15 research outputs found
Modeling Living Shorelines in a Wave Tank: Quantifying Wave Attenuation to Find the Most Effective Shoreline Restoration
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv
Caenorhabditis elegans Semi-Automated Liquid Screen Reveals a Specialized Role for the Chemotaxis Gene cheB2 in Pseudomonas aeruginosa Virulence
Pseudomonas aeruginosa is an opportunistic human pathogen that causes infections in a variety of animal and plant hosts. Caenorhabditis elegans is a simple model with which one can identify bacterial virulence genes. Previous studies with C. elegans have shown that depending on the growth medium, P. aeruginosa provokes different pathologies: slow or fast killing, lethal paralysis and red death. In this study, we developed a high-throughput semi-automated liquid-based assay such that an entire genome can readily be scanned for virulence genes in a short time period. We screened a 2,200-member STM mutant library generated in a cystic fibrosis airway P. aeruginosa isolate, TBCF10839. Twelve mutants were isolated each showing at least 70% attenuation in C. elegans killing. The selected mutants had insertions in regulatory genes, such as a histidine kinase sensor of two-component systems and a member of the AraC family, or in genes involved in adherence or chemotaxis. One mutant had an insertion in a cheB gene homologue, encoding a methylesterase involved in chemotaxis (CheB2). The cheB2 mutant was tested in a murine lung infection model and found to have a highly attenuated virulence. The cheB2 gene is part of the chemotactic gene cluster II, which was shown to be required for an optimal mobility in vitro. In P. aeruginosa, the main player in chemotaxis and mobility is the chemotactic gene cluster I, including cheB1. We show that, in contrast to the cheB2 mutant, a cheB1 mutant is not attenuated for virulence in C. elegans whereas in vitro motility and chemotaxis are severely impaired. We conclude that the virulence defect of the cheB2 mutant is not linked with a global motility defect but that instead the cheB2 gene is involved in a specific chemotactic response, which takes place during infection and is required for P. aeruginosa pathogenicity
Histone Methylation and Memory of Environmental Stress
Cellular adaptation to environmental stress relies on a wide range of tightly controlled regulatory mechanisms, including transcription. Changes in chromatin structure and organization accompany the transcriptional response to stress, and in some cases, can impart memory of stress exposure to subsequent generations through mechanisms of epigenetic inheritance. In the budding yeast Saccharomyces cerevisiae, histone post-translational modifications, and in particular histone methylation, have been shown to confer transcriptional memory of exposure to environmental stress conditions through mitotic divisions. Recent evidence from Caenorhabditis elegans also implicates histone methylation in transgenerational inheritance of stress responses, suggesting a more widely conserved role in epigenetic memory
Type II-dependent secretion of a Pseudomonas aeruginosa DING protein.
International audiencePseudomonas aeruginosa is an opportunistic bacterial pathogen that uses a wide range of protein secretion systems to interact with its host. Genes encoding the PAO1 Hxc type II secretion system are linked to genes encoding phosphatases (LapA/LapB). Microarray genotyping suggested that Pseudomonas aeruginosa clinical isolates, including urinary tract (JJ692) and blood (X13273) isolates, lacked the lapA/lapB genes. Instead, we show that they carry a gene encoding a protein of the PstS family. This protein, which we call LapC, also has significant similarities with LapA/LapB. LapC belongs to the family of DING proteins and displays the canonical DINGGG motif within its N terminus. DING proteins are members of a prokaryotic phosphate binding protein superfamily. We show that LapC is secreted in an Hxc-dependent manner and is under the control of the PhoB response regulator. The genetic organization hxc-lapC found in JJ692 and X13273 is similar to PA14, which is the most frequent P. aeruginosa genotype. While the role of LapA, LapB and LapC proteins remains unclear in P. aeruginosa pathogenesis, they are likely to be part of a phosphate scavenging or sensing system needed to survive and thrive when low phosphate environments are encountered within the host
Wave Attenuation Experiments Over Living Shorelines Over Time: A Wave Tank Study To Assess Recreational Boating Pressures
With sea level rise, erosion, and human disturbances affecting coastal areas, strategies to protect and stabilize existing shorelines are needed. One popular solution to stabilize while conserving intertidal habitat is the use of “living shoreline” techniques which are designed to mimic natural shoreline communities by using native plants and animals. However, little information is available on the success of living shoreline stabilization. This project evaluated the wave energy attenuation associated with living shorelines that contained Crassostrea virginica (eastern oyster) and/or Spartina alterniflora (smooth cordgrass) in a wave tank. Four living shoreline techniques were assessed, including a control (sediment only), oysters alone, cordgrass alone, and a combination of oysters plus cordgrass. Time since deployment (newly deployed, one-year after deployment) was also assessed to see how wave energy attenuation changed with natural oyster recruitment and plant growth. Wave energy was calculated for each newly deployed and one-year old shoreline stabilization treatment using capacitance wave gauges and generated waves that were representative of boat wakes in Mosquito Lagoon, a shallow-water estuary in Florida. All one-year old treatments attenuated significantly more energy than newly-deployed treatments. The combination of one-year old S. alterniflora plus live C. virginica was the most effective as this treatment reduced 67 % of the wave energy created by a single recreational boat wake, compared to bare sediment. Natural resource managers and landowners facing shoreline erosion issues can use this information to create effective stabilization protocols that preserve shorelines while conserving native intertidal habitats
Wave Attenuation Experiments Over Living Shorelines Over Time: A Wave Tank Study To Assess Recreational Boating Pressures
With sea level rise, erosion, and human disturbances affecting coastal areas, strategies to protect and stabilize existing shorelines are needed. One popular solution to stabilize while conserving intertidal habitat is the use of “living shoreline” techniques which are designed to mimic natural shoreline communities by using native plants and animals. However, little information is available on the success of living shoreline stabilization. This project evaluated the wave energy attenuation associated with living shorelines that contained Crassostrea virginica (eastern oyster) and/or Spartina alterniflora (smooth cordgrass) in a wave tank. Four living shoreline techniques were assessed, including a control (sediment only), oysters alone, cordgrass alone, and a combination of oysters plus cordgrass. Time since deployment (newly deployed, one-year after deployment) was also assessed to see how wave energy attenuation changed with natural oyster recruitment and plant growth. Wave energy was calculated for each newly deployed and one-year old shoreline stabilization treatment using capacitance wave gauges and generated waves that were representative of boat wakes in Mosquito Lagoon, a shallow-water estuary in Florida. All one-year old treatments attenuated significantly more energy than newly-deployed treatments. The combination of one-year old S. alterniflora plus live C. virginica was the most effective as this treatment reduced 67 % of the wave energy created by a single recreational boat wake, compared to bare sediment. Natural resource managers and landowners facing shoreline erosion issues can use this information to create effective stabilization protocols that preserve shorelines while conserving native intertidal habitats
Loss of SET1/COMPASS methyltransferase activity reduces lifespan and fertility in Caenorhabditis elegans
Abstract Post-translational modification of histones, particularly lysine methylation, are thought to play a crucial role in the aging process. Histone 3 lysine 4 (H3K4) methylation, a modification associated with active chromatin, is mediated by a family of SET1 methyltransferases acting within conserved multiprotein complexes known as COMPASS. Previous work in model organisms with partial or complete deletion of COMPASS subunits has yielded conflicting results about the requirement for H3K4 methylation during aging. Here, we reassessed the role of SET1/COMPASS-dependent H3K4 methylation in Caenorhabditis elegans lifespan regulation and fertility by generating set-2(syb2085) mutant animals that express a catalytically inactive form of SET-2, the C. elegans homolog of SET1. We show that animals bearing catalytically inactive SET-2 retain the ability to form COMPASS complexes but have a marked global loss of H3K4 dimethylation and trimethylation. Consistent with previous work, reduced H3K4 methylation was accompanied by loss of fertility; however, in striking contrast to earlier studies, set-2(syb2085) mutants displayed a significantly shortened, not extended, lifespan and had normal intestinal fat stores. Furthermore, other commonly used set-2 mutants were also short-lived, as was a cfp-1 mutant that lacks a non-catalytic SET1/COMPASS component and displays reduced H3K4 methylation. These results challenge previously held views and establish that wild-type H3K4 methylation levels are necessary to achieve a normal lifespan in C. elegans
Identification of the Enteropathogens Campylobacter jejuni and Campylobacter coli Based on the cadF Virulence Gene and Its Product
Campylobacter jejuni
and
Campylobacter coli
are common causes of gastroenteritis in humans. Infection with
C. jejuni
or
C. coli
is commonly acquired by eating undercooked chicken. The goal of this study was to develop specific detection assays for
C. jejuni
and
C. coli
isolates based on the
cadF
virulence gene and its product. The
cadF
gene from
C. jejuni
and
C. coli
encodes a 37-kDa outer membrane protein that promotes the binding of these pathogens to intestinal epithelial cells. A fragment of approximately 400 bp was amplified from 38 of 40 (95%)
C. jejuni
isolates and 5 of 6 (83.3%)
C. coli
isolates with primers designed to amplify an internal fragment of the
cadF
gene. PCR was then used to amplify
Campylobacter
DNA from store-bought chickens. A 400-bp band was amplified from 26 of the 27 chicken carcasses tested by the PCR-based assay. The CadF protein was detected in every
C. jejuni
and
C. coli
isolate tested, as judged by immunoblot analysis with a rabbit anti-
C. jejuni
37-kDa serum. In addition, methanol-fixed samples of whole-cell
C. jejuni
and
C. coli
were detected with the rabbit anti-37-kDa serum by using an indirect-immunofluorescence microscopy assay. These findings indicate that the
cadF
gene and its product are conserved among
C. jejuni
and
C. coli
isolates and that a PCR assay based on the
cadF
gene may be useful for the detection of
Campylobacter
organisms in food products
Caenorhabditis elegans SET1/COMPASS Maintains Germline Identity by Preventing Transcriptional Deregulation Across Generations
International audienc
Loss of SET1/COMPASS methyltransferase activity reduces lifespan and fertility in Caenorhabditis elegans
International audienceChanges in histone post-translational modifications are associated with aging through poorly defined mechanisms. Histone 3 lysine 4 (H3K4) methylation at promoters is deposited by SET1 family methyltransferases acting within conserved multiprotein complexes known as COMPASS. Previous work yielded conflicting results about the requirement for H3K4 methylation during aging. Here, we reassessed the role of SET1/COMPASS–dependent H3K4 methylation in Caenorhabditis elegans lifespan and fertility by generating set-2(syb2085) mutant animals that express a catalytically inactive form of SET-2, the C. elegans SET1 homolog. We show that set-2(syb2085) animals retain the ability to form COMPASS, but have a marked global loss of H3K4 di- and trimethylation (H3K4me2/3). Reduced H3K4 methylation was accompanied by loss of fertility, as expected; however, in contrast to earlier studies, set-2(syb2085) mutants displayed a significantly shortened, not extended, lifespan and had normal intestinal fat stores. Other commonly used set-2 mutants were also short-lived, as was a cfp-1 mutant that lacks the SET1/COMPASS chromatin-targeting component. These results challenge previously held views and establish that WT H3K4me2/3 levels are essential for normal lifespan in C. elegans