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Understanding the drivers that affect soil bacterial and fungal communities is essential to understanding and mitigating the impacts of human activity on vulnerable ecosystems like those on the Galápagos Islands. The volcanic slopes of these Islands lead to steep elevation gradients that generate distinct microclimates across small spatial scales. Although much is known about the impacts of invasive plant species on the above‐ground biodiversity of the Galápagos Islands, little is known about their resident soil microbial communities and the factors shaping them. Here, we investigate the bacterial and fungal soil communities associated with invasive and native plant species across three distinct microclimates on San Cristóbal Island (arid, transition zone and humid). At each site, we collected soil at three depths (rhizosphere, 5 cm and 15 cm) from multiple plants. Sampling location was the strongest driver of both bacterial and fungal communities, explaining 73% and 43% of variation in the bacterial and fungal community structure, respectively, with additional minor but significant impacts from soil depth and plant type (invasive vs. native). This study highlights the continued need to explore microbial communities across diverse environments and demonstrates how both abiotic and biotic factors impact soil microbial communities in the Galápagos archipelago. [ABSTRACT FROM AUTHOR]

FEMS Microbiology Reviews, 37 (5), 634 - 663. https://doi.org/10.1111/1574-6976.12028 21 Miura, C., Yagamuchi, K., Miyahara, R. et al. (2018) The mycoheterotrophic symbiosis between orchids and mycorrhizal fungi possesses major components shared with mutualistic plant-mycorrhizal symbioses. A comparison among the different mycorrhizal types has revealed some unique and shared features (Genre et al., [13]): the CSSP underpins all three endomycorrhizas (AMs, ericoid- and orchid mycorrhizas), probably regulating the symbiotic interface assembly, while a limited set of fungal carbohydrate-active enzymes is a common trait of AM - and ectomycorrhizal fungi. The resulting symbiosis (mycorrhizas) gives rise to one of the most pervasive ecological process of the planet: not only mycorrhizas probably appeared at the moment in which plants conquered the emerged lands in Devonian times, but also they are present in all the ecosystems, thanks to the relevant ecosystem services they offer. The variety of plant and fungal taxa involved in the symbiosis originates different types of mycorrhizas which diverge in symbiotic features, in evolutionary history, in physiology (Genre et al., [13]) as well as in their distribution (Tedersoo et al., [26]). [Extracted from the article]

The critical importance of the corresponding homeostasis is witnessed by the presence, in minimal genomes of autonomous organisms such as I Mycoplasma mycoides i Syn3.0, of conserved enzymes of purine metabolism ( I adk i , I apt i , I dgk i , I gmk i , I guaC i ), pyrimidine metabolism ( I cmk i , I dcd i , I pyrG i , I pyrH i , I tdk i , I tmk i , I udk i , I upp i ), and both purine and pyrimidine metabolism ( I dck i , I ndk, pnpA i ). Cells and organisms live for a long time in a stable state without growing, and this particular stage of life requires the expression of a limited number of functions that should be understood in priority. gl The necessary passage of time that all organisms face has led, during the long course of life's evolution, to a considerable number of solutions to the problems of development, maturation, ageing and death. Yet growth implies that, unless a particular metabolic control has emerged during the evolution of life, there will always be "too many" precursors to synthesize genes and genomes and thus pressure to lengthen genomes, not shorten them. It will also be necessary to implement concrete solutions to the question of growth homeostasis, which must control metabolism in such a way that the growth of a three-dimensional (3D) cytoplasm is consistent with that of two-dimensional membranes, and finally of one-dimensional genomes. [Extracted from the article]

Summary: As members of the plant microbiota, arbuscular mycorrhizal fungi (AMF, Glomeromycotina) symbiotically colonize plant roots. AMF also possess their own microbiota, hosting some uncultivable endobacteria. Ongoing research has revealed the genetics underlying plant responses to colonization by AMF, but the fungal side of the relationship remains in the dark. Here, we sequenced the genome of Gigaspora margarita, a member of the Gigasporaceae in an early diverging group of the Glomeromycotina. In contrast to other AMF, G. margarita may host distinct endobacterial populations and possesses the largest fungal genome so far annotated (773.104 Mbp), with more than 64% transposable elements. Other unique traits of the G. margarita genome include the expansion of genes for inorganic phosphate metabolism, the presence of genes for production of secondary metabolites and a considerable number of potential horizontal gene transfer events. The sequencing of G. margarita genome reveals the importance of its immune system, shedding light on the evolutionary pathways that allowed early diverging fungi to interact with both plants and bacteria. [ABSTRACT FROM AUTHOR]

Summary: Arbuscular Mycorrhizal Fungi (AMF) are key components of the plant microbiota. AMF genetic complexity is increased by the presence of endobacteria, which live inside many species. A further component of such complexity is the virome associated to AMF, whose knowledge is still very limited. Here, by exploiting transcriptomic data we describe the virome of Gigaspora margarita. A BLAST search for viral RNA‐dependent RNA polymerases sequences allowed the identification of four mitoviruses, one Ourmia‐like narnavirus, one Giardia‐like virus, and two sequences related to Fusarium graminearum mycoviruses. Northern blot and RT‐PCR confirmed the authenticity of all the sequences with the exception of the F. graminearum‐related ones. All the mitoviruses are replicative and functional since both positive strand and negative strand RNA are present. The abundance of the viral RNA molecules is not regulated by the presence or absence of Candidatus Glomeribacter gigasporarum, the endobacterium hosted by G. margarita, with the exception of the Ourmia‐like sequence which is absent in bacteria‐cured spores. In addition, we report, for the first time, DNA fragments corresponding to mitovirus sequences associated to the presence of viral RNA. These sequences are not integrated in the mitochondrial DNA and preliminary evidence seems to exclude integration in the nuclear genome. [ABSTRACT FROM AUTHOR]