Mesorhizobium alexandrii sp. nov., isolated from phycosphere microbiota of PSTs-producing marine dinoflagellate Alexandrium minutum amtk4

Yang, Xi; Jiang, Zhiwei; Zhang, Jing; Zhou, Xin; Lei, Wang; Yu, Ting; Wang, Zhilin; Bei, Jinlong; Dong, Bo; Dai, Zhangyan; Chen, Zhuang

doi:10.1007/s10482-020-01400-x

Cited by 22 publications

(9 citation statements)

References 35 publications

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“…Our RNA-seq analyses showed that the strain was maintained with some bacteria related to Mesorhizobium , Kyptococcus , and an unidentified Actinobacterium ( Supplementary Table 7 and Supplementary Figure 9 ). In particular, the Mesorhizobium genus contains symbiotic species capable of nitrogen fixation ( Jarvis et al, 1997 ) and nitrate reduction ( Yang et al, 2020 ), and has been isolated from marine environments ( Hagström et al, 2000 ; Yang et al, 2020 ). Therefore, this species can provide fixed ammonia to B. bigelowii by diffusion through the medium or phagocytosis (discussed below).…”

Section: Resultsmentioning

confidence: 99%

Unstable Relationship Between Braarudosphaera bigelowii (= Chrysochromulina parkeae) and Its Nitrogen-Fixing Endosymbiont

et al. 2021

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Marine phytoplankton are major primary producers, and their growth is primarily limited by nitrogen in the oligotrophic ocean environment. The haptophyte Braarudosphaera bigelowii possesses a cyanobacterial endosymbiont (UCYN-A), which plays a major role in nitrogen fixation in the ocean. However, host-symbiont interactions are poorly understood because B. bigelowii was unculturable. In this study, we sequenced the complete genome of the B. bigelowii endosymbiont and showed that it was highly reductive and closely related to UCYN-A2 (an ecotype of UCYN-A). We succeeded in establishing B. bigelowii strains and performed microscopic observations. The detailed observations showed that the cyanobacterial endosymbiont was surrounded by a single host derived membrane and divided synchronously with the host cell division. The transcriptome of B. bigelowii revealed that B. bigelowii lacked the expression of many essential genes associated with the uptake of most nitrogen compounds, except ammonia. During cultivation, some of the strains completely lost the endosymbiont. Moreover, we did not find any evidence of endosymbiotic gene transfer from the endosymbiont to the host. These findings illustrate an unstable morphological, metabolic, and genetic relationship between B. bigelowii and its endosymbiont.

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Section: Resultsmentioning

confidence: 99%

Unstable Relationship Between Braarudosphaera bigelowii (= Chrysochromulina parkeae) and Its Nitrogen-Fixing Endosymbiont

et al. 2021

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“…It can be clearly seen that the bioflocculanting activity reached the maximum of 96.7 ± 1.8% (means ± SD) at the EPS concentration of 0.60 g·L −1 . It exhibited a higher bioflocculanting capacity compared with other marine bacterial strains isolated from marine phycosphere niches that we previously reported [ 29 , 30 , 31 ]. These findings obviously indicate that strain NJES-13 may serve as a novel actinobacterial candidate with natural potential for the production of promising microbial bioflocculants derived from the unique mammalian gut microbiota niche in the antarctic habitat.…”

Section: Resultsmentioning

confidence: 71%

“…Initially, the transmission electron microscope observation of strain NJES-13 cells clearly demonstrated the presence of an EPS layer outside of the cells (Figure 1). Then, the extracted EPS produced by strain NJES-13 were subjected to the bioflocculanting activity screening assay to evaluate their production capacity of bacterial bioflocculants [29][30][31]. The comparison of bioflocculanting effects under a series of EPS concentrations was performed.…”

Section: Bioflocculanting Potential Of Bacterial Epsmentioning

confidence: 99%

Isolation, Phylogenetic and Gephyromycin Metabolites Characterization of New Exopolysaccharides-Bearing Antarctic Actinobacterium from Feces of Emperor Penguin

2021

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A new versatile actinobacterium designated as strain NJES-13 was isolated from the feces of the Antarctic emperor penguin. This new isolate was found to produce two active gephyromycin analogues and bioflocculanting exopolysaccharides (EPS) metabolites. Phylogenetic analysis based on pairwise comparison of 16S rRNA gene sequences showed that strain NJES-13 was closely related to Mobilicoccus pelagius Aji5-31T with a gene similarity of 95.9%, which was lower than the threshold value (98.65%) for novel species delineation. Additional phylogenomic calculations of the average nucleotide identity (ANI, 75.9–79.1%), average amino acid identity (AAI, 52.4–66.9%) and digital DNA–DNA hybridization (dDDH, 18.6–21.9%), along with the constructed phylogenomic tree based on the up-to-date bacterial core gene (UBCG) set from the bacterial genomes, unequivocally separated strain NJES-13 from its close relatives within the family Dermatophilaceae. Hence, it clearly indicated that strain NJES-13 represented a putative new actinobacterial species isolated from the gut microbiota of mammals inhabiting the Antarctic. The obtained complete genome of strain NJES-13 consisted of a circular 3.45 Mb chromosome with a DNA G+C content of 67.0 mol%. Furthering genome mining of strain NJES-13 showed the presence of five biosynthetic gene clusters (BGCs) including one type III PKS responsible for the biosynthesis of the core of gephyromycins, and a series of genes encoding for bacterial EPS biosynthesis. Thus, based on the combined phylogenetic and active metabolites characterization presented in this study, we confidently conclude that strain NJES-13 is a novel, fresh actinobacterial candidate to produce active gephyromycins and microbial bioflocculanting EPS, with potential pharmaceutical, environmental and biotechnological implications.

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“…All the results are expressed as means ± SD. The statistical significance was analyzed using t-test in SPSS Statistics (version 17.0) and plotted with Origin (version 8.0) [40][41][42][43]. A value of p < 0.05 was considered statistically significant.…”

Section: Bioactivity Evaluationsmentioning

confidence: 99%

Characterization of Bioactivities and Biosynthesis of Angucycline/Angucyclinone Derivatives Derived from Gephyromycinifex aptenodytis gen. nov., sp. nov.

et al. 2021

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Strain NJES-13T is the type strain and currently the only species of the newly established actinobacteria genera Aptenodytes in the family Dermatophilaceae isolated from the gut microbiota of the Antarctic emperor penguin. This strain demonstrated excellent bioflocculation activity with bacteria-derived exopolysaccharides (EPSs). Moreover, it produced bioactive angucycline/angucyclinone derivatives (ADs) and contained one type III polyketide synthase (T3PKS), thus demonstrating great potential to produce novel bioactive compounds. However, the low productivity of the potential new AD metabolite was the main obstacle for its chemical structure elucidation. In this study, to increase the concentration of targeted metabolites, the influence of cellular morphology on AD metabolism in strain NJES-13T was determined using glass bead-enhanced fermentation. Based on the cellular ultra-structural observation driven by bacterial EPSs, and quantitative analysis of the targeted metabolites, the successful increasing of the productivity of three AD metabolites was achieved. Afterward, a new frigocyclinone analogue was isolated and then identified as 2-hydroxy-frigocyclinone, as well as two other known ADs named 2-hydroxy-tetrangomycin (2-HT) and gephyromycin (GPM). Three AD metabolites were found to demonstrate different bioactivities. Both C-2 hydroxyl substitutes, 2-hydroxy-tetrangomycin and 2-hydroxy-frigocyclinone, exhibited variable inhibitory activities against Staphylococcus aureus, Bacillus subtilis and Candida albicans. Moreover, the newly identified 2-hydroxy-frigocyclinone also showed significant cytotoxicity against three tested human-derived cancerous cell lines (HL-60, Bel-7402 and A549), with all obtained IC50 values less than 10 µM. Based on the genetic analysis after genomic mining, the plausible biogenetic pathway of the three bioactive ADs in strain NJES-13T was also proposed.

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Mesorhizobium alexandrii sp. nov., isolated from phycosphere microbiota of PSTs-producing marine dinoflagellate Alexandrium minutum amtk4

Cited by 22 publications

References 35 publications

Unstable Relationship Between Braarudosphaera bigelowii (= Chrysochromulina parkeae) and Its Nitrogen-Fixing Endosymbiont

Unstable Relationship Between Braarudosphaera bigelowii (= Chrysochromulina parkeae) and Its Nitrogen-Fixing Endosymbiont

Isolation, Phylogenetic and Gephyromycin Metabolites Characterization of New Exopolysaccharides-Bearing Antarctic Actinobacterium from Feces of Emperor Penguin

Characterization of Bioactivities and Biosynthesis of Angucycline/Angucyclinone Derivatives Derived from Gephyromycinifex aptenodytis gen. nov., sp. nov.

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