bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Imposed Salinity Gradients on Dissimilatory Arsenate Reduction, Sulfate Reduction, and Other Microbial Processes in Sediments from Two California Soda Lakes
Authors: Kulp T. R. , Han S. , Saltikov C. W. , Lanoil B. D. , Zargar K. , Oremland R. S. 
Published: June 2007

ABSTRACT

Salinity effects on microbial community structure and on potential rates of arsenate reduction, arsenite oxidation, sulfate reduction, denitrification, and methanogenesis were examined in sediment slurries from two California soda lakes. We conducted experiments with Mono Lake and Searles Lake sediments over a wide range of salt concentrations (25 to 346 g liter
−1
). With the exception of sulfate reduction, rates of all processes demonstrated an inverse relationship to total salinity. However, each of these processes persisted at low but detectable rates at salt saturation. Denaturing gradient gel electrophoresis analysis of partial 16S rRNA genes amplified from As(V) reduction slurries revealed that distinct microbial populations grew at low (25 to 50 g liter
−1
), intermediate (100 to 200 g liter
−1
), and high (>300 g liter
−1
) salinity. At intermediate and high salinities, a close relative of a cultivated As-respiring halophile was present. These results suggest that organisms adapted to more dilute conditions can remain viable at high salinity and rapidly repopulate the lake during periods of rising lake level. In contrast to As reduction, sulfate reduction in Mono Lake slurries was undetectable at salt saturation. Furthermore, sulfate reduction was excluded from Searles Lake sediments at any salinity despite the presence of abundant sulfate. Sulfate reduction occurred in Searles Lake sediment slurries only following inoculation with Mono Lake sediment, indicating the absence of sulfate-reducing flora. Experiments with borate-amended Mono Lake slurries suggest that the notably high (0.46 molal) concentration of borate in the Searles Lake brine was responsible for the exclusion of sulfate reducers from that ecosystem.
Molecular Detection and Ecological Significance of the Cyanobacterial Genera
Geitlerinema
and
Leptolyngbya
in Black Band Disease of Corals
Authors: Myers Jamie L. , Sekar Raju , Richardson Laurie L. 
Published: June 2007

ABSTRACT

Black band disease (BBD) is a pathogenic, sulfide-rich microbial mat dominated by filamentous cyanobacteria that infect corals worldwide. We isolated cyanobacteria from BBD into culture, confirmed their presence in the BBD community by using denaturing gradient gel electrophoresis (DGGE), and demonstrated their ecological significance in terms of physiological sulfide tolerance and photosynthesis-versus-irradiance values. Twenty-nine BBD samples were collected from nine host coral species, four of which have not previously been investigated, from reefs of the Florida Keys, the Bahamas, St. Croix, and the Philippines. From these samples, seven cyanobacteria were isolated into culture. Cloning and sequencing of the 16S rRNA gene using universal primers indicated that four isolates were related to the genus
Geitlerinema
and three to the genus
Leptolyngbya
. DGGE results, obtained using
Cyanobacteria
-specific 16S rRNA primers, revealed that the most common BBD cyanobacterial sequence, detected in 26 BBD field samples, was related to that of an
Oscillatoria
sp. The next most common sequence, 99% similar to that of the
Geitlerinema
BBD isolate, was present in three samples. One
Leptolyngbya
- and one
Phormidium
-related sequence were also found. Laboratory experiments using isolates of BBD
Geitlerinema
and
Leptolyngbya
revealed that they could carry out sulfide-resistant oxygenic photosynthesis, a relatively rare characteristic among cyanobacteria, and that they are adapted to the sulfide-rich, low-light BBD environment. The presence of the cyanotoxin microcystin in these cultures and in BBD suggests a role in BBD pathogenicity. Our results confirm the presence of
Geitlerinema
in the BBD microbial community and its ecological significance, which have been challenged, and provide evidence of a second ecologically significant BBD cyanobacterium,
Leptolyngbya
.
Rhizobacterial Volatiles Affect the Growth of Fungi and
Arabidopsis thaliana
Authors: Vespermann Anja , Kai Marco , Piechulla Birgit 
Published: June 2007

ABSTRACT

Volatiles of
Stenotrophomonas
,
Serratia
, and
Bacillus
species inhibited mycelial growth of many fungi and
Arabidopsis thaliana
(40 to 98%), and volatiles of
Pseudomonas
species and
Burkholderia cepacia
retarded the growth to lesser extents.
Aspergillus niger
and
Fusarium
species were resistant, and
B. cepacia
and
Staphylococcus epidermidis
promoted the growth of
Rhizoctonia solani
and
A. thaliana
. Bacterial volatiles provide a new source of compounds with antibiotic and growth-promoting features.
Glutathione Protects
Lactococcus lactis
against Acid Stress
Authors: Zhang Juan , Fu Rui-Yan , Hugenholtz Jeroen , Li Yin , Chen Jian 
Published: June 2007

ABSTRACT

Previously we showed that glutathione (GSH) can protect
Lactococcus lactis
against oxidative stress (Y. Li et al., Appl. Environ. Microbiol. 69:5739-5745, 2003). In the present study, we show that the GSH imported by
L. lactis
subsp.
cremoris
SK11 or produced by engineered
L. lactis
subsp.
cremoris
NZ9000 can protect both strains against a long-term mild acid challenge (pH 4.0) and a short-term severe acid challenge (pH 2.5). This shows for the first time that GSH can protect a gram-positive bacterium against acid stress. During acid challenge, strain SK11 containing imported GSH and strain NZ9000 containing self-produced GSH exhibited significantly higher intracellular pHs than the control. Furthermore, strain SK11 containing imported GSH had a significantly higher activity of glyceraldehyde-3-phosphate dehydrogenase than the control. These results suggest that the acid stress resistance of starter culture can be improved by selecting
L. lactis
strains capable of producing or importing GSH.
Intracellular Siderophores Are Essential for Ascomycete Sexual Development in Heterothallic
Cochliobolus heterostrophus
and Homothallic
Gibberella zeae
Authors: Oide Shinichi , Krasnoff Stuart B. , Gibson Donna M. , Turgeon B. Gillian 
Published: June 2007

ABSTRACT

Connections between fungal development and secondary metabolism have been reported previously, but as yet, no comprehensive analysis of a family of secondary metabolites and their possible role in fungal development has been reported. In the present study, mutant strains of the heterothallic ascomycete
Cochliobolus heterostrophus
, each lacking one of 12 genes (
NPS1
to
NPS12
) encoding a nonribosomal peptide synthetase (NRPS), were examined for a role in sexual development. One type of strain (Δ
nps2
) was defective in ascus/ascospore development in homozygous Δ
nps2
crosses. Homozygous crosses of the remaining 11 Δ
nps
strains showed wild-type (WT) fertility. Phylogenetic, expression, and biochemical analyses demonstrated that the NRPS encoded by
NPS2
is responsible for the biosynthesis of ferricrocin, the intracellular siderophore of
C. heterostrophus
. Functional conservation of
NPS2
in both heterothallic
C. heterostrophus
and the unrelated homothallic ascomycete
Gibberella zeae
was demonstrated.
G. zeae
Δ
nps2
strains are concomitantly defective in intracellular siderophore (ferricrocin) biosynthesis and sexual development. Exogenous application of iron partially restored fertility to
C. heterostrophus
and
G. zeae
Δ
nps2
strains, demonstrating that abnormal sexual development of Δ
nps2
strains is at least partly due to their iron deficiency. Exogenous application of the natural siderophore ferricrocin to
C. heterostrophus
and
G. zeae
Δ
nps2
strains restored WT fertility.
NPS1
, a
G. zeae NPS
gene that groups phylogenetically with
NPS2
, does not play a role in sexual development. Overall, these data demonstrate that iron and intracellular siderophores are essential for successful sexual development of the heterothallic ascomycete
C. heterostrophus
and the homothallic ascomycete
G. zeae
.
Gliotoxin Is a Virulence Factor of
Aspergillus fumigatus
:
gliP
Deletion Attenuates Virulence in Mice Immunosuppressed with Hydrocortisone
Authors: Sugui Janyce A. , Pardo Julian , Chang Yun C. , Zarember Kol A. , Nardone Glenn , Galvez Eva M. , Müllbacher Arno , Gallin John I. , Simon Markus M. , Kwon-Chung Kyung J. 
Published: June 2007

ABSTRACT

Gliotoxin is an immunosuppressive mycotoxin long suspected to be a potential virulence factor of
Aspergillus fumigatus
. Recent studies using mutants lacking gliotoxin production, however, suggested that the mycotoxin is not important for pathogenesis of
A. fumigatus
in neutropenic mice resulting from treatment with cyclophosphomide and hydrocortisone. In this study, we report on the pathobiological role of gliotoxin in two different mouse strains, 129/Sv and BALB/c, that were immunosuppressed by hydrocortisone alone to avoid neutropenia. These strains of mice were infected using the isogenic set of a wild type strain (B-5233) and its mutant strain (
gliP
Δ) and the the
glip
reconstituted strain (
gliP
R
). The
gliP
gene encodes a nonribosomal peptide synthase that catalyzes the first step in gliotoxin biosynthesis. The
gliP
Δ strain was significantly less virulent than strain B-5233 or
gliP
R
in both mouse models. In vitro assays with culture filtrates (CFs) of B-5233,
gliP
Δ, and
gliP
R
strains showed the following: (i) deletion of
gliP
abrogated gliotoxin production, as determined by high-performance liquid chromatography analysis; (ii) unlike the CFs from strains B-5233 and
gliP
R
,
gliP
Δ CFs failed to induce proapoptotic processes in EL4 thymoma cells, as tested by Bak conformational change, mitochondrial-membrane potential disruption, superoxide production, caspase 3 activation, and phosphatidylserine translocation. Furthermore, superoxide production in human neutrophils was strongly inhibited by CFs from strain B-5233 and the
gliP
R
strain, but not the
gliP
Δ strain. Our study confirms that gliotoxin is an important virulence determinant of
A. fumigatus
and that the type of immunosuppression regimen used is important to reveal the pathogenic potential of gliotoxin.
MpkA-Dependent and -Independent Cell Wall Integrity Signaling in
Aspergillus nidulans
Authors: Fujioka Tomonori , Mizutani Osamu , Furukawa Kentaro , Sato Natsuko , Yoshimi Akira , Yamagata Youhei , Nakajima Tasuku , Abe Keietsu 
Published: June 2007

ABSTRACT

Cell wall integrity signaling (CWIS) maintains cell wall biogenesis in fungi, but only a few transcription factors (TFs) and target genes downstream of the CWIS cascade in filamentous fungi are known. Because a mitogen-activated protein kinase (MpkA) is a key CWIS enzyme, the transcriptional regulation of
mpkA
and of cell wall-related genes (CWGs) is important in cell wall biogenesis. We cloned
Aspergillus nidulans mpkA
;
rlmA
, a TF gene orthologous to
Saccharomyces cerevisiae RLM1
that encodes Rlm1p, a major Mpk1p-dependent TF that regulates the transcription of
MPK1
besides that of CWGs; and An
swi4
and An
swi6
, homologous to
S. cerevisiae SWI4
and
SWI6
, encoding the Mpk1p-activating TF complex Swi4p-Swi6p, which regulates CWG transcription in a cell cycle-dependent manner.
A. nidulans rlmA
and
mpkA
cDNA functionally complemented
S. cerevisiae rlm1
Δ and
mpk1
Δ mutants, respectively, but An
swi4
and An
swi6
cDNA did not complement
swi4
Δ and
swi6
Δ mutants. We constructed
A. nidulans rlmA
, An
swi4
and An
swi6
, and
mpkA
disruptants (
rlmA
Δ, An
swi4
Δ An
swi6
Δ, and
mpkA
Δ strains) and analyzed
mpkA
and CWG transcripts after treatment with a β-1,3-glucan synthase inhibitor (micafungin) that could activate MpkA via CWIS. Levels of
mpkA
transcripts in the mutants as well as those in the wild type were changed after micafungin treatment. The β-glucuronidase reporter gene controlled by the
mpkA
promoter was expressed in the wild type but not in the
mpkA
Δ strain. Thus,
mpkA
transcription seems to be autoregulated by CWIS via MpkA but not by RlmA or AnSwi4-AnSwi6. The transcription of most CWGs except α-1,3-glucan synthase genes (
agsA
and
agsB
) was independent of RlmA and AnSwi4-AnSwi6 and seemed to be regulated by non-MpkA signaling. The transcriptional regulation of
mpkA
and of CWGs via CWIS in
A. nidulans
differs significantly from that in
S. cerevisiae
.
The Plant Pathogen
Ralstonia solanacearum
Needs Aerotaxis for Normal Biofilm Formation and Interactions with Its Tomato Host
Authors: Yao Jian , Allen Caitilyn 
Published: June 2007

ABSTRACT

Ralstonia solanacearum
is a soilborne pathogen that causes bacterial wilt of diverse plant species. To locate and infect host plant roots
R. solanacearum
needs taxis, the ability to move toward more favorable conditions. However, the specific signals that attract this pathogen were unknown. One candidate is aerotaxis, or energy taxis, which guides bacteria toward optimal intracellular energy levels. The
R. solanacearum
genome encodes two putative aerotaxis transducers. Cloned
R. solanacearum aer1
and
aer2
genes restored aerotaxis to an
Escherichia coli aer
mutant, demonstrating that both genes encode heterologously functional aerotaxis transducers. Site-directed mutants lacking
aer1
,
aer2
, or both
aer1
and
aer2
were significantly less able to move up an oxygen gradient than the wild-type parent strain; in fact, the aerotaxis of the
aer
mutants was indistinguishable from that of a completely nonmotile strain. Tomato plants inoculated with either the
aer2
or the
aer1/aer2
mutant had slightly delayed wilt disease development. Furthermore, the
aer1/aer2
double mutant was significantly impaired in the ability to rapidly localize on tomato roots compared to its wild-type parent. Unexpectedly, all nonaerotactic mutants formed thicker biofilms on abiotic surfaces than the wild type. These results indicate that energy taxis contributes significantly to the ability of
R. solanacearum
to locate and effectively interact with its host plants.
Interaction of the Gifsy-1 Xis Protein with the Gifsy-1
attP
Sequence
Authors: Flanigan Asa , Gardner Jeffrey F. 
Published: June 2007

ABSTRACT

The Gifsy-1 phage integrates site specifically into the
Salmonella
chromosome via an integrase-mediated site-specific recombination mechanism. Initial genetic analysis suggests that Gifsy-1 integrase-mediated excision of the Gifsy-1 phage is influenced by proteins encoded by both the Gifsy-1 and the Gifsy-2 phages. Our studies show that the Gifsy-1 Xis protein regulates the directionality of integrase-mediated excision of the Gifsy-1 phage. Electrophoretic mobility shift assays, DNase I footprinting, dimethyl sulfate (DMS) interference assays, and DMS protection assays were used to identify a 31-base-pair sequence in the
attP
region to which the Gifsy-1 protein binds. The results suggest that this recombination directionality factor binds in vitro to three imperfect direct repeats, spaced 10 base pairs apart, in a sequential and cooperative manner in the absence of other phage-encoded proteins. Our studies suggest that, while the Gifsy-1 Xis does not require additional factors for specific and high-affinity binding, it may form a microfilament on DNA similar to that described for the phage lambda Xis protein.
Identification of the Major Protein Component of the Pneumococcal Eclipse Complex
Authors: Morrison Donald A. , Mortier-Barrière Isabelle , Attaiech Laetitia , Claverys Jean-Pierre 
Published: June 2007

ABSTRACT

During genetic transformation of
Streptococcus pneumoniae
, single strands from native donor DNA enter competent cells, where they associate with an unidentified protein with a molecular mass of 15 to 20 kDa to form the eclipse complex. Using Western blotting, we identify the principal protein cofractionating with donor DNA in this complex as SsbB.
Identification of a Biosynthetic Gene Cluster and the Six Associated Lipopeptides Involved in Swarming Motility ofPseudomonas syringaepv. tomato DC3000
Authors: Berti Andrew D. , Greve Nathan J. , Christensen Quin H. , Thomas Michael G. 
Published: June 2007

ABSTRACTPseudomonasspecies are known to be prolific producers of secondary metabolites that are synthesized wholly or in part by nonribosomal peptide synthetases. In an effort to identify additional nonribosomal peptides produced by these bacteria, a bioinformatics approach was used to “mine” the genome ofPseudomonas syringaepv. tomato DC3000 for the metabolic potential to biosynthesize previously unknown nonribosomal peptides. Herein we describe the identification of a nonribosomal peptide biosynthetic gene cluster that codes for proteins involved in the production of six structurally related linear lipopeptides. Structures for each of these lipopeptides were proposed based on amino acid analysis and mass spectrometry analyses. Mutations in this cluster resulted in the loss of swarming motility ofP. syringaepv. tomato DC3000 on medium containing a low percentage of agar. This phenotype is consistent with the loss of the ability to produce a lipopeptide that functions as a biosurfactant. This work gives additional evidence that mining the genomes of microorganisms followed by metabolite and phenotypic analyses leads to the identification of previously unknown secondary metabolites.
Alginate Production by
Pseudomonas putida
Creates a Hydrated Microenvironment and Contributes to Biofilm Architecture and Stress Tolerance under Water-Limiting Conditions
Authors: Chang Woo-Suk , van de Mortel Martijn , Nielsen Lindsey , Nino de Guzman Gabriela , Li Xiaohong , Halverson Larry J. 
Published: June 2007

ABSTRACT

Biofilms exist in a variety of habitats that are routinely or periodically not saturated with water, and residents must integrate cues on water abundance (matric stress) or osmolarity (solute stress) into lifestyle strategies. Here we examine this hypothesis by assessing the extent to which alginate production by
Pseudomonas putida
strain mt-2 and by other fluorescent pseudomonads occurs in response to water limitations and how the presence of alginate in turn influences biofilm development and stress tolerance. Total exopolysaccharide (EPS) and alginate production increased with increasing matric, but not solute, stress severity, and alginate was a significant component, but not the major component, of EPS. Alginate influenced biofilm architecture, resulting in biofilms that were taller, covered less surface area, and had a thicker EPS layer at the air interface than those formed by an mt-2
algD
mutant under water-limiting conditions, properties that could contribute to less evaporative water loss. We examined this possibility and show that alginate reduces the extent of water loss from biofilm residents by using a biosensor to quantify the water potential of individual cells and by measuring the extent of dehydration-mediated changes in fatty acid composition following a matric or solute stress shock. Alginate deficiency decreased survival of desiccation not only by
P. putida
but also by
Pseudomonas aeruginosa
PAO1 and
Pseudomonas syringae
pv. syringae B728a. Our findings suggest that in response to water-limiting conditions, pseudomonads produce alginate, which influences biofilm development and EPS physiochemical properties. Collectively these responses may facilitate the maintenance of a hydrated microenvironment, protecting residents from desiccation stress and increasing survival.
Relationship between hip strength and frontal plane posture of the knee during a forward lunge
Authors: Thijs Youri , Van Tiggelen Damien , Willems Tine , De Clercq Dirk , Witvrouw Erik 
Published: June 2007

Objective:Excessive frontal plane knee movement during forward lunge movements might be associated with the occurrence of knee injuries in tennis. Here, we attempt to determine whether hip muscle strength is related to the frontal plane motion of the knee during a functional lunge movement.Design:A correlational study.Participants:A total of 84 healthy subjects (76 men, 8 women), with no history of knee or lower leg complaints.Interventions:Muscle strength of six hip muscle groups was measured using a handheld dynamometer. Subjects were videotaped during a forward lunge and peak knee valgus or varus angles were determined using a digital video analysis software program.Main outcome measurements:A correlation was examined between hip muscle strength and the amount of frontal plane movement of the knee during a forward lunge.Results:There were no significant differences in hip muscle strength between the valgus group and the varus group during the forward lunge movement. No significant correlation was found between the strength of the assessed hip muscles and the amount of movement into valgus/varus. In the varus group a moderate positive correlation was found between the External Rotation/Internal Rotation force ratio and the amount of knee varus during the forward lunge movement (r = 0.31, p = 0.03).Conclusions:The findings suggest that in healthy subjects hip muscle strength is not correlated to the amount of valgus/varus movement of the knee during a forward lunge. This suggests that other factors (eg, proprioception, core hip stability) might be more important in controlling knee movement during this tennis-specific movement.
Effect of a multistage ultra-endurance triathlon on body composition: World Challenge Deca Iron Triathlon 2006
Authors: Knechtle B , Salas Fraire O , Andonie J L , Kohler G 
Published: June 2007

Objective:To investigate the effect of a multistage ultra-endurance triathlon on body composition in ultra-triathletes.Design:Descriptive field study.Setting:The “World Challenge Deca Iron Triathlon 2006” in Monterrey, Mexico, in which every day for 10 consecutive days athletes had to perform the distance of one Ironman triathlon.Subjects:Eight male ultra-endurance athletes (mean (SD) age 40.6 (10.7) years, weight 76.4 (8.4) kg, height 175 (4) cm and body mass index (BMI) 24.7 (2.2) kg/m2).Interventions:None.Main outcome measurements:Determination of body mass, protein mass, body fat, per cent body fat, mineral mass, total body water, intracellular water, extracellular water and lean body mass with a direct segmental multifrequency bioelectrical impedance method before the race and after each stage in order to show changes in body composition.Results:A statistically significant decrease of body mass (−2.4 kg, p = 0.014), body fat (−5 kg, p = 0.0078) and per cent body fat (−6.4%, p = 0.0078) occurred at the end of the first day compared to values taken in the pre-race period. In contrast, at the same time, a statistically significant increase of protein mass (+0.7 kg, p = 0.035), mineral mass (+0.2 kg, p = 0.04), total body water (+1.8 litres, p = 0.042), intracellular water (+1.6 litres, p = 0.034) and lean body mass (+2.6 kg, p = 0.023) was shown. After the first day until the end of the challenge, body fat (−3 kg, p>0.05) and per cent body fat (−3.9%, p>0.05) showed a statistically significant decrease, whereas the other parameters showed no changes.Conclusions:Athletes taking part in a multistage ultra-endurance triathlon over 10 Ironman triathlon distances in 10 consecutive days lost 3 kg of body fat; skeletal muscle mass, mineral mass and body water were unchanged.