bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purification and Characterization of a High-Molecular-Weight Insecticidal Protein Complex Produced by the Entomopathogenic Bacterium
Photorhabdus luminescens
Authors: Bowen David J. , Ensign Jerald C. 
Published: December 2019

ABSTRACT

Photorhabdus luminescens
is a gram-negative enteric bacterium that is found in association with entomopathogenic nematodes of the family
Heterorhabditidae
. The nematodes infect a variety of soil-dwelling insects. Upon entering an insect host, the nematode releases
P. luminescens
cells from its intestinal tract, and the bacteria quickly establish a lethal septicemia. When grown in peptone broth, in the absence of the nematodes, the bacteria produce a protein toxin complex that is lethal when fed to, or injected into the hemolymph of,
Manduca sexta
larvae and several other insect species. The toxin purified as a protein complex which has an estimated molecular weight of 1,000,000 and contains no protease, phospholipase, or hemolytic activity and only a trace of lipase activity. The purified toxin possesses insecticidal activity whether injected or given orally. Analyses of the denatured complex by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed it to be composed of several protein subunits ranging in size from 30 to 200 kDa. The complex was further separated by native gel electrophoresis into three components, two of which retained insecticidal activity. The purified native toxin complex was found to be active in nanogram concentrations against insects representing four orders of the class
Insecta
.
The Requirement of RpoN (Sigma Factor ς
54
) in Denitrification by
Pseudomonas stutzeri
Is Indirect and Restricted to the Reduction of Nitrite and Nitric Oxide
Authors: Härtig Elisabeth , Zumft Walter G. 
Published: December 2019

ABSTRACT

The
rpoN
region of
Pseudomonas stutzeri
was cloned, and an
rpoN
null mutant was constructed. RpoN was not essential for denitrification in this bacterium but affected the expression levels and enzymatic activities of cytochrome
cd
1
nitrite reductase and nitric oxide reductase, whereas those of respiratory nitrate reductase and nitrous oxide reductase were comparable to wild-type levels. Since the transcription of the structural genes
nirS
and
norCB
, coding for nitrite reductase and the nitric oxide reductase complex, respectively, proceeded unabated, our data indicate a posttranslational process for the two key enzymes of denitrification depending on RpoN.
Humic Acids as Electron Acceptors for Anaerobic Microbial Oxidation of Vinyl Chloride and Dichloroethene
Authors: Bradley Paul M. , Chapelle Francis H. , Lovley Derek R. 
Published: December 2019

ABSTRACT

Anaerobic oxidation of [1,2-
14
C]vinyl chloride and [1,2-
14
C]dichloroethene to
14
CO
2
under humic acid-reducing conditions was demonstrated. The results indicate that waterborne contaminants can be oxidized by using humic acid compounds as electron acceptors and suggest that natural aquatic systems have a much larger capacity for contaminant oxidation than previously thought.
Transformation of the Ionic X-Ray Contrast Agent Diatrizoate and Related Triiodinated Benzoates by
Trametes versicolor
Authors: Rode Ulrike , Müller Rudolf 
Published: December 2019

ABSTRACT

Iodinated X-ray contrast agents are considered to be nondegradable by microorganisms. The decomposition of the ionic X-ray contrast agents Diatrizoate (3,5-di(acetamido)-2,4,6-triiodobenzoic acid) and Iodipamide (3,3′-adipoyl-diimino-di(2,4,6-triiodobenzoic acid) and related triiodinated benzoates (Acetrizoate [3-acetylamino-2,4,6-triiodobenzoic acid] and Aminotrizoate [3-amino-2,4,6-triiodobenzoic acid]) by
Trametes versicolor
has been investigated. The fungus was able to transform all tested triiodinated benzoates cometabolically. During transformation of these compounds, iodide was released, but deiodination was not complete.
T. versicolor
liberated traces of
14
CO
2
from uniformly ring-
14
C-labeled Diatrizoate (3,5-di(acetamido)-2,4,6-triiodobenzoate). Various extracellular metabolites were detected during transformation of the different substances. In the transformation of Diatrizoate, the three main metabolites were identified as 3,5-di(acetamido)-2,6-diiodobenzoic acid, 3,5-di(acetamido)-2,4-diiodobenzoic acid, and 3,5-di(acetamido)-2-iodobenzoic acid, suggesting reductive deiodinations in steps as initial transformation steps.
Reverse Transcriptase PCR Detection of Astrovirus, Hepatitis A Virus, and Poliovirus in Experimentally Contaminated Mussels: Comparison of Several Extraction and Concentration Methods
Authors: Traore Ousmane , Arnal Charlotte , Mignotte Berengere , Maul Armand , Laveran Henri , Billaudel Sylviane , Schwartzbrod Louis 
Published: December 2019

ABSTRACT
Four methods of extraction and three methods of concentration of three enteric viruses from mussels were comparatively evaluated by reverse transcriptase PCR (RT-PCR). Shellfish were experimentally contaminated by immersion in seawater seeded with astrovirus, hepatitis A virus, or poliovirus. Sixty-gram samples of mussel tissues were processed by using borate buffer, glycine solution, saline beef, and saline beef-Freon extraction methods. The viruses were concentrated by precipitation with polyethylene glycol 6000 (PEG 6000) or PEG 8000 or by organic flocculation. RT-PCR was performed with RNA extracts from crude shellfish extracts and concentrates with and without Sephadex LH20 filtration. The glycine solution and borate buffer extraction methods resulted in significantly more RT-PCR-positive samples than the saline beef extraction method. We assessed the efficiency of 20 combinations of extraction and concentration methods. The borate buffer-organic flocculation, borate buffer-PEG 6000, and glycine solution-PEG 6000 combinations gave RT-PCR-positive results for all 27 samples analyzed for the three viruses. Detoxification of the samples by Sephadex LH20 filtration significantly decreased the efficiency of RT-PCR virus detection.
Variations of Bacterial Populations in Human Feces Measured by Fluorescent In Situ Hybridization with Group-Specific 16S rRNA-Targeted Oligonucleotide Probes
Authors: Franks Alison H. , Harmsen Hermie J. M. , Raangs Gerwin C. , Jansen Gijsbert J. , Schut Frits , Welling Gjalt W. 
Published: December 2019

ABSTRACT

Six 16S rRNA-targeted oligonucleotide probes were designed, validated, and used to quantify predominant groups of anaerobic bacteria in human fecal samples. A set of two probes was specific for species of the
Bacteroides fragilis
group and the species
Bacteroides distasonis
. Two others were designed to detect species of the
Clostridium histolyticum
and the
Clostridium lituseburense
groups. Another probe was designed for the genera
Streptococcus
and
Lactococcus
, and the final probe was designed for the species of the
Clostridium coccoides-Eubacterium rectale
group. The temperature of dissociation of each of the probes was determined. The specificities of the probes for a collection of target and reference organisms were tested by dot blot hybridization and fluorescent in situ hybridization (FISH). The new probes were used in initial FISH experiments to enumerate human fecal bacteria. The combination of the two
Bacteroides
-specific probes detected a mean of 5.4 × 10
10
cells per g (dry weight) of feces; the
Clostridium coccoides-Eubacterium rectale
group-specific probe detected a mean of 7.2 × 10
10
cells per g (dry weight) of feces. The
Clostridium histolyticum
,
Clostridium lituseburense
, and
Streptococcus-Lactococcus
group-specific probes detected only numbers of cells ranging from 1 × 10
7
to 7 × 10
8
per g (dry weight) of feces. Three of the newly designed probes and three additional probes were used in further FISH experiments to study the fecal flora composition of nine volunteers over a period of 8 months. The combination of probes was able to detect at least two-thirds of the fecal flora. The normal biological variations within the fecal populations of the volunteers were determined and indicated that these variations should be considered when evaluating the effects of agents modulating the flora.
Genetic Characterization and Physiological Role of Endopeptidase O from
Lactobacillus helveticus
CNRZ32
Authors: Chen Yo-Shen , Steele James L. 
Published: December 2019

ABSTRACT

A previously identified insert expressing an endopeptidase from a
Lactobacillus helveticus
CNRZ32 genomic library was characterized. Nucleotide sequence analysis revealed an open reading frame of 1,941 bp encoding a putative protein of 71.2 kDa which contained a zinc-protease motif. Protein homology searches revealed that this enzyme has 40% similarity with endopeptidase O (PepO) from
Lactococcus lactis
P8-2-47. Northern hybridization revealed that
pepO
is monocistronic and is expressed throughout the growth phase. CNRZ32 derivatives lacking PepO activity were constructed via gene replacement. Enzyme assays revealed that the PepO mutant had significantly reduced endopeptidase activity when compared to CNRZ32 with two of the three substrates examined. Growth studies indicated that PepO has no detectable effect on growth rate or acid production by
Lactobacillus helveticus
CNRZ32 in amino acid defined or skim milk medium.
Genetic Analysis of
Comamonas acidovorans
Polyhydroxyalkanoate Synthase and Factors Affecting the Incorporation of 4-Hydroxybutyrate Monomer
Authors: Sudesh Kumar , Fukui Toshiaki , Doi Yoshiharu 
Published: December 2019

ABSTRACT

The polyhydroxyalkanoate (PHA) synthase gene of
Comamonas acidovorans
DS-17 (

phaC
Ca

) was cloned by using the synthase gene of
Alcaligenes eutrophus
as a heterologous hybridization probe. Complete sequencing of a 4.0-kbp
Sma
I-
Hin
dIII (SH40) subfragment revealed the presence of a 1,893-bp PHA synthase coding region which was followed by a 1,182-bp β-ketothiolase gene (

phaA
Ca

). Both the translated products of these genes showed significant identity, 51.1 and 74.2%, respectively, to the primary structures of the products of the corresponding genes in
A. eutrophus
. The arrangement of PHA biosynthesis genes in
C. acidovorans
was also similar to that in
A. eutrophus
except that the third gene,
phaB
, coding for acetoacetyl-coenzyme A reductase, was not found in the region downstream of

phaA
Ca

. The cloned fragment complemented a PHA-negative mutant of
A. eutrophus
, PHB
−
4, resulting in poly-3-hydroxybutyrate accumulation of up to 73% of the dry cell weight when fructose was the carbon source. The heterologous expression enabled the incorporation of 4-hydroxybutyrate (4HB) and 3-hydroxyvalerate monomers. The PHA synthase of
C. acidovorans
does not appear to show any preference for 4-hydroxybutyryl-coenzyme A as a substrate. This leads to the suggestion that in
C. acidovorans
, it is the metabolic pathway, and not the specificity of the organism’s PHA synthase, that drives the incorporation of 4HB monomers, resulting in the efficient accumulation of PHA with a high 4HB content.
New Nitrogen-Fixing Microorganisms Detected in Oligotrophic Oceans by Amplification of Nitrogenase (
nifH
) Genes
Authors: Zehr Jonathan P. , Mellon Mark T. , Zani Sabino 
Published: December 2019

ABSTRACT

Oligotrophic oceanic waters of the central ocean gyres typically have extremely low dissolved fixed inorganic nitrogen concentrations, but few nitrogen-fixing microorganisms from the oceanic environment have been cultivated. Nitrogenase gene (
nifH
) sequences amplified directly from oceanic waters showed that the open ocean contains more diverse diazotrophic microbial populations and more diverse habitats for nitrogen fixers than previously observed by classical microbiological techniques. Nitrogenase genes derived from unicellular and filamentous cyanobacteria, as well as from the α and γ subdivisions of the class
Proteobacteria
, were found in both the Atlantic and Pacific oceans.
nifH
sequences that cluster phylogenetically with sequences from sulfate reducers or clostridia were found associated with planktonic crustaceans. Nitrogenase sequence types obtained from invertebrates represented phylotypes distinct from the phylotypes detected in the picoplankton size fraction. The results indicate that there are in the oceanic environment several distinct potentially nitrogen-fixing microbial assemblages that include representatives of diverse phylotypes.
Induction of Acid Resistance of
Salmonella typhimurium
by Exposure to Short-Chain Fatty Acids
Authors: Kwon Y. M. , Ricke S. C. 
Published: December 2019

ABSTRACT

Exposure to short-chain fatty acids (SCFA) is one of the stress conditions
Salmonella typhimurium
encounters during its life cycle, because SCFA have been widely used as food preservatives and SCFA are also present at high concentrations in the gastrointestinal tracts of host animals. The effects of SCFA on the acid resistance of the organism were examined in an attempt to understand the potential role of SCFA in the pathogenesis of
S. typhimurium
. The percent survival of
S. typhimurium
at pH 3.0 was determined after exposure to SCFA for 1 h at pH 7.0. The percent acid survival, which varied depending on the SCFA species and the concentration used, was 42 after exposure to 100 mM propionate at pH 7.0 under aerobic incubation conditions, while less than 1% could survive without exposure. The SCFA-induced acid resistance was markedly enhanced by anaerobiosis (64%), lowering pH conditions (138% at pH 5.0), or increasing incubation time (165% with 4 h) during exposure to propionic acid. When protein synthesis during exposure to propionate was blocked by chloramphenicol, the percent acid survival was less than 1, indicating that the protein synthesis induced by exposure to propionate is required for the induction of the acid resistance. The percent acid survival determined with the isogenic mutant strains defective in acid tolerance response revealed that AtrB protein is necessary for the full induction of acid resistance by exposure to propionate, while unexpectedly, inactivation of PhoP significantly increased acid resistance over that of the wild type (
P
< 0.05). The results suggest that the virulence of
S. typhimurium
may be enhanced by increasing acid resistance upon exposure to SCFA during its life cycle and further enhanced by anaerobiosis, low pH, and prolonged exposure time.
Discrimination of Psychrotrophic and Mesophilic Strains of the
Bacillus cereus
Group by PCR Targeting of Major Cold Shock Protein Genes
Authors: Francis Kevin P. , Mayr Ralf , von Stetten Felix , Stewart Gordon S. A. B. , Scherer Siegfried 
Published: December 2019

ABSTRACT

Detection of psychrotrophic strains (those able to grow at or below 7°C) of the
Bacillus cereus
group (
Bacillus cereus
,
Bacillus thuringiensis
, and
Bacillus mycoides
) in food products is at present extremely slow with conventional microbiology. This is due to an inability to discriminate these cold-adapted strains from their mesophilic counterparts (those able to grow only above 7°C) by means other than growth at low temperature, which takes 5 to 10 days for detection. Here we report the development of a single PCR assay that, using major cold shock protein-specific primers and appropriate annealing temperatures, is capable of both rapidly identifying bacteria of the
B. cereus
group and discriminating between psychrotrophic and mesophilic strains. It is intended that this development help to more accurately predict the shelf life of refrigerated pasteurized food and dairy products and to reduce the incidence of food poisoning by psychrotrophic strains of the
B. cereus
group.
Purification and Properties of Two Thermostable Alkaline Xylanases from an Alkaliphilic
Bacillus
sp
Authors: Gessesse Amare 
Published: December 2019

ABSTRACT

Two xylanases, designated XylA and XylB, were purified from the culture supernatant of the alkaliphilic
Bacillus
sp. strain AR-009. The molecular masses of the two enzymes were estimated to be 23 kDa (XylA) and 48 kDa (XylB) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The optimum pHs for activity were 9 for XylA and 9 to 10 for XylB. The temperature optima for the activity of XylA were 60°C at pH 9 and 70°C at pH 8. XylB was optimally active at 75°C at pH 9 and 70°C at pH 8. Both enzymes were stable in a broad pH range and showed good stability when incubated at 60 and 65°C in pH 8 and 9 buffers.
Expression of
Phanerochaete chrysosporium
Genes Encoding Lignin Peroxidases, Manganese Peroxidases, and Glyoxal Oxidase in Wood
Authors: Janse Bernard J. H. , Gaskell Jill , Akhtar Masood , Cullen Daniel 
Published: December 2019

ABSTRACT

Expression of
Phanerochaete chrysosporium
genes encoding ligninolytic enzymes was assessed in wood. Poly(A) RNA was extracted from colonized wood chips by magnetic capture, and specific transcripts were quantified by competitive reverse transcriptase PCR. mRNA levels varied substantially among lignin peroxidase genes, and transcript patterns were dramatically different from those in previous studies with defined media.
Degradation of 3-Chlorobenzoate under Low-Oxygen Conditions in Pure and Mixed Cultures of the Anoxygenic PhotoheterotrophRhodopseudomonas palustrisDCP3 and an AerobicAlcaligenesSpecies
Authors: Krooneman Janneke , van den Akker Sytske , Pedro Gomes Teresa M. , Forney Larry J. , Gottschal Jan C. 
Published: December 2019

ABSTRACTThe presence or absence of molecular oxygen has been shown to play a crucial role in the degradability of haloaromatic compounds. In the present study, it was shown that anaerobic phototrophic 3-chlorobenzoate (3CBA) metabolism byRhodopseudomonas palustrisDCP3 is oxygen tolerant up to a concentration of 3 μM O2. Simultaneous oxidation of an additional carbon source permitted light-dependent anaerobic 3CBA degradation at oxygen input levels which, in the absence of such an additional compound, would result in inhibition of light-dependent dehalogenation. Experiments under the same experimental conditions with strain DCP3 in coculture with an aerobic 3CBA-utilizing heterotroph,Alcaligenessp. strain L6, revealed that light-dependent dehalogenation of 3CBA did not occur. Under both oxygen limitation (O2< 0.1 μM) and low oxygen concentrations (3 μM O2), all the 3CBA was metabolized by the aerobic heterotroph. These data suggest that biodegradation of (halo)aromatics by photoheterotrophic bacteria such asR. palustrisDCP3 may be restricted to anoxic photic environments.
Ergosterol Content in Various Fungal Species and Biocontaminated Building Materials
Authors: Pasanen Anna-Liisa , Yli-Pietilä Kati , Pasanen Pertti , Kalliokoski Pentti , Tarhanen Juhani 
Published: December 2019

ABSTRACT

This paper reports the ergosterol content for microbial cultures of six filamentous fungi, three yeast species, and one actinomycete and the ergosterol levels in 40 samples of building materials (wood chip, gypsum board, and glass wool) contaminated by microorganisms. The samples were hydrolyzed in alkaline methanol, and sterols were silylated and analyzed by gas chromatography-mass spectrometry. The average ergosterol content varied widely among the fungal species over the range of 2.6 to 42 μg/ml of dry mass or 0.00011 to 17 pg/spore or cell. Ergosterol could not be detected in the actinomycete culture. The results for both the fungal cultures and building material samples supported the idea that the ergosterol content reflects the concentration of filamentous fungi but it underestimates the occurrence of yeast cells. The ergosterol content in building material samples ranged from 0.017 to 68 μg/g of dry mass of material. A good agreement between the ergosterol concentration and viable fungal concentrations was detected in the wood chip (
r
> 0.66,
P
≤ 0.009) and gypsum board samples (
r
> 0.48,
P
≤ 0.059), whereas no relationship between these factors was observed in the glass wool samples. For the pooled data of the building materials, the ergosterol content correlated significantly with the viable fungal levels (
r
> 0.63,
P
< 0.0001). In conclusion, the ergosterol concentration could be a suitable marker for estimation of fungal concentrations in contaminated building materials with certain reservations, including the underestimation of yeast concentrations.
Production of Biogenic Mn Oxides by
Leptothrix discophora
SS-1 in a Chemically Defined Growth Medium and Evaluation of Their Pb Adsorption Characteristics
Authors: Nelson Yarrow M. , Lion Leonard W. , Ghiorse William C. , Shuler Michael L. 
Published: December 2019

ABSTRACT

Biogenic Mn oxides were produced by the bacterium
Leptothrix discophora
SS-1 (= ATCC 3182) in a chemically defined mineral salts medium, and the Pb binding and specific surface area of these oxides were characterized. Growth of SS-1 in the defined medium with pyruvate as a carbon and energy source required the addition of vitamin B
12
. Complete oxidation of Mn(II) within 60 h required the addition of ≥0.1 μM FeSO
4
. Pb adsorption isotherms were determined for the biogenic Mn oxides (and associated cells with their extracellular polymer) and compared to the Pb adsorption isotherms of cells and exopolymer alone, as well as to abiotic Mn oxides. The Pb adsorption to cells and exopolymer with biogenic Mn oxides (0.8 mmol of Mn per g) at pH 6.0 and 25°C was 2 orders of magnitude greater than the Pb adsorption to cells and exopolymer alone (on a dry weight basis). The Pb adsorption to the biogenic Mn oxide was two to five times greater than the Pb adsorption to a chemically precipitated abiotic Mn oxide and several orders of magnitude greater than the Pb adsorption to two commercially available crystalline MnO
2
minerals. The N
2
Brunauer-Emmet-Teller specific surface areas of the biogenic Mn oxide and fresh Mn oxide precipitate (224 and 58 m
2
/g, respectively) were significantly greater than those of the commercial Mn oxide minerals (0.048 and 4.7 m
2
/g). The Pb adsorption capacity of the biogenic Mn oxide also exceeded that of a chemically precipitated colloidal hydrous Fe oxide under similar solution conditions. These results show that amorphous biogenic Mn oxides similar to those produced by SS-1 may play a significant role in the control of trace metal phase distribution in aquatic systems.
Cloning and Characterization of the Polyhydroxybutyrate Depolymerase Gene of
Pseudomonas stutzeri
and Analysis of the Function of Substrate-Binding Domains
Authors: Ohura Takeshi , Kasuya Ken-Ichi , Doi Yoshiharu 
Published: December 2019

ABSTRACT

The extracellular polyhydroxybutyrate (PHB) depolymerase gene (

phaZ
Pst

) of
Pseudomonas stutzeri
was cloned and sequenced.

phaZ
Pst

was composed of 1,728 bp encoding a protein of 576 amino acids. Analyses of the N-terminal amino acid sequence and the matrix-assisted laser desorption/ionization–time-of-flight (MALDI-TOF) mass spectrum of the purified enzyme showed that the mature enzyme consisted of 538 amino acids with a deduced molecular mass of 57,506 Da. Analysis of the deduced amino acid sequence of the protein revealed a domain structure containing a catalytic domain, putative linker region, and two putative substrate-binding domains (SBDI and SBDII). The putative linker region was similar to the repeating units of the cadherin-like domain of chitinase A from
Vibrio harveyi
and chitinase B from
Clostridium paraputrificum
. The binding characteristics of SBDs to poly([
R
]-3-hydroxybutyrate) [P(3HB)] and chitin granules were characterized by using fusion proteins of SBDs with glutathione S -transferase (GST). These GST fusion proteins with SBDII and SBDI showed binding activity toward P(3HB) granules but did not bind on chitin granules. It has been suggested that the SBDs of the depolymerase interact specifically with the surface of P(3HB). In addition, a kinetic analysis for the enzymatic hydrolysis of 3-hydroxybutyrate oligomers of various sizes has suggested that the catalytic domain of the enzyme recognizes at least two monomeric units as substrates.