The complete sequence of the plasmid pNDM-1_Dok01 carrying New Delhi metallo-β-lactamase (NDM-1) was determined by whole genome shotgun sequencing using
Escherichia coli
strain NDM-1_Dok01 ...(multilocus sequence typing type: ST38) and the transconjugant
E. coli
DH10B. The plasmid is an IncA/C incompatibility type composed of 225 predicted coding sequences in 195.5 kb and partially shares a sequence with
bla
CMY-2
-positive IncA/C plasmids such as
E. coli
AR060302 pAR060302 (166.5 kb) and
Salmonella enterica
serovar Newport pSN254 (176.4 kb). The
bla
NDM-1
gene in pNDM-1_Dok01 is terminally flanked by two IS
903
elements that are distinct from those of the other characterized NDM-1 plasmids, suggesting that the
bla
NDM-1
gene has been broadly transposed, together with various mobile elements, as a cassette gene. The chaperonin
groES
and
groEL
genes were identified in the
bla
NDM-1
-related composite transposon, and phylogenetic analysis and guanine-cytosine content (GC) percentage showed similarities to the homologs of plant pathogens such as
Pseudoxanthomonas
and
Xanthomonas
spp., implying that plant pathogens are the potential source of the
bla
NDM-1
gene. The complete sequence of pNDM-1_Dok01 suggests that the
bla
NDM-1
gene was acquired by a novel composite transposon on an extensively disseminated IncA/C plasmid and transferred to the
E. coli
ST38 isolate.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In contrast to animals and lower plant species, sperm cells of flowering plants are non-motile and are transported to the female gametes via the pollen tube, i.e. the male gametophyte. Upon arrival ...at the female gametophyte two sperm cells are discharged into the receptive synergid cell to execute double fertilization. The first players involved in inter-gametophyte signaling to attract pollen tubes and to arrest their growth have been recently identified. In contrast the physiological mechanisms leading to pollen tube burst and thus sperm discharge remained elusive. Here, we describe the role of polymorphic defensin-like cysteine-rich proteins ZmES1-4 (Zea mays embryo sac) from maize, leading to pollen tube growth arrest, burst, and explosive sperm release. ZmES1-4 genes are exclusively expressed in the cells of the female gametophyte. ZmES4-GFP fusion proteins accumulate in vesicles at the secretory zone of mature synergid cells and are released during the fertilization process. Using RNAi knock-down and synthetic ZmES4 proteins, we found that ZmES4 induces pollen tube burst in a species-preferential manner. Pollen tube plasma membrane depolarization, which occurs immediately after ZmES4 application, as well as channel blocker experiments point to a role of K(+)-influx in the pollen tube rupture mechanism. Finally, we discovered the intrinsic rectifying K(+) channel KZM1 as a direct target of ZmES4. Following ZmES4 application, KZM1 opens at physiological membrane potentials and closes after wash-out. In conclusion, we suggest that vesicles containing ZmES4 are released from the synergid cells upon male-female gametophyte signaling. Subsequent interaction between ZmES4 and KZM1 results in channel opening and K(+) influx. We further suggest that K(+) influx leads to water uptake and culminates in osmotic tube burst. The species-preferential activity of polymorphic ZmES4 indicates that the mechanism described represents a pre-zygotic hybridization barrier and may be a component of reproductive isolation in plants.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this classic work that continues to inspire its many readers, Jim Lovelock puts forward his idea that life on earth functions as a single organism. Written for non-scientists, Gaia is a journey ...through time and space in search of evidence with which to support a new and radically different model of our planet. In contrast to conventional belief that living matter is passive in the face of threats to its existence, the book explores the hypothesis that
the earth's living matter air, ocean, and land surfaces forms a complex system that has the capacity to keep the Earth a fit place for life.
Since Gaia was first published, many of Jim Lovelock's predictions have come true and his theory has become a hotly argued topic in scientific circles. In a new Preface to this reissued title, he outlines his present state of the debate.
Despite the accepted health benefits of consuming dietary fiber, little is known about the mechanisms by which fiber deprivation impacts the gut microbiota and alters disease risk. Using a ...gnotobiotic mouse model, in which animals were colonized with a synthetic human gut microbiota composed of fully sequenced commensal bacteria, we elucidated the functional interactions between dietary fiber, the gut microbiota, and the colonic mucus barrier, which serves as a primary defense against enteric pathogens. We show that during chronic or intermittent dietary fiber deficiency, the gut microbiota resorts to host-secreted mucus glycoproteins as a nutrient source, leading to erosion of the colonic mucus barrier. Dietary fiber deprivation, together with a fiber-deprived, mucus-eroding microbiota, promotes greater epithelial access and lethal colitis by the mucosal pathogen, Citrobacter rodentium. Our work reveals intricate pathways linking diet, the gut microbiome, and intestinal barrier dysfunction, which could be exploited to improve health using dietary therapeutics.
Display omitted
•Characterized synthetic bacterial communities enable functional insights in vivo•Low-fiber diet promotes expansion and activity of colonic mucus-degrading bacteria•Purified prebiotic fibers do not alleviate degradation of the mucus layer•Fiber-deprived gut microbiota promotes aggressive colitis by an enteric pathogen
Regular consumption of dietary fiber helps prevent erosion of the intestinal mucus barrier by the gut microbiome, blunting pathogen infection and reducing the incidence of colitis.
Vascular abnormalities contribute to many diseases such as cancer and diabetic retinopathy. In angiogenesis new blood vessels, headed by a migrating tip cell, sprout from pre-existing vessels in ...response to signals, e.g., vascular endothelial growth factor (VEGF). Tip cells meet and fuse (anastomosis) to form blood-flow supporting loops. Tip cell selection is achieved by Dll4-Notch mediated lateral inhibition resulting, under normal conditions, in an interleaved arrangement of tip and non-migrating stalk cells. Previously, we showed that the increased VEGF levels found in many diseases can cause the delayed negative feedback of lateral inhibition to produce abnormal oscillations of tip/stalk cell fates. Here we describe the development and implementation of a novel physics-based hierarchical agent model, tightly coupled to in vivo data, to explore the system dynamics as perpetual lateral inhibition combines with tip cell migration and fusion. We explore the tipping point between normal and abnormal sprouting as VEGF increases. A novel filopodia-adhesion driven migration mechanism is presented and validated against in vivo data. Due to the unique feature of ongoing lateral inhibition, 'stabilised' tip/stalk cell patterns show sensitivity to the formation of new cell-cell junctions during fusion: we predict cell fates can reverse. The fusing tip cells become inhibited and neighbouring stalk cells flip fate, recursively providing new tip cells. Junction size emerges as a key factor in establishing a stable tip/stalk pattern. Cell-cell junctions elongate as tip cells migrate, which is shown to provide positive feedback to lateral inhibition, causing it to be more susceptible to pathological oscillations. Importantly, down-regulation of the migratory pathway alone is shown to be sufficient to rescue the sprouting system from oscillation and restore stability. Thus we suggest the use of migration inhibitors as therapeutic agents for vascular normalisation in cancer.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Haloferax volcanii is an easily culturable moderate halophile that grows on simple defined media, is readily transformable, and has a relatively stable genome. This, in combination with its ...biochemical and genetic tractability, has made Hfx. volcanii a key model organism, not only for the study of halophilicity, but also for archaeal biology in general.
We report here the sequencing and analysis of the genome of Hfx. volcanii DS2, the type strain of this species. The genome contains a main 2.848 Mb chromosome, three smaller chromosomes pHV1, 3, 4 (85, 438, 636 kb, respectively) and the pHV2 plasmid (6.4 kb).
The completed genome sequence, presented here, provides an invaluable tool for further in vivo and in vitro studies of Hfx. volcanii.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Bacterial infection is highly prevalent in patients who have had a stroke. Despite the potential contribution of micro-aspiration in post-stroke pneumonia, we found that the majority of the ...microorganisms detected in the patients who developed infections after having a stroke were common commensal bacteria that normally reside in the intestinal tracts. In a mouse model of ischemic stroke, post-stroke infection was only observed in mice that were born and raised in specific-pathogen-free facilities; this was not seen in mice that were born and raised in germ-free facilities. Using high-throughput 16S rRNA gene amplicon sequencing and bioinformatics analyses, we provide evidence demonstrating that the source of the bacteria forming the microbial community in the lungs of post-stroke mice was indeed the host small intestine. Additionally, stroke-induced gut barrier permeability and dysfunction preceded the dissemination of orally inoculated bacteria to peripheral tissues. This study identifies a novel pathway in which stroke promotes the translocation and dissemination of selective strains of bacteria that originated from the host gut microbiota.
From the author of The Emperor of All Maladies, winner of the Pulitzer Prize, and The Gene, a #1 New York Times bestseller, comes his most spectacular book yet, an exploration of medicine and our ...radical new ability to manipulate cells. Rich with Mukherjee's revelatory and exhilarating stories of scientists, doctors, and the patients whose lives may be saved by their work, The Song of the Cell is the third book in this extraordinary writer's exploration of what it means to be human.Mukherjee begins this magnificent story in the late 1600s, when a distinguished English polymath, Robert Hooke, and an eccentric Dutch cloth-merchant, Antonie van Leeuwenhoek looked down their handmade microscopes. What they saw introduced a radical concept that swept through biology and medicine, touching virtually every aspect of the two sciences, and altering both forever. It was the fact that complex living organisms are assemblages of tiny, self-contained, self-regulating units. Our organs, our physiology, our selveshearts, blood, brainsare built from these compartments. Hooke christened them ';cells'. The discovery of cellsand the reframing of the human body as a cellular ecosystemannounced the birth of a new kind of medicine based on the therapeutic manipulations of cells. A hip fracture, a cardiac arrest, Alzheimer's dementia, AIDS, pneumonia, lung cancer, kidney failure, arthritis, COVID pneumoniaall could be reconceived as the results of cells, or systems of cells, functioning abnormally. And all could be perceived as loci of cellular therapies. In The Song of the Cell, Mukherjee tells the story of how scientists discovered cells, began to understand them, and are now using that knowledge to create new humans. He seduces you with writing so vivid, lucid, and suspenseful that complex science becomes thrilling. Told in six parts, laced with Mukherjee's own experience as a researcher, a doctor, and a prolific reader, The Song of the Cell is both panoramic and intimatea masterpiece.
PDF
