Plagiostachys lourdesiae (Zingiberaceae), a new species from Mindanao,Philippines

A new species, Plagiostachys lourdesiae, from Mindanao, Philippines is described here. Plagiostachys escritorii, which also occurs in Mindanao, is the most closely related species. The new species differs from P. escritorii in its petiolate lamina, lax inflorescence, red and strongly curved upward labellum, and globose to subglobose maroon fruit. A colour plate, notes on its distribution, habitat, phenology, conservation status as well as a key to Plagiostachys species in the Philippines are provided.     

The effects of fire on the thermal environment of sagebrush communities

Thermal heterogeneity provides options for organisms during extreme temperatures that can contribute to their fitness. Sagebrush (Artemisia spp.) communities exhibit vegetation heterogeneity that creates thermal variation at fine spatial scales. However, fire can change vegetation and thereby variation within the thermal environment of sagebrush communities. To describe spatial and temporal thermal variation of sagebrush communities following wildfire, we measured black bulb temperature (T_bb) at 144 random points dispersed within unburned and burned communities, for 24-h at each random point. We observed a wide thermal gradient in unburned (−7.3° to 63.3 °C) and burned (−4.6° to 64.8 °C) sagebrush communities. Moreover, unburned and burned sagebrush communities displayed high thermal heterogeneity relative to ambient temperature (T_air). Notably, T_bb varied by 47 °C in both unburned and burned communities when T_air was 20 °C. However, fire greatly reduced the buffering capacity and thermal refuge of Wyoming big sagebrush (A. tridentata wyomingensis) communities during low and high T_air. Furthermore, fire increased T_bb in Wyoming big sagebrush and mountain big sagebrush (A. t. vaseyana) during the mid-day hours. These results demonstrate how fire changes the thermal environment of big sagebrush communities and the importance of shrub structure which can provide thermal refuge for organisms in burned communities during extreme low and high T_air.     

The interplay between local and landscape scales on the density of pond-dwelling anurans in subtropical grasslands

We investigated the role of local and landscape environmental variables on anurans density classified as habitat specialists and generalists in grassland landscapes, known as South Brazilian grasslands (SBG). In this region, we surveyed 187 ponds distributed over 40 landscape sampling units. For each pond, 31 local environmental variables were measured. Each landscape sampling unit was embedded within a larger regional sampling unit with different landscape properties. For each landscape and regional sampling units, 16 landscape metrics were extracted from a land cover and use map. We recorded 35 species, eleven of which are specialists in the SBG. The specialists were affected by 11 local and 2 landscape environmental variables, while generalists were affected by 14 local and one landscape environmental variable. Thus, specialists and generalists presented different relationships with local and landscape variables, but in general local variables had a greater influence on the density of anurans than the landscape variables. However, the landscape indirectly influenced local variables because higher quality ponds were in landscapes with higher percentages of natural habitat. In conclusion, reproductive sites with higher local quality and located within landscapes with higher percentages of natural grasslands are essential to conserve anurans in this habitat. Effective conservation of such sites would benefit from further studies that assess effects of land use and biotic integrity of ponds, which can help to determine (a) the relative effects of local habitat quality of ponds and (b) the effectiveness of protecting ponds and their local surroundings for anuran conservation in SBG. Abstract in Portuguese is available with online material.     

Paleofloristic diversity and paleoenvironmental interpretation of new Cisuralian localities in the south-central sector of the Anticlinorium of Huayacocotla,Hidalgo, Mexico

The Anticlinorium of Huayacocotla has several outcrops of geological and paleontological importance. However, reports of localities with paleoflora have been scarce so far. In this study, we report three new localities in the Cisuralian, the diversity and composition of which lead us to propose that the paleoflora may have been derived from vegetation that grew in an arid environment with seasonal wetness. The plant remains from the localities of Papaxtla and Calnali are highly transported and their diversity indicates the presence of several groups of plants that were shared with the La Virgen locality, which yielded the best preserved plant fossils. Changes in paleoenvironmental conditions indicate that the preservation of the flora was affected by the tectonic evolution of the region associated with sea level changes. The data presented here increase our knowledge of both the Cisuralian fossil flora and paleoenvironment in the south-central region of the Huayacocotla Anticlinorium, Hidalgo state.     

Interaction of trap colour attractiveness with morphological variability of the thrips Frankliniella occidentalis (Pergande 1895)

In the latitude of Kiev, 80% of Frankliniella occidentalis (Pergande 1895) population was caught on the colour traps from 11 a.m. to 5 p.m. in summer and from 11 a.m. to 3 p.m. in winter. Meanwhile, 10% of the population did not react to the colour traps at all (“passive” individuals), whereas for 20% of the population it was impossible to determine the clear colour with attractive properties. The thrips attracted with blue and yellow color traps, had more massive and variable body parts to be connected with their flight. Their antennae and segment sizes were significantly smaller than compared to the control variant, which could be explained by eyesight domination over other organs of sensory orientation. The indices of heterogeneity of morphological features can be used as evaluation criteria for the adaptive variability and stability of the thrips population.     

Microbial Metabolism as an Evolutionary Response: The Cybernetic Approach to Modeling

ABSTRACT:?

The growth and metabolic capabilities of microorganisms depend on their interactions with the culture medium. Many media contain two or more key substrates, and an organism may have different preferences for the components. Microorganisms adjust their preferences according to the prevailing conditions so as to favor their own survival. Cybernetic modeling describes this evolutionary strategy by defining a goal that an organism tries to attain optimally at all times. The goal is often, but not always, maximization of growth, and it may require the cells to manipulate their metabolic processes in response to changing environmental conditions.

The cybernetic approach overcomes some of the limitations of metabolic control analysis (MCA), but it does not substitute MCA. Here we review the development of the cybernetic modeling of microbial metabolism, how it may be combined with MCA, and what improvements are needed to make it a viable technique for industrial fermentation processes.

IMTECH communication no.001/2001     

Transmembrane Helix Packing of ErbB/Neu Receptor in Membrane Environment: A Molecular Dynamics Study

Abstract

Dimerization or oligomerization of the ErbB/Neu receptors are necessary but not sufficient for initiation of receptor signaling. The two intracellular domains must be properly oriented for the juxtaposition of the kinase domains allowing trans-phosphorylation. This suggests that the transmembrane (TM) domain acts as a guide for defining the proper orientation of the intracellular domains.

Two structural models, with the two helices either in left-handed or in right-handed coiling have been proposed as the TM domain structure of the active receptor. Because experimental data do not distinguish clearly helix-helix packing, molecular dynamics (MD) simulations are used to investigate the energetic factors that drive Neu TM-TM interactions of the wild and the oncogenic receptor (Val664/Glu mutation) in DMPC or in POPC environments. MD results indicate that helix-lipid interactions in the bilayer core are extremely similar in the two environments and raise the role of the juxtamembrane residues in helix insertion and helix-helix packing. The TM domain shows a greater propensity to adopt a left-handed structure in DMPC, with helices in optimal position for strong inter-helical Hbonds induced by the Glu mutation. In POPC, the right-handed structure is preferentially formed with the participation of water in inter-helical Hbonds. The two structural arrangements of the NeuTM helices both with GG4 residue motif in close contact at the interface are permissible in the membrane environment. According to the hypothesis of a monomer-dimer equilibrium of the proteins it is likely that the bilayer imposes structural constraints that favor dimerization- competent structure responsible of the proper topology necessary for receptor activation.     

Diatoms in Acid Mine Drainage and Their Role in the Formation of Iron-Rich Stromatolites

Adverse conditions in the acid mine drainage (AMD) system at the Green Valley mine, Indiana, limit diatom diversity to one species, Nitzschia tubicola. It is present in three distinct microbial consortia: Euglena mutabilis-dominated biofilm, diatomdominated biofilm, and diatom-exclusive biofilm. E. mutabilis dominates the most extensive biofilm, with lesser numbers of N. tubicola, other eukaryotes, and bacteria. Diatom-dominated biofilm occurs as isolated patches containing N. tubicola with minor fungal hyphae, filamentous algae, E. mutabilis, and bacteria. Diatom-exclusive biofilm is rare, composed entirely of N. tubicola.

Diatom distribution is influenced by seasonal and intraseasonal changes in water temperature and chemistry. Diatoms are absent in winter due to cool water temperatures. In summer, isolated patchy communities are present due to warmer water temperatures. In 2001, the diatom community expanded its distribution following a major rainfall that temporarily diluted the effluent, creating hospitable conditions for diatom growth. After several weeks when effluent returned to preexisting conditions, the diatom biofilm retreated to isolated patches, and E. mutabilis biofilm flourished.

Iron-rich stromatolites underlie the biofilms and consist of distinct laminae, recording spatial and temporal oscillations in physicochemical conditions and microbial activity. The stromatolites are composed of thin, wavy laminae with partially decayed E. mutabilis biofilm, representing microbial activity and iron precipitation under normal AMD conditions. Alternating with the wavy layers are thicker, porous, spongelike laminae composed of iron precipitated on and incorporated into radiating colonies of diatoms. These layers indicate episodic changes in water chemistry, allowing diatoms to temporarily dominate the system.     

Mineral and Bacterial Diversities of Desert Sand Grains from South-East Morocco

Mineralogy and microbiology of sand from Merzouga (Morocco) were simultaneously characterized, with the purpose of contributing to a better understanding of the geomicrobiology of deserts. In spite of very low measured bacterial biomass, bacterial diversity on each of the five defined mineralogical classes, was found high. An original grain by grain cultivation method enabled to obtain bacterial isolates with an unusually high recovery rate. The results of this study show that the genus Arthrobacter is well adapted to this environment with a preference for grains other than the dominant mineral quartz, and that the genera Chelatococcus and Saccharotrix are strongly attached to the grains.     

Active Bacterial Populations and Grazing Impact Revealed by an In Situ Experiment in a Shallow Aquifer

To elucidate bacterial population dynamics in an aquifer, we attempted to reveal the impact of protozoan grazing on bacterial productivity and community structure by an in situ incubation experiment using a diffusion chamber. The abundance and vertical distribution of bacteria and protozoa in the aquifer were revealed using wells that were drilled in a sedimentary rock system in Itako, Ibaraki, Japan. The water column in the wells possessed aerobic and anaerobic layers. Active bacterial populations under the grazing pressure of protozoa were revealed through in situ incubation with grazer eliminating experiment by the filtration. On August 19, 2003, the total number of bacteria (TDC) decreased from 1.5 × 10⁶ cells ml^{? 1} at 2.2 m depth to 3.0 × 10⁵ cells ml^{? 1} at 10 m depth. The relative contribution of the domain Bacteria to TDC ranged between 63% and 84%. Protozoa existed at a density of 4.2 × 10⁴ to 1.9 × 10⁵ cells ml^{? 1} in both aerobic and microaerobic conditions. A grazing elimination experiment in situ for 6 days brought about clearly different bacterial community profiles between the 2.2 m and 10 m samples. The bacterial composition of the initial community was predominantly β- and γ -proteobacteria at 2.2 m, while at 10 m β-, α - and γ -proteobacteria represented 56%, 26% and 13% of the community, respectively. The distribution of bacterial abundance, community composition and growth rates in the subsurface were influenced by grazing as well as by geochemical factors (dissolved oxygen and concentrations of organic carbon, methane and sulfate). Results of the in situ incubation experiment suggested that protozoan grazing contributes significantly to bacterial population dynamics.