Glucosyltransferase phase variation in Streptococcus gordonii modifies adhesion to saliva-coated hydroxyapatite surfaces in a sucrose-independent manner

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72317/1/j.1399-302X.1992.tb00521.x.pd

Molecular analysis of representative Streptococcus gordonii Spp phase variants reveals no differences in the glucosyltransferase structural gene, gtfG

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73398/1/j.1399-302X.1997.tb00622.x.pd

Sortase A Substrate Specificity in GBS Pilus 2a Cell Wall Anchoring

Streptococcus agalactiae, also referred to as Group B Streptococcus (GBS), is one of the most common causes of life-threatening bacterial infections in infants. In recent years cell surface pili have been identified in several Gram-positive bacteria, including GBS, as important virulence factors and promising vaccine candidates. In GBS, three structurally distinct types of pili have been discovered (pilus 1, 2a and 2b), whose structural subunits are assembled in high-molecular weight polymers by specific class C sortases. In addition, the highly conserved housekeeping sortase A (SrtA), whose main role is to link surface proteins to bacterial cell wall peptidoglycan by a transpeptidation reaction, is also involved in pili cell wall anchoring in many bacteria. Through in vivo mutagenesis, we demonstrate that the LPXTG sorting signal of the minor ancillary protein (AP2) is essential for pilus 2a anchoring. We successfully produced a highly purified recombinant SrtA (SrtAΔN40) able to specifically hydrolyze the sorting signal of pilus 2a minor ancillary protein (AP2-2a) and catalyze in vitro the transpeptidation reaction between peptidoglycan analogues and the LPXTG motif, using both synthetic fluorescent peptides and recombinant proteins. By contrast, SrtAΔN40 does not catalyze the transpeptidation reaction with substrate-peptides mimicking sorting signals of the other pilus 2a subunits (the backbone protein and the major ancillary protein). Thus, our results add further insight into the proposed model of GBS pilus 2a assembly, in which SrtA is required for pili cell wall covalent attachment, acting exclusively on the minor accessory pilin, representing the terminal subunit located at the base of the pilus

Identifying Low pH Active and Lactate-Utilizing Taxa within Oral Microbiome Communities from Healthy Children Using Stable Isotope Probing Techniques

<div><h3>Background</h3><p>Many human microbial infectious diseases including dental caries are polymicrobial in nature. How these complex multi-species communities evolve from a healthy to a diseased state is not well understood. Although many health- or disease-associated oral bacteria have been characterized <em>in vitro</em>, their physiology within the complex oral microbiome is difficult to determine with current approaches. In addition, about half of these species remain uncultivated to date with little known besides their 16S rRNA sequence. Lacking culture-based physiological analyses, the functional roles of uncultivated species will remain enigmatic despite their apparent disease correlation. To start addressing these knowledge gaps, we applied a combination of Magnetic Resonance Spectroscopy (MRS) with RNA and DNA based Stable Isotope Probing (SIP) to oral plaque communities from healthy children for <em>in vitro</em> temporal monitoring of metabolites and identification of metabolically active and inactive bacterial species.</p> <h3>Methodology/Principal Findings</h3><p>Supragingival plaque samples from caries-free children incubated with ¹³C-substrates under imposed healthy (buffered, pH 7) and diseased states (pH 5.5 and pH 4.5) produced lactate as the dominant organic acid from glucose metabolism. Rapid lactate utilization upon glucose depletion was observed under pH 7 conditions. SIP analyses revealed a number of genera containing cultured and uncultivated taxa with metabolic capabilities at pH 5.5. The diversity of active species decreased significantly at pH 4.5 and was dominated by <em>Lactobacillus</em> and <em>Propionibacterium</em> species, both of which have been previously found within carious lesions from children.</p> <h3>Conclusions/Significance</h3><p>Our approach allowed for identification of species that metabolize carbohydrates under different pH conditions and supports the importance of Lactobacilli and Propionibacterium in the development of childhood caries. Identification of species within healthy subjects that are active at low pH can lead to a better understanding of oral caries onset and generate appropriate targets for preventative measures in the early stages.</p> </div

Long-Term Continuous Suppression With Once-Yearly Histrelin Subcutaneous Implants for the Treatment of Central Precocious Puberty: A Final Report of a Phase 3 Multicenter Trial

CONTEXT AND OBJECTIVE: The histrelin implant has proven to be an effective method of delivering GnRH analog (GnRHa) therapy to children with central precocious puberty (CPP), yet there are limited data available regarding hormonal suppression and auxological changes during an extended course of therapy. DESIGN: This was a phase 3, prospective, open-label study. SETTING AND PARTICIPANTS: Thirty-six children with CPP who participated in a phase 3, open-label study and required further GnRHa therapy were eligible to continue treatment receiving a new implant upon removal of the prior 12-month histrelin implant during a long-term extension phase. OUTCOME MEASURES: Hormone levels and auxologic parameters were measured periodically for up to 6 years of treatment and up to 1 year of posttreatment follow-up. RESULTS: Hormonal suppression was maintained throughout the study in patients who had prior GnRHa therapy (n = 16) and in treatment-naive patients (n = 20). Bone age to chronological age ratio decreased from 1.417 (n = 20) at baseline to 1.18 (n = 8) at 48 months in treatment-naive children (P < .01). Predicted adult height in girls increased from 151.9 cm at baseline to 166.5 cm at month 60 (n = 6; P < .05), with a 10.7-cm height gain observed among treatment-naive children (n = 5). No adverse effect on growth or recovery of the hypothalamic-pituitary-gonadal axis was observed with hormonal suppression. The histrelin implant was generally well tolerated during long-term therapy. CONCLUSIONS: Long-term histrelin implant therapy provided sustained gonadotropin suppression safely and effectively and improved predicted adult height in children with CPP