RESUMO
Lateral transduction (LT) is the process by which temperate phages mobilize large sections of bacterial genomes. Despite its importance, LT has only been observed during prophage induction. Here, we report that superantigen-carrying staphylococcal pathogenicity islands (SaPIs) employ a related but more versatile and complex mechanism of gene transfer to drive chromosomal hypermobility while self-transferring with additional virulence genes from the host. We found that after phage infection or prophage induction, activated SaPIs form concatamers in the bacterial chromosome by switching between parallel genomic tracks in replication bubbles. This dynamic life cycle enables SaPIbov1 to piggyback its LT of staphylococcal pathogenicity island vSaα, which encodes an array of genes involved in host-pathogen interactions, allowing both islands to be mobilized intact and transferred in a single infective particle. Our findings highlight previously unknown roles of pathogenicity islands in bacterial virulence and show that their evolutionary impact extends beyond the genes they carry.
Assuntos
Ilhas Genômicas , Fagos de Staphylococcus , Staphylococcus , Genoma Bacteriano , Staphylococcus/genética , Staphylococcus/patogenicidade , Virulência , Transdução GenéticaRESUMO
Many of the lipids found on the cuticles of insects function as pheromones and communicate information about age, sex, and reproductive status. In Drosophila, the composition of the information-rich lipid profile is dynamic and changes over the lifetime of an individual. However, the molecular basis of this change is not well understood. To identify genes that control cuticular lipid production in Drosophila, we performed a RNA interference screen and used Direct Analysis in Real Time and gas chromatography mass spectrometry to quantify changes in the chemical profiles. Twelve putative genes were identified whereby transcriptional silencing led to significant differences in cuticular lipid production. Amongst them, we characterized a gene which we name spidey, and which encodes a putative steroid dehydrogenase that has sex- and age-dependent effects on viability, pheromone production, and oenocyte survival. Transcriptional silencing or overexpression of spidey during embryonic development results in pupal lethality and significant changes in levels of the ecdysone metabolite 20-hydroxyecdysonic acid and 20-hydroxyecdysone. In contrast, inhibiting gene expression only during adulthood resulted in a striking loss of oenocyte cells and a concomitant reduction of cuticular hydrocarbons, desiccation resistance, and lifespan. Oenocyte loss and cuticular lipid levels were partially rescued by 20-hydroxyecdysone supplementation. Taken together, these results identify a novel regulator of pheromone synthesis and reveal that ecdysteroid signaling is essential for the maintenance of cuticular lipids and oenocytes throughout adulthood.
Assuntos
Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Feromônios/metabolismo , Transdução de Sinais/genética , Esteroides/metabolismo , Animais , Ecdisterona/genética , Ecdisterona/metabolismo , Feminino , Hidrocarbonetos/metabolismo , Lipídeos/genética , Masculino , Oxirredutases/genética , Oxirredutases/metabolismo , Feromônios/genética , Interferência de RNA/fisiologia , Reprodução , Caracteres SexuaisRESUMO
Drosophila melanogaster is a major model organism for numerous lipid-related diseases. While comprehensive lipidomic profiles have been generated for D. melanogaster, little information is available on the localization of individual lipid classes and species. Here, we show the use of matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) to profile lipids in D. melanogaster tissue sections. The preparation of intact cryosections from whole insects presents a challenge due to the brittle hydrophobic cuticle surrounding the body and heterogeneous tissue types beneath the cuticle. However, the introduction of a novel sucrose infiltration step and gelatin as an embedding media greatly improved the quality of tissue sections. We generated MS image profiles of six major lipid classes: phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylserine, and triacylglycerides. In addition, signals corresponding to two male-specific sex pheromones were detected in the ejaculatory bulb, a specialized site of pheromone production. MSI performed with 35 µm lateral resolution provided high sensitivity detection of at least 92 different lipid species, based on exact mass. In contrast, MSI with 10 µm lateral resolution enabled the detection of 36 lipid species but allowed lipid profiling of individual organs. The ability to localize lipid classes in intact sections from whole Drosophila provides a powerful tool for characterizing the effects of diet, age, stress, and environment on lipid production and distribution.
Assuntos
Drosophila melanogaster/química , Lipídeos/análise , Lipídeos/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , AnimaisRESUMO
Lysogenic induction ends the stable association between a bacteriophage and its host, and the transition to the lytic cycle begins with early prophage excision followed by DNA replication and packaging (ERP). This temporal program is considered universal for P22-like temperate phages, though there is no direct evidence to support the timing and sequence of these events. Here we report that the long-standing ERP program is an observation of the experimentally favored Salmonella phage P22 tsc229 heat-inducible mutant, and that wild-type P22 actually follows the replication-packaging-excision (RPE) program. We find that P22 tsc229 excises early after induction, but P22 delays excision to just before it is detrimental to phage production. This allows P22 to engage in lateral transduction. Thus, at minimal expense to itself, P22 has tuned the timing of excision to balance propagation with lateral transduction, powering the evolution of its host through gene transfer in the interest of self-preservation.
Assuntos
Bacteriófago P22/genética , Replicação do DNA/fisiologia , Replicação do DNA/genética , Transdução GenéticaRESUMO
Genetic transduction is a major evolutionary force that underlies bacterial adaptation. Here we report that the temperate bacteriophages of Staphylococcus aureus engage in a distinct form of transduction we term lateral transduction. Staphylococcal prophages do not follow the previously described excision-replication-packaging pathway but instead excise late in their lytic program. Here, DNA packaging initiates in situ from integrated prophages, and large metameric spans including several hundred kilobases of the S. aureus genome are packaged in phage heads at very high frequency. In situ replication before DNA packaging creates multiple prophage genomes so that lateral-transducing particles form during normal phage maturation, transforming parts of the S. aureus chromosome into hypermobile regions of gene transfer.
Assuntos
Fagos de Staphylococcus/fisiologia , Staphylococcus aureus/virologia , Transdução Genética , Cromossomos Bacterianos/genética , Cromossomos Bacterianos/virologia , Empacotamento do DNA , Genoma Bacteriano , Lisogenia/genética , Lisogenia/fisiologia , Prófagos/genética , Prófagos/fisiologia , Fagos de Staphylococcus/genética , Staphylococcus aureus/genética , Ativação Viral/genética , Ativação Viral/fisiologia , Replicação ViralRESUMO
In animals, commensal microbes modulate various physiological functions, including behavior. While microbiota exposure is required for normal behavior in mammals, it is not known how widely this dependency is present in other animal species. We proposed the hypothesis that the microbiome has a major influence on the behavior of the vinegar fly (Drosophila melanogaster), a major invertebrate model organism. Several assays were used to test the contribution of the microbiome on some well-characterized behaviors: defensive behavior, sleep, locomotion, and courtship in microbe-bearing, control flies and two generations of germ-free animals. None of the behaviors were largely influenced by the absence of a microbiome, and the small or moderate effects were not generalizable between replicates and/or generations. These results refute the hypothesis, indicating that the Drosophila microbiome does not have a major influence over several behaviors fundamental to the animal's survival and reproduction. The impact of commensal microbes on animal behaviour may not be broadly conserved.
Assuntos
Comportamento Animal/fisiologia , Drosophila melanogaster/fisiologia , Vida Livre de Germes/fisiologia , Interações entre Hospedeiro e Microrganismos/fisiologia , Microbiota/fisiologia , Animais , Corte , Drosophila melanogaster/microbiologia , Feminino , Locomoção/fisiologia , Masculino , Sono/fisiologia , Simbiose/fisiologiaRESUMO
Intracellular accumulation of lipids and swollen dysfunctional lysosomes are linked to several neurodegenerative diseases, including lysosomal storage disorders (LSD). Detailed characterization of lipid metabolic changes in relation to the onset and progression of neurodegeneration is currently missing. We systematically analyzed lipid perturbations in spinster (spin) mutants, a Drosophila model of LSD-like neurodegeneration. Our results highlight an imbalance in brain ceramide and sphingosine in the early stages of neurodegeneration, preceding the accumulation of endomembranous structures, manifestation of altered behavior, and buildup of lipofuscin. Manipulating levels of ceramidase and altering these lipids in spin mutants allowed us to conclude that ceramide homeostasis is the driving force in disease progression and is integral to spin function in the adult nervous system. We identified 29 novel physical interaction partners of Spin and focused on the lipid carrier protein, Lipophorin (Lpp). A subset of Lpp and Spin colocalize in the brain and within organs specialized for lipid metabolism (fat bodies and oenocytes). Reduced Lpp protein was observed in spin mutant tissues. Finally, increased levels of lipid metabolites produced by oenocytes in spin mutants allude to a functional interaction between Spin and Lpp, underscoring the systemic nature of lipid perturbation in LSD.
Assuntos
Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Metabolismo dos Lipídeos/genética , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Animais , Proteínas de Transporte/metabolismo , Modelos Animais de Doenças , Drosophila/metabolismo , Lipídeos/genética , Lipídeos/fisiologia , Lipoproteínas/metabolismo , Doenças por Armazenamento dos Lisossomos/metabolismo , Lisossomos/metabolismo , Mutação , Sistema Nervoso/metabolismo , Doenças Neurodegenerativas/metabolismo , FenótipoRESUMO
Uninfected female rats (Rattus novergicus) exhibit greater attraction to the males infected with protozoan parasite Toxoplasma gondii. This phenomenon is contrary to the aversion towards infected males observed in multitude of other host-parasite associations. In this report, we describe a proximate mechanism for this anomaly. We demonstrate that T. gondii infection enhances hepatic production and urinary excretion of α2u-globulins in rats. We further demonstrate that α2u-globulins are sufficient to recapitulate male sexual attractiveness akin to effects of the infection. This manipulation possibly results in greater horizontal transmission of this parasite between the infected male and the uninfected female. It supports the notion that in some evolutionary niches parasites can alter host sexual signaling, likely leading to an increased rate of sexual transmission.