bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Disruption of Homocitrate Synthase Genes on
Nostoc
sp. Strain PCC 7120 Photobiological Hydrogen Production and Nitrogenase
Authors: Masukawa Hajime , Inoue Kazuhito , Sakurai Hidehiro 
Published: October 2007

ABSTRACT

In the case of nitrogenase-based photobiological hydrogen production systems of cyanobacteria, the inactivation of uptake hydrogenase (Hup) leads to significant increases in hydrogen production activity. However, the high-level-activity stage of the Hup mutants lasts only a few tens of hours under air, a circumstance which seems to be caused by sufficient amounts of combined nitrogen supplied by active nitrogenase. The catalytic FeMo cofactor of nitrogenase binds homocitrate, which is required for efficient nitrogen fixation. It was reported previously that the nitrogenase from the homocitrate synthase gene (
nifV
) disruption mutant of
Klebsiella pneumoniae
shows decreased nitrogen fixation activity and increased hydrogen production activity under N
2
. The cyanobacterium
Nostoc
sp. strain PCC 7120 has two homocitrate synthase genes,
nifV1
and
nifV2
, and with the Δ
hupL
variant of
Nostoc
sp. strain PCC 7120 as the parental strain, we have constructed two single mutants, the Δ
hupL
Δ
nifV1
strain (with the
hupL
and
nifV1
genes disrupted) and the Δ
hupL
Δ
nifV2
strain, and a double mutant, the Δ
hupL
Δ
nifV1
Δ
nifV2
strain. Diazotrophic growth rates of the two
nifV
single mutants and the double mutant were decreased moderately and severely, respectively, compared with the rates of the parent Δ
hupL
strain. The hydrogen production activity of the Δ
hupL
Δ
nifV1
mutant was sustained at higher levels than the activity of the parent Δ
hupL
strain after about 2 days of combined-nitrogen step down, and the activity in the culture of the former became higher than that in the culture of the latter. The presence of N
2
gas inhibited hydrogen production in the Δ
hupL
Δ
nifV1
Δ
nifV2
mutant less strongly than in the parent Δ
hupL
strain and the Δ
hupL
Δ
nifV1
and Δ
hupL
Δ
nifV2
mutants. The alteration of homocitrate synthase activity can be a useful strategy for improving sustained photobiological hydrogen production in cyanobacteria.
Enumeration of Viable
Listeria monocytogenes
Cells by Real-Time PCR with Propidium Monoazide and Ethidium Monoazide in the Presence of Dead Cells
Authors: Pan Y. , Breidt F. 
Published: October 2007

ABSTRACT

Propidium monoazide (PMA) and ethidium monoazide were used for enumeration of viable
Listeria monocytogenes
cells in the presence of dead cells. PMA had no antimicrobial effect on
L. monocytogenes
. Viable cell counts were linearly related to real-time PCR threshold cycle values for PMA-treated cells from planktonic and biofilm sources over a 4-log range.
Different Genotypes of Anatoxin-Producing Cyanobacteria Coexist in the Tarn River, France
Authors: Cadel-Six Sabrina , Peyraud-Thomas Caroline , Brient Luc , de Marsac Nicole Tandeau , Rippka Rosmarie , Méjean Annick 
Published: October 2007

ABSTRACT

Repeated dog deaths occurred in 2002, 2003, and 2005 after the animals drank water from the shoreline of the Tarn River in southern France. Signs of intoxication indicated acute poisoning due to a neurotoxin. Floating scum and biofilms covering pebbles were collected in the summers of 2005 and 2006 from six different sites along 30 km from the border of this river. The cyanobacterial neurotoxic alkaloid anatoxin-a and/or its methyl homolog, homoanatoxin-a, was detected in the extracts of most samples examined by gas chromatography-mass spectrometry. Fifteen filamentous cyanobacteria of the order
Oscillatoriales
were isolated and displayed four distinct phenotypes based on morphological characteristics and pigmentation. Three of the phenotypes can be assigned to the genus
Oscillatoria
or
Phormidium
, depending on the taxonomic treatises (bacteriological/botanical) employed for identification. The fourth phenotype is typical of the genus
Geitlerinema
Anagnostidis 1989. Eight strains rendered axenic were analyzed for production of anatoxin-a and homoanatoxin-a, and all strains of
Oscillatoria
/
Phormidium
proved to be neurotoxic. The genetic relatedness of the new isolates was evaluated by comparison of the intergenic transcribed spacer sequences with those of six oscillatorian strains from the Pasteur Culture Collection of Cyanobacteria. These analyses showed that the neurotoxic representatives are composed of five different genotypes, three of which correspond to phenotypes isolated in this study. Our findings prove that neurotoxic oscillatorian cyanobacteria exist in the Tarn River and thus were most likely implicated in the reported dog poisonings. Furthermore, they reemphasize the importance of monitoring benthic cyanobacteria in aquatic environments to fully assess the health risks associated with these organisms.
Occurrence of Human Adenoviruses at Two Recreational Beaches of the Great Lakes
Authors: Xagoraraki Irene , Kuo David H.-W. , Wong Kelvin , Wong Mark , Rose Joan B. 
Published: October 2007

ABSTRACT

Human adenoviruses (HAdVs) have been related to several waterborne diseases such as acute gastroenteritis, conjunctivitis, and respiratory illness, and it has been shown that an important human exposure pathway is through recreational waters. However, HAdV occurrence at recreational freshwater beaches has not been previously investigated. In this study, a total of 58 water samples were collected from two recreational beaches on Lake Michigan (i.e., Silver Beach and Washington Park Beach) during the summer of 2004. Occurrences of HAdVs in these lake samples were determined using two hexon-based real-time PCR assays (one for monitoring all 51 serotypes of HAdVs and another for specifically detecting F species HAdVs, i.e., serotypes 40 and 41) and compared to an integrated cell culture (ICC) PCR method. The real-time PCR results showed that 8 of 30 Silver Beach samples and 6 of 28 Washington Park Beach samples contained HAdVs, and F species HAdVs were detected in three of these positive samples. The concentrations of HAdVs ranged from (1.7 ± 0.7) × 10
1
to (3.4 ± 0.8) × 10
2
and from (7 ± 2) × 10
0
to (3.8 ± 0.3) × 10
3
virus particles/liter for Silver Beach and Washington Park Beach, respectively. F species HAdVs were detected at levels ranging from (4.8 ± 0.8) × 10
1
to (4.6 ± 1.5) × 10
2
virus particles/liter. Approximately 60% of the ICC-PCR analyses agreed with the real-time PCR results. This study revealed the occurrence of HAdVs at Lake Michigan recreational beaches. Given the potential health risks, further assessment regarding sources, virus transport, and survival is needed to improve the safety of the region.
Comparative Analyses of Prophage-Like Elements Present in Two
Lactococcus lactis
Strains
Authors: Ventura Marco , Zomer Aldert , Canchaya Carlos , O'Connell-Motherway Mary , Kuipers Oscar , Turroni Francesca , Ribbera Angela , Foroni Elena , Buist Girbe , Wegmann Udo , Shearman Claire , Gasson Michael J. , Fitzgerald Gerald F. , Kok Jan , van Sinderen Douwe 
Published: October 2007

ABSTRACT

In this study, we describe the genetic organizations of six and five apparent prophage-like elements present in the genomes of the
Lactococcus lactis
subsp.
cremoris
strains MG1363 and SK11, respectively. Phylogenetic investigation as well bioinformatic analyses indicates that all 11 prophages belong to subdivisions of the lactococcal P335 group of temperate bacteriophages.
Production of Eight Different Hydride Complexes and Nitrite Release from 2,4,6-Trinitrotoluene by
Yarrowia lipolytica
Authors: Ziganshin Ayrat M. , Gerlach Robin , Borch Thomas , Naumov Anatoly V. , Naumova Rimma P. 
Published: October 2007

ABSTRACT

2,4,6-Trinitrotoluene (TNT) transformation by the yeast strain
Yarrowia lipolytica
AN-L15 was shown to occur via two different pathways. Direct aromatic ring reduction was the predominant mechanism of TNT transformation, while nitro group reduction was observed to be a minor pathway. Although growth of
Y. lipolytica
AN-L15 was inhibited initially in the presence of TNT, TNT transformation was observed, indicating that the enzymes necessary for TNT reduction were present initially. Aromatic ring reduction resulted in the transient accumulation of eight different TNT-hydride complexes, which were characterized using high-performance liquid chromatography, UV-visible diode array detection, and negative-mode atmospheric pressure chemical ionization mass spectrometry (APCI-MS). APCI-MS analysis revealed three different groups of TNT-hydride complexes with molecular ions at
m/z
227, 228, and 230, which correspond to TNT-mono- and dihydride complexes and protonated dihydride isomers, respectively. One of the three protonated dihydride complex isomers detected appears to release nitrite in the presence of strain AN-L15. This release of nitrite is of particular interest since it can provide a pathway towards complete degradation and detoxification of TNT.
Molecular Epidemiology of
bla
CMY-2
Plasmids Carried by
Salmonella enterica
and
Escherichia coli
Isolates from Cattle in the Pacific Northwest
Authors: Daniels Joshua B. , Call Douglas R. , Besser Thomas E. 
Published: October 2007

ABSTRACT

Restriction analyses of
bla
CMY-2
-bearing plasmids and
Salmonella
and
Escherichia coli
hosts identified (i) shared highly similar plasmids in these species in rare cases, (ii) a clonal host-plasmid relationship in
Salmonella enterica
serotype Newport, and (iii) a very high diversity of strain types and plasmids among commensal
E. coli
isolates.
Enhancement of Shiga Toxin Production in Enterohemorrhagic
Escherichia coli
Serotype O157:H7 by DNase Colicins
Authors: Toshima Hirono , Yoshimura Ayana , Arikawa Kentaro , Hidaka Ayumi , Ogasawara Jun , Hase Atsushi , Masaki Haruhiko , Nishikawa Yoshikazu 
Published: October 2007

ABSTRACT

Colicins are proteins produced by and active against several strains of
Escherichia coli
. Previously we reported that colicinogenic bacteria seemed beneficial in preventing the clinical manifestations of infectious disease caused by enterohemorrhagic
E. coli
O157 in humans. The inhibitory effects could be due to a decrease in O157 levels and/or pathogenicity. This study investigated the effects of colicinogenic
E. coli
on the production of Shiga toxin (Stx) by O157. Standard strains of colicinogenic bacteria carrying plasmids for each type of colicin (E3/5/8/9) were used for the study. The O157 strains were cultured in the presence of colicinogenic bacteria or extracted colicins. Compared with results for controls, DNase colicins (E8/9) facilitated an 8- to 64-fold increase in production of Stx2, while RNase colicins (E3/5) suppressed Stx production in only two strains. Stx prophages were induced in synchrony with Stx production. Semiquantitative real-time reverse transcription-PCR (RT-PCR) was then performed to examine SOS gene expression. The RT-PCR results clearly indicated a marked increase in mRNA levels of SOS reaction-associated genes after the addition of DNase colicins. We believe that Stx prophages are induced by the SOS response to DNA damage caused by DNase colicins, thus leading to higher Stx production. These findings suggest that while colicinogenic bacteria can be antagonistic to O157 infection, DNase colicins may enhance Stx production. Thus, colicinogenic flora is likely to be involved in the complex pathogenic pathways of O157 infection, and further investigation should be performed before the use of colicinogenic bacteria as an intervention method.
Anaerobic Metabolism of 1-Amino-2-Naphthol-Based Azo Dyes (Sudan Dyes) by Human Intestinal Microflora
Authors: Xu Haiyan , Heinze Thomas M. , Chen Siwei , Cerniglia Carl E. , Chen Huizhong 
Published: October 2007

ABSTRACT

The rates of metabolism of Sudan I and II and Para Red by human intestinal microflora were high compared to those of Sudan III and IV under anaerobic conditions. Metabolites of the dyes were identified as aniline, 2,4-dimethylaniline,
o
-toluidine, and 4-nitroaniline through high-performance liquid chromatography and liquid chromatography electrospray ionization tandem mass spectrometry analyses. These data indicate that human intestinal bacteria are able to reduce Sudan dyes to form potentially carcinogenic aromatic amines.
Conservation of the Chitin Utilization Pathway in the
Vibrionaceae
Authors: Hunt Dana E. , Gevers Dirk , Vahora Nisha M. , Polz Martin F. 
Published: October 2007

ABSTRACT

Vibrionaceae
are regarded as important marine chitin degraders, and attachment to chitin regulates important biological functions; yet, the degree of chitin pathway conservation in
Vibrionaceae
is unknown. Here, a core chitin degradation pathway is proposed based on comparison of 19
Vibrio
and
Photobacterium
genomes with a detailed metabolic map assembled for
V. cholerae
from published biochemical, genomic, and transcriptomic results. Further, to assess whether chitin degradation is a conserved property of
Vibrionaceae
, a set of 54 strains from 32 taxa were tested for the ability to grow on various forms of chitin. All strains grew on
N
-acetylglucosamine (GlcNAc), the monomer of chitin. The majority of isolates grew on α (crab shell) and β (squid pen) chitin and contained chitinase A (
chiA
) genes.
chiA
sequencing and phylogenetic analysis suggest that this gene is a good indicator of chitin metabolism but appears subject to horizontal gene transfer and duplication. Overall, chitin metabolism appears to be a core function of
Vibrionaceae
, but individual pathway components exhibit dynamic evolutionary histories.
Evaluation of Removal of Noroviruses during Wastewater Treatment, Using Real-Time Reverse Transcription-PCR: Different Behaviors of Genogroups I and II
Authors: da Silva Allegra Kyria , Le Saux Jean-Claude , Parnaudeau Sylvain , Pommepuy Monique , Elimelech Menachem , Le Guyader Françoise S. 
Published: October 2007

ABSTRACT

Noroviruses, an important cause of gastroenteritis, are excreted by infected individuals and are therefore present in wastewater. We quantified norovirus genogroup I (GI) and GII in wastewater at different locations in France and evaluated removal by a range of treatment types, including basic (waste stabilization pond), current industry standard (activated sludge), and state-of-the-art (submerged membrane bioreactor) treatments. Noroviruses were quantified using real-time reverse transcription-PCR (rRT-PCR). Mengovirus was used as a virus extraction control, and internal controls were used to verify the level of GI and GII rRT-PCR inhibition. A total of 161 (81 influent and 79 effluent) samples were examined; GI and GII were detected in 43 and 88% of the influent samples, respectively, and in 24 and 14% of the effluent samples, respectively. Physicians in France report far more cases of GII than GI during outbreaks; thus, the frequent presence of GI was unexpected. The GI influent concentrations were more variable, the peak GI influent concentrations were higher than the peak GII influent concentrations at all four sites (up to 1 × 10
9
and 6 × 10
7
genome copies/liter, respectively), and the average positive influent concentrations of GI were higher than the average positive influent concentrations of GII. The maximum effluent breakthrough concentrations were 6 × 10
6
and 3 × 10
6
genome copies/liter for GI and GII, respectively, indicating that the four treatment systems studied decreased the norovirus contamination load in receiving waters.
Physiological and Transcriptional Responses of
Saccharomyces cerevisiae
to Zinc Limitation in Chemostat Cultures
Authors: De Nicola Raffaele , Hazelwood Lucie A. , De Hulster Erik A. F. , Walsh Michael C. , Knijnenburg Theo A. , Reinders Marcel J. T. , Walker Graeme M. , Pronk Jack T. , Daran Jean-Marc , Daran-Lapujade Pascale 
Published: October 2007

ABSTRACT

Transcriptional responses of the yeast
Saccharomyces cerevisiae
to Zn availability were investigated at a fixed specific growth rate under limiting and abundant Zn concentrations in chemostat culture. To investigate the context dependency of this transcriptional response and eliminate growth rate-dependent variations in transcription, yeast was grown under several chemostat regimens, resulting in various carbon (glucose), nitrogen (ammonium), zinc, and oxygen supplies. A robust set of genes that responded consistently to Zn limitation was identified, and the set enabled the definition of the Zn-specific Zap1p regulon, comprised of 26 genes and characterized by a broader zinc-responsive element consensus (MHHAACCBYNMRGGT) than so far described. Most surprising was the Zn-dependent regulation of genes involved in storage carbohydrate metabolism. Their concerted down-regulation was physiologically relevant as revealed by a substantial decrease in glycogen and trehalose cellular content under Zn limitation. An unexpectedly large number of genes were synergistically or antagonistically regulated by oxygen and Zn availability. This combinatorial regulation suggested a more prominent involvement of Zn in mitochondrial biogenesis and function than hitherto identified.
Intestinal Integrity and
Akkermansia muciniphila
, a Mucin-Degrading Member of the Intestinal Microbiota Present in Infants, Adults, and the Elderly
Authors: Collado M. Carmen , Derrien Muriel , Isolauri Erika , de Vos Willem M. , Salminen Seppo 
Published: October 2007

ABSTRACT

Fluorescence in situ hybridization and real-time PCR analysis targeting the 16S rRNA gene of
Akkermansia muciniphila
were performed to determine its presence in the human intestinal tract. These techniques revealed that an
A. muciniphila
-like bacterium is a common member of the human intestinal tract and that its colonization starts in early life and develops within a year to a level close to that observed in adults (10
8
cells/g) but decreases (
P
< 0.05) in the elderly.
Purification and Characterization of Two Highly Thermophilic Alkaline Lipases fromThermosyntropha lipolytica
Authors: Salameh Moh'd A. , Wiegel Juergen 
Published: October 2007

ABSTRACTTwo thermostable lipases were isolated and characterized fromThermosyntropha lipolyticaDSM 11003, an anaerobic, thermophilic, alkali-tolerant bacterium which grows syntrophically with methanogens on lipids such as olive oil, utilizing only the liberated fatty acid moieties but not the glycerol. Lipases LipA and LipB were purified from culture supernatants to gel electrophoretic homogeneity by ammonium sulfate precipitation and hydrophobic interaction column chromatography. The apparent molecular masses of LipA and LipB determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 50 and 57 kDa, respectively. The temperature for maximal activity of LipA and LipB was around 96°C, which is, so far as is known, the highest temperature for maximal activity among lipases, and the pH optima for growth determined at 25°C (pH25°Coptima) were 9.4 and 9.6, respectively. LipA and LipB at 100°C and pH25°C8.0 retained 50% activity after 6 and 2 h of incubation, respectively. Both enzymes exhibited high activity with long-chain fatty acid glycerides, yielding maximum activity with trioleate (C18:1) and, among thep-nitrophenyl esters, withp-nitrophenyl laurate. Hydrolysis of glycerol ester bonds occurred at positions 1 and 3. The activities of both lipases were totally inhibited by 10 mM phenylmethylsulfonyl fluoride and 10 mM EDTA. Metal analysis indicated that both LipA and LipB contain 1 Ca2+and one Mn2+ion per monomeric enzyme unit. The addition of 1 mM MnCl2to dialyzed enzyme preparations enhanced the activities at 96°C of both LipA and LipB by threefold and increased the durations of their thermal stability at 60°C and 75°C, respectively, by 4 h.
Improving the Insecticidal Activity against Resistant
Culex quinquefasciatus
Mosquitoes by Expression of Chitinase Gene
chiAC
in
Bacillus sphaericus
Authors: Cai Yajun , Yan Jianpin , Hu Xiaomin , Han Bei , Yuan Zhiming 
Published: October 2007

ABSTRACT

Expression of a chitinase gene,
chiAC
, from
Bacillus thuringiensis
in
B. sphaericus
2297 using the binary toxin promoter yielded a recombinant strain that was 4,297-fold more toxic than strain 2297 against resistant
Culex quinquefasciatus
. These results show that this chitinase can synergize the toxicity of the binary toxin against mosquitoes and thus may be useful in managing mosquito resistance to
B. sphaericus
.
Role of Iron in Human Serum Resistance of the Clinical and Environmental
Vibrio vulnificus
Genotypes
Authors: Bogard Ryan W. , Oliver James D. 
Published: October 2007

ABSTRACT

We recently reported a simple PCR procedure that targets a sequence variation of the virulence-correlated gene locus
vcg
. It was found that 90% of all clinical isolates possessed the
vcgC
sequence variant, while 93% of all environmental isolates possessed the
vcgE
sequence variant. Here we report that the clinical genotype of
Vibrio vulnificus
is significantly better able to survive in human serum than is the environmental genotype. The presence of a siderophore-encoding gene,
viuB
, influenced serum survivability among all isolates of
V. vulnificus
tested. Those strains positive for
viuB
(all C-type strains but very few E-type strains) showed greater serum survivability than those lacking
viuB
(most E-type strains). The addition of iron (in the form of ferric ammonium citrate) to human serum restored the survival of E-type strains lacking
viuB
to levels not significantly different from those of C-type and E-type strains that possess
viuB
. These findings suggest that
viuB
may dictate serum survival in both C- and E-type strains of
V. vulnificus
and may explain why some strains (C- and E-type strains) are pathogenic and others (predominately E-type strains) are not. Additionally, C-type strains exhibited a cross-protective response against human serum, not exhibited by E-type strains, after incubation under nutrient and osmotic downshift conditions that mimicked estuarine waters. This suggests that the nutrient/osmotic environment may influence the survival of
V. vulnificus
following entry into the human body, leading to selection of the C genotype over the E genotype.
Aged HCT-8 Cell Monolayers Support
Cryptosporidium parvum
Infection
Authors: Sifuentes Laura Y. , Di Giovanni George D. 
Published: October 2007

ABSTRACT

Cell culture assays in various formats have been used to study the infectivity of
Cryptosporidium
spp. as well as to determine the infectivity of naturally occurring oocysts in water. Currently, cell culture assays for infectious
Cryptosporidium
spp. in water have largely been limited to practice in research laboratories. One obstacle to the routine use of
Cryptosporidium
cell culture assays for the analysis of water samples is the coordination of water sample collection and processing with readiness of cell culture monolayers. For most
Cryptosporidium
cell culture assays, monolayers are allowed to develop for 24 to 48 h to reach 80 to 100% confluence prior to inoculation. In this study, we used immunofluorescent assay microscopy to evaluate freshly confluent (2-day-old) and aged (8- to 67-day-old) HCT-8 cell monolayers for their ability to support
Cryptosporidium parvum
infection. HCT-8 monolayers as old as 67 days were clearly shown to support infection. In two of three experiments, aged monolayers (8- to 11-day-old and 11- to 22-day-old, respectively) developed the same number of
C. parvum
clusters of infection as freshly confluent monolayers. Results suggest that it may be possible to use cell monolayers from freshly confluent to 3 weeks old on hand for infectivity assays without having to schedule sample processing to coincide with development of freshly confluent monolayers. This would make
Cryptosporidium
cell culture assays much more feasible for water quality and utility laboratories.