Incorporation of fluorophore-cholesterol conjugates into liposomal and mycobacterial membranes.

Fluorescently-labeled steroids that emit intense blue light in nonpolar solvent (λem (CH2Cl2)≈440nm, ΦF=0.70) were prepared by treating cholesteryl chloroformate with 4-amino-1,8-naphthalimides. The lipid portion of the conjugates embeds into liposomal membrane bilayers in minutes, leaving the fluorophore exposed to the external aqueous environment.

The ferrous iron transporter FtrABCD is required for the virulence of Brucella abortus 2308 in mice.

Iron transport has been linked to the virulence of Brucella strains in both natural and experimental hosts. The genes designated BAB2_0837-0840 in the Brucella abortus 2308 genome sequence are predicted to encode a CupII-type ferrous iron transporter homologous to the FtrABCD transporter recently described in Bordetella. To study the role of the Brucella FtrABCD in iron transport, an isogenic ftrA mutant was constructed from B.

SodA is a major metabolic antioxidant in Brucella abortus 2308 that plays a significant, but limited, role in the virulence of this strain in the mouse model.

The gene designated BAB1_0591 in the Brucella abortus 2308 genome sequence encodes the manganese-cofactored superoxide dismutase SodA. An isogenic sodA mutant derived from B. abortus 2308, designated JB12, displays a small colony phenotype, increased sensitivity in vitro to endogenous superoxide generators, hydrogen peroxide and exposure to acidic pH, and a lag in growth when cultured in rich and minimal media that can be rescued by the addition of all 20 amino acids to the growth medium.

Mur regulates the gene encoding the manganese transporter MntH in Brucella abortus 2308.

MntH is the only high-affinity manganese transporter identified in Brucella. A previous study showed that MntH is required for the wild-type virulence of Brucella abortus 2308 in mice (Anderson ES, et al., Infect.

The iron-responsive regulator irr is required for wild-type expression of the gene encoding the heme transporter BhuA in Brucella abortus 2308.

Irr and RirA, rather than Fur, serve as the major iron-responsive regulators in the alphaproteobacteria. With only a few exceptions, however, the relative contributions of these transcriptional regulators to the differential expression of specific iron metabolism genes in Brucella strains are unclear. The gene encoding the outer membrane heme transporter BhuA exhibits maximum expression in Brucella abortus 2308 during growth under iron-deprived conditions, and mutational studies indicate that this pattern of bhuA expression is mediated by the iron-responsive regulator Irr.

Survival of the fittest: how Brucella strains adapt to their intracellular niche in the host.

Brucella strains produce abortion and infertility in their natural hosts and a zoonotic disease in humans known as undulant fever. These bacteria do not produce classical virulence factors, and their capacity to successfully survive and replicate within a variety of host cells underlies their pathogenicity. Extensive replication of the brucellae in placental trophoblasts is associated with reproductive tract pathology in natural hosts, and prolonged persistence in macrophages leads to the chronic infections that are a hallmark of brucellosis in both natural hosts and humans.

The manganese transporter MntH is a critical virulence determinant for Brucella abortus 2308 in experimentally infected mice.

The gene designated BAB1_1460 in the Brucella abortus 2308 genome sequence is predicted to encode the manganese transporter MntH. Phenotypic analysis of an isogenic mntH mutant indicates that MntH is the sole high-affinity manganese transporter in this bacterium but that MntH does not play a detectable role in the transport of Fe(2+), Zn(2+), Co(2+), or Ni(2+). Consistent with the apparent selectivity of the corresponding gene product, the expression of the mntH gene in B.

The AraC-like transcriptional regulator DhbR is required for maximum expression of the 2,3-dihydroxybenzoic acid biosynthesis genes in Brucella abortus 2308 in response to iron deprivation.

Phenotypic evaluation of isogenic mutants derived from Brucella abortus 2308 indicates that the AlcR homolog DhbR (2,3-dihydroxybenzoic acid [2,3-DHBA] biosynthesis regulator) modulates the expression of the genes involved in 2,3-DHBA production, employing 2,3-DHBA or brucebactin as a coinducer.

Brucella abortus requires the heme transporter BhuA for maintenance of chronic infection in BALB/c mice.

The gene annotated BAB2_1150 in the Brucella abortus 2308 genome sequence is predicted to encode a homolog of the well-characterized heme transporter ShuA of Shigella dysenteriae and accordingly has been given the designation bhuA (Brucella heme utilization). Phenotypic analysis of an isogenic bhuA mutant derived from B. abortus 2308 verified that there is a link between BhuA and the ability of the parent strain to use heme as an iron source in in vitro assays.

Truncation of herpes simplex virus type 2 glycoprotein B increases its cell surface expression and activity in cell-cell fusion, but these properties are unrelated.

Formation of small polykaryons by cell-cell fusion is characteristic of herpes simplex virus (HSV) lesions, but the great majority of viruses isolated from such lesions produce only limited cell fusion in tissue culture. Because of this, HSV laboratory strains that produce extensive cell fusion (syncytium formation) in culture are regarded as variants or mutants. Furthermore, the rarity of clinical isolates able to produce syncytia in culture suggests that extensive cell fusion is deleterious in vivo.