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July 7, 2019  |  

Tryptorubin A: A polycyclic peptide from a fungus-derived Streptomycete.

Fungus-growing ants engage in complex symbiotic relationships with their fungal crop, specialized fungal pathogens, and bacteria that provide chemical defenses. In an effort to understand the evolutionary origins of this multilateral system, we investigated bacteria isolated from fungi. One bacterial strain (Streptomyces sp. CLI2509) from the bracket fungus Hymenochaete rubiginosa, produced an unusual peptide, tryptorubin A, which contains heteroaromatic links between side chains that give it a rigid polycyclic globular structure. The three-dimensional structure was determined by NMR and MS, including a (13)C-(13)C COSY of isotopically enriched material, degradation, derivatives, and computer modeling. Whole genome sequencing identified a likely pair of biosynthetic genes responsible for tryptorubin A’s linear hexapeptide backbone. The genome also revealed the close relationship between CLI2509 and Streptomyces sp. SPB78, which was previously implicated in an insect-bacterium symbiosis.


July 7, 2019  |  

Complete genome sequence of Mesorhizobium ciceri bv. biserrulae WSM1497, an efficient nitrogen-fixing microsymbiont of the forage legume Biserrula pelecinus.

We report here the complete genome sequence of Mesorhizobium ciceri bv. biserrulae strain WSM1497, the efficient nitrogen-fixing microsymbiont and commercial inoculant in Australia of the forage legume Biserrula pelecinus The genome consists of 7.2 Mb distributed across a single chromosome (6.67 Mb) and a single plasmid (0.53 Mb). Copyright © 2017 Brewer et al.


July 7, 2019  |  

Complete genome sequence of Paenibacillus yonginensis DCY84(T), a novel plant symbiont that promotes growth via induced systemic resistance.

This article reports the full genome sequence of Paenibacillus yonginensis DCY84(T) (KCTC33428, JCM19885), which is a Gram-positive rod-shaped bacterium isolated from humus soil of Yongin Forest in Gyeonggi Province, South Korea. The genome sequence of strain DCY84(T) provides greater understanding of the Paenibacillus species for practical use. This bacterium displays plant growth promotion via induced systemic resistance of abiotic stresses.


July 7, 2019  |  

The complete genome sequence of Ensifer meliloti strain CCMM B554 (FSM-MA), a highly effective nitrogen-fixing microsymbiont of Medicago truncatula Gaertn.

Strain CCMM B554, also known as FSM-MA, is a soil dwelling and nodule forming, nitrogen-fixing bacterium isolated from the nodules of the legume Medicago arborea L. in the Maamora Forest, Morocco. The strain forms effective nitrogen fixing nodules on species of the Medicago, Melilotus and Trigonella genera and is exceptional because it is a highly effective symbiotic partner of the two most widely used accessions, A17 and R108, of the model legume Medicago truncatula Gaertn. Based on 16S rRNA gene sequence, multilocus sequence and average nucleotide identity analyses, FSM-MA is identified as a new Ensifer meliloti strain. The genome is 6,70 Mbp and is comprised of the chromosome (3,64 Mbp) harboring 3574 predicted genes and two megaplasmids, pSymA (1,42 Mbp) and pSymB (1,64 Mbp) with respectively 1481 and 1595 predicted genes. The average GC content of the genome is 61.93%. The FSM-MA genome structure is highly similar and co-linear to other E. meliloti strains in the chromosome and the pSymB megaplasmid while, in contrast, it shows high variability in the pSymA plasmid. The large number of strain-specific sequences in pSymA as well as strain-specific genes on pSymB involved in the biosynthesis of the lipopolysaccharide and capsular polysaccharide surface polysaccharides may encode novel symbiotic functions explaining the high symbiotic performance of FSM-MA.


July 7, 2019  |  

Feathermoss and epiphytic Nostoc cooperate differently: expanding the spectrum of plant-cyanobacteria symbiosis.

Dinitrogen (N2)-fixation by cyanobacteria in symbiosis with feathermosses is the primary pathway of biological nitrogen (N) input into boreal forests. Despite its significance, little is known about the cyanobacterial gene repertoire and regulatory rewiring needed for the establishment and maintenance of the symbiosis. To determine gene acquisitions and regulatory changes allowing cyanobacteria to form and maintain this symbiosis, we compared genomically closely related symbiotic-competent and -incompetent Nostoc strains using a proteogenomics approach and an experimental set up allowing for controlled chemical and physical contact between partners. Thirty-two gene families were found only in the genomes of symbiotic strains, including some never before associated with cyanobacterial symbiosis. We identified conserved orthologs that were differentially expressed in symbiotic strains, including protein families involved in chemotaxis and motility, NO regulation, sulfate/phosphate transport, and glycosyl-modifying and oxidative stress-mediating exoenzymes. The physical moss-cyanobacteria epiphytic symbiosis is distinct from other cyanobacteria-plant symbioses, with Nostoc retaining motility, and lacking modulation of N2-fixation, photosynthesis, GS-GOGAT cycle and heterocyst formation. The results expand our knowledge base of plant-cyanobacterial symbioses, provide a model of information and material exchange in this ecologically significant symbiosis, and suggest new currencies, namely nitric oxide and aliphatic sulfonates, may be involved in establishing and maintaining the cyanobacteria-feathermoss symbiosis.


July 7, 2019  |  

Genetic and functional characterization of an extracellular modular GH6 endo-ß-1,4-glucanase from an earthworm symbiont, Cellulosimicrobium funkei HY-13.

The gene (1608-bp) encoding a GH6 endo-ß-1,4-glucanase (CelL) from the earthworm-symbiotic bacterium Cellulosimicrobium funkei HY-13 was cloned from its whole genome sequence, expressed recombinantly, and biochemically characterized. CelL (56.0 kDa) is a modular enzyme consisting of an N-terminal catalytic GH6 domain (from Val57 to Pro396), which is 71 % identical to a GH6 protein (accession no.: WP_034662937) from Cellulomonas sp. KRMCY2, together with a C-terminal CBM 2 domain (from Cys429 to Cys532). The highest catalytic activity of CelL toward carboxymethylcellulose (CMC) was observed at 50 °C and pH 5.0, and was relatively stable at a broad pH range of 4.0-10.0. The enzyme was capable of efficiently hydrolyzing the cellulosic polymers in the order of barley ß-1,3-1,4-D-glucan > CMC > lichenan > Avicel > konjac glucomannan. However, cellobiose, cellotriose, p-nitrophenyl derivatives of mono- and disaccharides, or structurally unrelated carbohydrate polymers including ß-1,3-D-glucan, ß-1,4-D-galactomannan, and ß-1,4-D-xylan were not susceptible to CelL. The enzymatic hydrolysis of cellopentaose resulted in the production of a mixture of 68.6 % cellobiose and 31.4 % cellotriose but barley ß-1,3-1,4-D-glucan was 100 % degraded to cellotriose by CelL. The enzyme strongly bound to Avicel, ivory nut mannan, and chitin but showed relatively weak binding affinity to lichenan, lignin, or poly(3-hydroxybutyrate) granules.


July 7, 2019  |  

Complete genome sequences of the obligate symbionts “Candidatus Sulcia muelleri” and “Ca. Nasuia deltocephalinicola” from the pestiferous leafhopper Macrosteles quadripunctulatus (Hemiptera: Cicadellidae).

Two bacterial symbionts of the European pest leafhopper, Macrosteles quadripunctulatus (Hemiptera: Cicadellidae), were fully sequenced. “Candidatus Sulcia muelleri” and “Ca. Nasuia deltocephalinicola” represent two of the smallest known bacterial genomes at 190 kb and 112 kb, respectively. Genome sequences are nearly identical to strains reported from the closely related host species, M. quadrilineatus. Copyright © 2016 Bennett et al.


July 7, 2019  |  

The genome analysis of Candidatus Burkholderia crenata reveals that secondary metabolism may be a key function of the Ardisia crenata leaf nodule symbiosis.

A majority of Ardisia species harbour Burkholderia sp. bacteria within specialized leaf nodules. The bacteria are transmitted hereditarily and have not yet been cultured outside of their host. Because the plants cannot develop beyond the seedling stage without their symbionts, the symbiosis is considered obligatory. We sequenced for the first time the genome of Candidatus Burkholderia crenata (Ca. B. crenata), the leaf nodule symbiont of Ardisia crenata. The genome of Ca. B. crenata is the smallest Burkholderia genome to date. It contains a large amount of insertion sequences and pseudogenes and displays features consistent with reductive genome evolution. The genome does not encode functions commonly associated with plant symbioses such as nitrogen fixation and plant hormone metabolism. However, we identified unique genes with a predicted role in secondary metabolism in the genome of Ca. B. crenata. Specifically, we provide evidence that the bacterial symbionts are responsible for the synthesis of compound FR900359, a cyclic depsipeptide with biomedical properties previously isolated from leaves of A.?crenata. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.


July 7, 2019  |  

Evidence of horizontal gene transfer between obligate leaf nodule symbionts.

Bacteria of the genus Burkholderia establish an obligate symbiosis with plant species of the Rubiaceae and Primulaceae families. The bacteria, housed within the leaves, are transmitted hereditarily and have not yet been cultured. We have sequenced and compared the genomes of eight bacterial leaf nodule symbionts of the Rubiaceae plant family. All of the genomes exhibit features consistent with genome erosion. Genes potentially involved in the biosynthesis of kirkamide, an insecticidal C7N aminocyclitol, are conserved in most Rubiaceae symbionts. However, some have partially lost the kirkamide pathway due to genome erosion and are unable to synthesize the compound. Kirkamide synthesis is therefore not responsible for the obligate nature of the symbiosis. More importantly, we find evidence of intra-clade horizontal gene transfer (HGT) events affecting genes of the secondary metabolism. This indicates that substantial gene flow can occur at the early stages following host restriction in leaf nodule symbioses. We propose that host-switching events and plasmid conjugative transfers could have promoted these HGTs. This genomic analysis of leaf nodule symbionts gives, for the first time, new insights in the genome evolution of obligate symbionts in their early stages of the association with plants.


July 7, 2019  |  

Complete genome sequence of Bradyrhizobium sp. strain CCGE-LA001, isolated from field nodules of the enigmatic wild bean Phaseolus microcarpus.

We present the complete genome sequence of Bradyrhizobium sp. strain CCGE-LA001, a nitrogen-fixing bacterium isolated from nodules of Phaseolus microcarpus. Strain CCGE-LA001 represents the first sequenced bradyrhizobial strain obtained from a wild Phaseolus sp. Its genome revealed a large and novel symbiotic island. Copyright © 2016 Servín-Garcidueñas et al.


July 7, 2019  |  

Whole-genome sequence of Erysipelothrix larvae LV19(T) (=KCTC 33523(T)), a useful strain for arsenic detoxification, from the larval gut of the rhinoceros beetle, Trypoxylus dichotomus.

Erysipelothrix larvae LV19(T) was preliminary isolated from the larval gut of a rhinoceros beetle, Trypoxylus dichotomus in Korea. Here, we present the whole genome sequence of E. larvae LV19(T) strain, which consisted of 2,511,486 base pairs with a GC content of 37.4% and one plasmid. Unlike other Erysipelothrix strains (SY 1027, Fujisawa and ATCC 19414), the arsenic-resistance genes were identified in LV19(T) strain. Copyright © 2016 Elsevier B.V. All rights reserved.


July 7, 2019  |  

Insight into the evolution of the Solanaceae from the parental genomes of Petunia hybrida.

Petunia hybrida is a popular bedding plant that has a long history as a genetic model system. We report the whole-genome sequencing and assembly of inbred derivatives of its two wild parents, P. axillaris N and P. inflata S6. The assemblies include 91.3% and 90.2% coverage of their diploid genomes (1.4 Gb; 2n?=?14) containing 32,928 and 36,697 protein-coding genes, respectively. The genomes reveal that the Petunia lineage has experienced at least two rounds of hexaploidization: the older gamma event, which is shared with most Eudicots, and a more recent Solanaceae event that is shared with tomato and other solanaceous species. Transcription factors involved in the shift from bee to moth pollination reside in particularly dynamic regions of the genome, which may have been key to the remarkable diversity of floral colour patterns and pollination systems. The high-quality genome sequences will enhance the value of Petunia as a model system for research on unique biological phenomena such as small RNAs, symbiosis, self-incompatibility and circadian rhythms.


July 7, 2019  |  

Complete genome sequence of Mesorhizobium ciceri bv. biserrulae strain WSM1284, an efficient nitrogen-fixing microsymbiont of the pasture legume Biserrula pelecinus.

We report the complete genome sequence of Mesorhizobium ciceri bv. biserrulae strain WSM1284, a nitrogen-fixing microsymbiont of the pasture legume Biserrula pelecinus The genome consists of 6.88 Mb distributed between a single chromosome (6.33 Mb) and a single plasmid (0.55 Mb). Copyright © 2016 Haskett et al.


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