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MBio Jun 2024Transmission of by fleas depends on the formation of condensed bacterial aggregates embedded within a gel-like matrix that localizes to the proventricular valve in the...
UNLABELLED
Transmission of by fleas depends on the formation of condensed bacterial aggregates embedded within a gel-like matrix that localizes to the proventricular valve in the flea foregut and interferes with normal blood feeding. This is essentially a bacterial biofilm phenomenon, which at its end stage requires the production of a exopolysaccharide that bridges the bacteria together in a cohesive, dense biofilm that completely blocks the proventriculus. However, bacterial aggregates are evident within an hour after a flea ingests , and the bacterial exopolysaccharide is not required for this process. In this study, we characterized the biochemical composition of the initial aggregates and demonstrated that the yersinia murine toxin (Ymt), a phospholipase D, greatly enhances rapid aggregation following infected mouse blood meals. The matrix of the bacterial aggregates is complex, containing large amounts of protein and lipid (particularly cholesterol) derived from the flea's blood meal. A similar incidence of proventricular aggregation occurred after fleas ingested whole blood or serum containing , and intact, viable bacteria were not required. The initial aggregation of in the flea gut is likely due to a spontaneous physical process termed depletion aggregation that occurs commonly in environments with high concentrations of polymers or other macromolecules and particles such as bacteria. The initial aggregation sets up subsequent binding aggregation mediated by the bacterially produced exopolysaccharide and mature biofilm that results in proventricular blockage and efficient flea-borne transmission.
IMPORTANCE
, the bacterial agent of plague, is maintained in nature in mammal-flea-mammal transmission cycles. After a flea feeds on a mammal with septicemic plague, the bacteria rapidly coalesce in the flea's digestive tract to form dense aggregates enveloped in a viscous matrix that often localizes to the foregut. This represents the initial stage of biofilm development that potentiates transmission of when the flea later bites a new host. The rapid aggregation likely occurs via a depletion-aggregation mechanism, a non-canonical first step of bacterial biofilm development. We found that the biofilm matrix is largely composed of host blood proteins and lipids, particularly cholesterol, and that the enzymatic activity of a phospholipase D (Ymt) enhances the initial aggregation. transmitted by flea bite is likely associated with this host-derived matrix, which may initially shield the bacteria from recognition by the host's intradermal innate immune response.
Topics: Yersinia pestis; Phospholipase D; Siphonaptera; Biofilms; Plague; Extracellular Polymeric Substance Matrix; Polysaccharides; Microscopy, Electron, Transmission; Proteome; Animals; Mice; Lipids
PubMed: 38722159
DOI: 10.1128/mbio.00124-24 -
International Journal of Systematic and... Feb 2024Four yeast isolates collected from flowers from different ecosystems in Brazil, one from fruit of in Argentina, three from flowers of in Chile and one obtained from...
Four yeast isolates collected from flowers from different ecosystems in Brazil, one from fruit of in Argentina, three from flowers of in Chile and one obtained from the proventriculus of a female bumblebee in Canada were demonstred, by analysis of the sequences of the internal transcribed spacer (ITS) region and D1/D2 domains of the large subunit rRNA gene, to represent two novel species of the genus . These species are described here as f.a, sp. nov. (CBS 16166; Mycobank MB 851206) and f.a., sp. nov. (PYCC 8997; Mycobank MB 851207). The results of a phylogenomic analysis using 1037 single-copy orthogroups indicated that is a member of a subclade that contains , and . The results also indicated that is phylogenetically related to . The two isolates of were obtained from flowers in Brazil and were probably vectored by insects that visit these substrates. has a wide geographical distribution having been isolated in flowers from Brazil and Chile, fruit from Argentina and a bumblebee from Canada.
Topics: Animals; Ecosystem; Phylogeny; Sequence Analysis, DNA; RNA, Ribosomal, 16S; DNA, Bacterial; Bacterial Typing Techniques; Base Composition; Fatty Acids; Saccharomycetales; Insecta
PubMed: 38407127
DOI: 10.1099/ijsem.0.006270 -
Comparative Biochemistry and... Mar 2024Zymosan is a fungi-derived pathogen-associated molecular pattern. It activates the immune system and induces the reduction of feed passage rate in the gastrointestinal...
Zymosan is a fungi-derived pathogen-associated molecular pattern. It activates the immune system and induces the reduction of feed passage rate in the gastrointestinal tract of vertebrates including birds. However, the mechanism mediating the zymosan-induced inhibition of feed passage in the gastrointestinal tract remains unknown. Since the medulla oblongata regulates the digestive function, it is plausible that the medulla oblongata is involved in the zymosan-induced inhibition of feed passage. The present study was performed to identify the genes that were affected by zymosan within the medulla oblongata of chicks (Gallus gallus) using an RNA sequencing approach. We found that mRNAs of several bioactive molecules including neuropeptide Y (NPY) were increased with an intraperitoneal (IP) injection of zymosan. The increase of mRNA expression of NPY in the medulla oblongata was also observed after the IP injection of lipopolysaccharide, derived from gram-negative bacteria. These results suggest that medullary NPY is associated with physiological changes during fungal and bacterial infection. Furthermore, we found that intracerebroventricular injection of NPY and its receptor agonists reduced the feed passage from the crop. Additionally, the injection of NPY reduced the feed passage from the proventriculus to lower digestive tract. NPY also suppressed the activity of duodenal activities of amylase and trypsin. The present study suggests that fungi- and bacteria-induced activation of the immune system may activate the NPY neurons in the medulla oblongata and thereby reduce the digestive function in chicks.
Topics: Animals; Neuropeptide Y; Lipopolysaccharides; Zymosan; Chickens; Medulla Oblongata; Gastrointestinal Tract
PubMed: 38147959
DOI: 10.1016/j.cbpa.2023.111565 -
Proceedings of the National Academy of... Apr 2024Despite the conservation of genetic machinery involved in eye development, there is a strong diversity in the placement of eyes on the head of animals. Morphogen...
Despite the conservation of genetic machinery involved in eye development, there is a strong diversity in the placement of eyes on the head of animals. Morphogen gradients of signaling molecules are vital to patterning cues. During eye development, Wingless (Wg), a ligand of Wnt/Wg signaling, is expressed anterolaterally to form a morphogen gradient to determine the eye- versus head-specific cell fate. The underlying mechanisms that regulate this process are yet to be fully understood. We characterized ( ortholog of human SATB1), a K50 homeodomain transcription factor, as a dorsal eye gene, which regulates Wg signaling to determine eye versus head fate. Across species, Dve is expressed in the dorsal head vertex region where it regulates transcription. Second, Dve suppresses eye fate by down-regulating retinal determination genes. Third, the -expressing dorsal head vertex region is important for Wg-mediated inhibition of retinal cell fate, as eliminating the Dve-expressing cells or preventing Wg transport from these -expressing cells leads to a dramatic expansion of the eye field. Together, these findings suggest that Dve regulates Wg expression in the dorsal head vertex, which is critical for determining eye versus head fate. Gain-of-function of SATB1 exhibits an eye fate suppression phenotype similar to Dve. Our data demonstrate a conserved role for Dve/SATB1 in the positioning of eyes on the head and the interocular distance by regulating Wg. This study provides evidence that dysregulation of the Wg morphogen gradient results in developmental defects such as hypertelorism in humans where disproportionate interocular distance and facial anomalies are reported.
Topics: Animals; Humans; Drosophila Proteins; Matrix Attachment Region Binding Proteins; Wnt1 Protein; Drosophila; Retina; Transcription Factors; Gene Expression Regulation, Developmental; Drosophila melanogaster; Body Patterning
PubMed: 38588419
DOI: 10.1073/pnas.2316244121