Inhibition of sialidase activity and cellular invasion by the bacterial vaginosis pathogen Gardnerella vaginalis

Bacterial vaginosis is a genital tract infection, thought to be caused by transformation of a lactobacillus-rich flora to a dysbiotic microbiota enriched in mixed anaerobes. The most prominent of these is Gardnerella vaginalis (GV), an anaerobic pathogen that produces sialidase enzyme to cleave terminal sialic acid residues from human glycans. Notably, high sialidase activity is associated with preterm birth and low birthweight. We explored the potential of the sialidase inhibitor Zanamavir against GV whole cell sialidase activity using methyl-umbelliferyl neuraminic acid (MU-NANA) cleavage assays, with Zanamavir causing a 30% reduction in whole cell GV sialidase activity (p < 0.05). Furthermore, cellular invasion assays using HeLa cervical epithelial cells, infected with GV, demonstrated that Zanamivir elicited a 50% reduction in cell association and invasion (p < 0.05). Our data thus highlight that pharmacological sialidase inhibitors are able to modify BV-associated sialidase activity and influence host-pathogen interactions and may represent novel therapeutic adjuncts

Fumaric acid production from sugarcane trash hydrolysate using Rhizopus oryzae NIIST 1

Production of organic acids through fermentation of biomass feedstock is a potent strategy for co-product generation and improving economics in lignocellulose biorefinery. Sugar cane trash (SCT), a surplus available agro-residue, was exploited for the production of fumaric acid - a dicarboxylic acid with applications in the synthesis of polyester resins, as mordant and as a food additive. The isolate NIIST 1 which showed the production of fumaric acid was identified as Rhizopus oryzae. Media engineering was carried out and a maximum production of fumaric acid in SCT hydrolysate incorporated media was 5.2 g/L. Response surface analyses of the interaction of parameters indicated the importance of maintaining a high C/N ratio. Results indicate the scope for developing the Rhizopus oryzae strain NIIST 1 as a potent organism for fumaric acid production, since only a few microorganisms have the ability to produce industrially relevant compounds using lignocellulose biomass hydrolysates

Fumaric acid production from sugarcane trash hydrolysate using Rhizopus oryzae NIIST1

548-556Production of organic acids through fermentation of biomass feedstock is a potent strategy for co-product generation and improving economics in lignocellulose biorefinery. Sugar cane trash (SCT), a surplus available agro-residue, was exploited for the production of fumaric acid - a dicarboxylic acid with applications in the synthesis of polyester resins, as mordant and as a food additive. The isolate NIIST1 which showed the production of fumaric acid was identified as Rhizopus oryzae. Media engineering was carried out and a maximum production of fumaric acid in SCT hydrolysate incorporated media was 5.2 g/L. Response surface analyses of the interaction of parameters indicated the importance of maintaining a high C/N ratio. Results indicate the scope for developing the Rhizopus oryzae strain NIIST1 as a potent organism for fumaric acid production, since only a few microorganisms have the ability to produce industrially relevant compounds using lignocellulose biomass hydrolysates

Sialyl Residues Modulate LPS-Mediated Signaling through the Toll-Like Receptor 4 Complex

We previously reported that neuraminidase (NA) pretreatment of human PBMCs markedly increased their cytokine response to lipopolysaccharide (LPS). To study the mechanisms by which this occurs, we transfected HEK293T cells with plasmids encoding TLR4, CD14, and MD2 (three components of the LPS receptor complex), as well as a NFκB luciferase reporting system. Both TLR4 and MD2 encoded by the plasmids are α-2,6 sialylated. HEK293T cells transfected with TLR4/MD2/CD14 responded robustly to the addition of LPS; however, omission of the MD2 plasmid abrogated this response. Addition of culture supernatants from MD2 (sMD2)-transfected HEK293T cells, but not recombinant, non-glycosylated MD2 reconstituted this response. NA treatment of sMD2 enhanced the LPS response as did NA treatment of the TLR4/CD14-transfected cell supplemented with untreated sMD2, but optimal LPS-initiated responses were observed with NA-treated TLR4/CD14-transfected cells supplemented with NA-treated sMD2. We hypothesized that removal of negatively charged sialyl residues from glycans on the TLR4 complex would hasten the dimerization of TLR4 monomers required for signaling. Co-transfection of HEK293T cells with separate plasmids encoding either YFP- or FLAG-tagged TLR4, followed by treatment with NA and stimulation with LPS, led to an earlier and more robust time-dependent dimerization of TLR4 monomers on co-immunoprecipitation, compared to untreated cells. These findings were confirmed by fluorescence resonance energy transfer (FRET) analysis. Overexpression of human Neu1 increased LPS-initiated TLR4-mediated NFκB activation and a NA inhibitor suppressed its activation. We conclude that (1) sialyl residues on TLR4 modulate LPS responsiveness, perhaps by facilitating clustering of the homodimers, and that (2) sialic acid, and perhaps other glycosyl species, regulate MD2 activity required for LPS-mediated signaling. We speculate that endogenous sialidase activity mobilized during cell activation may play a role in this regulation