Electricity production and microbial biofilm characterization in cellulose-fed microbial fuel cells.

Converting biodegradable materials into electricity, microbial fuel cells (MFCs) present a promising technology for renewable energy production in specific applications. Unlike typical soluble substrates that have been used as electron donors in MFC studies, cellulose is unique because it requires a microbial consortium that can metabolize both an insoluble electron donor (cellulose) and electron acceptor (electrode). In this study, electricity generation and the microbial ecology of cellulose-fed MFCs were analyzed using a defined co-culture of Clostridium cellulolyticum and Geobacter sulfurreducens. Fluorescent in situ hybridization and quantitative PCR showed that when particulate MN301 cellulose was used as sole substrate, most Clostridium cells were found adhered to cellulose particles in suspension, while most Geobacter cells were attached to the electrode. By comparison, both bacteria resided in suspension and biofilm samples when soluble carboxymethyl cellulose was used. This distinct function-related distribution of the bacteria suggests an opportunity to optimize reactor operation by settling cellulose and decanting supernatant to extend cellulose hydrolysis and improve cellulose-electricity conversion.

Proximal caries in juvenile periodontitis patients.

BACKGROUND: Caries is recognized as the prevalent proximal dental disease in adolescents, while proximal bone loss is minimal to non-existent in this population. Adolescents demonstrating an inverse disease pattern, i.e., minimal caries and active periodontitis, could provide powerful clues with regard to both diseases. However, data are inconsistent. This study was designed to clarify this relationship by comparing proximal caries prevalence in a juvenile periodontitis (JP) group to a matched non-periodontally diseased control group. METHODS: Two groups (cases [JPs] and control patients [CPs]) were matched for age, sex, and race and evaluated for decayed, missing, filled teeth and surfaces (DMFS) by radiographic analysis. Statistical analysis was performed by ANOVA and Student t test. The study consisted of four phases. Phase I was based on data from a previous study that failed to include race in the analysis. Thus, the original 23 JP patients (mostly African-Americans from New York City) were rematched for race as well as sex and age with CPs from Newark, NJ. The effect of water fluoridation (found in NYC) was evaluated in Phase II by matching the 23 original CPs (mostly Caucasian from NYC) with 23 CPs from NJ. Since differences were seen, we rematched our original JPs from NYC with a new set of race-matched CPs from NYC (Phase III). Finally, 13 JP patients from the University of Medicine and Dentistry of New Jersey (UMDNJ) were matched with CPs from NJ (Phase IV). RESULTS: Phase I and III indicated that JP patients had significantly less proximal caries than their matched CPs (P < or =0.05). Phase II confirmed the role of fluoride in caries reduction. Phase IV (NJ sample) supported our previous data and suggested that JP patients had less proximal caries than CPs (P < or =0.05). CONCLUSIONS: JP patients had significantly less proximal caries than their matched CPs when groups were balanced and radiographic evaluations were performed. In-depth studies of JP patients could provide important clues about both caries and periodontal disease etiology and pathogenesis.

A model for clinical evaluation of anti-microbial effects of agents on plaque colonization.

PURPOSE: To evaluate a new improved method of microbial analysis in a cross-over clinical study by investigating the efficacy of a single application of an essential oil-containing (EOC) dentifrice as compared to its vehicle control (VC) over a 6-hr period. MATERIALS AND METHODS: Acrylic stents with retention areas for 7, 3 mm x 3 mm hydroxyapatite (HA) squares were fabricated for 12 subjects. 30 min following stent placement, one HA square was removed and sampled for viable microflora. After stent replacement, subjects were assigned either the EOC dentifrice or its VC and brushed under supervision for 1 min. Stents remained in place for the next 6 hrs. A HA square was removed at hourly intervals for 6 hrs following brushing. The microflora was analyzed for total anaerobes on Schaedler's media, for total gram-negative anaerobes on Schaedler-NV selective media, and for total Fusobacterium species on CVE selective media. Plates were incubated anaerobically at 37 degrees C for 2-5 days. Colony forming units were calculated. For each time point, pairwise t-tests were performed using the adjusted means and the pooled error term from the analysis of variance (ANOVA). RESULTS: Treatment with the EOC dentifrice resulted in a statistically reduced plaque growth. Differences were seen as reductions in: (1) total gram-negative anaerobes seen from 1-6 hrs (P < or = 0.011), (2) total anaerobic bacteria which achieved significance at 3 hrs and continued through 6 hrs (P < or = 0.005), and (3) Fusobacterium species as seen from 4-6 hrs (P < or = 0.002).

Effect of sucralose in coffee on plaque pH in human subjects.

Our earlier work demonstrated that the sweetener sucralose, C12 H19 CI3 O8, mixed with water had no effect on intraoral plaque pH. The current study compared the effect on resting plaque pH of sucralose to sucrose when these sweeteners were used in hot coffee at equivalent sweetness levels. Twelve subjects with an identified acidogenic plaque were tested at dicrete sessions, using coffee as vehicle with: (1) sucrose; (2) sucralose; (3) sucralose plus maltodextrin (SM); (4) sucralose plus dextrose and maltodextrin (SMD), and (5) no additional sweetener. Each subject rinsed for 1 min with the test rinse, expectorated, and plaque pH was measured at six dental sites for 60 min using an antimony touch electrode method. Data were summarized for baseline pH, delta pH (baseline pH minus lowest pH attained), minimum pH, and area under the pH curve (AUC). Baseline pH was not different throughout all tests. Quantification of AUC in the various groups showed that sucralose with coffee had no statistically significant impact on plaque acidogenesis. AUC, minimum pH and delta pH were least changed by coffee and sucralose, while the SM and SMD combinations generally led to intermediate changes as compared with coffee sweetened with sucrose or sucralose. Because of its acidic nature, unsweetened coffee led to a modest pH depression, the effect of which appears to be blunted by sucralose. This study confirms that sucralose is non-acidogenic and indicates that sucralose may reduce the acidogenic potential of coffee.

Effect of aqueous solutions of sucralose on plaque pH.

PURPOSE: To compare the effect on in vivo plaque pH of rinsing with an aqueous solution of sucralose (alone or in combination with maltodextrin or maltodextrin and dextrose) to the effect of rinsing with an aqueous solution of sucrose. MATERIALS AND METHODS: Each solution (four in total) had a sweetness equivalent to two teaspoons of sucrose in 6 oz. of water. The four test solutions were administered randomly over four test visits (one solution per visit) to 10 subjects presenting 2-day resting plaque. Before, and at specified time intervals over 60 minutes following the rinse, in vivo plaque pH was monitored at six designated sites using a Beckman 3500 digital pH meter. Data were analyzed by ANOVA. RESULTS: The mean pH minimum for the sucralose rinse (6.56) was significantly higher than the sucralose/maltodextrin (SM), sucralose/maltodextrin/dextrose (SMD), and sucrose rinses (6.15, 5.84, and 5.29, respectively). The mean delta pH (difference between resting and minimum pH) for the sucralose rinse (0.45) was significantly lower when compared to the SM (0.79), SMD (1.14), and sucrose (1.69) rinses. The differences seen in mean pH minimum and mean delta pH for the SM and SMD groups vs. the sucrose group were also statistically significant. Mean areas under the pH vs. time curve for the sucralose, SM and SMD rinses were all significantly less compared to the sucrose rinse. Rinsing with aqueous solutions of sucralose, or of sucralose in combination with maltodextrin and/or dextrose (commercially available formulations, of sucralose) was less acidogenic than rinsing with a sucrose solution of equivalent sweetness.

Remineralizing potential, antiplaque and antigingivitis effects of xylitol and sorbitol sweetened chewing gum.

The objective of this study was to investigate the effects of xylitol and sorbitol sweetened chewing gums on plaque accumulation, gingival inflammation and remineralizing potential of plaque following six weeks of use. Twenty-eight consenting individuals were randomly assigned to each of three phases (six weeks in duration) consisting of chewing xylitol gum, chewing sorbitol gum and a non-chewing phase. Subjects chewed one stick after every meal and at two other times for a total of five sticks per day. At the completion of each treatment phase, plaque and gingival indexes were performed and plaque was later collected. Calcium concentration in plaque was determined by atomic absorption spectophotometry. Reductions in plaque indexes were significant for both xylitol gum (p < 0.001) and sorbitol gum (p < 0.05) when compared to the no chewing period. The gingival indexes reflected a decrement in gingival inflammation with both xylitol and sorbitol, though only sorbitol values were statistically significant (p < 0.05). Chewing xylitol and sorbitol gums reduced plaque accumulation and gingival inflammation. In addition, both gums enhanced the remineralization potential of plaque. Xylitol gum showed a superior effect with respect to remineralization potential and plaque reduction. Sorbitol gum had a superior effect on gingival health but not significantly so.

Multiparameter flow cytometric analysis of human fetal bone marrow B cells.

Maturation of adult human bone marrow (BM) B cells is accompanied by the sequential acquisition and loss of characteristic cell surface antigens (Loken et al., Blood 70:1316). Little is known about these changes in fetal BM B cells. In order to compare fetal with adult B cell development, we performed three-color, flow cytometric analyses of cell surface antigens, as well as nuclear TdT staining, on lymphoid cells from fetal BM. Mononuclear cells isolated from fetal BM (18-22 weeks) were stained with combinations of antibodies against CD3, CD10, CD19, CD20, CD21, CD22, CD34, CD45, PCA-1, IgM, and HLA-DR. Analysis of six separate fetal BM specimens indicated that combinations of cell surface antigens were expressed on analogous populations in fetal and adult BM. Consistent with adult BM, greater than 95% of TdT+ cells within the CD10+ population were CD34+, whereas less than 5% were CD34-. This CD10+/CD34+/TdT+ population constituted 30-40% of the total B cell compartment, compared with 10% in adults. Quantitative changes in CD45 expression on fetal BM B cells defined three clear populations, as has been observed in adults. In striking contrast to adult BM, greater than 95% of CD19+ and greater than 95% of surface IgM+ cells were CD10+, indicating that CD10 is a pan-B cell antigen in fetal BM. Virtually no mature B cells expressing CD21, CD22, or PCA-1 were detected in fetal BM. Our results indicate a preponderance of immature phenotypes exist in the fetal BM B cell compartment. These immature cells can be grouped into three distinct populations, and probably correspond to expanded populations found less frequently in adult BM. This striking increase in the earliest identifiable stages of B cell ontogeny is consistent with an active expansion of cells destined to constitute the humoral immune system during fetal development.