Orientador: Guilherme de Siqueira Ferreira Anzaloni Saavedra / Coorientadora: Anelyse Arata / Banca: Dolores Ribeiro Ricci Lazar / Banca: João Paulo Barros Machado / Banca: Renata Marques de Melo Marinho / Banca: Estevão Tomomitsu Kimpara / Resumo: Neste estudo avaliou-se por caracterização mecânica e microestrutural, a degradação em meio bucal e in vitro da cerâmica Y-TZP sinterizada por energia de micro-ondas em comparação ao método convencional. Foram confeccionados noventa e seis discos por CAD-CAM (ISO 6872), sinterizados de modo convencional (C) 1530°C/120 minutos e por energia de micro-ondas (M) 1450°C/15 minutos. E submetidos à degradação hidrotérmica em reator pressurizado (E) (1,5h/150°C/3 bar) e à degradação in situ (B) (240 horas em meio bucal), formando-se 8 grupos (n = 12): M, C, ME, CE, MB, CB, MEB e CEB. Foram realizadas análises de contração volumétrica, difração de raios-X (DRX), rugosidade superficial (Ra e Rz), ângulo de contato, microscopia eletrônica de varredura (MEV), quantificação do biofilme por UFC/mL e análise de resistência mecânica por flexão biaxial. Os resultados obtidos foram analisados estatisticamente por t-Student, Anova dois e três fatores, e teste de Tukey (5%). Por DRX observou-se transformação de fase tetragonal para monoclínica (t-m) nos grupos envelhecidos, exceto para o grupo MB. Não foram observadas diferenças significantes na contração volumétrica (p=0,274), na rugosidade Ra (p=0,137) e Rz (p=0,187), assim como nos valores de ângulo de contato entre os métodos de sinterização (p=0,669). Por MEV observou-se a presença de formação de biofilme inicial e na contagem de Unidades Formadoras de Colônias (UFC/mL) foi maior quando os espécimes foram previamente envelhecidos in vitro (... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this study ir was evaluated the effect of in situ low temperature degradation of yttrium oxide stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics sintered by microwave energy in comparison to the conventional method. Ninety-six discs milled by CAD/CAM (ISO 6872) were divided in: conventionally sintered (C) at 1530 ° C / 120 minutes and microwave energy (M) 1450°C / 15 minutes. Specimens were submitted to hydrothermal degradation in a pressurized reactor (E) (1.5h / 150°C / 3 bar) and in situ degradation (B) (240 hours in the buccal medium), forming eight groups (n=12): M, C, ME, CE, MB, CB, MEB and CEB. Specimens were evaluated through analysis of volumetric contraction, X-ray diffraction (XRD), surface roughness (Ra and Rz), contact angle, scanning electron microscopy (SEM), biofilm quantification by CFU / mL and biaxial flexural strength. Results were statistically analyzed through t-Student, two, three-way Anova and Tukey tests (5%). By XRD, tetragonal to monoclinic phase transformation (t-m) was observed in the aged groups, except for the MB group. No significant differences were observed in the volumetric contraction (p = 0.274), Ra roughness (p = 0.137) and Rz (p = 0.187), as well as contact angle values between sintering methods (p = 0.669). SEM images showed that the initial biofilm formation was observed after 8 hours in situ, an increase of CFU / mL occurred when the specimens were previously aged in vitro (p = 0.001). Regarding biaxial flexural strength... (Complete abstract click electronic access below) / Doutor

Many illnesses and infections are exacerbated and/or caused by biofilms. Neisseria gonorrhoeae, the etiologic agent of gonorrhea, is frequently asymptomatic in women, which can lead to persistent infection. Persistent infection can result in pelvic inflammatory disease, tubo-ovarian abscesses, infertility, and ectopic pregnancy. N. gonorrhoeae has been shown to form biofilms over glass, primary and immortalized cervical cells, and during natural cervical infection. Asymptomatic infection occurs in only 1% of infected males, and the infection site is subject to periodic rapid fluid flow, which may limit biofilm formation. Thus, biofilm formation may specifically play an important role in the infection of women and could contribute to the infrequent occurrence of symptoms. Prior to work presented in this dissertation, little was known about biofilm formation by N. gonorrhoeae. Therefore, we elected to compare the transcriptional profiles of biofilms to their planktonic counterparts, to identify genetic pathways involved in biofilm formation and maintenance. We found that 3.8% of the genome was differentially regulated, and that genes involved in anaerobic metabolism and oxidative stress tolerance were up-regulated in biofilm, while genes involved in aerobic metabolism were down-regulated. We determined that expression of aniA , ccp, and norB is required for robust biofilm formation over glass and human cervical cells, and anaerobic respiration occurs in the substratum of gonococcal biofilms. Disruption of the norB gene resulted in severe attenuation of biofilm formation. We determined that the accumulation of nitric oxide (NO) contributes to the phenotype of a norB mutant and can retard biofilm formation when present at sublethal concentrations. However, higher concentrations of NO can enhance biofilm formation in the absence of nitrite. NO enhances biofilm formation in an aniA mutant, but cannot completely restore biofilm formation, suggesting that NO can support anaerobic growth, although nitrite is preferred. We determined that the majority of the genes involved in gonococcal oxidative stress tolerance are required for normal biofilm formation, as mutations in the following genes resulted in biofilm attenuation over cervical cells and/or glass: oxyR, gor, prx, mntABC, trxB, and estD. Overall, biofilm formation may represent an adaptation for coping with the stresses present in the female genitourinary tract.

Safe drinking water is paramount to a healthy society. Close to a hundred contaminants are regulated by the government. Utilities are using chloramines to disinfect water to reduce harmful byproducts that may present themselves with the use of chlorine alone. Using chlorine and ammonia to disinfect, ammonia oxidizing bacteria can present themselves in an unsuspecting utilities distribution network. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Periodontitis is an inflammatory disease of the oral cavity induced by anaerobic bacteria, that remains to be the primary cause of tooth loss in adults worldwide. Finding an anti-microbial therapeutic to selectively target periodontal pathogens has proven to be difficult, and current treatment modalities only provide a transient benefit. Amixicile is a non-toxic, readily bioavailable novel antimicrobial that targets strict anaerobes through inhibition of the activity of Pyruvate Ferredoxin Oxidoreductase (PFOR), a major enzyme mediating oxidative decarboxylation of pyruvate, a critical step in metabolism. Our study aimed to evaluate the efficacy of amixicile in inhibiting the growth of bacteria harvested from the complex sub-gingival biofilm of patients with chronic periodontitis. We hypothesize that amixicile will selectively inhibit pathogenic anaerobic bacteria collected from patients, with the same efficacy as metronidazole, the current accepted treatment modality. Plaque samples were harvested from patients with severe chronic periodontitis and cultured under anaerobic conditions. The microbiomes were grown in the presence of amixicile and metronidazole and the growth was compared to that of bacteria grown in the absence of the antimicrobials. Following 24 hour incubation, bacterial DNA was isolated and bacterial quantity was evaluated by quantitative PCR (qPCR) using primers specific for 12 bacterial species: P. gingivalis (Pg), P. intermedia (Pi), F.nucleatum (Fn), S.gordonii (Sg), S. anginosus (Sa), V. atypical (Va), L. acidophilus (La), A.actinomycetemcomitans (Aa), T.denticola (Td), S.mutans (Sm), S.sanguis (Ss), and 16s. Individual qPCR runs were combined to represent an overall average of CT value differences. Amixicile treatment groups exhibited statistical significant reductions (PP. intermedia, F. nucleatum and Veillonella atypical. When comparing amixicile to metronidazole, amixicile performed with similar efficacy with the largest effect seen for PFOR bacteria. Our conclusion supports amixicile as a potent inhibitor of anaerobic bacteria, and could be a potential new therapeutic antimicrobial in the treatment of periodontal disease

Upon forming a biofilm, bacteria undergo several changes that prevent them from being eradicated with antimicrobials alone. These biofilms manifest as persistent infections and biofouling in the medical and industrial world, respectively, constituting an ongoing medical crisis and creating a huge financial burden. Biofilms on implanted medical devices cause thousands of patients each year to undergo multiple surgeries to explant and replace the implant, driving billions of dollars in increased health care costs due to the lack of viable treatment options for in situ biofilm eradication. Heat has been used to reliably eliminate biofilms for many years, but the temperatures employed are infeasible for many applications, particularly in vivo medical treatment. Remotely activated localized heat can be applied through a superparamagnetic iron oxide nanoparticle polymer coating when paired with an alternating magnetic field. However, there is very little known about the temperatures required to kill the biofilms and the effects of the heat in conjunction with antibiotics. To better understand the required parameters to effectively kill off bacteria in biofilms a variety of heat treatments were investigated for a variety of Pseudomonas aeruginosa biofilms grown in different conditions. Additionally, these heat treatments were combined with antibiotics to better understand any combined effects of the two orthogonal treatment plans. It was found that heat is an effective method for killing the bacteria in biofilms. Temperatures ranging from body temperature, 37 °C, to 80 °C were used to heat shock the biofilms for 1 to 30 minutes. Higher temperatures for short exposure times yielded similar results to lower temperatures for longer exposure time. Biofilms grown in different conditions did vary in their susceptibility to the heat shocks; however, at the higher temperatures the differences became negligible. Therefore, the more effective treatments were the higher temperature heat shocks with shorter exposure times to maximize bacterial cell death and minimize the potential heat transfer to the surrounding tissue. Regrowth studies indicate a critical post-shock bacterial loading (~103 CFU/cm2) below which the biofilms were no longer viable, while films above that loading slowly regrew to their previous population density. Combined treatments with antibiotics had synergistic effects for all antibiotics across a window of heat shock conditions. Erythromycin in particular, which showed no effect on the biofilm alone, decreased biofilm population by six orders of magnitude at temperatures which had no effect in the absence of antibiotics. These studies will evolve the understanding of biofilms and how to efficiently eradicate them on implant surfaces. The introduction of such a novel coating in conjunction with antibiotics could obviate thousands of surgeries and save billions of dollars spent on explantation, recovery, and re-implantation.

This study was carried out on algal biofilms grown using rotating algal biofilm reactors (RABRs) with the aim of: i) characterizing their growth in terms of photosynthetic activity and morphology ii) evaluating their performance as a wastewater treatment option and a feedstock for biofuels production, and iii) examining the algal-bacteria interactions. A review of algal biofilm technologies currently employed in wastewater treatment processes was made to compare nutrient removal efficiencies, factors that influenced algal biofilm growth, and the different bioproducts generated from algal biomass. Consequently, research efforts were directed towards addressing pertinent issues identified in literature in order to optimize these systems for wastewater treatment and bioproducts production. Successful growth of algal biofilms in municipal wastewater and subsequent removal of nutrients from the wastewater was demonstrated. Photosynthetic and respiration rates observed with depth of the biofilm were influenced by the biofilm composition (single vs. mixed species), culturing conditions (laboratory vs. outdoor), orientation to the light, nitrogen availability (N-replete vs. N-deplete), and dissolved inorganic carbon availability (presence or absence of bicarbonate). Slight enhancement in lipid production was also observed as a result of nitrogen stress and bicarbonate addition. However, the accumulated lipids were not as much as expected or as reported in suspended cultures. Presence of bacteria positively influenced microalgae growth in the mixed cultures but the reverse was not true. In conclusion, photosynthetic activity and biofilm structure were characterized with methods developed for the algal biofilms in this study. For now, productivity of the algal biofilms needs to be maximized in order to fully utilize its potential as a biofuel feedstock and nutrient removal option. Further research on algae-bacteria interactions using species native to the wastewater grown algal biofilms is recommended.

The emergent resistance of bacteria against the conventional antibiotics has motivated the search for novel antimicrobial agents. Nature abounds with a number of antimicrobial peptides that are a part of our innate immune system and protect us against a variety of pathogenic bacteria. While they are broad-spectrum in their activity and show less drug-resistance induction, their intrinsic metabolic stability limits their potential therapeutic applications. Herein we describe the development of novel broad-spectrum bioactive antimicrobial peptidomimetics AA-peptides. AApeptides were designed based on chiral PNA backbone. Substitution of nucleobases yields AApeptides that are resistant to proteolysis and capable of mimicking peptides. Two types of AApeptides are discussed in this dissertation "[aacute]-AApeptides" and " ã-AApeptides" The therapeutic potential of these AApeptides were accessed by conducting antibacterial assays against a series of both gram-positive, gram-negative bacteria and fungi. These oligomers were characterized using MALDI-TOF and Circular Dichroism spectroscopy (CD). Their invitro toxicity was evaluated against human erythrocytes .We attempted to study their mechanism of action via membrane depolarization assay. We have successfully identified them as antimicrobial agents, pro-inflammatory immune response suppressing agents and as anti-biofilm agents.

The marine bacterium Pseudoalteromonas tunicata produces target-specific inhibitory compounds against bacteria, algae, fungi and invertebrate larvae and is frequently found in association with living surfaces in the marine environment. This study examined the ability of P. tunicata to form biofilms under continuous culture conditions within the laboratory. P. tunicata biofilms exhibited a characteristic architecture consisting of differentiated microcolonies surrounded by water-channels. Interestingly, a repeatable pattern of cell death in the centre of microcolonies was observed. The antibacterial and autolytic protein, AlpP, produced by P. tunicata was found to be involved in this biofilm killing and a

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 5, 2007) Includes bibliographical references (p. 55-60).

Microaerophilic and chemotaxic diazotrophs, azospirilla are found in close association with certain cereals such as durum wheat and maize and are active in enriching these ecological niches with the macronutrient nitrogen as ammonia. Regarded as highly pleomorphic, Azospirillum spp. are highly motile, using either a single polar flagellum when grown in liquid environments or peritrichous lateral flagella in viscous environments. Additionally, azospirilla are able to adhere onto surfaces as a biological film or aggregate cell-to-cell as nonproliferating flocculi, and these two processes having been suggested as positively affecting the survival and dispersal of the bacteria in the soil. Even though both biofilm formation and flocculation have been characterized via the presence of bacterial extracellular polysaccharides, the nature of the observed exopolysaccharides is still obscure, as are the underlying molecular mechanisms facilitating their organization. Here, we identified the optimal conditions for biofilm formation as a high C:N ratio under conditions of low aeration. Cells showed an increased preference for hydrophobic plastic rather than hydrophilic glass when the bacteria were first grown in a rich medium, TY, then were subcultured in a minimal media under these conditions. Using transposon mutagenesis, we also identified metabolic and cell-surface functions perhaps involved in the flocculation potential of these bacteria and we present an initial characterization of their contribution to this cellular differentiation process.