be found on the chromosomes of nonpathogenic soil and freshwaterBetaproteobacteria. Here they exhibit structural and sequence diversity, an absence of antibiotic resistance genes, and a phylogenetic signature of lateral transfer. Some examples are almost identical to the core of the class 1 integrons now found in pathogens, leading us to conclude that environmentalBetaproteobacteriawere the original source of these genetic elements. Because these elements appear to be readily mobilized, their lateral transfer into human commensals and pathogens was inevitable, especially given thatBetaproteobacteriacarrying class 1 integrons are common in natural environments that intersect with the human food chain. The strong selection pressure imposed by the human use of antimicrobial compounds then ensured their fixation and global spread into new species.
Contribution of Trimeric Autotransporter C-Terminal Domains of Oligomeric Coiled-Coil Adhesin (Oca) Family Members YadA, UspA1, EibA, and Hia to Translocation of the YadA Passenger Domain and Virulence ofYersinia enterocolitica
Authors: Ackermann Nikolaus , Tiller Maximilian , Anding Gisela , Roggenkamp Andreas , Heesemann Jürgen 
Published: May 2008

ABSTRACTThe Oca family is a novel class of autotransporter-adhesins with highest structural similarity in their C-terminal transmembrane region, which supposedly builds a beta-barrel pore in the outer membrane (OM). The prototype of the Oca family is YadA, an adhesin ofYersinia enterocoliticaandYersinia pseudotuberculosis. YadA forms a homotrimeric lollipop-like structure on the bacterial surface. The C-terminal regions of three YadA monomers form a barrel in the OM and translocate the trimeric N-terminal passenger domain, consisting of stalk, neck, and head region to the exterior. To elucidate the structural and functional role of the C-terminal translocator domain (TLD) and to assess its promiscuous capability with respect to transport of related passenger domains, we constructed chimeric YadA proteins, which consist of the N-terminal YadA passenger domain and C-terminal TLDs of Oca family members UspA1 (Moraxella catarrhalis), EibA (Escherichia coli), and Hia (Haemophilus influenzae). These constructs were expressed inY. enterocoliticaand compared for OM localization, surface exposure, oligomerization, adhesion properties, serum resistance, and mouse virulence. We demonstrate that all chimeric YadA proteins translocated the YadA passenger domain across the OM.Y. enterocoliticastrains producing YadA chimeras or wild-type YadA showed comparable binding to collagen and epithelial cells. However, strains producing YadA chimeras were attenuated in serum resistance and mouse virulence. These results demonstrate for the first time that TLDs of Oca proteins of different origin are efficient translocators of the YadA passenger domain and that the cognate TLD of YadA is essential for bacterial survival in human serum and mouse virulence.
A Family of Insertion Sequences That Impacts Integrons by Specific Targeting of Gene Cassette Recombination Sites, the IS1111-attCGroup
Authors: Tetu Sasha G. , Holmes Andrew J. 
Published: May 2008

ABSTRACTIntegrons facilitate the evolution of complex phenotypes by physical and transcriptional linkage of genes. They can be categorized as chromosomal integrons (CIs) or mobile resistance integrons (MRIs). The significance of MRIs for the problem of multiple antibiotic resistance is well established. CIs are more widespread, but their only demonstrated significance is as a reservoir of gene cassettes for MRIs. In characterizing CIs associated withPseudomonas, we discovered a subfamily of insertion sequences, termed the IS1111-attCgroup, that insert into the recombination sites of gene cassettes (attCsite) by site-specific recombination. IS1111-attCelements appear to have recently spread fromPseudomonasspecies to clinical class 1 integrons. Such elements are expected to significantly impact integrons. To explore this further, we examined CIs in 24 strains representing multiple levels of evolutionary divergence within the genusPseudomonas. Cassette arrays frequently had a degenerated “footprint” of an IS1111-attCgroup element at their terminus and in three cases were occupied by multiple functional IS1111-attCelements. WithinPseudomonasspp. the IS-integron interaction appears to follow an evolutionarily rapid cycle of infection, expansion, and extinction. The final outcome is extinction of the IS element and modification of the right-hand boundary of the integron. This system represents an unusual example of convergent evolution whereby heterologous families of site-specific recombinases of distinct genetic elements have adopted the same target site. The interactions described here represent a model for evolutionary processes that offer insights to a number of aspects of the biology of integrons and other mosaic genetic elements.
Symbiosis-Promoting and Deleterious Effects of NopT, a Novel Type 3 Effector of
Rhizobium
sp. Strain NGR234
Authors: Dai Wei-Jun , Zeng Yong , Xie Zhi-Ping , Staehelin Christian 
Published: May 2008

ABSTRACT

Establishment of symbiosis between certain host plants and nitrogen-fixing bacteria (“rhizobia”) depends on type 3 effector proteins secreted via the bacterial type 3 secretion system (T3SS). Here, we report that the open reading frame y4zC of strain NGR234 encodes a novel rhizobial type 3 effector, termed NopT (for nodulation outer protein T). Analysis of secreted proteins from NGR234 and T3SS mutants revealed that NopT is secreted via the T3SS. NopT possessed autoproteolytic activity when expressed in
Escherichia coli
or human HEK 293T cells. The processed NopT exposed a glycine (G50) to the N terminus, which is predicted to be myristoylated in eukaryotic cells. NopT with a point mutation at position C93, H205, or D220 (catalytic triad) showed strongly reduced autoproteolytic activity, indicating that NopT is a functional protease of the YopT-AvrPphB effector family. When transiently expressed in tobacco plants, proteolytically active NopT elicited a rapid hypersensitive reaction.
Arabidopsis
plants transformed with
nopT
showed chlorotic and necrotic symptoms, indicating a cytotoxic effect. Inoculation experiments with mutant derivatives of NGR234 indicated that NopT affected nodulation either positively (
Phaseolus vulgaris
cv. Yudou No. 1;
Tephrosia vogelii
) or negatively (
Crotalaria juncea
). We suggest that NopT-related polymorphism may be involved in evolutionary adaptation of NGR234 to particular host legumes.
Biochemical and Mutational Analyses of AcuA, the Acetyltransferase Enzyme That Controls the Activity of the Acetyl Coenzyme A Synthetase (AcsA) in
Bacillus subtilis
Authors: Gardner Jeffrey G. , Escalante-Semerena Jorge C. 
Published: May 2008

ABSTRACT

The
acuABC
genes of
Bacillus subtilis
comprise a putative posttranslational modification system. The AcuA protein is a member of the
G
cn5-related
N
-
a
cetyl
t
ransferase (GNAT) superfamily, the AcuC protein is a class I histone deacetylase, and the role of the AcuB protein is not known. AcuA controls the activity of acetyl coenzyme A synthetase (AcsA; EC 6.2.1.1) in this bacterium by acetylating residue Lys549. Here we report the kinetic analysis of wild-type and variant AcuA proteins. We contrived a genetic scheme for the identification of AcuA residues critical for activity. Changes at residues H177 and G187 completely inactivated AcuA and led to its rapid turnover. Changes at residues R42 and T169 were less severe. In vitro assay conditions were optimized, and an effective means of inactivating the enzyme was found. The basic kinetic parameters of wild-type and variant AcuA proteins were obtained and compared to those of eukaryotic GNATs. Insights into how the isolated mutations may exert their deleterious effect were investigated by using the crystal structure of an AcuA homolog.
Phage SPP1 Reversible Adsorption toBacillus subtilisCell Wall Teichoic Acids Accelerates Virus Recognition of Membrane Receptor YueB
Authors: Baptista Catarina , Santos Mário A. , São-José Carlos 
Published: May 2008

ABSTRACTBacteriophage SPP1 targets the host cell membrane protein YueB to irreversibly adsorb and infectBacillus subtilis. Interestingly, SPP1 still binds to the surface ofyueBmutants, although in a completely reversible way. We evaluated here the relevance of a reversible step in SPP1 adsorption and identified the receptor(s) involved. We show that reversible adsorption is impaired inB. subtilismutants defective in the glucosylation pathway of teichoic acids or displaying a modified chemical composition of these polymers. The results indicate that glucosylated poly(glycerolphosphate) cell wall teichoic acid is the major target for SPP1 reversible binding. Interaction with this polymer is characterized by a fast adsorption rate showing low-temperature dependence, followed by a rapid establishment of an equilibrium state between adsorbed and free phages. This equilibrium is basically determined by the rate of phage dissociation, which exhibits a strong dependence on temperature compatible with an Arrhenius law. This allowed us to determine an activation energy of 22.6 kcal/mol for phage release. Finally, we show that SPP1 reversible interaction strongly accelerates irreversible binding to YueB. Our results support a model in which fast SPP1 adsorption to and desorption from teichoic acids allows SPP1 to scan the bacterial surface for rapid YueB recognition.
An OmpA Family Protein, a Target of the GinI/GinR Quorum-Sensing System in
Gluconacetobacter intermedius
, Controls Acetic Acid Fermentation
Authors: Iida Aya , Ohnishi Yasuo , Horinouchi Sueharu 
Published: May 2008

ABSTRACT

Via
N
-acylhomoserine lactones, the GinI/GinR quorum-sensing system in
Gluconacetobacter intermedius
NCI1051, a gram-negative acetic acid bacterium, represses acetic acid and gluconic acid fermentation. Two-dimensional polyacrylamide gel electrophoretic analysis of protein profiles of strain NCI1051 and
ginI
and
ginR
mutants identified a protein that was produced in response to the GinI/GinR regulatory system. Cloning and nucleotide sequencing of the gene encoding this protein revealed that it encoded an OmpA family protein, named GmpA.
gmpA
was a member of the gene cluster containing three adjacent homologous genes,
gmpA
to
gmpC
, the organization of which appeared to be unique to vinegar producers, including “
Gluconacetobacter polyoxogenes
.” In addition, GmpA was unique among the OmpA family proteins in that its N-terminal membrane domain forming eight antiparallel transmembrane β-strands contained an extra sequence in one of the surface-exposed loops. Transcriptional analysis showed that only
gmpA
of the three adjacent
gmp
genes was activated by the GinI/GinR quorum-sensing system. However,
gmpA
was not controlled directly by GinR but was controlled by an 89-amino-acid protein, GinA, a target of this quorum-sensing system. A
gmpA
mutant grew more rapidly in the presence of 2% (vol/vol) ethanol and accumulated acetic acid and gluconic acid in greater final yields than strain NCI1051. Thus, GmpA plays a role in repressing oxidative fermentation, including acetic acid fermentation, which is unique to acetic acid bacteria and allows ATP synthesis via ethanol oxidation. Consistent with the involvement of
gmpA
in oxidative fermentation, its transcription was also enhanced by ethanol and acetic acid.
Functional Characterization and Localization of the TcpH Conjugation Protein fromClostridium perfringens
Authors: Teng Wee Lin , Bannam Trudi L. , Parsons Jennifer A. , Rood Julian I. 
Published: May 2008

ABSTRACTInClostridium perfringens, conjugative plasmids encode important virulence factors, such as toxins and resistance determinants. All of these plasmids carry a conjugation locus that consists of 11 genes:intPandtcpAtotcpJ. Three proteins, TcpA, a potential coupling protein, TcpF, a putative ATPase that is similar to ORF15 from Tn916, and TcpH, which contains VirB6-like domains, are essential for conjugation in the prototype conjugative plasmid pCW3. To analyze the functional domains of TcpH, a putative structural component of the mating-pair formation complex and deletion and site-directed mutants were constructed and analyzed. The results showed that the N-terminal 581 residues and the conserved242VQQPW246motif were required for conjugative transfer. Bacterial two-hybrid and biochemical studies showed that TcpH interacted with itself and with TcpC. An analysis of thetcpHmutants demonstrated that the region required for these interactions also was localized to the N-terminal 581 residues and that the function of the C-terminal region of TcpH was independent of protein-protein interactions. Finally, immunofluorescence studies showed that TcpH and TcpF were located at both cell poles of donorC. perfringenscells. The results provide evidence that TcpH is located in the cell membrane, where it oligomerizes and interacts with TcpC to form part of the mating-pair formation complex, which is located at the cell poles and is closely associated with TcpF.
The
c
-Type Cytochrome OmcA Localizes to the Outer Membrane upon Heterologous Expression in
Escherichia coli
Authors: Donald James W. , Hicks Matthew G. , Richardson David J. , Palmer Tracy 
Published: May 2008

ABSTRACT

We have functionally produced the outer membrane cytochrome OmcA from
Shewanella oneidensis
in
Escherichia coli
. Substrate accessibility experiments indicate that OmcA is surface exposed in an
E. coli
B strain but not in a K-12 strain. We show that a functional type II secretion system is required for surface localization.