Specific Symbiosis Research Articles

Bacillus velezensis S141 improves the root growth of soybean under drought conditions.

Bacillus velezensis S141 helps soybean establish specific symbiosis with strains of Bradyrhizobium diazoefficiens to form larger nodules and improve nitrogen fixation efficiency. In this study, we found that the dry weight of soybean roots increased significantly in the presence of S141 alone under drought conditions. Hence, S141 improved the root growth of soybean under limited water supply conditions. S141 can produce some auxin, which might be involved in the improved nodulation. Inactivating IPyAD of S141, which is required for auxin biosynthesis, did not alter the beneficial effects of S141, suggesting that the root growth was independent of auxin produced by S141. Under drought conditions, soybean exhibited some responses to resist osmotic and oxidative stresses; however, S141 was relevant to none of these responses. Although the mechanism remains unclear, S141 might produce some substances that stimulate the root growth of soybean under drought conditions.

Three cuticular amides in the tripartite symbiosis of leafcutter ants.

Cuticular hydrocarbons (CHCs) play various roles in insects' chemical ecology. As leafcutter ants live in a specific symbiosis with fungi, they harvest and with different bacteria, some of these CHCs might be associated with a mutualistic function within this symbiosis. To obtain a more precise picture in that respect we compared the CHC profiles of the leafcutter ants, Atta sexdens, Atta cephalotes, and Acromyrmex octospinosus inhabited by mutualistic bacteria with the profiles of Polyrhachis dives and Messor aciculatus by GC-EI-MS analysis and 28 other ant species by data from the literature. We were able to identify three alkyl amides (hexadecanamide, hexadecenamide, and tetradecanamide), occurring only in the CHC profiles of leafcutter ants inhabited by symbiotic bacteria. Our results lead to the conclusion that those alkyl amides could have a function in the tripartite symbiosis of leafcutter ants.

Microbiome specificity and fluxes between two distant plant taxa in Iberian forests

BackgroundPlant-associated microbial communities play important roles in host nutrition, development and defence. In particular, the microbes living within internal plant tissues can affect plant metabolism in a more intimate way. Understanding the factors that shape plant microbial composition and discovering enriched microbes within endophytic compartments would thus be valuable to gain knowledge on potential plant–microbial coevolutions. However, these interactions are usually studied through reductionist approaches (in vitro models or crop controlled systems). Here, we investigate these ecological factors in wild forest niches using proximally located plants from two distant taxa (blueberry and blackberry) as a model.ResultsAlthough the microbial communities were quite similar in both plants, we found that sampling site had a high influence on them; specifically, its impact on the rhizosphere communities was higher than that on the roots. Plant species and sample type (root vs. rhizosphere) affected the bacterial communities more than the fungal communities. For instance, Xanthobacteraceae and Helotiales taxa were more enriched in roots, while the abundance of Gemmatimonadetes was higher in rhizospheres. Acidobacteria abundance within the endosphere of blueberry was similar to that in soil. Several taxa were significantly associated with either blackberry or blueberry samples regardless of the sampling site. For instance, we found a significant endospheric enrichment of Nevskia in blueberry and of Sphingobium, Novosphingobium and Steroidobacter in blackberry.ConclusionsThere are selective enrichment and exclusion processes in the roots of plants that shapes a differential composition between plant species and sample types (root endosphere—rhizosphere). The special enrichment of some microbial taxa in each plant species might suggest the presence of ancient selection and/or speciation processes and might imply specific symbiosis. The selection of fungi by the host is more pronounced when considering the fungal trait rather than the taxonomy. This work helps to understand plant–microbial interactions in natural ecosystems and the microbiome features of plants.

Novel symbiovars ingae, lysilomae and lysilomaefficiens in bradyrhizobia from tree-legume nodules

Inga vera and Lysiloma tree legumes form nodules with Bradyrhizobium spp. from the japonicum group that represent novel genomospecies, for which we describe here using genome data, symbiovars lysilomae, lysilomaefficiens and ingae. Genes encoding Type three secretion system (TTSS) that could affect host specificity were found in ingae but not in lysilomae nor in lysilomaefficiens symbiovars and uptake hydrogenase hup genes (that affect nitrogen fixation) were observed in bradyrhizobia from the symbiovars ingae and lysilomaefficiens. nolA gene was found in the symbiovar lysilomaefficiens but not in strains from lysilomae. We discuss that multiple genes may dictate symbiosis specificity. Besides, toxin-antitoxin genes were found in the symbiosis islands in bradyrhizobia from symbiovars ingae and lysilomaefficiens. A limit (95%) to define symbiovars with nifH gene sequences was proposed here.

Comparative genome analysis of Sesbania cannabina-nodulating Rhizobium spp. revealing the symbiotic and transferrable characteristics of symbiosis plasmids.

Symbiotic nitrogen fixation between legumes and rhizobia makes a great contribution to the terrestrial ecosystem. The successful symbiosis between the partners mainly depends on the nod and nif genes in rhizobia, while the specific symbiosis is mainly determined by the structure of Nod factors and the corresponding secretion systems (type III secretion system; T3SS), etc. These symbiosis genes are usually located on symbiotic plasmids or a chromosomal symbiotic island, both could be transferred interspecies. In our previous studies, Sesbania cannabina-nodulating rhizobia across the world were classified into 16 species of four genera and all the strains, especially those of Rhizobium spp., harboured extraordinarily highly conserved symbiosis genes, suggesting that horizontal transfer of symbiosis genes might have happened among them. In order to learn the genomic basis of diversification of rhizobia under the selection of host specificity, we performed this study to compare the complete genome sequences of four Rhizobium strains associated with S. cannabina, YTUBH007, YTUZZ027, YTUHZ044 and YTUHZ045. Their complete genomes were sequenced and assembled at the replicon level. Each strain represents a different species according to the average nucleotide identity (ANI) values calculated using the whole-genome sequences; furthermore, except for YTUBH007, which was classified as Rhizobium binae, the remaining three strains were identified as new candidate species. A single symbiotic plasmid sized 345-402 kb containing complete nod, nif, fix, T3SS and conjugal transfer genes was detected in each strain. The high ANI and amino acid identity (AAI) values, as well as the close phylogenetic relationships among the entire symbiotic plasmid sequences, indicate that they have the same origin and the entire plasmid has been transferred among different Rhizobium species. These results indicate that S. cannabina stringently selects a certain symbiosis gene background of the rhizobia for nodulation, which might have forced the symbiosis genes to transfer from some introduced rhizobia to the related native or local-condition-adapted bacteria. The existence of almost complete conjugal transfer related elements, but not the gene virD, indicated that the self-transfer of the symbiotic plasmid in these rhizobial strains may be realized via a virD-independent pathway or through another unidentified gene. This study provides insight for the better understanding of high-frequency symbiotic plasmid transfer, host-specific nodulation and the host shift for rhizobia.

Symbiont-specific responses to environmental cues in a threesome lichen symbiosis.

Photosymbiodemes are a special case of lichen symbiosis where one lichenized fungus engages in symbiosis with two different photosynthetic partners, a cyanobacterium and a green alga, to develop two distinctly looking photomorphs. We compared gene expression of thallus sectors of the photosymbiodeme-forming lichen Peltigera britannica containing cyanobacterial photobionts with thallus sectors with both green algal and cyanobacterial photobionts and investigated differential gene expression at different temperatures representing mild and putatively stressful conditions. First, we quantified photobiont-mediated differences in fungal gene expression. Second, because of known ecological differences between photomorphs, we investigated symbiont-specific responses in gene expression to temperature increases. Photobiont-mediated differences in fungal gene expression could be identified, with upregulation of distinct biological processes in the different morphs, showing that interaction with specific symbiosis partners profoundly impacts fungal gene expression. Furthermore, high temperatures expectedly led to an upregulation of genes involved in heat shock responses in all organisms in whole transcriptome data and to an increased expression of genes involved in photosynthesis in both photobiont types at 15 and 25°C. The fungus and the cyanobacteria exhibited thermal stress responses already at 15°C, the green algae mainly at 25°C, demonstrating symbiont-specific responses to environmental cues and symbiont-specific ecological optima.

Microbiome of Nodules and Roots of Soybean and Common Bean: Searching for Differences Associated with Contrasting Performances in Symbiotic Nitrogen Fixation.

Biological nitrogen fixation (BNF) is a key process for the N input in agriculture, with outstanding economic and environmental benefits from the replacement of chemical fertilizers. However, not all symbioses are equally effective in fixing N2, and a major example relies on the high contribution associated with the soybean (Glycine max), contrasting with the low rates reported with the common bean (Phaseolus vulgaris) crop worldwide. Understanding these differences represents a major challenge that can help to design strategies to increase the contribution of BNF, and next-generation sequencing (NGS) analyses of the nodule and root microbiomes may bring new insights to explain differential symbiotic performances. In this study, three treatments evaluated in non-sterile soil conditions were investigated in both legumes: (i) non-inoculated control; (ii) inoculated with host-compatible rhizobia; and (iii) co-inoculated with host-compatible rhizobia and Azospirillum brasilense. In the more efficient and specific symbiosis with soybean, Bradyrhizobium presented a high abundance in nodules, with further increases with inoculation. Contrarily, the abundance of the main Rhizobium symbiont was lower in common bean nodules and did not increase with inoculation, which may explain the often-reported lack of response of this legume to inoculation with elite strains. Co-inoculation with Azospirillum decreased the abundance of the host-compatible rhizobia in nodules, probably because of competitiveness among the species at the rhizosphere, but increased in root microbiomes. The results showed that several other bacteria compose the nodule microbiomes of both legumes, including nitrogen-fixing, growth-promoters, and biocontrol agents, whose contribution to plant growth deserves further investigation. Several genera of bacteria were detected in root microbiomes, and this microbial community might contribute to plant growth through a variety of microbial processes. However, massive inoculation with elite strains should be better investigated, as it may affect the root microbiome, verified by both relative abundance and diversity indices, that might impact the contribution of microbial processes to plant growth.

Prosthetic Symbiosis

Prosthetic Symbiosis

Sugar transporters of the SWEET family and their role in arbuscular mycorrhiza.

Plant sugar transporters play an essential role in the organism’s productivity by carrying out carbohydrate transportation from source cells in the leaves to sink cells in the cortex. In addition, they aid in the regulation of a substantial part of the exchange of nutrients with microorganisms in the rhizosphere (bacteria and fungi), an ty essential to the formation of symbiotic relationships. This review pays special attention to carbohydrate nutrition during the development of arbuscular mycorrhiza (AM), a symbiosis of plants with fungi from the Glomeromycotina subdivision. This relationship results in the host plant receiving micronutrients from the mycosymbiont, mainly phosphorus, and the fungus receiving carbon assimilation products in return. While the eff icient nutrient transport pathways in AM symbiosis are yet to be discovered, SWEET sugar transporters are one of the three key families of plant carbohydrate transporters. Specif ic AM symbiosis transporters can be identif ied among the SWEET proteins. The survey provides data on the study history, structure and localization, phylogeny and functions of the SWEET proteins. A high variability of both the SWEET proteins themselves and their functions is noted along with the fact that the same proteins may perform different functions in different plants. A special role is given to the SWEET transporters in AM development. SWEET transporters can also play a key role in abiotic stress tolerance, thus allowing plants to adapt to adverse environmental conditions. The development of knowledge about symbiotic systems will contribute to the creation of microbial preparations for use in agriculture in the Russian Federation.

«Красные похороны». Новая похоронная обрядность в молодой Советской России

The article analyzes the emergence of the so-called red funeral ritual in the 1920s in Soviet Russia as an important component of political everyday life. The first part of the article examines the funeral rituals of representatives of the Bolshevik elite. The second part attempts to characterize the transformation of funeral rites among the “common” population. The analysis undertaken clearly shows the undoubted political and public nature of funeral rituals in early Soviet Russia. Initially, Soviet funeral rituals were powerfully influenced by radical utilitarianism and total nihilistic denial of the religious worldview, intensified by the excesses of the World War, Revolution and Civil War. Nevertheless, nihilism and utilitarianism, the highest expression of which was the idea of cremation, were quickly pushed out by a new funeral ritual, the key elements of which were demonstration and “theatrical ritual” with its music, processions, pretentious speeches and fireworks, in many respects borrowed from military funerals. The main role in the emergence of the red funeral ritual was played by the cult of fallen heroes, which in turn was a guarantee of political immortality of the Bolshevik leaders. As a result, the red funeral became an important element of the alternative Bolshevik culture. The concept of Vladimir Buldakov, who characterized revolutionary funeral rituals as “neo-pagan”, is at least controversial. The attempt to make funerals of the Bolshevik elites a model for mass funerals collided with conservative rituals, especially in the countryside. With regard to the 1920s, at best, we can talk about the emergence of a kind of “the effect of dual faith", a specific symbiosis of red and religious funeral rites. Thus, in the 1920s, the process of a new Soviet ritualism development was far from complete, including the Soviet party and state elites, as evidenced by the fluctuations between party asceticism with its utilitarian attitude to ashes and splendid funerals of leaders.

Species and geographic specificity between endophytic fungi and host supported by parasitic Cynomorium songaricum and its host Nitraria tangutorum distributed in desert.

This study was aimed to investigate whether host plant species and lifestyles, and environmental conditions in the desert affect endophytic fungi composition. Endophytic fungal communities from parasitic plant Cynomorium songaricum and its host Nitraria tangutorum were investigated from three sites including Tonggu Naoer, Xilin Gaole, and Guazhou in Tengger and Badain Jaran Deserts in China using the next-generation sequencing of a ribosomal RNA gene region. Similarity and difference in endophytic fungal composition from different geographic locations were evaluated through multivariate statistical analysis. It showed that plant genetics was a deciding factor affecting endophytic fungal composition even when C. songaricum and N. tangutorum grow together tightly. Not only that, the fungal composition was also greatly affected by the local environment and rainfall. However, the distribution and richness of fungal species indicated that the geographical distance exerted little influence on characterizing the fungal composition. Overall, the findings suggested that plant species, parasitic or non-parasitic lifestyles of the plant, and local environment strongly affected the number and diversity of the endophytic fungal species, which may provide valuable insights into the microbe ecology, symbiosis specificity, and the tripartite relationship among parasitic plant, host, and endophytic fungi, especially under desert environment.

Recent development and new insight of diversification and symbiosis specificity of legume rhizobia: mechanism and application

Currently, symbiotic rhizobia (sl., rhizobium) refer to the soil bacteria in α- and β-Proteobacteria that can induce root and/or stem nodules on some legumes and a few of nonlegumes. In the nodules, rhizobia convert the inert dinitrogen gas (N2 ) into ammonia (NH3 ) and supply them as nitrogen nutrient to the host plant. In general, this symbiotic association presents specificity between rhizobial and leguminous species, and most of the rhizobia use lipochitooligosaccharides, so called Nod factor (NF), for cooperating with their host plant to initiate the formation of nodule primordium and to inhibit the plant immunity. Besides NF, effectors secreted by type III secretion system (T3SS), exopolysaccharides and many microbe-associated molecular patterns in the rhizobia also play important roles in nodulation and immunity response between rhizobia and legumes. However, the promiscuous hosts like Glycine max and Sophora flavescens can nodulate with various rhizobial species harbouring diverse symbiosis genes in different soils, meaning that the nodulation specificity/efficiency might be mainly determined by the host plants and regulated by the soil conditions in a certain cases. Based on previous studies on rhizobial application, we propose a '1+n-N' model to promote the function of symbiotic nitrogen fixation (SNF) in agricultural practice, where '1' refers to appreciate rhizobium; '+n' means the addition of multiple trace elements and PGPR bacteria; and '-N' implies the reduction of chemical nitrogen fertilizer. Finally, open questions in the SNF field are raised to future think deeply and researches.

Exogenous ACC Deaminase Is Key to Improving the Performance of Pasture Legume-Rhizobial Symbioses in the Presence of a High Manganese Concentration.

Manganese (Mn) toxicity is a very common soil stress around the world, which is responsible for low soil fertility. This manuscript evaluates the effect of the endophytic bacterium Pseudomonas sp. Q1 on different rhizobial-legume symbioses in the absence and presence of Mn toxicity. Three legume species, Cicer arietinum (chickpea), Trifolium subterraneum (subterranean clover), and Medicago polymorpha (burr medic) were used. To evaluate the role of 1-aminocyclopropane-1-carboxylate (ACC) deaminase produced by strain Q1 in these interactions, an ACC deaminase knockout mutant of this strain was constructed and used in those trials. The Q1 strain only promoted the symbiotic performance of Rhizobium leguminosarum bv. trifolii ATCC 14480T and Ensifer meliloti ATCC 9930T, leading to an increase of the growth of their hosts in both conditions. Notably, the acdS gene disruption of strain Q1 abolished the beneficial effect of this bacterium as well as causing this mutant strain to act deleteriously in those specific symbioses. This study suggests that the addition of non-rhizobia with functional ACC deaminase may be a strategy to improve the pasture legume–rhizobial symbioses, particularly when the use of rhizobial strains alone does not yield the expected results due to their difficulty in competing with native strains or in adapting to inhibitory soil conditions.

Genetic Characterization and Diversity of Rhizobia Isolated from Root Nodules of Green Gram (Vigna radiata L.) found in Central Plateau of India

Background: Plant growth promoting rhizobia play an important in agricultural ecosystem through symbiotic association with a wide range of leguminous plants. Legume-rhizobia association is a host specific symbiosis hence the need to identify the strains and the diversity of rhizobia associated with specific type of legume for better bio-prospecting of the associated benefits. A wide range of variation is present among the distribution of rhizobia and greatly affected by geographical locality, edaphic factors and environmental variation with time and space. Molecular techniques have been developed to aid the traditional phenotypic and morpho-cultural techniques in distinguishing the different microbial genera, species and strains. The present study aimed at isolation and morpho-molecular characterization of rhizobia from root nodule of green gram cultivated in central part of India.Methods: In the field-laboratory investigation during 2018-2019, various locations of central India with contrasting agro climatic conditions were surveyed and rhizobia trapping done. A total of 40 rhizobia were retrieved from nodules of green gram and characterized in laboratory based on morphological, biochemical and molecular techniques and results validated for taxonomic identification.Result: In our investigation all forty isolated rhizobia were found phosphate solubilizers, 38 IAA producers and 37 ammonia excretors and grew well at 28oC and 37oC. In carbohydrate fermentation test 34 isolates changed the broth colour from red to yellow with gas formation in durum tubes. Twenty diverse rhizobia isolates were selected with respect to their multifunctional properties and studied for molecular characterization. Based on 16S rRNA gene sequencing, these bacterial strains were identified under two genera: Rhizobium and Brady Rhizobium. Phylogenetic analysis divided 20 rhizobia isolates into two clusters. Major group included 12 strains and minor group included 8 strains.

Algal Diversity in Paramecium bursaria: Species Identification, Detection of Choricystis parasitica, and Assessment of the Interaction Specificity

The ‘green’ ciliate Paramecium bursaria lives in mutualistic symbiosis with green algae belonging to the species Chlorella variabilis or Micractinium conductrix. We analysed the diversity of algal endosymbionts and their P. bursaria hosts in nine strains from geographically diverse origins. Therefore, their phylogenies using different molecular markers were inferred. The green paramecia belong to different syngens of P. bursaria. The intracellular algae were assigned to Chl. variabilis, M. conductrix or, surprisingly, Choricystis parasitica. This usually free-living alga co-occurs with M. conductrix in the host’s cytoplasm. Addressing the potential status of Chor. parasitica as second additional endosymbiont, we determined if it is capable of symbiosis establishment and replication within a host cell. Symbiont-free P. bursaria were generated by cycloheximid treatment. Those aposymbiotic P. bursaria were used for experimental infections to investigate the symbiosis specificity not only between P. bursaria and Chor. parasitica but including also Chl. variabilis and M. conductrix. For each algae we observed the uptake and incorporation in individual perialgal vacuoles. These host-symbiont associations are stable since more than five months. Thus, Chor. parasitica and P. bursaria can form an intimate and long-term interaction. This study provides new insights into the diversity of P. bursaria algal symbionts.

Symbiosis Signaling: Solanaceae Symbiotic LCO Receptors Are Functional for Rhizobium Perception in Legumes.

A new study shows that plant receptor genes necessary for the ancient and widespread symbiosis with arbuscular mycorrhizal fungi were co-opted in legume plants, without modifications, to establish the evolutionarily more recent and more specific symbiosis with their bacterial rhizobium partners.

Acidic pH promotes lipopolysaccharide modification and alters colonization in a bacteria-animal mutualism.

Environmental pH can be an important cue for symbiotic bacteria as they colonize their eukaryotic hosts. Using the model mutualism between the marine bacterium Vibrio fischeri and the Hawaiian bobtail squid, we characterized the bacterial transcriptional response to acidic pH experienced during the shift from planktonic to host-associated lifestyles. We found several genes involved in outer membrane structure were differentially expressed based on pH, indicating alterations in membrane physiology as V. fischeri initiates its symbiotic program. Exposure to host-like pH increased the resistance of V. fischeri to the cationic antimicrobial peptide polymixin B, which resembles antibacterial molecules that are produced by the squid to select V. fischeri from the ocean microbiota. Using a forward genetic screen, we identified a homolog of eptA, a predicted phosphoethanolamine transferase, as critical for antimicrobial defense. We used MALDI-MS to verify eptA as an ethanolamine transferase for the lipid-A portion of V. fischeri lipopolysaccharide. We then used a DNA pulldown approach to discover that eptA transcription is activated by the global regulator H-NS. Finally, we revealed that eptA promotes successful squid colonization by V. fischeri, supporting its potential role in initiation of this highly specific symbiosis.

Adaptations and evolution of a heritable leaf nodule symbiosis between Dioscorea sansibarensis and Orrella dioscoreae.

Various plant species establish intimate symbioses with bacteria within their aerial organs. The bacteria are contained within nodules or glands often present in distinctive patterns on the leaves in what is commonly referred to as leaf nodule symbiosis. We describe here a highly specific symbiosis between a wild yam species from Madagascar, Dioscorea sansibarensis and bacteria of the species Orrella dioscoreae. Using whole-genome sequencing of plastids and bacteria from wild-collected samples, we show phylogenetic patterns consistent with a dominant vertical mode of transmission of the symbionts. Unique so far among leaf nodule symbioses, the bacteria can be cultured and are amenable to comparative transcriptomics, revealing a potential role in complementing the host's arsenal of secondary metabolites. We propose a recent establishment of a vertical mode of transmission in this symbiosis which, together with a large effective population size explains the cultivability and apparent lack of genome reductive evolution in O. dioscoreae. We leverage these unique features to reveal pathways and functions under positive selection in these specialized endophytes, highlighting the candidate mechanisms enabling a permanent association in the phyllosphere.

The Muskau Bend: Mining Space from Different Perspectives

The article analyses and assesses the phenomena and problems of the Muskau Bend – the Polish-German mining space, specific for natural and cultural conditions, and diversification in terms of the state of mining, as well as the directions of transformation and exploitation of elements resulting from the mining activity. The article is based on the author’s field research carried out in 2013 and 2016, within the framework of the activity conducted at the Institute of City and Regional Design, at the Faculty of Architecture of the Cracow University of Technology. The way of thinking is conducted in three main directions: from the German, Polish and cross-border perspective, which serves to emphasise the distinctness of processes characteristic of the Muskau Bend areas located in Germany and Poland, but at the same time within the borders of the European Union. Such an approach to the subject provokes discussion about the present development and the future role of the Muskau Bend as a space connecting two neighbouring countries, where Poland and Germany function in a specific symbiosis, at the same time being markedly distinctive. The conclusions drawn can be useful both for the Muskau Bend itself, and for other mining and post-mining regions of a crossborder nature.

Home selection and regular welcome (and not so much) guests in Iberian Hermit Crabs

Home selection and regular welcome (and not so much) guests in Iberian Hermit Crabs