Women with bacterial vaginosis (BV), an imbalance of the vaginal microbiome, are more likely to be colonized by potential pathogens such as Fusobacterium nucleatum, a bacterium linked with intrauterine infection and preterm birth. However, the conditions and mechanisms supporting pathogen colonization during vaginal dysbiosis remain obscure. We demonstrate that sialidase activity, a diagnostic feature of BV, promoted F. nucleatum foraging and growth on mammalian sialoglycans, a nutrient resource that was otherwise inaccessible because of the lack of endogenous F. nucleatum sialidase. In mice with sialidase-producing vaginal microbiotas, mutant F. nucleatum unable to consume sialic acids was impaired in vaginal colonization. These experiments in mice also led to the discovery that F. nucleatum may also "give back" to the community by reinforcing sialidase activity, a biochemical feature of human dysbiosis. Using human vaginal bacterial communities, we show that F. nucleatum supported robust outgrowth of Gardnerella vaginalis, a major sialidase producer and one of the most abundant organisms in BV. These results illustrate that mutually beneficial relationships between vaginal bacteria support pathogen colonization and may help maintain features of dysbiosis. These findings challenge the simplistic dogma that the mere absence of "healthy" lactobacilli is the sole mechanism that creates a permissive environment for pathogens during vaginal dysbiosis. Given the ubiquity of F. nucleatum in the human mouth, these studies also suggest a possible mechanism underlying links between vaginal dysbiosis and oral sex.
Escherichia coli
infection of the female reproductive tract is a significant cause of disease in humans and animals, but simple animal models are lacking. Here we report that vaginal inoculation of uropathogenic
E
.
coli
strains UTI89 and CFT073 in non-pregnant, estrogen-treated mice resulted in robust colonization of the vagina and uterine horns, whereas titers of the lab strain MG1655 were significantly lower. Non-estrogenized mice also became colonized, but there was more variation in titers. A dose of 10
4
colony-forming units (CFU) UTI89 was sufficient to result in colonization in all estrogenized mice, and we also observed bacterial transfer between inoculated and uninoculated estrogenized cage mates. UTI89 infection led to inflammation and leukocyte infiltration into the uterine horns as evidenced by tissue histology. Flow cytometry experiments revealed that neutrophil, monocyte and eosinophil populations were significantly increased in infected uterine horns. This model is a simple way to study host-pathogen interactions in
E
.
coli
vaginal colonization and uterine infection. There are immediate implications for investigators studying urinary tract infection using mouse models, as few
E
.
coli
are required to achieve reproductive colonization, resulting in an additional, underappreciated mucosal reservoir.
Mucin-type O-glycans form one of the most abundant
and complex post-translational modifications (PTM) on cell surface
proteins that govern adhesion, migration, and trafficking of hematopoietic
cells. Development of targeted approaches to probe functions of O-glycans is at an early stage. Among several approaches,
small molecules with unique chemical functional groups that could
modulate glycan biosynthesis form a critical tool. Herein, we show
that metabolism of peracetyl N-acyl-d-galactosamine
derivatives carrying an N-thioglycolyl (Ac5GalNTGc, 1) moietybut not N-glycolyl (Ac5GalNGc, 2) and N-acetyl (Ac4GalNAc, 3)through the N-acetyl-d-galactosamine (GalNAc) salvage pathway
induced abrogation of MAL-II and PNA epitopes in Jurkat cells. Mass
spectrometry of permethylated O-glycans from Jurkat
cells confirmed the presence of significant amounts of elaborated O-glycans (sialyl-T and disialyl-T) which were inhibited
upon treatment with 1. O-Glycosylation
of CD43, a cell surface antigen rich in O-glycans,
was drastically reduced by 1 in a thiol-dependent manner.
By contrast, only mild effects were observed for CD45 glycoforms.
Direct metabolic incorporation of 1 was confirmed by
thiol-selective Michael addition reaction of immunoprecipitated CD43-myc/FLAG.
Mechanistically, CD43 glycoforms were unperturbed by peracetylated N-(3-acetylthiopropanoyl) (4), N-(4-acetylthiobutanoyl) (5), and N-methylthioacetyl
(6) galactosamine derivatives, N-thioglycolyl-d-glucosamine (7, C-4 epimer of 1),
and α-O-benzyl 2-acetamido-2-deoxy-d-galactopyranoside (8), confirming the critical requirement
of both free sulfhydryl and galactosamine moieties for inhibition
of mucin-type O-glycans. Similar, yet differential,
effects of 1 were observed for CD43 glycoforms in multiple
hematopoietic cells. Development of small molecules that could alter
glycan patterns in an antigen-selective and cell-type selective manner
might provide avenues for understanding biological functions of glycans.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.