bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of a Military Parenting Program on Parental Distress and Suicidal Ideation: After Deployment Adaptive Parenting Tools
Authors: Gewirtz Abigail H. , DeGarmo David S. , Zamir Osnat 
Published: April 2016

Few studies have examined whether parenting prevention programs might mitigate risk for suicidality in parents, yet parent suicidality is a strong risk factor for offspring suicidality. We report results from a randomized controlled trial of a parenting program for deployed National Guard and Reserve families with a school‐aged child. Intent‐to‐treat analyses showed that random assignment to the parenting program (ADAPT) was associated with improved parenting locus of control (LOC). Improved parenting LOC was concurrently associated with strengthened emotion regulation which predicted reductions in psychological distress and suicidal ideation at 12 months postbaseline. Results are discussed in the context of ongoing efforts to reduce suicide rates in military populations.
Environmental Stability of Swine and Human Pandemic Influenza Viruses in Water under Variable Conditions of Temperature, Salinity, and pH
Authors: Poulson R. L. , Tompkins S. M. , Berghaus R. D. , Brown J. D. , Stallknecht D. E. 
Published: April 2016

ABSTRACT
The movement of influenza A viruses (IAVs) from wild bird reservoirs to domestic animals and humans is well established, but the transmission mechanisms that facilitate efficient movement across and within these host populations are not fully defined. Although predominant routes of transmission vary between host populations, the extent of environmental stability needed for efficient IAV transmission also may vary. Because of this, we hypothesized that virus stability would differ in response to varied host-related transmission mechanisms; if correct, such phenotypic variation might represent a potential marker for the emergence of novel animal or human influenza viruses. Here, the objective was to evaluate the ability of eight swine and six human IAV isolates to remain infective under various pH, temperature, and salinity conditions using a preestablished distilled water system. Swine and human viruses persisted longest at near-neutral pH, at cold temperatures, or under “freshwater” conditions. Additionally, no significant differences in persistence were observed between pandemic and nonpandemic IAVs. Our results indicate that there have been no apparent changes in the environmental stability of the viruses related to host adaptation.

IMPORTANCE
This study assessed the environmental stability of eight swine and six human influenza A viruses (IAVs), including viruses associated with the 2009 H1N1 pandemic, in a distilled water system. The important findings of this work are that IAV persistence can be affected by environmental variables and that no marked changes were noted between human and swine IAVs or between pandemic and nonpandemic IAVs.
Modified Deacetylcephalosporin C Synthase for the Biotransformation of Semisynthetic Cephalosporins
Authors: Balakrishnan Nataraj , Ganesan Sadhasivam , Rajasekaran Padma , Rajendran Lingeshwaran , Teddu Sivaprasad , Durairaaj Micheal 
Published: April 2016

ABSTRACT

Deacetylcephalosporin C synthase (DACS), a 2-oxoglutarate-dependent oxygenase synthesized by
Streptomyces clavuligerus
, transforms an inert methyl group of deacetoxycephalosporin C (DAOC) into an active hydroxyl group of deacetylcephalosporin C (DAC) during the biosynthesis of cephalosporin. It is a step which is chemically difficult to accomplish, but its development by use of an enzymatic method with DACS can facilitate a cost-effective technology for the manufacture of semisynthetic cephalosporin intermediates such as 7-amino-cephalosporanic acid (7ACA) and hydroxymethyl-7-amino-cephalosporanic acid (HACA) from cephalosporin G. As the native enzyme showed negligible activity toward cephalosporin G, an unnatural and less expensive substrate analogue, directed-evolution strategies such as random, semirational, rational, and computational methods were used for systematic engineering of DACS for improved activity. In comparison to the native enzyme, several variants with improved catalytic efficiency were found. The enzyme was stable for several days and is expressed in soluble form at high levels with significantly higher
k
cat
/

K
m

values. The efficacy and industrial scalability of one of the selected variants, CefF
GOS
, were demonstrated in a process showing complete bioconversion of 18 g/liter of cephalosporin G into deacetylcephalosporin G (DAG) in about 80 min and showed reproducible results at higher substrate concentrations as well. DAG could be converted completely into HACA in about 30 min by a subsequent reaction, thus facilitating scalability toward commercialization. The experimental findings with several mutants were also used to rationalize the functional conformation deduced from homology modeling, and this led to the disclosure of critical regions involved in the catalysis of DACS.

IMPORTANCE
7ACA and HACA serve as core intermediates for the manufacture of several semisynthetic cephalosporins. As they are expensive, a cost-effective enzyme technology for the manufacture of these intermediates is required. Deacetylcephalosporin C synthase (DACS) was identified as a candidate enzyme for the development of technology from cephalosporin G in this study. Directed-evolution strategies were employed to enhance the catalytic efficiency of deacetylcephalosporin C synthase. One of the selected mutants of deacetylcephalosporin C synthase could convert high concentrations of cephalosporin G into DAG, which subsequently could be converted into HACA completely. As cephalosporin G is inexpensive and readily available, the technology would lead to a substantial reduction in the cost for these intermediates upon commercialization.
Increased Biomass Production by Mesophilic Food-Associated Bacteria through Lowering the Growth Temperature from 30°C to 10°C
Authors: Seel Waldemar , Derichs Julia , Lipski André 
Published: April 2016

ABSTRACT

Five isolates from chilled food and refrigerator inner surfaces and closely related reference strains of the species
Escherichia coli
,
Listeria monocytogenes
,
Staphylococcus xylosus
,
Bacillus cereus
,
Pedobacter nutrimenti
, and
Pedobacter panaciterrae
were tested for the effect of growth temperature (30°C and 10°C) on biomass formation. Growth was monitored via optical density, and biomass formation was measured at the early stationary phase based on the following parameters in complex and defined media: viable cell count, total cell count, cell dry weight, whole-cell protein content, and cell morphology. According to the lack of growth at 1°C, all strains were assigned to the thermal class of mesophiles. Glucose and ammonium consumption related to cell yield were analyzed in defined media. Except for the protein content, temperature had a significant (
t
test,
P
< 0.05) effect on all biomass formation parameters for each strain. The results show a significant difference between the isolates and the related reference strains. Isolates achieved an increase in biomass production between 20% and 110% at the 10°C temperature, which is 15 to 25°C lower than their maximum growth rate temperatures. In contrast, reference strains showed a maximum increase of only about 25%, and some reference strains showed no increase or a decrease of approximately 25%. As expected, growth rates for all strains were higher at 30°C than at 10°C, while biomass production for isolates was higher at 10°C than at 30°C. In contrast, the reference strains showed similar growth yields at the two temperatures. This also demonstrates for mesophilic bacterial strains more efficient nutrient assimilation during growth at low temperatures. Until now, this characteristic was attributed only to psychrophilic microorganisms.

IMPORTANCE
For several psychrophilic species, increased biomass formation was described at temperatures lower than optimum growth temperatures, which are defined by the highest growth rate. This work shows increased biomass formation at low growth temperatures for mesophilic isolates. A comparison with closely related reference strains from culture collections showed a significantly smaller increase or no increase in biomass formation. This indicates a loss of specific adaptive mechanisms (e.g., cold adaptation) for mesophiles during long-term cultivation. The increased biomass production for mesophiles under low-temperature conditions opens new avenues for a more efficient biotechnological transformation of nutrients to microbial biomass. These findings may also be important for risk assessment of cooled foods since risk potential is often correlated with the cell numbers present in food samples.
Use of Colistin and Other Critical Antimicrobials on Pig and Chicken Farms in Southern Vietnam and Its Association with Resistance in Commensal Escherichia coli Bacteria
Authors: Nguyen Nhung T. , Nguyen Hoa M. , Nguyen Cuong V. , Nguyen Trung V. , Nguyen Men T. , Thai Hieu Q. , Ho Mai H. , Thwaites Guy , Ngo Hoa T. , Baker Stephen , Carrique-Mas Juan 
Published: April 2016

ABSTRACT

Antimicrobial resistance (AMR) is a global health problem, and emerging semi-intensive farming systems in Southeast Asia are major contributors to the AMR burden. We accessed 12 pig and chicken farms at key stages of production in Tien Giang Province, Vietnam, to measure antimicrobial usage and to investigate the prevalence of AMR to five critical antimicrobials (β-lactams, third-generation cephalosporins, quinolones, aminoglycosides, and polymyxins) and their corresponding molecular mechanisms among 180
Escherichia coli
isolates. Overall, 94.7 mg (interquartile range [IQR], 65.3 to 151.1) and 563.6 mg (IQR, 398.9 to 943.6) of antimicrobials was used to produce 1 kg (live weight) of chicken and pig, respectively. A median of 3 (out of 8) critical antimicrobials were used on pig farms.
E. coli
isolates exhibited a high prevalence of resistance to ampicillin (97.8% and 94.4% for chickens and pigs, respectively), ciprofloxacin (73.3% and 21.1%), gentamicin (42.2% and 35.6%), and colistin (22.2% and 24.4%). The prevalence of a recently discovered colistin resistance gene,
mcr-1
, was 19 to 22% and had strong agreement with phenotypic colistin resistance. We conducted plasmid conjugation experiments with 37
mcr-1
gene-positive
E. coli
isolates and successfully observed transfer of the gene in 54.0% of isolates through a plasmid of approximately 63 kb, consistent with one recently identified in China. We found no significant correlation between total use of antimicrobials at the farm level and AMR. These data provide additional insight into the role of
mcr-1
in colistin resistance on farms and outline the dynamics of phenotypic and genotypic AMR in semi-intensive farming systems in Vietnam.

IMPORTANCE
Our study provides accurate baseline information on levels of antimicrobial use, as well as on the dynamics of phenotypic and genotypic resistance for antimicrobials of critical importance among
E. coli
over the different stages of production in emerging pig and poultry production systems in Vietnam.
E. coli
isolates showed a high prevalence of resistance (>20%) to critically important antimicrobials, such as colistin, ciprofloxacin, and gentamicin. The underlying genetic mechanisms identified for colistin (the
mcr-1
gene) and quinolone (
gyrA
gene mutations) are likely to play a major role in AMR to those compounds. Conjugation experiments led to the identification of a 63-kb plasmid, similar to one recently identified in China, as the potential carrier of the
mcr-1
gene. These results should encourage greater restrictions of such antimicrobials in Southeast Asian farming systems.
Ultrastructural and Single-Cell-Level Characterization Reveals Metabolic Versatility in a Microbial Eukaryote Community from an Ice-Covered Antarctic Lake
Authors: Li Wei , Podar Mircea , Morgan-Kiss Rachael M. 
Published: April 2016

ABSTRACT

The McMurdo Dry Valleys (MCM) of southern Victoria Land, Antarctica, harbor numerous ice-covered bodies of water that provide year-round liquid water oases for isolated food webs dominated by the microbial loop. Single-cell microbial eukaryotes (protists) occupy major trophic positions within this truncated food web, ranging from primary producers (e.g., chlorophytes, haptophytes, and cryptophytes) to tertiary predators (e.g., ciliates, dinoflagellates, and choanoflagellates). To advance the understanding of MCM protist ecology and the roles of MCM protists in nutrient and energy cycling, we investigated potential metabolic strategies and microbial interactions of key MCM protists isolated from a well-described lake (Lake Bonney). Fluorescence-activated cell sorting (FACS) of enrichment cultures, combined with single amplified genome/amplicon sequencing and fluorescence microscopy, revealed that MCM protists possess diverse potential metabolic capabilities and interactions. Two metabolically distinct bacterial clades (
Flavobacteria
and
Methylobacteriaceae
) were independently associated with two key MCM lake microalgae (
Isochrysis
and
Chlamydomonas
, respectively). We also report on the discovery of two heterotrophic nanoflagellates belonging to the Stramenopila supergroup, one of which lives as a parasite of
Chlamydomonas
, a dominate primary producer in the shallow, nutrient-poor layers of the lake.

IMPORTANCE
Single-cell eukaryotes called protists play critical roles in the cycling of organic matter in aquatic environments. In the ice-covered lakes of Antarctica, protists play key roles in the aquatic food web, providing the majority of organic carbon to the rest of the food web (photosynthetic protists) and acting as the major consumers at the top of the food web (predatory protists). In this study, we utilized a combination of techniques (microscopy, cell sorting, and genomic analysis) to describe the trophic abilities of Antarctic lake protists and their potential interactions with other microbes. Our work reveals that Antarctic lake protists rely on metabolic versatility for their energy and nutrient requirements in this unique and isolated environment.
Amino Sugars Enhance the Competitiveness of Beneficial Commensals with Streptococcus mutans through Multiple Mechanisms
Authors: Zeng Lin , Farivar Tanaz , Burne Robert A. 
Published: April 2016

ABSTRACT

Biochemical and genetic aspects of the metabolism of the amino sugars
N
-acetylglucosamine (GlcNAc) and glucosamine (GlcN) by commensal oral streptococci and the effects of these sugars on interspecies competition with the dental caries pathogen
Streptococcus mutans
were explored. Multiple
S. mutans
wild-type isolates displayed long lag phases when transferred from glucose-containing medium to medium with GlcNAc as the primary carbohydrate source, but commensal streptococci did not. Competition in liquid coculture or dual-species biofilms between
S. mutans
and
Streptococcus gordonii
showed that
S. gordonii
was particularly dominant when the primary carbohydrate was GlcN or GlcNAc. Transcriptional and enzymatic assays showed that the catabolic pathway for GlcNAc was less highly induced in
S. mutans
than in
S. gordonii
. Exposure to H
2
O
2
, which is produced by
S. gordonii
and antagonizes the growth of
S. mutans
, led to reduced mRNA levels of
nagA
and
nagB
in
S. mutans
. When the gene for the transcriptional regulatory NagR was deleted in
S. gordonii
, the strain produced constitutively high levels of
nagA
(GlcNAc-6-P deacetylase),
nagB
(GlcN-6-P deaminase), and
glmS
(GlcN-6-P synthase) mRNA. Similar to NagR of
S. mutans
(NagR
Sm
), the
S. gordonii
NagR protein (NagR
Sg
) could bind to consensus binding sites (
dre
) in the
nagA
,
nagB
, and
glmS
promoter regions of
S. gordonii
. Notably, NagR
Sg
binding was inhibited by GlcN-6-P, but G-6-P had no effect, unlike for NagR
Sm
. This study expands the understanding of amino sugar metabolism and NagR-dependent gene regulation in streptococci and highlights the potential for therapeutic applications of amino sugars to prevent dental caries.

IMPORTANCE
Amino sugars are abundant in the biosphere, so the relative efficiency of particular bacteria in a given microbiota to metabolize these sources of carbon and nitrogen might have a profound impact on the ecology of the community. Our investigation reveals that several oral commensal bacteria have a much greater capacity to utilize amino sugars than the dental pathogen
Streptococcus mutans
and that the ability of the model commensal
Streptococcus gordonii
to compete against
S. mutans
is substantively enhanced by the presence of amino sugars commonly found in the oral cavity. The mechanisms underlying the greater capacity and competitive enhancements of the commensal are shown to depend on how the genes for the catabolic enzymes are regulated, the role of the allosteric modulators affecting such regulation, and the ability of amino sugars to enhance certain activities of the commensal that are antagonistic to
S. mutans
.
tRNA-Dependent Aminoacylation of an Amino Sugar Intermediate in the Biosynthesis of a Streptothricin-Related Antibiotic
Authors: Maruyama Chitose , Niikura Haruka , Izumikawa Miho , Hashimoto Junko , Shin-ya Kazuo , Komatsu Mamoru , Ikeda Haruo , Kuroda Makoto , Sekizuka Tsuyoshi , Ishikawa Jun , Hamano Yoshimitsu 
Published: April 2016

ABSTRACT

The antibiotic streptothricin (ST) possesses an amino sugar bound to an
l
-β-lysine (β-Lys) residue via a peptide bond. The peptide bond formation has been shown to be catalyzed by a nonribosomal peptide synthetase (NRPS) during ST biosynthesis. The focus of this study is the closely related ST analogue BD-12, which carries a glycine-derived side chain rather than a β-Lys residue. Here, in
Streptomyces luteocolor
NBRC13826, we describe our biosynthetic studies of BD-12, which revealed that the peptide bond between the amino sugar and the glycine residue is catalyzed by a Fem-like enzyme (Orf11) in a tRNA-dependent manner rather than by an NRPS. Although there have been several reports of peptide bond-forming tRNA-dependent enzymes, to our knowledge, Orf11 is the first enzyme that can accept an amino sugar as a substrate. Our findings clearly demonstrate that the structural diversity of the side chains of ST-type compounds in nature is generated in an unusual manner via two distinct peptide bond-forming mechanisms. Moreover, the identification and functional analysis of Orf11 resulted in not only the production of new ST-related compounds, but also the provision of new insights into the structure-activity relationship of the ST-related antibiotics.

IMPORTANCE
The antibiotic streptothricin (ST) possesses an amino sugar bound to an
l
-β-lysine (β-Lys) side chain via a peptide bond formed by a nonribosomal peptide synthetase (NRPS). BD-12, an analogue of ST, carries a glycine-derived side chain rather than β-Lys, and here, we describe the BD-12-biosynthetic gene cluster from
Streptomyces
luteocolor
NBRC13826, which contains the
orf11
gene encoding a novel tRNA-dependent peptide bond-forming enzyme. The unique Fem-like enzyme (Orf11) accepts the amino sugar as a substrate and mediates the peptide formation between the amino sugar intermediate and glycine. Our studies demonstrate that the structural diversity of the side chains of ST-related compounds in nature is generated via two distinct peptide bond-forming mechanisms.
Photobacterium damselae subsp. damselae, an Emerging Fish Pathogen in the Black Sea: Evidence of a Multiclonal Origin
Authors: Terceti Mateus S. , Ogut Hamdi , Osorio Carlos R. 
Published: April 2016

ABSTRACT

Photobacterium damselae
subsp.
damselae
is considered to be an emerging pathogen of marine fish of importance in aquaculture, with a notable increase in its geographical distribution during the last several years. In this study, we carried out for the first time to our knowledge a genetic and pathobiological characterization of 14 strains isolated from sea bass (
Dicentrarchus labrax
) reared in the Southeastern Black Sea, where high mortalities were observed at two aquaculture farms during the summer and autumn of 2011. Heterogeneity was evidenced among strains in phenotypical traits, such as sucrose fermentation, motility, and hemolysis. Although 11 of 14 isolates were hemolytic, we found that all of the isolates lacked the pPHDD1 virulence plasmid that encodes the phospholipase-D damselysin (Dly) and the pore-forming toxin PhlyP, two hemolysins previously reported to constitute major virulence factors for turbot. Subsequent PCR and sequencing analyses demonstrated that the 11 hemolytic isolates harbored a complete
hlyA
ch
gene, a chromosome I-borne gene that encodes HlyA
ch
hemolysin, whereas the three nonhemolytic isolates contained
hlyA
ch
pseudogenes caused by insertion sequence elements. Virulence challenges with two representative strains revealed that, albeit less virulent than the pPHDD1-harboring strain RM-71, the plasmidless
hlyA
ch
-positive and
hlyA
ch
-negative Black Sea isolates were pathogenic for sea bass. A phylogenetic analysis based on the
toxR
gene sequence uncovered a greater diversity in the isolates, indicating that the presence of this pathogen in the Black Sea was not caused by the introduction and spread of a single virulent clone but by the proliferation of different clones.

IMPORTANCE
The geographical distribution of marine bacterial pathogens is undergoing a worldwide increase. In particular, bacteria of the group vibrios are increasingly being isolated as the causative agents of disease in novel species of cultivated fish in areas where they had not been previously reported. Here we characterize for the first time to our knowledge a collection of isolates of the fish and human pathogen
Photobacterium damselae
subsp.
damselae
from diseased sea bass reared in the Black Sea. We uncovered great genetic diversity in the Black Sea isolates of this pathogen, suggesting a multiclonal origin. We also demonstrate for the first time that these isolates bear pathogenic potential for sea bass cultures by virulence challenges.