Distinct ecotypes within a natural haloarchaeal population enable adaptation to changing environmental conditions without causing population sweeps

Microbial communities thriving in hypersaline brines of solar salterns are highly resistant and resilient to environmental changes, and salinity is a major factor that deterministically influences community structure. Here, we demonstrate that this resilience occurs even after rapid osmotic shocks caused by a threefold change in salinity (a reduction from 34 to 12% salts) leading to massive amounts of archaeal cell lysis. Specifically, our temporal metagenomic datasets identified two co-occurring ecotypes within the most dominant archaeal population of the brines Haloquadratum walsbyi that exhibited different salt concentration preferences. The dominant ecotype was generally more abundant and occurred in high-salt conditions (34%); the low abundance ecotype always co-occurred but was enriched at salinities around 20% or lower and carried unique gene content related to solute transport and gene regulation. Despite their apparent distinct ecological preferences, the ecotypes did not outcompete each other presumably due to weak functional differentiation between them. Further, the osmotic shock selected for a temporal increase in taxonomic and functional diversity at both the Hqr. walsbyi population and whole-community levels supporting the specialization-disturbance hypothesis, that is, the expectation that disturbance favors generalists. Altogether, our results provide new insights into how intraspecies diversity is maintained in light of substantial gene-content differences and major environmental perturbations.Subject terms: Water microbiology, Microbial ecology     

Electrophysiological properties of pyridine receptors in the crayfish walking leg

Summary Responses of pyridine sensitive units on walking legs of the crayfishOrconectes limosus have been studied using extracellular recording techniques.Post-stimulus-time histograms were established and the mean values of the maximal frequencies were plotted in dose-response curves. The curves can be separated into two groups having a slope of 0.3 and 1 in double logarithmic plots and a sensitivity range of 4 and 2 decades, respectively. This implies two different types of pyridine receptors.Abbreviation vH van Harreveld solution     

Diet composition,food intake,body condition,and fecal consistency in captive tapirs (Tapirus spp.) in UK collections

Intake measurements were carried out in 22 tapirs from seven UK zoological collections. Dry matter intake (DMI) ranged from 48 to 86 g/kg^0.75/d. Across collections, the highest proportion of the ingested diet consisted of pelleted feeds (including grains and bread) at 46±17% DMI, followed by commercial produce at 26±12% DMI, roughage (excluding browse) at 17±11% DMI, and browse at 11±11% DMI. The proportion of roughage, crude protein, crude fiber, and neutral detergent fiber levels in the diets investigated were well below levels recommended for domestic horses and other ungulates. Intakes of digestible energy (DE) as estimated from food nutrients using of a standard equation for domestic horses ranged from 0.58 to 0.88 MJ/DE/kg^0.75/d, with many individuals exceeding the assumed maintenance requirement of 0.6 MJ/DE/kg^0.75/d for hindgut fermenters. At values exceeding this DE intake, animals had higher than ideal body condition scores (BCS). Animals with higher BCS (i.e. more obese animals) generally had higher fecal scores (FS) (i.e. softer feces), and both BCS and FS were positively correlated to DMI and calculated DE intake. This suggests that the population studied was generally overfed, with resulting obesity and softer fecal consistency. The use of highly digestible feeds such as commercial produce and pelleted feeds should be restricted in the diets of these animals and roughage intake promoted in order to attempt to achieve normal BCS and FS in this captive population. Zoo Biol 28:279–291, 2009. © 2009 Wiley-Liss, Inc.     

The interaction of areneboronic acids with monosaccharides

The interaction of benzeneboronic acid, 4-methoxybenzeneboronic acid, and 3-nitrobenzeneboronic acid with d-glucose, d-mannose, and d-fructose at various pH values has been investigated by means of optical rotation methods. The effects of (a) various molar ratios of sugar and acid and (b) overall concentration on the extent of complex formation are reported.     

Comparative study on the growth of juvenile Galapagos giant tortoises (Geochelone nigra) at the Charles Darwin Research Station (Galapagos Islands,Ecuador) and Zoo Zurich (Zurich,Switzerland)

In this study, the growth rates of a group of Galapagos giant tortoises raised in their natural habitat at the Charles Darwin Research Station (CDRS; Galapagos Islands, Ecuador) and a group of captive‐bred specimens (Zoo Zurich, Zurich, Switzerland) were compared for the first time. A great discrepancy in growth rates was observed after the first year. When the animals were 4 years old, the carapace in the Zurich specimens was approximately twice as long as that in the CDRS tortoises, and the Zurich animals weighed approximately 10 times more than the CDRS animals. The zoo diet was modified by a reduction in nutrients and an increase in fiber to produce a more natural growth rate. Zoo Biol 23:177‐183, 2004. © 2004 Wiley‐Liss, Inc.     

Cloning, functional expression and characterization of a human olfactory receptor.

The human olfactory system can recognize and discriminate a large number of different odorant molecules. The detection of chemically distinct odorants begins with the binding of an odorant ligand to a specific receptor protein on the olfactory neuron cell surface. To address the problem of olfactory perception at a molecular level, we have cloned, functionally expressed and characterized the first human olfactory receptor (OR 17-40). Application of a mixture of hundred different odorants elicited a transient increase in intracellular calcium at HEK 293-cells which were transfected with a plasmid containing the receptor encoding DNA and a membrane import sequence. By subdividing the odorant mixture in smaller groups we could identify a single component which represented the only effective substance: helional. Testing some structurally closely related molecules we found only one other compound which also could activate the receptor: heliotropyl acetone. All other compounds tested were completely ineffective. These findings represent the beginning of molecular understanding of odorant recognition in humans.