Productive Symbiosis Research Articles

Influence of cultivation techniques on productivity and quality of meadow clover

Meadow clover (red clover) is the most important fodder plant in most parts of Russia. Positive characteristics of this plant are the presence of a significant amount of reserve nutrients (crude protein, protein, nitrogenfree extractive substances) in the composition of plant tissues, which provides high fodder value. As a legume, meadow clover accumulates in the soil organically bound nitrogen, a large amount of organic mass of crop root residues, enriching the soil with nutrients and contributing to the increase of its physical and mechanical properties. The disadvantage of this crop is its short productive life. In this regard, it is necessary to intensify the cultivation methods for a short period of use in order to obtain the greatest return from the crop in the fodder and agronomic aspect. Intensification of cultivation methods means everything that contributes to the increase of plant productivity: application of mineral and organic fertilizers to improve mineral nutrition, inoculation of seeds before sowing to mobilize and activate soil microflora and productive symbiosis between plants and microbiota, use of growth regulators to optimize photosynthesis processes. The study of the influence of these intensification methods was the purpose of our research. It was found that the use of estimated doses of mineral fertilizers contributed most optimally to the processes of yield formation and final productivity of clover grass. Among all the strains of nodule bacteria studied, inoculant strain 348a was the most effective because it is speciesspecific for meadow clover. The use of growth regulators Ribav Extra and Root Super is a positive technique that provides optimal growth and development of plants during vegetation. The methods studied also had a positive effect on the seed productivity of the clover plants, increasing yield and seed quality.

Animali in città

More and more wild animals find refuge in cities, due to the growth of urbanized areas, the devastation of natural habitats and the intensive transformation of agricultural spaces. The presence of wildlife increases conflicts but is also generating interesting considerations on the relationship between man and nature, based on empathy and the comprehension of animal. New co-evolution paths within cities, anthropic habitat par excellence, imply a different way of relating to the "wild" or "feral" to produce generative alliances and new shared habitat. The landscape project must come out of the comfort zone of a design conceived exclusively for human consumption and well-being: spaces of interspecies co-operation (productive symbiosis), generating responses of mutual adaptation to environmental and climatic changes; new places of co-habitat for both humans and animals; immersive spaces, for empathic and emotional cognition capable to sensitizing became aware of the interconnections between all living species and their common habitat.

Animali in città

More and more wild animals find refuge in cities, due to the growth of urbanized areas, the devastation of natural habitats and the intensive transformation of agricultural spaces. The presence of wildlife increases conflicts but is also generating interesting considerations on the relationship between man and nature, based on empathy and the comprehension of animal. New co-evolution paths within cities, anthropic habitat par excellence, imply a different way of relating to the ‘wild’ or ‘feral’ to produce generative alliances and new shared habitat. The landscape project must come out of the comfort zone of a design conceived exclusively for human consumption and well-being: spaces of interspecies co-operation (productive symbiosis), generating responses of mutual adaptation to environmental and climatic changes; new places of co-habitat for both humans and animals; immersive spaces, for empathic and emotional cognition capable to sensitizing became aware of the interconnections between all living species and their common habitat.

Lifelong learning and personal learning environments: a productive symbiosis in higher education

The aim of this study was to analyze lifelong learning (LLL) and its relationship with the educational approach of the personal learning environment (PLE). In the last year students do various degrees at a university in Costa Rica. METHOD. Using a non-experimental, transactional design, we applied a probabilistic questionnaire where the representative sample was (n=1187). RESULTS. The results show that the LLL scale used is a valid, and the tool used to explore the topic is reliable. In addition, we saw a moderate inclination towards lifelong learning in the students, mainly about all the application capability of new knowings and skills in practical surroundings, and how they relate to the new learning with previous acquisitions. DISCUSSION. It is observed a significant relationship among this training approach and personal learning environments, characterized by the use of the potential offered by technological tools. It has been found significant differences by gender, knowledge area, academic performance, and internet connection hours. Among the conclusions, it is pointed out that the universities must foster the linked competences with LLL to boost the PLE of the learners and propitiate its optimum social and professional insertion along their vital route.

Sinorhizobium medicae WSM419 Genes That Improve Symbiosis between Sinorhizobium meliloti Rm1021 and Medicago truncatula Jemalong A17 and in Other Symbiosis Systems.

Some soil bacteria, called rhizobia, can interact symbiotically with legumes, in which they form nodules on the plant roots, where they can reduce atmospheric dinitrogen to ammonia, a form of nitrogen that can be used by growing plants. Rhizobium-plant combinations can differ in how successful this symbiosis is: for example, Sinorhizobium meliloti Rm1021 forms a relatively ineffective symbiosis with Medicago truncatula Jemalong A17, but Sinorhizobium medicae WSM419 is able to support more vigorous plant growth. Using proteomic data from free-living and symbiotic S. medicae WSM419, we previously identified a subset of proteins that were not closely related to any S. meliloti Rm1021 proteins and speculated that adding one or more of these proteins to S. meliloti Rm1021 would increase its effectiveness on M. truncatula A17. Three genes, Smed_3503, Smed_5985, and Smed_6456, were cloned into S. meliloti Rm1021 downstream of the E. coli lacZ promoter. Strains with these genes increased nodulation and improved plant growth, individually and in combination with one another. Smed_3503, renamed iseA (increased symbiotic effectiveness), had the largest impact, increasing M. truncatula biomass by 61%. iseA homologs were present in all currently sequenced S. medicae strains but were infrequent in other Sinorhizobium isolates. Rhizobium leguminosarum bv. viciae 3841 containing iseA led to more nodules on pea and lentil. Split-root experiments with M. truncatula A17 indicated that S. meliloti Rm1021 carrying the S. medicae iseA is less sensitive to plant-induced resistance to rhizobial infection, suggesting an interaction with the plant's regulation of nodule formation. IMPORTANCE Legume symbiosis with rhizobia is highly specific. Rhizobia that can nodulate and fix nitrogen on one legume species are often unable to associate with a different species. The interaction can be more subtle. Symbiotically enhanced growth of the host plant can differ substantially when nodules are formed by different rhizobial isolates of a species, much like disease severity can differ when conspecific isolates of pathogenic bacteria infect different cultivars. Much is known about bacterial genes essential for a productive symbiosis, but less is understood about genes that marginally improve performance. We used a proteomic strategy to identify Sinorhizobium genes that contribute to plant growth differences that are seen when two different strains nodulate M. truncatula A17. These genes could also alter the symbiosis between R. leguminosarum bv. viciae 3841 and pea or lentil, suggesting that this approach identifies new genes that may more generally contribute to symbiotic productivity.

Determinants of Host Range Specificity in Legume-Rhizobia Symbiosis.

Leguminous plants possess the almost unique ability to enter symbiosis with soil-resident, nitrogen fixing bacteria called rhizobia. During this symbiosis, the bacteria physically colonize specialized organs on the roots of the host plant called nodules, where they reduce atmospheric nitrogen into forms that can be assimilated by the host plant and receive photosynthates in return. In order for nodule development to occur, there is extensive chemical cross-talk between both parties during the formative stages of the symbiosis. The vast majority of the legume family are capable of forming root nodules and typically rhizobia are only able to fix nitrogen within the context of this symbiotic association. However, many legume species only enter productive symbiosis with a few, or even single rhizobial species or strains, and vice-versa. Permitting symbiosis with only rhizobial strains that will be able to fix nitrogen with high efficiency is a crucial strategy for the host plant to prevent cheating by rhizobia. This selectivity is enforced at all stages of the symbiosis, with partner choice beginning during the initial communication between the plant and rhizobia. However, it can also be influenced even once nitrogen-fixing nodules have developed on the root. This review sets out current knowledge about the molecular mechanisms employed by both parties to influence host range during legume-rhizobia symbiosis.

Spectroscopic Kernel Quality from a Symbiotic Corn Production

The management of the inoculation of a plant’s roots, by means of biofertilizers (BF) containing arbuscular mycorrhizal (AM) fungi, is aimed at inducing modifications of the quality of the seeds. It is here shown that a seed-soil treatment can be elicited in the fingerprints of a symbiotic treatment using Near Infra Red (NIR)-SCiO NIR-SCiO spectra collections of single kernels: overall, a sensitivity of 73% and a specificity of 73% have been achieved, thus suggesting that it may be possible to assign the symbiotic origin of corn from just twenty kernels, provided that the dataset is adequately representative of the cultivar and AM. A global correlation study has shown a positive general trend (R2 0.45) of quality vs. quantity, in the sense that an increase in yield corresponded to an increase in the spectral differences between the symbiotic spectra and the control ones, but the inverse was also true, as a result of the parasitic behaviour of the BF treatments. The efficacy of the symbiosis can be back predicted from the NIR spectra; in fact, around 90% of the positive yield outcome results were discriminated from the negative ones. A reduction in the foliar pH (R2 0.37) and an increase in the foliar protein (R2 0.43) were observed as immediate phenotypic signs of a productive symbiosis. The commercial raw composition of the kernels appeared to only be affected slightly by the BF treatments; thus, till now uncharted secondary compounds of the maize kernels are involved, as supported by animal performances.

Ese quimérico museo de formas inconstantes. (Notas sobre el relato «Funes el memorioso», de J.L. Borges)

This article analyzes the meaning and philosophical scope of «Funes el memorioso», a short story by J.L.Borges. «Funes el memorioso» participates in the productive symbiosis between literature and philosophy, a characteristic which is evident in most of Borges’ work and which has taken Borge’s creations to the summit of Western culture. Furthermore, by reading «Funes el memorioso» we can draw connections between the work of J.L.Borges and some of the most important authors in the History of Philosophy. We try to show that the epistemologies of Plato and Hume, authors that Borges knew perfectly, influenced the creation of this short story in a decisive manner.

“Innovation has a lot to do with your ability to recognise surprising and unusual phenomena.”―Herbert Simon

“Innovation has a lot to do with your ability to recognise surprising and unusual phenomena.”―Herbert Simon

Health, environment and colonial legacies: Situating the science of pesticides, bananas and bodies in Ecuador

Pesticide-related health impacts in Ecuador's banana industry illustrate the need to understand science's social production in the context of major North-South inequities. This paper explores colonialism's ongoing context-specific relationships to science, and what these imply for population health inquiry and praxis. Themes in postcolonial science and technology studies and critical Latin American scholarship guide this exploration, oriented around an ethnographic case study of bananas, pesticides and health in Ecuador. The challenge of explaining these impacts prompts us to explore discursive and contextual dynamics of pesticide toxicology and phytopathology, two disciplines integral to understanding pesticide-health linkages. The evolution of banana phytopathology reflects patterns of banana production and plant science in settings made accessible to scientists by European colonialism and American military interventions. Similarly, American foreign policy in Cold War-era Latin America created conditions for widespread pesticide exposures and accompanying health science research. Neocolonial representations of the global South interacted with these material realities in fostering generation of scientific knowledge. Implications for health praxis include troubling celebratory portrayals of global interconnectedness in the field of global health, motivating critical political economy and radical community-based approaches in their place. Another implication is a challenge to conciliatory corporate engagement approaches in health research, given banana production's symbiosis of scientifically ‘productive’ military and corporate initiatives. Similarly, the origins and evolution of toxicology should promote humility and precautionary approaches in addressing environmental injustices such as pesticide toxicity, given the role of corporate actors in promoting systematic underestimation of risk to vulnerable populations. Perhaps most unsettlingly, the very structures and processes that drive health inequities in Ecuador's banana industry simultaneously shape production of knowledge about those inequities. Public health scholars should thus move beyond simply carrying out more, or better, studies, and pursue the structural changes needed to redress historical and ongoing injustices.

The Multilevel Nature of Customer Experience Research: An Integrative Review and Research Agenda

AbstractOver the last three decades, customer experience (CE) has developed from a burgeoning concept to a widely recognized phenomenon in terms of both research and practice. To account for the complexity of consumption decisions, the CE literature encompasses both the rational information processing approach to consumer decision‐making and the experiential approach, which includes emotions, feelings and sub‐consciousness. The authors classify and examine CE research on two levels. Studies on static CE analyze experiences during touchpoints at one point in time, while studies on dynamic CE assess how experiences evolve over time. Furthermore, both static and dynamic CE research take place from two distinct theoretical perspectives: the organization and the consumer. As both theoretical perspectives essentially deal with the same phenomenon – the organizational perspective with the creation of CEs and the consumer perspective with the perception of customer experiences – there is potential for a productive symbiosis between them. The authors propose that connecting insights from both perspectives can contribute to a better understanding of what constitutes a CE for consumers and how firms can effectively manage it. First, the authors discuss the development of CE and argue that it has evolved into a broad and fragmented ‘umbrella construct’. Second, after distinguishing and defining static and dynamic CE, they systematically evaluate the state of knowledge in both the organizational and consumer perspectives. Finally, they develop an agenda for future research that integrates the consumer perspective into organizational CE research.

With God and Guitars: Popular Music, Socialism, and the Church in East Germany

In the socialist German Democratic Republic (GDR), the Church entered into a long-term, complex and productive symbiosis with popular music. Beginning in the 1950s, reform-minded pastors opened their doors to jazz, and, later, almost the entire spectrum of popular music could be found in their churches: from pop hits, beat, rock, blues to singer/songwriters and punk. The interplay between the Church and popular music gave rise to a highly unique communicative space, a counterpart to the rigidly organized public realm. Here, political dissidents took refuge from a repressive system and were free to examine their society critically. This political force infused the alliance of the Church and popular music in East Germany with an explosive quality. To examine the specifics of this alliance, this article traces three major trends: the assimilation of African-American music, the reform of the traditional religious hymn, and the linking of youth ministry with popular music. The analysis of these three trends illuminates the particularities of the relationship between the Church and popular music in the GDR from a quantitative, qualitative, and historical perspective.

Проблемы и перспективы вовлечения символических ресурсов в сферу туризма (на примере Пермского края)

The article analyses aspects of the development of human and cultural geography and the concepts of «geographic image of a territory» and «cultural landscape». From the point of view of modern tourist requirements it is necessary to allocate along with the natural and historical-cultural the symbolic resources of tourism. The author agrees with experts that offer productive symbiosis of geography and mythogeography when such studies are part of humanitarian-geographical and cultural developments. The study of spatial representations produced by them, and geographical images and any other interpretations of the space, is of great interest in applied key. Based on the structural-semiotic approach the legend can be considered as an ancient symbolic form, so the myths of a particular area are not only a basic part of the symbolic resources, but also access to the group of potential customers in tourism. Legends of specific places, is the basis for the emergence of tourist motive and trip. Popular tourism legend or myth, used in socicultural design, is often superior to the real tourist attractiveness of the territory, with the prospects of regional image and brand. Involving the legends in tourism, in turn, are encouraged to consider as the practical direction of cultural geography and an effective marketing mechanism for the tourism development of a territory, its image and way to attract potential consumers, who perceive geographical space as the images of various degrees of subjectivity. Using the example of Perm region the author demonstrates the problems and prospects of involvement of symbolic resources in regional tourism, in which myths and legends play an important role.

Function of Succinoglycan Polysaccharide in Sinorhizobium meliloti Host Plant Invasion Depends on Succinylation, Not Molecular Weight

ABSTRACTThe acidic polysaccharide succinoglycan produced by the rhizobial symbiont Sinorhizobium meliloti 1021 is required for this bacterium to invade the host plant Medicago truncatula and establish a nitrogen-fixing symbiosis. S. meliloti mutants that cannot make succinoglycan cannot initiate invasion structures called infection threads in plant root hairs. S. meliloti exoH mutants that cannot succinylate succinoglycan are also unable to form infection threads, despite the fact that they make large quantities of succinoglycan. Succinoglycan produced by exoH mutants is refractory to cleavage by the glycanases encoded by exoK and exsH, and thus succinoglycan produced by exoH mutants is made only in the high-molecular-weight (HMW) form. One interpretation of the symbiotic defect of exoH mutants is that the low-molecular-weight (LMW) form of succinoglycan is required for infection thread formation. However, our data demonstrate that production of the HMW form of succinoglycan by S. meliloti 1021 is sufficient for invasion of the host M. truncatula and that the LMW form is not required. Here, we show that S. meliloti strains deficient in the exoK- and exsH-encoded glycanases invade M. truncatula and form a productive symbiosis, although they do this with somewhat less efficiency than the wild type. We have also characterized the polysaccharides produced by these double glycanase mutants and determined that they consist of only HMW succinoglycan and no detectable LMW succinoglycan. This demonstrates that LMW succinoglycan is not required for host invasion. These results suggest succinoglycan function is not dependent upon the presence of a small, readily diffusible form.

Teaching and Learning Transformative Processes (The Winter School Program)

Scientific studies never replace or supplant subjective theories, but in the best case, enter a productive symbiosis; they can contribute to reflecting on and understanding one's own assumptions and thereby make them available to change. It is pedagogically sensible to address this tension between scientific and subjective theory, and thereby make pedagogical reflection accessible. For this reason, we bring forward the argument that practical experience in the field of education must precede a course of study using the scientific, theory-oriented approach to teacher training. This turns conventional education theory upside down: normally a well-grounded scientific education is required first, followed by cautious experiences in practical areas. Consequently, a valuable source of pedagogical knowledge is underrated, and regretfully also often discredited. The awareness and reflection of one's own subjective theories have to, however, be an integral part of any educational discussion of pedagogy and learning. The idea of allowing educational experiences without previous scientific education was tested in the Winter School Program, Modern Teaching Methods, at Telavi State University. The participants in the Winter School Program were students from different disciplines. None had previously studied in the field of education. The participants were thus highly heterogeneous with respect to their educational training, but homogeneous with respect to their inexperience in educational studies. The interaction of the participants with theoretical assumptions of and models of pedagogy, on the one hand, and their own experiences, on the other, generated a productive tension that makes continuing related learning very probable.

“A Story Telling and a Story Reading Age”: Textuality and Sociability in the Romantic Frame Tale

MARK ITTENSOHN “A Story Telling and a Story Reading Age”: Textuality and Sociability in the Romantic Frame Tale I N RECENT YEARS, ROMANTIC STUDIES HAS COME TO DEVOTE MORE AND more attention to the period’s conception of sociability in connection with the production and dissemination of literary texts.1 What is often stressed in contemporary scholarship is that behind Romanticism’s ro­ mance with individualism and solitariness lay an environment of sociable and interpersonal exchange that decisively conditioned the parameters un­ der which texts were actually produced. As William St. Clair notes: “[w]hatever the initial transfer from mind to paper, the creation of a text was seldom a solitary activity. ”2 In Romantic Sociability, their recent standard volume on the topic, Gillian Russell and Clara Tuite stress that the elucida­ tion of individual modes and forms of sociability during the Romantic pe­ riod has two chief benefits. First, it helps further contextualize Romantic works, since, as they note, various types ofinterpersonal exchange “formed i. The best classic examples are without a doubt Jeffrey N. Cox, Poetry and Politics in the Cockney School: Keats, Shelley, Hunt and their Circle (Cambridge: Cambridge University Press, 1998) and Jack Stillinger, Multiple Authorship and the Myth of the Solitary Genius (New York and Oxford: Oxford University Press, 1991). More recently, these studies have been joined by more broad and internationally wide-ranging works such as: Angela Esterhammer, Ro­ manticism and Improvisation, 1750—1850 (Cambridge: Cambridge University Press, 2008); Tim Fulford, Romantic Poetry and Literary Coteries: The Dialect of the Tribe (New York: Palgrave Macmillan, 2015); Jon Mee, Conversable Worlds: Literature, Contention and Community 1762 to 1850 (Oxford: Oxford University Press, 2011); Gilllian Russell, Women, Sociability and Theatre in Georgian London (Cambridge: Cambridge University Press, 2007); Russell and Tuite, eds., Romantic Sociability: Social Networks and Literary Culture in Britain, 1770—1840 (Cambridge: Cambridge University Press, 2002); Susanne Schmid, ed., Einsamkeit und Geselligkeit um 1800 (Heidelberg: Universitatsverlag Winter, 2008); Susan Wolfson, Romantic Interactions: Social Being and the Turns of Literary Action (Baltimore: Johns Hopkins University Press, 2010). 2. St. Clair, The Reading Nation in the Romantic Period (Cambridge: Cambridge University Press, 2004), 158. SiR, 55 (Fall 2016) 393 394 MARK ITTENSOHN the sociable contexts in which literary production was discussed, circulated and sometimes created.”3 Second, and more importantly, Russell and Tuite emphasize that an engagement with the period’s conceptions of interper­ sonal exchange reveals sociability as a “kind of text in its own right,” one that was not solely restricted to real life exchanges (dinner parties, debating clubs, salons), but that came to be reiterated in particular text-types of the period such as diaries, letters, and, above all, periodical publications.4 Such observations not only generate additional knowledge about the period, they also carry considerable revisionist traction. Romantic sociability, these views suggest, has too long been overshadowed by an overt emphasis on textuality and its function as a substitutional medium. It is commonly acknowledged that the Enlightenment conceived of writing as an effective aid to sociability since it enabled conversation across geographical or national-political boundaries.5 Such perceptions no longer subordinated the written to the spoken word, but merged them into a pro­ ductive symbiosis, thereby reworking such classic conceptualizations as Plato’s in Phaedrus where texts are figured as particularly incompetent social beings.6 As critics ofthe early Romantic period have emphasized, however, this more or less equated relationship between the written and the sociable was undergoing a broad shift in cultural response by the turn of the cen­ tury.7 In 1790s Britain, the production and dissemination of textuality was steadily rising, aided by increased literacy rates and new publishing technol­ ogies, while the traditional eighteenth-century values ofsociability seemed, by contrast, to lose their footing. Haunted by governmental repression of free speech and radical thinking, and in many ways sublimated by the pos­ sibilities of (anonymous) textual production, the famous model of coffee­ house sociability, so vital to the project ofthe eighteenth-century Republic ofLetters, moved more and more into the cultural margin.8 In 1790, for in­ stance, the Edinburgh journal The Bee suggested to its readers that the tex3 . Russell and Tuite, “Introducing Romantic Sociability,” in...

An antimicrobial peptide essential for bacterial survival in the nitrogen-fixing symbiosis

In the nitrogen-fixing symbiosis between legume hosts and rhizobia, the bacteria are engulfed by a plant cell membrane to become intracellular organelles. In the model legume Medicago truncatula, internalization and differentiation of Sinorhizobium (also known as Ensifer) meliloti is a prerequisite for nitrogen fixation. The host mechanisms that ensure the long-term survival of differentiating intracellular bacteria (bacteroids) in this unusual association are unclear. The M. truncatula defective nitrogen fixation4 (dnf4) mutant is unable to form a productive symbiosis, even though late symbiotic marker genes are expressed in mutant nodules. We discovered that in the dnf4 mutant, bacteroids can apparently differentiate, but they fail to persist within host cells in the process. We found that the DNF4 gene encodes NCR211, a member of the family of nodule-specific cysteine-rich (NCR) peptides. The phenotype of dnf4 suggests that NCR211 acts to promote the intracellular survival of differentiating bacteroids. The greatest expression of DNF4 was observed in the nodule interzone II-III, where bacteroids undergo differentiation. A translational fusion of DNF4 with GFP localizes to the peribacteroid space, and synthetic NCR211 prevents free-living S. meliloti from forming colonies, in contrast to mock controls, suggesting that DNF4 may interact with bacteroids directly or indirectly for its function. Our findings indicate that a successful symbiosis requires host effectors that not only induce bacterial differentiation, but also that maintain intracellular bacteroids during the host-symbiont interaction. The discovery of NCR211 peptides that maintain bacterial survival inside host cells has important implications for improving legume crops.

RELIGION AND HUMAN RIGHTS: TOWARDS A BETTER UNDERSTANDING

This article affirms the complex relationship be­tween religious teachings and human rights prin­ciples in today's world, and is aimed at contributing approaches towards a better understanding of the relationship. It attempts to explore and promote necessary means of realising a harmonious co-existence between them. The article provides a general analysis of the different theoretical per­spectives of the relationship between religion and human rights, highlighting the key framework that could facilitate a better understanding between the two systems. It commences with a bnef analysis of both religion and human rights as interdependent forms of social ordering, followed by an analysis of the theoretical conceptualisations of the relation­ship by suggesting three relevant theoretical mo­dels: the separationist, the accomodationist and the double-edged conceptions. Indicating preference for the second, this article demonstrates the possibility of a healthy and productive symbiosis between religion and human rights.

The Succinoglycan Endoglycanase Encoded by exoK Is Required for Efficient Symbiosis of Sinorhizobium meliloti 1021 with the Host Plants Medicago truncatula and Medicago sativa (Alfalfa)

The acidic polysaccharide succinoglycan produced by the nitrogen-fixing rhizobial symbiont Sinorhizobium meliloti 1021 is required for this bacterium to invade the host plant Medicago truncatula and to efficiently invade the host plant M. sativa (alfalfa). The β-glucanase enzyme encoded by exoK has previously been demonstrated to cleave succinoglycan and participate in producing the low molecular weight form of this polysaccharide. Here, we show that exoK is required for efficient S. meliloti invasion of both M. truncatula and alfalfa. Deletion mutants of exoK have a substantial reduction in symbiotic productivity on both of these plant hosts. Insertion mutants of exoK have an even less productive symbiosis than the deletion mutants with the host M. truncatula that is caused by a secondary effect of the insertion itself, and may be due to a polar effect on the expression of the downstream exoLAMON genes.

Genetic determinants of swimming motility in the squid light‐organ symbiont Vibrio fischeri

Bacterial flagellar motility is a complex cellular behavior required for the colonization of the light-emitting organ of the Hawaiian bobtail squid, Euprymna scolopes, by the beneficial bioluminescent symbiont Vibrio fischeri. We characterized the basis of this behavior by performing (i) a forward genetic screen to identify mutants defective in soft-agar motility, as well as (ii) a transcriptional analysis to determine the genes that are expressed downstream of the flagellar master regulator FlrA. Mutants with severe defects in soft-agar motility were identified due to insertions in genes with putative roles in flagellar motility and in genes that were unexpected, including those predicted to encode hypothetical proteins and cell division–related proteins. Analysis of mutants for their ability to enter into a productive symbiosis indicated that flagellar motility mutants are deficient, while chemotaxis mutants are able to colonize a subset of juvenile squid to light-producing levels. Thirty-three genes required for normal motility in soft agar were also downregulated in the absence of FlrA, suggesting they belong to the flagellar regulon of V. fischeri. Mutagenesis of putative paralogs of the flagellar motility genes motA motB, and fliL revealed that motA1 motB1, and both fliL1 and fliL2, but not motA2 and motB2, likely contribute to soft-agar motility. Using these complementary approaches, we have characterized the genetic basis of flagellar motility in V. fischeri and furthered our understanding of the roles of flagellar motility and chemotaxis in colonization of the juvenile squid, including identifying 11 novel mutants unable to enter into a productive light-organ symbiosis.