Biomedical subjects

F L de los Reyes

Publications and source records attributed to F L de los Reyes.

6 recordsLinked to original sources

PubMed2006

Microbial community structure of activated sludge during aerobic granulation in an annular gap bioreactor.

A novel annular gap reactor was designed to create a controlled shear environment in which aerobic granular sludge could be developed. The bacterial and eukaryal community structures during two aerobic granular sludge experiments were tracked using denaturing gradient gel electrophoresis (DGGE). The first granule cultivation experiment, using an organic loading rate of 1.6 kg/m3d COD, resulted in biomass that was dominated by filamentous bacteria and Zoogloea ramigera colonies. A second experiment with a higher organic loading rate of 6 kg/m3d COD developed a granule-like morphology but was ultimately dominated by filamentous fungi. Species identification via DGGE band purification and DNA sequencing closely matched the observed sludge morphology and behavior.

Aerobiosis↗

PubMed2005

Changes in the rRNA levels of specific microbial groups in activated sludge during sample handling and storage.

AIMS: To quantitatively analyse the changes in group-specific rRNA levels in activated sludge as a function of sample handling and storage procedure. METHODS AND RESULTS: Quantitative membrane hybridizations with (32)P-labelled oligonucleotide probes were used to analyse the effects of different sample handling and storage conditions on the relative rRNA levels of the alpha, beta, and gamma-Proteobacteria, the Cytophaga-Flavobacteria group, and the mycolic acid-containing actinomycetes in activated sludge. Group-specific rRNA levels, expressed as percentages of total 16S rRNA detected with a universal probe, in samples maintained at room temperature significantly changed after 48 h. Group-specific rRNA levels in samples treated with chloramphenicol showed significant change after 72 h. CONCLUSIONS: Sample storage at room temperature is a viable option if freezing or analysis can be performed within 24 h, while treatment with chlorampenicol can extend that time to at least 48 h. SIGNIFICANCE AND IMPACT OF THE STUDY: Handling, shipping, and storage of environmental samples under several conditions may result in inaccurate determination of the microbial populations in microbial ecology studies.

Actinobacteria↗

PubMed2002

Optimization of activated sludge designs using genetic algorithms.

We describe a framework in which a genetic algorithm (GA) and a static activated sludge (AS) treatment plant design model (WRC AS model) are used to identify low cost activated sludge designs that meet specified effluent limits (e.g. for BOD, N, and P). Once the user has chosen a particular process (Bardenpho, Biodenipho, UCT or SBR), this approach allows the parameterizations for each AS unit process to be optimized systematically and simultaneously. The approach is demonstrated for a wastewater treatment plant design problem and the GA-based performance is compared to that of a classical nonlinear optimization approach. The use of GAs for multiobjective problems such as AS design is demonstrated and their application for reliability-based design and alternative generation is discussed.

Algorithms↗

PubMed2001

Quantifying filamentous microorganisms in activated sludge before, during, and after an incident of foaming by oligonucleotide probe hybridizations and antibody staining.

Quantitative oligonucleotide probe hybridizations, immunostaining, and a simple foaming potential test were used to follow an incident of seasonal filamentous foaming at the Urbana-Champaign Sanitary District, Northeast Wastewater Treatment Plant. A positive correlation was observed between an increase in foaming potential and the appearance of foam on the surfaces of aeration basins and secondary clarifiers. In addition, during the occurrence of foaming, the mass and activity of Gordonia spp. increased as measured by fluorescence in situ hybridization, antibody staining, and quantitative membrane hybridization of RNA extracts. An increase in Gordonia spp. rRNA levels from 0.25 to 1.4% of total rRNA was observed using quantitative membrane hybridizations, whereas during the same period, the fraction of mixed liquor volatile suspended solids attributed to Gordonia spp. increased from 4% to more than 32% of the total mixed liquor volatile suspended solids. These results indicate that both the activity and biomass level of Gordonia spp. in activated sludge increased relative to the activity aid the biomass level of the complete microbial community during a seasonal occurrence of filamentous foaming. Thus, Gordonia spp. may represent a numerically dominant but metabolically limited fraction of the total biomass, and the role of Gordonia spp. in filamentous foaming may be linked more tightly to the physical presence of filamentous microorganisms than to the metabolic activity of the cells.

Actinomycetales↗

PubMed1998

Quantification of Gordona amarae strains in foaming activated sludge and anaerobic digester systems with oligonucleotide hybridization probes.

Previous studies have shown the predominance of mycolic acid-containing filamentous actinomycetes (mycolata) in foam layers in activated sludge systems. Gordona (formerly Nocardia) amarae often is considered the major representative of this group in activated sludge foam. In this study, small-subunit rRNA genes of four G. amarae strains were sequenced, and the resulting sequences were compared to the sequence of G. amarae type strain SE-6. Comparative sequence analysis showed that the five strains used represent two lines of evolutionary descent; group 1 consists of strains NM23 and ASAC1, and group 2 contains strains SE-6, SE-102, and ASF3. The following three oligonucleotide probes were designed: a species-specific probe for G. amarae, a probe specific for group 1, and a probe targeting group 2. The probes were characterized by dissociation temperature and specificity studies, and the species-specific probe was evaluated for use in fluorescent in situ hybridizations. By using the group-specific probes, it was possible to place additional G. amarae isolates in their respective groups. The probes were used along with previously designed probes in membrane hybridizations to determine the abundance of G. amarae, group 1, group 2, bacterial, mycolata, and Gordona rRNAs in samples obtained from foaming activated sludge systems in California, Illinois, and Wisconsin. The target groups were present in significantly greater concentrations in activated sludge foam than in mixed liquor and persisted in anaerobic digesters. Hybridization results indicated that the presence of certain G. amarae strains may be regional or treatment plant specific and that previously uncharacterized G. amarae strains may be present in some systems.

Anaerobiosis↗

PubMed1997

Group-specific small-subunit rRNA hybridization probes to characterize filamentous foaming in activated sludge systems.

Foaming in activated sludge systems is characterized by the formation of a thick, chocolate brown-colored scum that floats on the surface of aeration basins and secondary clarifiers. These viscous foams have been associated with the presence of filamentous mycolic acid-containing actinomycetes. To aid in evaluating the microbial representation in foam, we developed and characterized group-, genus-, and species-specific oligonucleotide probes targeting the small subunit rRNA of the Mycobacterium complex, Gordona spp., and Gordona (Nocardia) amarae, respectively. The use of a universal base analog, 5-nitroindole, in oligonucleotide probe design was evaluated by comparing the characteristics of two different versions of the Mycobacterium complex probe. The temperature of dissociation of each probe was determined. Probe specificity studies with a diverse collection of 67 target and nontarget rRNAs demonstrated the specificity of the probes to the target groups. Whole-cell hybridizations with fluorescein- and rhodamine-labeled probes were performed with pure cultures of various members of the Mycobacterium complex as well as with environmental samples from a full-scale activated sludge plant which experienced foaming. Quantitative membrane hybridizations with activated sludge and anaerobic digester foam showed that 15.0 to 18.3% of the total small-subunit rRNAs could be attributed to members of the Mycobacterium complex, of which a vast majority consisted of Gordona rRNA. Several G. amarae strains made up only a very small percentage of the Gordona strains present. We demonstrated that group-specific rRNA probes are useful tools for the in situ monitoring and identification of filamentous bacteria in activated sludge systems.

Corynebacterium↗