Rhizospheric bacterial community of endemic rhododendron arboreum sm. ssp. delavayi along eastern himalayan slope in tawang

Information on rhizosphere microbiome of endemic plants from high mountain ecosystems against those of cultivated plantations is inadequate. Comparative bacterial profiles of endemic medicinal plant Rhododendron arboreum Sm. subsp. delavayi rhizosphere pertaining to four altitudinal zonation Pankang Thang (PTSO), Nagula, Y-junction and Bum La (Indo-China border; in triplicates each) along cold adapted Eastern slope of Himalayan Tawang region, India is described here. Significant differences in DGGE profile between below ground bulk vs. rhizospheric community profile associated with the plant was identified. Tagged 16S amplicon sequencing from PTSO (3912 m) to Burn La (4509 m), revealed that soil pH, total nitrogen (TN), organic matter (OM) significantly influenced the underlying bacterial community structure at different altitudes. The relative abundance of Acidobacteria was inversely related to pH, as opposed to TN which was positively correlated to Acidobacteria and Proteobacteria abundance. TN was also the significant predictor for less abundant taxonomic groups Chioroflexi, Gemmatimonadetes. and Nitrospirae. Bum La soil harbored less bacterial diversity compared to other sites at lower altitudes. The most abundant phyla at 3% genetic difference were Acidobacteria, Actinobacteria, and Proteobacteria amongst others. Analysis of similarity indicated greater similarity within lower altitudinal than higher altitudinal group (ANOSIM, R = 0.287, p = 0.02). Constraining the ordination with the edaphic factor explained 83.13% of variation. Unique phylotypes of Bradyrhizobium and uncultured Rhizobiales were found in significant proportions at the four regions. With over 1% relative abundance Actinobacteria (42.6%), Acidobacteria (24.02%), Proteobacteria (16.00%), AD3 (9.23%), WPS-2 (5.1%), and Chloroflexi (1.48%) dominated the core microbiome

Antimicrobial biosynthetic potential and genetic diversity of endophytic actinomycetes associated with medicinal plants

Endophytic actinomycetes are one of the primary groups that share symbiotic relationships with medicinal plants and are key reservoir of biologically active compounds. In this study, six selective medicinal plants were targeted for the first time for endophytic actinomycetes isolation from Gibbon Wild Life Sanctuary, Assam, India, during winter and summer and 76 isolates were obtained. The isolates were found to be prevalent in roots followed by stem and leaves. 16S rRNA gene sequence analysis revealed 16 genera, including rare genera, Verrucosispora, Isoptericola and Kytococcus, which have never been previously reported as endophytic. The genus Streptomyces (66%) was dominant in both seasons. Shannon's diversity index showed that Azadirachta indica (1.49), Rauwolfia serpentina (1.43) and Emblica officinalis (1.24) were relatively good habitat for endophytic actinomycetes. Antimicrobial strains showed prevalence of polyketide synthase (PKS) type-II (85%) followed by PKS type-I (14%) encoded in the genomes. Expression studies showed 12-fold upregulation of PKSII gene in seventh day of incubation for Streptomyces antibioticus (EAAG90). Our results emphasize that the actinomycetes assemblages within plant tissue exhibited biosynthetic systems encoding for important biologically active compounds

Antimicrobial biosynthetic potential and genetic diversity of endophytic actinomycetes associated with medicinal plants

Endophytic actinomycetes are one of the primary groups that share symbiotic relationships with medicinal plants and are key reservoir of biologically active compounds. In this study, six selective medicinal plants were targeted for the first time for endophytic actinomycetes isolation from Gibbon Wild Life Sanctuary, Assam, India, during winter and summer and 76 isolates were obtained. The isolates were found to be prevalent in roots followed by stem and leaves. 16S rRNA gene sequence analysis revealed 16 genera, including rare genera, Verrucosispora, Isoptericola and Kytococcus, which have never been previously reported as endophytic. The genus Streptomyces (66%) was dominant in both seasons. Shannon\u27s diversity index showed that Azadirachta indica (1.49), Rauwolfia serpentina (1.43) and Emblica officinalis (1.24) were relatively good habitat for endophytic actinomycetes. Antimicrobial strains showed prevalence of polyketide synthase (PKS) type-II (85%) followed by PKS type-I (14%) encoded in the genomes. Expression studies showed 12-fold upregulation of PKSII gene in seventh day of incubation for Streptomyces antibioticus (EAAG90). Our results emphasize that the actinomycetes assemblages within plant tissue exhibited biosynthetic systems encoding for important biologically active compounds

Community Profiling of Culturable Fluorescent Pseudomonads in the Rhizosphere of Green Gram (<i>Vigna radiata</i> L.)

<div><p>Study on microbial diversity in the unexplored rhizosphere is important to understand their community structure, biology and ecological interaction with the host plant. This research assessed the genetic and functional diversity of fluorescent pseudomonads [FP] in the green gram rhizophere. One hundred and twenty types of morphologically distinct fluorescent pseudomonads were isolated during vegetative as well as reproductive growth phase of green gram. Rep PCR, ARDRA and RISA revealed two distinct clusters in each case at 75, 61 and 70% similarity coefficient index respectively. <i>16S rRNA</i> partial sequencing analysis of 85 distantly related fluorescent pseudomonads depicted <i>Pseudomonas aeruginosa</i> as the dominant group. Out of 120 isolates, 23 (19%) showed antagonistic activity towards phytopathogenic fungi. These bacterial isolates showed varied production of salicylic acid, HCN and chitinase, 2, 4-diacetylphloroglucinol (DAPG), phenazine-1-carboxylic acid (PCA) and pyoluteorin (PLT). Production efficiency of inherent level of plant growth promoting (PGP) traits among the 120 isolates demonstrated that 10 (8%) solubilised inorganic phosphates, 25 (20%) produced indoles and 5 (4%) retained ACC deaminase activity. <i>Pseudomonas aeruginosa</i> GGRJ21 showed the highest production of all antagonistic and plant growth promoting (PGP) traits. In a greenhouse experiment, GGRJ21 suppressed root rot disease of green gram by 28–93% (p = 0.05). Consistent up regulation of three important stress responsive genes, i.e., <i>acdS</i>, <i>KatA</i> and <i>gbsA</i> and elevated production efficiency of different PGP traits could promote GGRJ21 as a potent plant growth regulator.</p></div

Phylogenetic analyses of fluorescent pseudomonads based on the nucleotide sequence of <i>16S rRNA</i>.

<p>The multiple sequence alignment was done in CLUSTALW program embedded in MEGA version 5.10. The pair-wise evolutionary distances were calculated using Kimura-2 parameter model. The phylogenetic tree was constructed by Neighbor-Joining (NJ) method with 1000 replicates using bootstrap. A total of 5 reference fluorescent pseudomonad strains were used for the tree construction. Bar, .0.005 shows the substitutions per nucleotide position.</p

Effect of <i>Pseudomonas aeruginosa</i> GGRJ21 on root rot disease suppression of green gram during infection with <i>Rhizoctonia solani</i>.

<p>Means within a column sharing same superscript are not significantly different according to Turkey’s test at p = 0.05; ± means standard deviation (SD).</p><p>Effect of <i>Pseudomonas aeruginosa</i> GGRJ21 on root rot disease suppression of green gram during infection with <i>Rhizoctonia solani</i>.</p

Antagonostic activity of fluorescent pseudomonads against phytopathogenic fungi. Activity was monitored on the basis of inhibition zone.

<p>Means within a column sharing same superscript are not significantly different according to Turkey’s test at p = 0.05; ± means standard deviation (SD) and - means no activity.</p><p>Antagonostic activity of fluorescent pseudomonads against phytopathogenic fungi. Activity was monitored on the basis of inhibition zone.</p

Relative gene expression level of, a) <i>acdS</i>, b) <i>katA</i> and c) <i>gbsA</i> in <i>P</i>. <i>aeruginosa</i> (GGRJ21) growing in different osmotic stress condition.

<p>A-GGRJ 21 grown in normal NB medium, B-GGRJ21 grown in –0.3<b> </b>mPA, C-GGRJ21 grown in 0.49<b> </b>mPA and D-GGRJ21 grown in –0.73<b> </b>mPA.</p

Primers for real time PCR: sequences, final concentration, product size, T_m and Efficiency of PCR amplification.

<p>T_m means melting temperature; ±SD means standard deviation of the mean value.</p><p>Primers for real time PCR: sequences, final concentration, product size, T_m and Efficiency of PCR amplification.</p