Microbial communities associated with anaerobic benzene degradation in a petroleum-contaminated aquifer.

Microbial community composition associated with benzene oxidation under in situ Fe(III)-reducing conditions in a petroleum-contaminated aquifer located in Bemidji, Minn., was investigated. Community structure associated with benzene degradation was compared to sediment communities that did not anaerobically oxidize benzene which were obtained from two adjacent Fe(III)-reducing sites and from methanogenic and uncontaminated zones. Denaturing gradient gel electrophoresis of 16S rDNA sequences amplified with bacterial or Geobacteraceae-specific primers indicated significant differences in the composition of the microbial communities at the different sites. Most notable was a selective enrichment of microorganisms in the Geobacter cluster seen in the benzene-degrading sediments. This finding was in accordance with phospholipid fatty acid analysis and most-probable-number-PCR enumeration, which indicated that members of the family Geobacteraceae were more numerous in these sediments. A benzene-oxidizing Fe(III)-reducing enrichment culture was established from benzene-degrading sediments and contained an organism closely related to the uncultivated Geobacter spp. This genus contains the only known organisms that can oxidize aromatic compounds with the reduction of Fe(III). Sequences closely related to the Fe(III) reducer Geothrix fermentans and the aerobe Variovorax paradoxus were also amplified from the benzene-degrading enrichment and were present in the benzene-degrading sediments. However, neither G. fermentans nor V. paradoxus is known to oxidize aromatic compounds with the reduction of Fe(III), and there was no apparent enrichment of these organisms in the benzene-degrading sediments. These results suggest that Geobacter spp. play an important role in the anaerobic oxidation of benzene in the Bemidji aquifer and that molecular community analysis may be a powerful tool for predicting a site's capacity for anaerobic benzene degradation.

Humics as an electron donor for anaerobic respiration.

The possibility that microorganisms might use reduced humic substances (humics) as an electron donor for the reduction of electron acceptors with a more positive redox potential was investigated. All of the Fe(III)- and humics-reducing microorganisms evaluated were capable of oxidizing reduced humics and/or the reduced humics analogue anthrahydroquinone-2,6,-disulphonate (AHODS), with nitrate and/or fumarate as the electron acceptor. These included Geobacter metallireducens, Geobacter sulphurreducens, Geothrix fermentans, Shewanella alga, Wolinella succinogenes and 'S. barnesii'. Several of the humics-oxidizing microorganisms grew in medium with AHQDS as the sole electron donor and fumarate as the electron acceptor. Even though it does not reduce Fe(III) or humics, Paracoccus denitrificans could use AHQDS and reduced humics as electron donors for denitrification. However, another denitrifier, Pseudomonas denitrificans, could not. AHODS could also serve as an electron donor for selenate and arsenate reduction by W. succinogenes. Electron spin resonance studies demonstrated that humics oxidation was associated with the oxidation of hydroquinone moieties in the humics. Studies with G. metallireducens and W. succinogenes demonstrated that the anthraquinone-2,6-disulphonate (AQDS)/AHQDS redox couple mediated an interspecies electron transfer between the two organisms. These results suggest that, as microbially reduced humics enter less reduced zones of soils and sediments, the reduced humics may serve as electron donors for microbial reduction of several environmentally significant electron acceptors.

Theta waves and behavioral manifestations of alertness and dreaming activity in the rat.

Electro-oscillographic recordings show that when rats wake up, behavioral manifestations such as head dorsal extension and snout and eye movements (which occur in this sequence), occasionally followed by brief ear and limb twitches, are preceded by and are simultaneous with theta waves (around 6.5 Hz in frequency) in neocortical areas 3 and 17 and in the hippocampus. Heart rate increases when the animal passes from synchronized sleep to relaxed wakefulness to exploratory behavior. During desynchronized sleep theta waves, similar to those found during alertness, usually precede and are simultaneous with rostrum and eye movements and brief ear and limb twitches. Heart rate also increases during dreaming activity. A high degree of coherence (near 1.0) was found among theta bursts in different hippocampal areas in both highly attentive alertness and dreaming. It is suggested that theta waves are related to attention as part of some kinds of behavior and of the process of dream shaping and expression, both characterized by consciousness.

Theta waves and behavioral manifestations of alertness and dre4aming activity in the rat

Electro-oscillographic recordings show that when up, behavioral manifestations such as head dorsal extension and snout and eye movements (which occur in this sequence) occasionally followed by brief ear areas 3 and 17 and in the hippocampus. Heart rate increases when the animal passes from synchronized sleep to relaxed wakefulness to exploratory behavior. During desynchronized sleep theta waves, similar to those found during alertness, usually precede and are simultaneous with rostrum and eye movements and brief ear and limb twitches. Heart rate also increases during dreaming activity. A high degree of coherence (near 1.0) was found among theta bursts in different hippocampal areas in both highly attentive alertness and dreaming. It is suggested that theta waves are related to attention as part of some kinds of behavior and of the process of dream shaping and expression, both characterized by consciousness

Electrical activity of the posterior thalamic nucleus and the hippocampus during wakefulness and desynchronized sleep in the rat: a spectral analysis.

The electrical activity of the posterior thalamic nuclear complex was studied in rats and related to the simultaneous hippocampal electro-oscillogram. Electrocorticographic tracings and spectral analysis showed that during attentive wakefulness the electro-oscillogram peaked at 8 Hz and in desynchronized sleep it oscillated at regular frequencies between 8 and 9 Hz. In quiet wakefulness, frequency was lower (around 6 Hz) and during synchronized sleep rhythmicity disappeared. The electrophysiological patterns during wakefulness and desynchronized sleep are proposed to be linked to the retrieval and combination of information for the generation of attention and dream content.

Stationarity and normality of distribution of rat cortical brain waves.

Establishing the stationarity and statistical distribution of potentials recorded from the nervous system is crucial for the application of frequency analysis. Both parameters were determined in the electrocorticograms of six adult Wistar rats during wakefulness and desynchronized sleep, during both of which desynchronization prevails. Stationarity of the signals was found to occur during at least 20 s in both states of the wakefulness-sleep cycle. A normal distribution was also found for at least 6.7 s. These findings provide strong support for the use of frequency analysis of brain waves as a reliable method to quantify neural electro-oscillograms.

Electrical activity of the posterior thalamic nucleus and the hippocampus during wakefulness and desynchronized sleep in the rat: a spectral analysis

The electrical activity of the posterior thalamic nuclear complex was studied in rats and related to the simultaneous hippocampal electro-oscillogram. Electrocorticographic tracings and spectral analysis showed that during attentive wakefulness the electro-oscillogram peaked at 8 Hz and in desynchronized sleep it oscillated at regular frequencies between 8 and 9 Hz. In quiet wakefulness, frequency was lower (around 5 Hz) and during synchronized sleep rhytmicity disppeared. The electrophysiological patterns during wakefulness and desynchronized sleep are proposed to be linked to the retrieeval and combination of information for the generation of attention and dream content

Stationarity and normality of distribution of rat cortical brain waves

Establishing the stationarity and statistical distribution of potentials recorded from the nervous system is cricial for the application of frequency analysis. Both parameters were determined in the electrocorticograms of six adult Wistar rats during wakefulness and desynchronized sleep, during both of which desinchronization prevails. Stationarity of the signals was found to occur during at least 20 s in both states of the wakefulness-sleep cycle. A normal distribution was also found for at least 6.7 s. These findings provide strong support for the use of frequency analysis of brain waves as a reliable method to quantify neural electro-oscillograms