Tools for Metagenomic Analysis at Wastewater Treatment Plants:Application to a Foaming Episode.

Metagenomic analysis is a powerful approach for wholesale characterizations of microbial populations like those that operate within municipal wastewater treatment plants. It is well known that many problems are associated with the overgrowth or undergrowth of specific bacterial genera. We describe a database of the combined metagenomes of activated sludge aeration basins from around the globe and use it as a reference to study the population of a foamy activated sludge aeration basin. We show that foam production is associated with blooms of mycolic acid producing genera, especially Mycobacterium. We confirm this bloom using the acid-fast stain, and we show that genes involved with mycolic acid production are enriched in the foam-producing sample. In addition, we show that this sample has unusual nitrifying populations. We suggest that low-cost DNA sequencing and publicly available tools for shotgun metagenomic analyses, including those described here, might broadly facilitate wastewater treatment plant operation.

Camera Trap Methods and Drone Thermal Surveillance Provide Reliable, Comparable Density Estimates of Large, Free-Ranging Ungulates.

Camera traps and drone surveys both leverage advancing technologies to study dynamic wildlife populations with little disturbance. Both techniques entail strengths and weaknesses, and common camera trap methods can be confounded by unrealistic assumptions and prerequisite conditions. We compared three methods to estimate the population density of white-tailed deer (Odocoileus virgnianus) in a section of Pilot Mountain State Park, NC, USA: (1) camera trapping using mark-resight ratios or (2) N-mixture modeling and (3) aerial thermal videography from a drone platform. All three methods yielded similar density estimates, suggesting that they converged on an accurate estimate. We also included environmental covariates in the N-mixture modeling to explore spatial habitat use, and we fit models for each season to understand temporal changes in population density. Deer occurred in greater densities on warmer, south-facing slopes in the autumn and winter and on cooler north-facing slopes and in areas with flatter terrain in the summer. Seasonal density estimates over two years suggested an annual cycle of higher densities in autumn and winter than in summer, indicating that the region may function as a refuge during the hunting season.

Visual signals bias auditory targets in azimuth and depth.

In the psychophysical phenomenon visual bias, an accurately localized irrelevant signal, such as a light, impairs localization of a spatially discrepant target, such as a sound, when the two stimuli are perceived as unified. Many studies have demonstrated visual bias in azimuth, but none have tested directly or found this effect in depth. The current study was able to produce over 90% bias in azimuth and somewhat less (83%) bias in depth. A maximum likelihood estimate can predict bias by the variance in the localization of each unimodal signal in each dimension in space.

Visual biasing of auditory localization in azimuth and depth.

Correctly integrating sensory information across different modalities is a vital task, yet there are illusions which cause the incorrect localization of multisensory stimuli. A common example of these phenomena is the "ventriloquism effect". In this illusion, the localization of auditory signals is biased by the presence of visual stimuli. For instance, when a light and sound are simultaneously presented, observers may erroneously locate the sound closer to the light than its actual position. While this phenomenon has been studied extensively in azimuth at a single depth, little is known about the interactions of stimuli at different depth planes. In the current experiment, virtual acoustics and stereo-image displays were used to test the integration of visual and auditory signals across azimuth and depth. The results suggest that greater variability in the localization of sounds in depth may lead to a greater bias from visual stimuli in depth than in azimuth. These results offer interesting implications for understanding multisensory integration.

Dissecting the role of TRPV1 in detecting multiple trigeminal irritants in three behavioral assays for sensory irritation.

Polymodal neurons of the trigeminal nerve innervate the nasal cavity, nasopharynx, oral cavity and cornea. Trigeminal nociceptive fibers express a diverse collection of receptors and are stimulated by a wide variety of chemicals. However, the mechanism of stimulation is known only for relatively few of these compounds. Capsaicin, for example, activates transient receptor potential vanilloid 1 (TRPV1) channels. In the present study, wildtype (C57Bl/6J) and TRPV1 knockout mice were tested in three behavioral assays for irritation to determine if TRPV1 is necessary to detect trigeminal irritants in addition to capsaicin. In one assay mice were presented with a chemical via a cotton swab and their response scored on a 5 level scale. In another assay, a modified two bottle preference test, which avoids the confound of mixing irritants with the animal's drinking water, was used to assess aversion. In the final assay, an air dilution olfactometer was used to administer volatile compounds to mice restrained in a double-chambered plethysmograph where respiratory reflexes were monitored. TRPV1 knockouts showed deficiencies in the detection of benzaldehyde, cyclohexanone and eugenol in at least one assay. However, cyclohexanone was the only substance tested that appears to act solely through TRPV1.

Chromatic shadow compatibility and cone-excitation ratios.

Logvinenko [Perception 31, 201 (2002)] asserts that Adelson's wall-of-blocks illusion [Science 262, 2042 (1993)], where identical gray-cube surface tops appear to differ in brightness, arises when the surfaces surrounding the cube tops are shadow compatible, creating a concomitant illusion of transparency. We replicated Logvinenko's main findings in the chromatic domain across three experiments in which observers match cube tops in hue, saturation, and brightness. A second set of stimuli adjusted cone-excitation ratios across the apparent transparency border [Proc. R. Soc. London 257, 115 (1994)], which enhanced lightness and brightness constancy but only when the stimuli varied in both chromaticity and intensity.