Biology subjects

Bessaiah, H.

Publications and source records attributed to Bessaiah, H..

5 recordsLinked to original sources

bioRxiv2026

Amino Sugar Metabolism with AgaSY Coordinates Carbon Catabolism, Fimbrial Regulation, and Pathogenesis in Uropathogenic E. coli

Uropathogenic Escherichia coli (UPEC) exploit alternative carbon sources in order to adapt to the nutrient-limited urinary tract. While glucose is often scarce in healthy human urine, UPEC express a variety of sugar transport and catabolic systems that promote fitness during infection. In this study, we identify the agaSY genes in UPEC strain CFT073 as essential for the catabolism of the amino sugars N-acetyl-galactosamine (GalNAc or Aga) and galactosamine (GalN or Gam) and for the efficient use of additional amino sugars and carbon sources. Deletion of agaSY not only abolished Aga utilization but also impaired catabolism of multiple carbon sources including amino acids and sugars tested using phenotypic arrays. The {Delta}agaSY mutant exhibited significantly reduced type 1 fimbriae production, reduced biofilm formation, and increased motility, suggesting a link between amino sugar metabolism and the regulation of bacterial surface structures. Loss of agaSY did not affect growth and adherence to bladder cells and increased expression of genes encoding F9 fimbriae. Furthermore, the {Delta}agaSY mutant was significantly attenuated for bladder and kidney colonization in a murine urinary tract infection model, while complementation restored urinary tract colonization. The results indicate that a combination of deficiencies in nutrient acquisition, altered carbon metabolism, and regulation of virulence-associated factors contributes to reduced urinary tract colonization. Our findings highlight the interplay between metabolic flexibility and virulence regulation, as well as the central role that amino sugar metabolism plays in UPEC pathogenesis.

microbiology↗

bioRxiv2024

A rewiring of the earliest immune events leading to T-cell mediated disease following intestinal infection in a PINK1KO mouse model of Parkinsons disease

Parkinsons disease (PD) is characterized by a protracted period of non-motor symptoms, including gastrointestinal (GI) dysfunction, which can precede the development of the cardinal motor deficits by decades. This long prodrome of disease is highly suggestive of immune cell involvement in the initiation of disease, but currently the field lacks robust model systems to study such mechanisms. It has been hypothesized that pathology may be first initiated in the periphery due to environmental triggers, such as pathogens that enter the GI tract. We further speculate that the impact of such pathogens on the immune system could be exacerbated in genetically predisposed individuals. Our group has developed a GI-targeted pathogen-induced PD mouse model system in PINK1 KO mice with Gram-negative bacterial infections and found that T cells are a major player in driving PD-like motor symptoms at late stages following infection. Herein, we now map the initiating immune events at the site of infection at the earliest stages with the goal of shedding light on the earliest mechanisms triggering immune-mediated pathological processes relevant to PD. Using unbiased single cell sequencing, we demonstrate that myeloid cells are the earliest dysregulated immune cell type in PINK1 KO infected mice at 1-week post-infection, followed by a dysregulated T cell response shortly after, at 2 weeks post-infection. We find that these myeloid cells have an enhanced proinflammatory profile, are more mature, and develop enhanced capacity for antigen presentation. Using unbiased prediction analysis, our data suggest that cytotoxic T cells and myeloid cells are particularly poised for interacting with each other, and we identify possible direct cell-cell interaction pathways that might be implicated. Taken together, deciphering the earliest immune mechanisms in the periphery underpinning PD autoimmunity will be instrumental in the development of effective therapeutic targeting strategies before irrevocable neuronal damage ensues.

immunology↗

bioRxiv2024

Modeling gene-environment interactions in Parkinson's Disease: Helicobacter pylori infection of Pink1-/- mice induces CD8 T cell-dependent motor and cognitive dysfunction.

Parkinsons disease (PD) is a chronic neurodegenerative disorder characterized by progressive loss of motor function. Diagnosis occurs late: after motor symptom development downstream of the irreparable loss of a large proportion of the dopaminergic neurons in the substantia nigra of the brain. Understanding PD pathophysiology in its pre-motor prodromal phase is needed for earlier diagnosis and intervention. Genetic risk factors, environmental triggers, and dysregulated immunity have all been implicated in PD development. Here, we demonstrate in a mouse model deficient in the PD-associated gene Pink, that infection with the human PD-associated gastric bacterium Helicobacter pylori leads to development of motor and cognitive signs resembling prodromal features of PD. This was also associated with proliferation and activation of primary mitochondria-reactive CD8 T cells and infiltration of CD8 T cells into the brain. Development of the motor and cognitive phenotypes in the infected Pink1-/- mice was abrogated when CD8 T cells were depleted prior to infection. We anticipate that this new model, which integrates genetic PD susceptibility, a PD-relevant environmental trigger, and specific immune changes that are required for symptom development, will be a valuable tool for increasing our understanding of this complex disease.

immunology↗

bioRxiv2022

Adaptive radioresistance of Enterohemorrhagic Escherichia coli O157:H7 results in genomic loss of shiga toxin-encoding prophages

Enterohemorragic Escherichia coli (EHEC) O157:H7 is a foodborne pathogen producing shiga toxins (Stx1 and Stx2), can cause hemorrhagic diarrhea, and life-threatening infections. O157:H7 strain EDL933 carries prophages CP-933V and BP-933W that encode shiga toxin genes (stx1 and stx2 respectively). The aim of this work was to investigate the mechanisms of adaptive resistance of EHEC strain EDL933 to a typically "lethal" dose of {gamma}-irradiation (1.5 kGy). Adaptive selection through six passages of exposure to 1.5 kGy resulted in the loss of CP-933V and BP-933W prophages from the genome and mutations within three genes: wrbA, rpoA, and Wt_02639 (molY). Three selected EHEC clones that became irradiation-adapted to the 1.5 kGy dose (C1, C2 and C3) demonstrated increased resistance to oxidative stress, sensitivity to acid pH, and decreased cytotoxicity to Vero cells. To confirm that loss of prophages plays a role in increased radioresistance, C1 and C2 clones were exposed to bacteriophage containing lysates. Although, phage BP-933W could lysogenize C1, C2, and E.coli K-12 strain MG1655, it was not found to have integrated into the bacterial chromosome in C1-{Phi} and C2-{Phi} lysogens. Interestingly, for the E. coli K-12 lysogen (K12-{Phi}), BP-933W DNA had integrated at the wrbA gene (K12-{Phi}). Both C1-{Phi} and C2-{Phi} lysogens regained sensitivity to oxidative stress, were more effectively killed by a 1.5 kGy {gamma}-irradiation dose and had regained cytotoxicity and acid resistance phenotypes. Further, the K12-{Phi} lysogen became cytotoxic, more sensitive to {gamma}-irradiation and oxidative stress and slightly more acid resistant. ImportanceGamma ({gamma})-irradiation of food products can provide an effective means of eliminating bacterial pathogens such as enterohemorrhagic Escherichia coli (EHEC) O157:H7, a significant foodborne pathogen that can cause severe disease due to the production of Shiga toxins. To decipher the mechanisms of adaptive resistance of the O157:H7 strain EDL933, we evolved clones of this bacterium resistant to a lethal dose of {gamma}-irradiation by repeatedly exposing bacterial cells to irradiation following a growth restoration over six successive passages. Our findings provide evidence that adaptive selection involved modifications in the bacterial genome including deletion of the CP-933V and BP-933W prophages. These mutations in EHAC O157:H7 resulted in loss of stx1, stx2, loss of cytotoxicity to epithelial cells and decreased resistance to acidity, critical virulence determinants of EHEC, concomitant with increased resistance to lethal irradiation and oxidative stress. These findings demonstrate that the potential adaptation of EHEC to high doses of radiation would involve elimination of the Stx encoding phages and likely lead to a substantial attenuation of virulence.

microbiology↗

bioRxiv2021

A newly identified group of P-like (PL) fimbriae from extra-intestinal pathogenic Escherichia coli (ExPEC) encode distinct adhesin subunits and mediate adherence to host cells

Fimbrial adhesins play a critical role for bacterial adherence and biofilm formation. Sequencing of avian pathogenic Escherichia coli (APEC) strain QT598 identified a fimbrial gene cluster belonging to the {pi} group that we named PL (P-like) fimbriae, since genetic organization and sequence are similar to Pap and related fimbriae. Screening of genomic databases indicated that genes encoding PL fimbriae located on IncF plasmids are present in a diversity of E. coli isolates from poultry, human systemic infections, and other sources. As with P fimbriae, PL fimbriae exhibit sequence divergence in adhesin encoding genes, and strains could be divided into 5 classes based on differences in sequences of the PlfG adhesin protein. The plf genes from two predominant PlfG adhesin classes, PlfG-I and PlfG-II were cloned. PL fimbriae were visualized by electron microscopy, promoted biofilm formation, demonstrated distinct hemagglutination profiles and promoted adherence to human bladder and kidney epithelial cell lines. Hybrid fimbriae comprised of genes from plfQT598 wherein plfG was replaced by papG encoding adhesin genes were also shown to be functional and mediate adherence to epithelial cells, further indicating similarity and functional compatibility between these two types of fimbriae. Although deletion of plf genes did not significantly reduce colonization of the mouse urinary tract, plf gene expression was increased over 40-fold in the bladder compared to during in vitro culture. Overall, PL fimbriae represent a new group of fimbriae demonstrating both functional differences and similarities to P fimbriae and may contribute to adherence to cells and colonization of host tissues. ImportanceFimbriae are important colonization factors in many bacterial species. The identification of a new type of fimbriae encoded on some IncF plasmids in E. coli was investigated. Genomic sequences demonstrated these fimbrial gene clusters have genetic diversity, particularly in the adhesin encoding PlfG gene. Functional studies demonstrated differences in hemagglutination specificity, although both types of Plf adhesin under study mediated adherence to human urinary epithelial cells. Such fimbriae may represent previously unrecognized adhesins that could contribute to host specificity and tissue tropism of some E. coli strains.

microbiology↗