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Many ecological and evolutionary processes in animals depend upon microbial symbioses. In spiders, the role of the microbiome in these processes remains mostly unknown. We compared the microbiome between populations, individuals, and tissue types of a range-expanding spider, using 16S rRNA gene sequencing. Our study is one of the first to go beyond targeting known endosymbionts in spiders and characterizes the total microbiome across different body compartments (leg, prosoma, hemolymph, book lungs, ovaries, silk glands, midgut, and fecal pellets). Overall, the microbiome differed significantly between populations and individuals, but not between tissue types. The microbiome of the wasp spider Argiope bruennichi features a novel dominant bacterial symbiont, which is abundant in every tissue type in spiders from geographically distinct populations and that is also present in offspring. The novel symbiont is affiliated with the Tenericutes, but has low sequence identity (

The close interconnection of plants with rhizosphere- and root-associated microorganisms is well recognized, and high expectations are raised for considering their symbioses in the breeding of future crop varieties. However, it is unclear how consistently plant-mediated selection, a potential target in crop breeding, influences microbiome members compared to selection imposed by the agricultural environment. Landraces may have traits shaping their microbiome, which were lost during the breeding of modern varieties, but knowledge about this is scarce. We investigated prokaryotic community composition along the radial root axis of two European maize (Zea mays L.) landraces. A sampling gradient included bulk soil, a distal and proximal rhizosphere fraction, and the root compartment. Our study was replicated at two field locations with differing edaphic and climatic conditions. Further, we tested for differences between two plant developmental stages and two precipitation treatments. Community data were generated by metabarcoding of the V4 SSU rRNA region. While communities were generally distinct between field sites, the effects of landrace variety, developmental stage, and precipitation treatment were comparatively weak and not statistically significant. Under all conditions, patterns in community composition corresponded strongly to the distance to the root. Changes in a- and b-diversity, as well as abundance shifts of many taxa along this gradient, were similar for both landraces and field locations. Most affected taxa belonged to a core microbiome present in all investigated samples. Remarkably, we observed consistent enrichment of Actinobacteriota (particularly Streptomyces, Lechevalieria) and Pseudomonadota (particularly Sphingobium) toward the root. Further, we report a depletion of ammoniaoxidizers along this axis at both field sites. We identified clear enrichment and depletion patterns in microbiome composition along the radial root axis of Z. mays. Many of these were consistent across two distinct field locations, plant developmental stages, precipitation treatments, and for both landraces. This suggests a considerable influence of plant-mediated effects on the microbiome. We propose that the affected taxa have key roles in the rhizosphere and root microbiome of Z. mays. Understanding the functions of these taxa appears highly relevant for the development of methods aiming to promote microbiome services for crops. [ABSTRACT FROM AUTHOR]

Background and Aims Stomatal regulation allows plants to promptly respond to water stress. However, our understanding of the impact of above and belowground hydraulic traits on stomatal regulation remains incomplete. The objective of this study was to investigate how key plant hydraulic traits impact transpiration of maize during soil drying. We hypothesize that the stomatal response to soil drying is related to a loss in soil hydraulic conductivity at the root–soil interface, which in turn depends on plant hydraulic traits. Methods We investigate the response of 48 contrasting maize (Zea mays) genotypes to soil drying, utilizing a novel phenotyping facility. In this context, we measure the relationship between leaf water potential, soil water potential, soil water content and transpiration, as well as root, rhizosphere and aboveground plant traits. Key Results Genotypes differed in their responsiveness to soil drying. The critical soil water potential at which plants started decreasing transpiration was related to a combination of above and belowground traits: genotypes with a higher maximum transpiration and plant hydraulic conductance as well as a smaller root and rhizosphere system closed stomata at less negative soil water potentials. Conclusions Our results demonstrate the importance of belowground hydraulics for stomatal regulation and hence drought responsiveness during soil drying. Furthermore, this finding supports the hypothesis that stomata start to close when soil hydraulic conductivity drops at the root–soil interface. [ABSTRACT FROM AUTHOR]

The highly enriched deltaproteobacterial culture N47 anaerobically oxidizes the polycyelic aromatic hydrocarbons naphthalene and 2-methylnaphthalene, with sulfate as the electron acceptor. Combined genome sequencing and liquid chromatography-tandem mass spectrometry-based shotgun proteome analyses were performed to identify genes and proteins involved in anaerobic aromatic catabolism. Proteome analysis of 2-methylnaphthalene-grown N47 cells resulted in the identification of putative enzymes catalyzing the anaerobic conversion of 2-metbyluapbthalene to 2-naphthoyl eoenzyme A (2-naphthoyl-CoA), as well as the reductive ring cleavage of 2-naphthoyl-CoA, leading to the formation of acetyl-CoA and C[O.sub.2]. The glycyl radical-catalyzed fumarate addition to the methyl group of 2-methylnaphthalene is catalyzed by naphthyl-2-methyl-succinate synthase (Nms), composed of [alpha]-, [beta]-, and [gamma]-subunits that are encoded by the genes nmsABC. Located upstream of nmsABC is nmsD, encoding the Nms-activating enzyme, which harbors the characteristic [[Fe.sub.4][S.sub.4]] cluster sequence motifs of S-adenosylmethionine radical enzymes. The bns gene cluster, coding for enzymes involved in beta-oxidation reactions converting naphthyl-2-methyl-succinate to 2-naphthoyl-CoA, was found four intervening open reading frames further downstream. This cluster consists of eight genes (bnsABCDEFGH) corresponding to 8.1 kb, which are closely related to genes for enzymes involved in anaerobic toluene degradation within the denitrifiers 'Aromatoleum aromaticum' EbN1, Azoarcus sp. strain T, and Thauera aromatica. Another contiguous DNA sequence harbors the gene for 2-naphthoyl-CoA reductase (ncr) and 16 additional genes that were found to be expressed in 2-methylnaphthalene-grown cells. These genes code for enzymes that were supposed to catalyze the dearomatization and ring cleavage reactions converting 2-naphthoyl-CoA to acetylCoA and C[O.sub.2]. Comparative sequence analysis of the four encoding subunits (ncrABCD) showed the gene product to have the closest similarity to the Azoarcus type of benzoyl-CoA reductase. The present work provides the first insight into the genetic basis of anaerobic 2-methylnaphthalene metabolism and delivers implications for understanding contaminant degradation. doi: 10.1128/JB.00874-09

Research addresses potential bias in the polymerase chain reaction and their influence on terminal restriction fragment length polymorphism fingerprinting of methanogenic bacterial population structure in different habitats using small-subunit rRNA and the methyl-coenzyme M reductase genes as probes. Data reveal that small-subunit rRNA analysis is reproducible, whereas M reductase-based analysis is biased.

Different methanogenic bacteria are stimulated or inhibited when rice paddy soils are supplemented with ferrihydrite or gypsum. These electron acceptors are added to stimulate bacteria that would compete with methanogens. This is done to reduce methane emissions, which contribute to the greenhouse effect.

The first comprehensive analysis of the microbial community inside the gut of the termite Cubitermes orthognathus is described based on clonal analysis and terminal restriction fragment length polymorphism fingerprinting. This is also the first report of Crenarchaeota occurring in an arthropod intestinal tract.

Research has been conducted on the Archaea population dynamics after rice field soil flooding. The results of the molecular sequence retrieval and small-subunit rRNA gene fingerprinting are discussed.

The characterization of microbial community distribution across a high-resolution depth profile of a tar oil-impacted aquifer where benzene, toluene, ethylbenzene and xylene (BTEX) degradation has depended mainly on sulfate reduction is described. The results have shown that the distribution of specific aquifer microbiota and degradation processes in contaminated aquifers are tightly coupled, which are used for the assessment of natural attenuation based on intrinsic aquifer microbiota.

The first identification of active anaerobic microorganisms by stable-isotope probing (SIP), which are involved in the thermodyanimically unfavorable syntrophic oxidation of propionate under methanogenic conditions is presented. Three distinct lineages of syntrophic propionate oxidizers (Syntrophobacter, Smithella, and Pelotomaculum spp.) were identified to operate simultaneously in anoxic rice field soil slurries and their hydrogenotrophic and acetotrophic methanogenic partner organisms were also detected by assimilation of labeled intermediates.