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C M Santegoeds

Publications and source records attributed to C M Santegoeds.

6 recordsLinked to original sources
PubMed1999

Distribution of sulfate-reducing and methanogenic bacteria in anaerobic aggregates determined by microsensor and molecular analyses.

Using molecular techniques and microsensors for H(2)S and CH(4), we studied the population structure of and the activity distribution in anaerobic aggregates. The aggregates originated from three different types of reactors: a methanogenic reactor, a methanogenic-sulfidogenic reactor, and a sulfidogenic reactor. Microsensor measurements in methanogenic-sulfidogenic aggregates revealed that the activity of sulfate-reducing bacteria (2 to 3 mmol of S(2-) m(-3) s(-1) or 2 x 10(-9) mmol s(-1) per aggregate) was located in a surface layer of 50 to 100 microm thick. The sulfidogenic aggregates contained a wider sulfate-reducing zone (the first 200 to 300 microm from the aggregate surface) with a higher activity (1 to 6 mmol of S(2-) m(-3) s(-1) or 7 x 10(-9) mol s(-1) per aggregate). The methanogenic aggregates did not show significant sulfate-reducing activity. Methanogenic activity in the methanogenic-sulfidogenic aggregates (1 to 2 mmol of CH(4) m(-3) s(-1) or 10(-9) mmol s(-1) per aggregate) and the methanogenic aggregates (2 to 4 mmol of CH(4) m(-3) s(-1) or 5 x 10(-9) mmol s(-1) per aggregate) was located more inward, starting at ca. 100 microm from the aggregate surface. The methanogenic activity was not affected by 10 mM sulfate during a 1-day incubation. The sulfidogenic and methanogenic activities were independent of the type of electron donor (acetate, propionate, ethanol, or H(2)), but the substrates were metabolized in different zones. The localization of the populations corresponded to the microsensor data. A distinct layered structure was found in the methanogenic-sulfidogenic aggregates, with sulfate-reducing bacteria in the outer 50 to 100 microm, methanogens in the inner part, and Eubacteria spp. (partly syntrophic bacteria) filling the gap between sulfate-reducing and methanogenic bacteria. In methanogenic aggregates, few sulfate-reducing bacteria were detected, while methanogens were found in the core. In the sulfidogenic aggregates, sulfate-reducing bacteria were present in the outer 300 microm, and methanogens were distributed over the inner part in clusters with syntrophic bacteria.

Bacteria, Anaerobic↗
PubMed1999

On the occurrence of anoxic microniches, denitrification, and sulfate reduction in aerated activated sludge.

A combination of different methods was applied to investigate the occurrence of anaerobic processes in aerated activated sludge. Microsensor measurements (O(2), NO(2)(-), NO(3)(-), and H(2)S) were performed on single sludge flocs to detect anoxic niches, nitrate reduction, or sulfate reduction on a microscale. Incubations of activated sludge with (15)NO(3)(-) and (35)SO(4)(2-) were used to determine denitrification and sulfate reduction rates on a batch scale. In four of six investigated sludges, no anoxic zones developed during aeration, and consequently denitrification rates were very low. However, in two sludges anoxia in flocs coincided with significant denitrification rates. Sulfate reduction could not be detected in any sludge in either the microsensor or the batch investigation, not even under short-term anoxic conditions. In contrast, the presence of sulfate-reducing bacteria was shown by fluorescence in situ hybridization with 16S rRNA-targeted oligonucleotide probes and by PCR-based detection of genes coding for the dissimilatory sulfite reductase. A possible explanation for the absence of anoxia even in most of the larger flocs might be that oxygen transport is not only diffusional but enhanced by advection, i.e., facilitated by flow through pores and channels. This possibility is suggested by the irregularity of some oxygen profiles and by confocal laser scanning microscopy of the three-dimensional floc structures, which showed that flocs from the two sludges in which anoxic zones were found were apparently denser than flocs from the other sludges.

Anaerobiosis↗
PubMed1997

Biodiversity within hot spring microbial mat communities: molecular monitoring of enrichment cultures.

We have begun to examine the basis for incongruence between hot spring microbial mat populations detected by cultivation or by 16S rRNA methods. We used denaturing gradient gel electrophoresis (DGGE) to monitor enrichments and isolates plated therefrom. At near extincting inoculum dilutions we observed Chloroflexus-like and cyanobacterial populations whose 16S rRNA sequences have been detected in the 'New Pit' Spring Chloroflexus mat and the Octopus Spring cyanobacterial mat. Cyanobacterial populations enriched from 44 to 54 degrees C and 56 to 63 degrees C samples at near habitat temperatures were similar to those previously detected in mat samples of comparable temperatures. However, a lower temperature enrichment from the higher temperature sample selected for the populations found in the lower temperature sample. Three Thermus populations detected by both DGGE and isolation exemplify even more how enrichment may bias our view of community structure. The most abundant population was adapted to the habitat temperature (50 degrees C), while populations adapted to 65 degrees C and 70 degrees C were 10(2)- and 10(4)-fold less abundant, respectively. However, enrichment at 70 degrees C favored the least abundant strain. Inoculum dilution and incubation at the habitat temperature favored the more numerically relevant populations. We enriched many other aerobic chemoorganotrophic populations at various inoculum dilutions and substrate concentrations, most of whose 16S rRNA sequences have not been detected in mats. A common feature of numerically relevant cyanobacterial, Chloroflexus-like and aerobic chemorganotrophic populations, is that they grow poorly and resist cultivation on solidified medium, suggesting plating bias, and that the medium composition and incubation conditions may not reflect the natural microenvironments these populations inhabit.

Bacteria, Aerobic↗
PubMed1997

A nitrite microsensor for profiling environmental biofilms.

A highly selective liquid membrane nitrite microsensor based on the hydrophobic ion-carrier aquocyanocobalt(III)-hepta(2-phenylethyl)-cobrynate is described. The sensor has a tip diameter of 10 to 15 (mu)m. The response is log-linear in freshwater down to 1 (mu)M NO(inf2)(sup-) and in seawater to 10 (mu)M NO(inf2)(sup-). A method is described for preparation of relatively large polyvinyl chloride (PVC)-gelled liquid membrane microsensors with a tip diameter of 5 to 15 (mu)m, having a hydrophilic coating on the tip. The coating and increased tip diameter resulted in more sturdy sensors, with a lower detection limit and a more stable signal than uncoated nitrite sensors with a tip diameter of 1 to 3 (mu)m. The coating protects the sensor membrane from detrimental direct contact with biomass and can be used for all PVC-gelled liquid membrane sensors meant for profiling microbial mats, biofilms, and sediments. Thanks to these improvements, liquid membrane sensors can now be used in complex environmental samples and in situ, e.g., in operating bioreactors. Examples of measurements in denitrifying, nitrifying, and nitrifying/denitrifying biofilms from wastewater treatment plants are shown. In all of these biofilms high nitrite concentrations were found in narrow zones of less than 1 mm.

Journal Article↗
PubMed1996

Denaturing gradient gel electrophoresis used to monitor the enrichment culture of aerobic chemoorganotrophic bacteria from a hot spring cyanobacterial mat.

Previous studies investigating microbial diversity in the Octopus Spring cyanobacterial mat community (Yellowstone National Park) have shown a discrepancy between bacterial populations observed by molecular retrieval and cultivation techniques. To investigate how selective enrichment culture techniques affect species composition, we used denaturing gradient gel electrophoresis (DGGE) separation of PCR-amplified 16S rRNA gene fragments to monitor the populations contained within enrichment cultures of aerobic chemoorganotrophic bacteria from the ca. 50 degrees C region of the mat community. By varying the degree of dilution of the inoculum, medium composition, and enrichment conditions and duration and by analyzing the cultures by DGGE, we detected 14 unique 16S rRNA sequence types. These corresponded to alpha-, beta-, gamma-, and delta-proteobacteria, Thermus relatives, and gram-positive bacteria with high G + C ratio and, at the highest inoculum dilutions, Chloroflexus aurantiacus relatives, which were estimated to still be approximately 300 times less abundant than cells of the mat primary producer, Synechococcus spp. Only three of these populations were previously cultivated on solidified medium after similar enrichment. Only two of these population have 16S rRNA sequences which were previously cloned directly from the mat. These results reveal a diversity of bacterial populations in enrichment culture which were not detected by either molecular retrieval or strain purification techniques.

Bacteria, Aerobic↗