Symbiotic Capability Research Articles

The Social Embeddedness of Leadership: Unfolding the Trajectories of Individual Policy Capacity in Regional Development in East Java, Indonesia

Leadership competencies act as a precursor in catalysing bureaucratic reform and propelling long-term development, yet the multitude of political tensions and policy conundrums has called for a deeper examination of the individual capabilities needed to satisfy public expectations. Taking on a comparative case study approach in East Java, Indonesia, we dissect the dynamic relationship between leadership competencies, individual policy capacity and regional development, positioning that these three elements form a symbiotic capability matrix that transcends their individual boundaries. We unveil how autonomous and proactive leaders, while operating within established structures and networks, leverage the power of social embeddedness, thus crystallizing it as an integral pillar for successful regional development. Through the embodiment of interdependence and relational dynamics, we foster a paradigm shift from an individualistic perspective to a context-aware, relation-centred approach within leadership and regional development landscapes.

Tulasnella calospora (UAMH 9824) retains its effectiveness at facilitating orchid symbiotic germination in vitro after two decades of subculturing

BackgroundThe technique of symbiotic germination—using mycorrhizal fungi to propagate orchids from seed in vitro—has been used as one method to cultivate orchids in North America and abroad for > 30 years. A long-held assumption is that mycorrhizal fungi used for this purpose lose their effectiveness at germinating seeds over time with repeated subculturing.ResultsWe provide evidence for the lingering efficacy of one particular strain of Tulasnella calospora (266; UAMH 9824) to stimulate seed germination exemplified by the North American terrestrial orchid, Spiranthes cernua, as a case study. This fungus was originally acquired from roots from Spiranthes brevilabris in 1999 and sub-cultured during the two decades since. Seeds inoculated with the fungus in vitro developed to an advanced protocorm stage after 16 days, and leaf elongation was pronounced after 42 days. In a pilot study, seedlings co-cultured with Tulasnella calospora 266 were deflasked after 331 days and later transferred to soil under greenhouse conditions where they eventually initiated anthesis. During the course of two decades, seeds of 39 orchid species, cultivars and hybrids spanning 21 genera, germinated in vitro co-cultured with Tulasnella calospora 266. These orchids included temperate terrestrials and tropical epiphytes alike.ConclusionsThe sustained effectiveness of this fungus is noteworthy because it argues against the concept of mycorrhizal fungi losing their symbiotic capability through prolonged subculturing. This study serves as an example of why in situ habitat preservation is essential for the conservation of orchids as a source of potentially useful mycorrhizal fungi.

Proline auxotrophy in Sinorhizobium meliloti results in a plant-specific symbiotic phenotype.

In order to effectively manipulate rhizobium-legume symbioses for our benefit, it is crucial to first gain a complete understanding of the underlying genetics and metabolism. Studies with rhizobium auxotrophs have provided insight into the requirement for amino acid biosynthesis during the symbiosis; however, a paucity of available L-proline auxotrophs has limited our understanding of the role of L-proline biosynthesis. Here, we examined the symbiotic phenotypes of a recently described Sinorhizobium meliloti L-proline auxotroph. Proline auxotrophy was observed to result in a host-plant-specific phenotype. The S. meliloti auxotroph displayed reduced symbiotic capability with alfalfa (Medicago sativa) due to a decrease in nodule mass formed and therefore a reduction in nitrogen fixed per plant. However, the proline auxotroph formed nodules on white sweet clover (Melilotus alba) that failed to fix nitrogen. The rate of white sweet clover nodulation by the auxotroph was slightly delayed, but the final number of nodules per plant was not impacted. Examination of white sweet clover nodules by confocal microscopy and transmission electron microscopy revealed the presence of the S. meliloti proline auxotroph cells within the host legume cells, but few differentiated bacteroids were identified compared with the bacteroid-filled plant cells of WT nodules. Overall, these results indicated that L-proline biosynthesis is a general requirement for a fully effective nitrogen-fixing symbiosis, likely due to a transient requirement during bacteroid differentiation.

SYMBIOTIC EFFECTIVENESS AND COMPETITIVENESS OF CALOPO RHIZOBIAL ISOLATES IN AN ARGISSOLO VERMELHO-AMARELO UNDER THREE VEGETATION COVERS IN THE DRY FOREST ZONE OF PERNAMBUCO

Biological N fixation in forage legumes is an important alternative to reduce pasture degradation, and is strongly influenced by the inoculant symbiotic capability. This paper evaluates the effectiveness of Calopo (Calopogonium mucunoides) rhizobial isolated from soil under three vegetation covers of an Argissolo Vermelho-Amarelo of the Dry Forest Zone of Pernambuco. An experiment was conducted evaluating 25 isolates, aside from 5 uninoculated controls with 0; 309; 60; 90 and 120 kg ha-1 N, and a treatment inoculated with the SEMIA 6152 strain. The first cut was performed 45 days after inoculation and a second and third cut after 45-day-intervals. Shoot N content was quantified at all cuts. Shoot dry mass was affected by N rates at all cuts. Shoot dry mass increased from the first to the second cut in inoculated plants. There was no difference between rhizobial isolates from the different plant covers for any of the variables. Most variables were significantly and positively correlated.

Inactivation of the lpcC gene alters surface-related properties and symbiotic capability of Bradyrhizobium japonicum

We investigated the role of the Bradyrhizobium japonicum lpcC gene, encoding a mannosyl transferase, involved in the lipopolysaccharide (LPS) biosynthesis. The inactivation of the lpcC gene considerably altered the LPS structure and the cell surface properties. LPS analysis showed that the lpcC mutant JS715 had an abnormal LPS structure deficient in O-antigen. The cell surface hydrophobicity increased approximately threefold in JS715 compared to the wild type. The increased cell surface hydrophobicity is likely to be related with cell aggregation in the mutant culture. For the growth comparison, JS715 showed slower growth rate than the wild type. The motility of JS715 decreased in soft agar plates, but it showed enhanced biofilm-forming ability. Interestingly, JS715 was not able to nodulate the host legume soybean (Glycine max). This study shows not only that lpcC is involved in the biosynthesis of O-antigen in the B.japonicum LPS, but also that inactivation of the lpcC gene affects symbiotic capability of B.japonicum and surface-related properties such as cell hydrophobicity, biofilm formation and motility. This study demonstrates the role of the B.japonicum lpcC in nodulation with soybean and importance of cell surface hydrophobicity. The results also highlight that intact LPS is required for successful symbiosis between B.japonicum and soybeans. Our findings not only support previous studies emphasizing the necessity of LPS on the interaction between the two symbiotic partners, but also contribute to a better understanding of the symbiotic mechanisms.

Genome sequence of the acid-tolerant Burkholderia sp. strain WSM2232 from Karijini National Park, Australia.

Burkholderia sp. strain WSM2232 is an aerobic, motile, Gram-negative, non-spore-forming acid-tolerant rod that was trapped in 2001 from acidic soil collected from Karijini National Park (Australia) using Gastrolobium capitatum as a host. WSM2232 was effective in nitrogen fixation with G. capitatum but subsequently lost symbiotic competence during long-term storage. Here we describe the features of Burkholderia sp. strain WSM2232, together with genome sequence information and its annotation. The 7,208,311 bp standard-draft genome is arranged into 72 scaffolds of 72 contigs containing 6,322 protein-coding genes and 61 RNA-only encoding genes. The loss of symbiotic capability can now be attributed to the loss of nodulation and nitrogen fixation genes from the genome. This rhizobial genome is one of 100 sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.

Symbiotic capability of calopo rhizobia from an agrisoil with different crops in Pernambuco

Biological nitrogen fixation by rhizobium-legume symbiosis represents one of the most important nitrogen sources for plants and depends strongly on the symbiotic efficiency of the rhizobium strain. This study evaluated the symbiotic capacity of rhizobial isolates from calopo (CALOPOGONIUM MUCUNOIDES) taken from an agrisoil under BRACHIARIA DECUMBENS pasture, sabiá (MIMOSA CAESALPINIIFOLIA) plantations and Atlantic Forest areas of the Dry Forest Zone of Pernambuco. A total of 1,575 isolates were obtained from 398 groups. A single random isolate of each group was authenticated, in randomized blocks with two replications. Each plant was inoculated with 1 mL of a bacterial broth, containing an estimated population of 10(8) rhizobial cells mL-1. Forty-five days after inoculation, the plants were harvested, separated into shoots, roots and nodules, oven-dried to constant mass, and weighed. Next, the symbiotic capability was tested with 1.5 kg of an autoclaved sand:vermiculite (1:1) mixture in polyethylene bags. The treatments consisted of 122 authenticated isolates, selected based on the shoot dry matter, five uninoculated controls (treated with 0, 50, 100, 150, or 200 kg ha-1 N) and a control inoculated with SEMIA 6152 (=BR1602), a strain of BRADYRHIZOBIUM JAPONICUM The test was performed as described above. The shoot dry matter of the plants inoculated with the most effective isolates did not differ from that of plants treated with 150 kg ha-1 N. Shoot dry matter was positively correlated with all other variables. The proportion of effective isolates was highest among isolates from SABIÁ forests. There was great variation in nodule dry weight, as well as in N contents and total N.

A Mesorhizobium loti mutant with reduced glucan content shows defective invasion of its host plant Lotus japonicus

Random transposon mutagenesis led to the isolation of a novel Mesorhizobium loti mutant that is defective in nitrogen fixation during symbiosis with Lotus japonicus. The mutated locus, designated cep, encodes a putative cell-envelope protein displaying no significant sequence similarity to proteins with known functions. This mutant elicits the formation of nodule-like bumps and root-hair curling, but not the elongation of infection threads, on L. japonicus roots. This is reminiscent of the phenotypes of rhizobial mutants impaired in cyclic beta-glucan biosynthesis. The cep mutant exhibits partially reduced content of cell-associated glucans and intermediate deficiency of motility under hypo-osmotic conditions as compared to a glucan-deficient mutant. Second-site pseudorevertants of the cep mutant were isolated by selecting for restoration of symbiotic nitrogen fixation. A subset of pseudorevertants restored both symbiotic capability and glucan content to levels comparable to that of the wild-type. These results suggest that the Cep product acts on a successful symbiosis by affecting cell-associated glucan content.

Host specificity and phenotypic diversity of Rhizobium strains nodulating Leucaena, Acacia, and Sesbania in Egypt

Phenotypic diversity was studied among 13 Rhizobium strains selected from a total of 160 Rhizobium isolates from root nodules of Leucaena leucocephala. Two strains from Acacia saligna and two strains from Sesbania sesban plants were included in the examination for host range in the greenhouse. The Rhizobium sp. (Leucaena) strains were different from the reference strains and fell into three distinct groups for the utilization of 95 different carbon sources. Four of the best symbionts constituted a group, the majority of the strains fell into a second group, and strain DS 91 was the only member of the third group. Strains were effective symbionts for their original hosts. Nine strains were tolerant to elevated temperature (>42°C), and three strains were resistant to high salinity (>3% NaCl). All Rhizobium sp. (Leucaena) strains effectively nodulated L. leucocephala and L. culensii, but nitrogen fixation was greater with L. leucocephala than with L. culensii. These strains failed to form effective symbioses with two other species of Leucaena (L. retusa and L. divursiflora) or with alfalfa, Medicago sativa. Rhizobium sp. (Leucaena) strains DS 65, DS 78, and DS 158 nodulated and efficiently fixed nitrogen with Phaseolus vulgaris, with DS 65 showing the highest symbiotic capability. Strain DS 65 also nodulated and fixed nitrogen with Glycine max and Vigna sinensis. Nodulation of Leucaena by two Bradyrhizobium sp. (Acacia) strains was sparse. Strain DS 101 from Sesbania formed nodules on Leucaena, whereas the other strain from Sesbania, DS 110, failed to nodulate this genus.

Active N2 fixation in several Faidherbia albida provenances

For tree legumes, Faidherbia albida is among those with low symbiotic capability, and for which significant improvement is needed. An experiment was conducted in the greenhouse, using the 15N isotope dilution technique to measure differences in the proportion (%Ndfa) and total N fixed in seven F. albida provenances grown in an Arenosol soil in Senegal. Total dry matter and N yield values were not significantly different among the seven provenances. In contrast, significant variability was measured in N2 fixation, with %Ndfa ranging from 0% in two provenances to 38% in the Kabrousse provenance. Also, total N fixed was highest in Kabrousse, 0.44 g N plant‐1, compared with the 0 to 0.26 g plant‐1 fixed in the other provenances. Based on these results, Kabrouse was selected for further examination in the field, where still higher %Ndfa values were obtained, 54, 58, and 54% at 3, 6, and 15 months after transplanting (MAT), respectively. These are higher than the commonly reported values of %Ndfa for F. albida, and indicate the potential of screening as a tool for obtaining higher N2 fixation in NFTs. Total N fixed, unlike %Ndfa, which remained fairly constant during the three harvest periods, increased from 0.54 at 3 MAT to 1.41 g N plant‐1 at 15 MAT.

Symbiotic interactions in the EVOLVE III ecosystem model

Parasitic feeding mechanisms were introduced into the EVOLVE III ecosystem model. The modified system exhibited a number of interesting behaviors, including obligative and facultative parasitism, transient facultative mutualism and nonsymbiotic feeding. Speciation and massive die-offs were also observed. The introduction of a symbiotic capability altered the coevolutionary development of traits that exhibited an arms race when the symbiotic capability was not present. Stable mutualisms were not possible in the present version of the model due to the restriction that organisms were not allowed to feed both on other organisms and from the environment at the same time. The ecosystem biomass increased with increased symbiotic activity. Biomass was influenced by the balance of virulence and resistance traits in the population and decreased as these traits became more disparate.

Studies on induced variation in the rhizobia. II. Radiation sensitivity and induction of antibiotic-resistance markers.

The relation between survival and dose of ultraviolet (UV) light or X rays was, with only one exception, nonlinear for late-log-phase cultures of four species of Rhizobium. The ld(90) for different bacterial strains ranged from 400 to 3,000 ergs per mm(2) for UV treatment, and from 3.0 to 7.5 kr for X-ray treatment. Minor existing differences in response to some antibacterial compounds (disc tests) were usable as secondary markers for genetic experiments. Spontaneous and radiation-induced mutants, resistant to high levels of several antibiotics, notably dihydrostreptomycin and erythromycin, were isolated for primary marker purposes. A significant phenotypic lag for mutation to dihydrostreptomycin resistance was noted for UV-irradiated cells. The UV-induced frequency exceeded the X-ray-induced frequency by a factor of at least three, at a comparable level of lethality. No significant change in the symbiotic capability was observed in rhizobial strains marked with antibiotics resistance.

Studies on Induced Variation in the Rhizobia

The relation between survival and dose of ultraviolet (UV) light or X rays was, with only one exception, nonlinear for late-log-phase cultures of four species of Rhizobium. The ld(90) for different bacterial strains ranged from 400 to 3,000 ergs per mm(2) for UV treatment, and from 3.0 to 7.5 kr for X-ray treatment. Minor existing differences in response to some antibacterial compounds (disc tests) were usable as secondary markers for genetic experiments. Spontaneous and radiation-induced mutants, resistant to high levels of several antibiotics, notably dihydrostreptomycin and erythromycin, were isolated for primary marker purposes. A significant phenotypic lag for mutation to dihydrostreptomycin resistance was noted for UV-irradiated cells. The UV-induced frequency exceeded the X-ray-induced frequency by a factor of at least three, at a comparable level of lethality. No significant change in the symbiotic capability was observed in rhizobial strains marked with antibiotics resistance.