Synthetic glycans control gut microbiome structure and mitigate colitis in mice.

Relative abundances of bacterial species in the gut microbiome have been linked to many diseases. Species of gut bacteria are ecologically differentiated by their abilities to metabolize different glycans, making glycan delivery a powerful way to alter the microbiome to promote health. Here, we study the properties and therapeutic potential of chemically diverse synthetic glycans (SGs).

Inhibition of Pseudomonas aeruginosa and Mycobacterium tuberculosis disulfide bond forming enzymes.

In bacteria, disulfide bonds confer stability on many proteins exported to the cell envelope or beyond, including bacterial virulence factors. Thus, proteins involved in disulfide bond formation represent good targets for the development of inhibitors that can act as antibiotics or anti-virulence agents, resulting in the simultaneous inactivation of several types of virulence factors. Here, we present evidence that the disulfide bond forming enzymes, DsbB and VKOR, are required for Pseudomonas aeruginosa pathogenicity and Mycobacterium tuberculosis survival respectively.

The Disulfide Bond Formation Pathway Is Essential for Anaerobic Growth of Escherichia coli.

Disulfide bonds are critical to the stability and function of many bacterial proteins. In the periplasm of , intramolecular disulfide bond formation is catalyzed by the two-component disulfide bond forming (DSB) system. Inactivation of the DSB pathway has been shown to lead to a number of pleotropic effects, although cells remain viable under standard laboratory conditions.

Inhibition of virulence-promoting disulfide bond formation enzyme DsbB is blocked by mutating residues in two distinct regions.

Disulfide bonds contribute to protein stability, activity, and folding in a variety of proteins, including many involved in bacterial virulence such as toxins, adhesins, flagella, and pili, among others. Therefore, inhibitors of disulfide bond formation enzymes could have profound effects on pathogen virulence. In the disulfide bond formation pathway, the periplasmic protein DsbA introduces disulfide bonds into substrates, and then the cytoplasmic membrane protein DsbB reoxidizes DsbA's cysteines regenerating its activity.

The essential cell division protein FtsN contains a critical disulfide bond in a non-essential domain.

Disulfide bonds are found in many proteins associated with the cell wall of Escherichia coli, and for some of these proteins the disulfide bond is critical to their stability and function. One protein found to contain a disulfide bond is the essential cell division protein FtsN, but the importance of this bond to the protein's structural integrity is unclear. While it evidently plays a role in the proper folding of the SPOR domain of FtsN, this domain is non-essential, suggesting that the disulfide bond might also be dispensable.

Compounds targeting disulfide bond forming enzyme DsbB of Gram-negative bacteria.

In bacteria, disulfide bonds confer stability on many proteins exported to the cell envelope or beyond. These proteins include numerous bacterial virulence factors, and thus bacterial enzymes that promote disulfide bond formation represent targets for compounds inhibiting bacterial virulence. Here, we describe a new target- and cell-based screening methodology for identifying compounds that inhibit the disulfide bond-forming enzymes Escherichia coli DsbB (EcDsbB) or Mycobacterium tuberculosis VKOR (MtbVKOR), which can replace EcDsbB, although the two are not homologs.

Inactivation of a single gene enables microaerobic growth of the obligate anaerobe Bacteroides fragilis.

Bacteroides fragilis can replicate in atmospheres containing ≤0.05% oxygen, but higher concentrations arrest growth by an unknown mechanism. Here we show that inactivation of a single gene, oxe (i.

Fumarate reductase is a major contributor to the generation of reactive oxygen species in the anaerobe Bacteroides fragilis.

Despite the detrimental role that endogenously generated reactive oxygen species (ROS) may play in bacteria exposed to aerobic environments, very few sources of ROS have been identified in vivo. Such studies are often precluded by the presence of efficient ROS-scavenging pathways, like those found in the aerotolerant anaerobe Bacteroides fragilis. Here we demonstrate that deletion of the genes encoding catalase (Kat), alkylhydroperoxide reductase (AhpC) and thioredoxin-dependent peroxidase (Tpx) strongly inhibits H(2)O(2) detoxification in B.

Investigation of the unstable attenuation exhibited by a chicken anaemia virus isolate.

An attenuated chicken anaemia virus (CAV) isolate, cloned isolate 10, which was molecularly cloned from the Cuxhaven-1 CAV after 173 cell-culture passages, was shown previously to recover pathogenicity following 10 passages in young chicks. The consensus nucleotide sequence of the 'revertant' (Rev) virus, present as a tissue homogenate, differed from cloned isolate 10 at a single nucleotide residue (nucleotide 1739) that changed amino acid 287 of the capsid protein from alanine to aspartic acid. Subjecting Rev virus to 10 cell-culture passages reselected viruses with an alanine at this amino acid position.

Structure-dependent modulation of alpha interferon production by porcine circovirus 2 oligodeoxyribonucleotide and CpG DNAs in porcine peripheral blood mononuclear cells.

DNA sequences containing CpG motifs are recognized as immunomodulators in several species. Phosphodiester oligodeoxyribonucleotides (ODNs) representing sequences from the genome of porcine circovirus type 2 (PCV2) have been identified as potent inducers (ODN PCV2/5) or inhibitors (ODN PCV2/1) of alpha interferon (IFN-alpha) production by porcine peripheral blood mononuclear cells (poPBMCs) in vitro. In this study, the IFN-alpha-inducing or -inhibitory activities of specific phosphodiester ODNs were demonstrated to be dependent on their ability to form secondary structures.

Growth phase regulation of Vibrio cholerae RTX toxin export.

Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, secretes several "accessory" toxins, including RTX toxin, which causes the cross-linking of the actin cytoskeleton. RTX toxin is exported to the extracellular milieu by an atypical type I secretion system (T1SS), and we previously noted that RTX-associated activity is detectable only in supernatant fluids from log phase cultures. Here, we investigate the mechanisms for regulating RTX toxin activity in supernatant fluids.

Identification of a sequence from the genome of porcine circovirus type 2 with an inhibitory effect on IFN-alpha production by porcine PBMCs.

Porcine circovirus type 2 (PCV-2) has been identified as the causal agent of postweaning multisystemic wasting syndrome and has been associated with several other disease syndromes in pigs. To date, however, little is known regarding the mechanism(s) underlying the pathogenesis of PCV-2-induced diseases and the interaction of the virus with the host immune system. In the present study, oligodeoxynucleotides (ODNs), with central CpG motifs selected from the genome of PCV-2, were demonstrated to modulate the immune response of porcine PBMCs.

The contribution of accessory toxins of Vibrio cholerae O1 El Tor to the proinflammatory response in a murine pulmonary cholera model.

The contribution of accessory toxins to the acute inflammatory response to Vibrio cholerae was assessed in a murine pulmonary model. Intranasal administration of an El Tor O1 V. cholerae strain deleted of cholera toxin genes (ctxAB) caused diffuse pneumonia characterized by infiltration of PMNs, tissue damage, and hemorrhage.