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We describe a collection of aquatic and wetland habitats in an inland landscape, and their occurrence within a terrestrial matrix, as a "freshwater ecosystem mosaic" (FEM). Aquatic and wetland habitats in any FEM can vary widely, from permanently ponded lakes, to ephemerally ponded wetlands, to groundwater‐fed springs, to flowing rivers and streams. The terrestrial matrix can also vary, including in its influence on flows of energy, materials, and organisms among ecosystems. Biota occurring in a specific region are adapted to the unique opportunities and challenges presented by spatial and temporal patterns of habitat types inherent to each FEM. To persist in any given landscape, most species move to recolonize habitats and maintain mixtures of genetic materials. Species also connect habitats through time if they possess needed morphological, physiological, or behavioral traits to persist in a habitat through periods of unfavorable environmental conditions. By examining key spatial and temporal patterns underlying FEMs, and species‐specific adaptations to these patterns, a better understanding of the structural and functional connectivity of a landscape can be obtained. Fully including aquatic, wetland, and terrestrial habitats in FEMs facilitates adoption of the next generation of individual‐based models that integrate the principles of population, community, and ecosystem ecology. Research Impact Statement: Fully including aquatic, wetland, and terrestrial habitats facilitates adoption of next‐generation, individual‐based, models that integrate principles of population, community, and ecosystem ecology. [ABSTRACT FROM AUTHOR]

FNR is a well-studied global regulator of anaerobiosis, which is widely conserved across bacteria. Despite the importance of FNR and anaerobiosis in microbial lifestyles, the factors that influence its function on a genome-wide scale are poorly understood. Here, we report a functional genomic analysis of FNR action. We find that FNR occupancy at many target sites is strongly influenced by nucleoid-associated proteins (NAPs) that restrict access to many FNR binding sites. At a genome-wide level, only a subset of predicted FNR binding sites were bound under anaerobic fermentative conditions and many appeared to be masked by the NAPs H-NS, IHF and Fis. Similar assays in cells lacking H-NS and its paralog StpA showed increased FNR occupancy at sites bound by H-NS in WT strains, indicating that large regions of the genome are not readily accessible for FNR binding. Genome accessibility may also explain our finding that genome-wide FNR occupancy did not correlate with the match to consensus at binding sites, suggesting that significant variation in ChIP signal was attributable to cross-linking or immunoprecipitation efficiency rather than differences in binding affinities for FNR sites. Correlation of FNR ChIP-seq peaks with transcriptomic data showed that less than half of the FNR-regulated operons could be attributed to direct FNR binding. Conversely, FNR bound some promoters without regulating expression presumably requiring changes in activity of condition-specific transcription factors. Such combinatorial regulation may allow Escherichia coli to respond rapidly to environmental changes and confer an ecological advantage in the anaerobic but nutrient-fluctuating environment of the mammalian gut. [ABSTRACT FROM AUTHOR]

Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment. [ABSTRACT FROM AUTHOR]

This review attempted to follow the establishment of a novel branch of biology arisen at the interfaces between plant physiology, biochemistry, and molecular biology—plant anaerobic stress. Most attention was given to the early period of these investigations, the activity of the members of International Society for Plant Anaerobiosis in particular, and the contribution of Russian scientists, who played a significant role at that time in the establishment and international recognition of this new trend. In this connection, the following points are considered: (1) Crawford's metabolic theory, which could not withstand experimental verification but induced an active discussion, thus stimulating further investigations in this field; (2) a concept of two main strategies of plant adaptation to anaerobic stress (true and apparent adaptation), which was put forward based on the following experimental data: (a) a discovery of a paradoxical phenomenon of hyper-sensitivity, but not hyper-resistance to anoxia, of the flood-tolerant plant roots (“apparent” tolerance); (b) the elucidation of the physiological role of oxygen transported from aerated organs of flood-tolerant plants to the roots inhabiting anaerobic environment; (c) demonstration of the key role of both energy metabolism, and (d) substrate providing for glycolysis and ethanolic fermentation in plants manifesting “true” tolerance to oxygen deprivation; (3) the discovery of plant stress proteins; and finally (4) pH-stat theory put forward by Davies. [ABSTRACT FROM AUTHOR]

Natural flooding is a major component of the disturbance regime in many grassland ecosystems. The objective of this study was to analyze the relationship among constitutive and plastic root traits and tolerance to flooding in coexisting perennial species of the flooding pampa grasslands (Argentina). A mesocosm experiment was designed for five native species (Paspalidium paludivagum, Paspalum dilatatum, Bothriochloa laguroides, Eryngium ebracteatum, and Eclipta bellidioides) and two exotic ones (Mentha pulegium and Plantago lanceolata). Across species, constitutive root porosity was positively correlated with the tolerance to soil flooding. Moreover, the generation of additional aerenchyma was larger in species with intermediate values of constitutive root porosity and lower in species with low or high constitutive root porosity. This differential increase in the root porosity of each species, combined with the values of constitutive root porosity, resulted in a stronger correlation between final root porosity and tolerance under flooding conditions. Native grasses increased the proportion of root aerenchyma, showing a small change in the number of lysed cells but a significant increase in the cortex proportion and diameter of roots. Exotic dicots generated lysigenous aerenchyma throughout their cortex; in contrast, native dicot species maintained the cell layers adjacent to the stele. A lag in the development of secondary growth during flooding was detected in both groups of dicots, a response that was particularly evident in the exotic species, contrasting with their prominent growth under nonflooded conditions. In general, our results indicate that constitutive and plastic root traits are very significant in terms of the effects of periodic flooding on the abundance of coexisting species of the flooding pampa grasslands. [ABSTRACT FROM AUTHOR]

1. Ten Arctic species of Collembola and two species of cryptostigmatic mites survived anoxia at 5 °C over periods ranging from 1 to 36 days. 2. Highly active, surface-dwelling collembolans such as Isotoma anglicana, Isotoma tschernovi, and Sminthurides malmgreni were the most susceptible to anoxia. Mites and Collembola living deeper in the soil or in wet habitats, such as Camisia anomia and Hypogastrura viatica, were most tolerant. Tolerance, however, appears more closely linked to taxonomic relatedness than to ecological groupings per se, although the two may coincide. 3. Implications for life-history strategies, including metabolic cold adaptation in its broadest sense, are discussed. [ABSTRACT FROM AUTHOR]