Decoding the mojo of plant-growth-promoting microbiomes

Mulani, Rinkal; Mehta, Krina; Saraf, Meenu; Goswami, Dweipayan

doi:10.1016/j.pmpp.2021.101687

Cited by 23 publications

(9 citation statements)

References 133 publications

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“…The use of Streptomyces venezuelae as a biofertilizer, for example, increased maize production under drought conditions due to its ability to secrete high levels of IAA and L-aminocyclopropane (ACC; Chukwuneme et al, 2020 ); ACC is an immediate precursor of the gaseous hormone, ethylene. Plant growth promoting bacteria (PGPB) play an important role lowering plant stress by reducing ethylene levels by hydrolyzing ACC to ammonia, α-ketobutyrate and methionine thereby regulating ethylene production ( Mulani et al, 2021 ); plants inoculated with ACC-deaminase producing bacteria are more resistant to abiotic and biotic stress ( Gupta and Pandey, 2019 ). In the present study, representative isolates from the Atacama Desert and pine forest sampling sites produced ammonia and IAA, solubilised phosphate and synthesised siderophores.…”

Section: Discussionmentioning

confidence: 99%

Generation of a high quality library of bioactive filamentous actinomycetes from extreme biomes using a culture-based bioprospecting strategy

2023

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IntroductionFilamentous actinomycetes, notably members of the genus Streptomyces, remain a rich source of new specialized metabolites, especially antibiotics. In addition, they are also a valuable source of anticancer and biocontrol agents, biofertilizers, enzymes, immunosuppressive drugs and other biologically active compounds. The new natural products needed for such purposes are now being sought from extreme habitats where harsh environmental conditions select for novel strains with distinctive features, notably an ability to produce specialized metabolites of biotechnological value.MethodsA culture-based bioprospecting strategy was used to isolate and screen filamentous actinomycetes from three poorly studied extreme biomes. Actinomycetes representing different colony types growing on selective media inoculated with environmental suspensions prepared from high-altitude, hyper-arid Atacama Desert soils, a saline soil from India and from a Polish pine forest soil were assigned to taxonomically predictive groups based on characteristic pigments formed on oatmeal agar. One hundred and fifteen representatives of the colour-groups were identified based on 16S rRNA gene sequences to determine whether they belonged to validly named or to putatively novel species. The antimicrobial activity of these isolates was determined using a standard plate assay. They were also tested for their capacity to produce hydrolytic enzymes and compounds known to promote plant growth while representative strains from the pine forest sites were examined to determine their ability to inhibit the growth of fungal and oomycete plant pathogens.ResultsComparative 16S rRNA gene sequencing analyses on isolates representing the colour-groups and their immediate phylogenetic neighbours showed that most belonged to either rare or novel species that belong to twelve genera. Representative isolates from the three extreme biomes showed different patterns of taxonomic diversity and characteristic bioactivity profiles. Many of the isolates produced bioactive compounds that inhibited the growth of one or more strains from a panel of nine wild strains in standard antimicrobial assays and are known to promote plant growth. Actinomycetes from the litter and mineral horizons of the pine forest, including acidotolerant and acidophilic strains belonging to the genera Actinacidiphila,Streptacidiphilus and Streptomyces, showed a remarkable ability to inhibit the growth of diverse fungal and oomycete plant pathogens.DiscussionIt can be concluded that selective isolation and characterization of dereplicated filamentous actinomyctes from several extreme biomes is a practical way of generating high quality actinomycete strain libraries for agricultural, industrial and medical biotechnology.

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Section: Discussionmentioning

confidence: 99%

Generation of a high quality library of bioactive filamentous actinomycetes from extreme biomes using a culture-based bioprospecting strategy

2023

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“…Ethylene is an essential metabolite for plant development, but under extreme stress conditions, ethylene levels can rise drastically and affect plant development. Endophytic actinobacteria can reduce the stress caused by increased ethylene concentrations by releasing ACC deaminase, which can hydrolyze ACC into ammonia, methionine, and alpha-ketobutyrate to regulate ethylene synthesis ( Mulani et al., 2021 ). Previous literature showed that ACC deaminase-producing endophytic actinobacteria promoted plant growth by reducing ET levels in different hosts ( El-Tarabily et al., 2019 ).…”

Section: Discussionmentioning

confidence: 99%

Phylogenetic affiliation of endophytic actinobacteria associated with selected orchid species and their role in growth promotion and suppression of phytopathogens

2022

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Endophytic actinobacteria aid in plant development and disease resistance by boosting nutrient uptake or producing secondary metabolites. For the first time, we investigated the culturable endophytic actinobacteria associated with ten epiphytic orchid species of Assam, India. 51 morphologically distinct actinobacteria were recovered from surface sterilized roots and leaves of orchids and characterized based on different PGP and antifungal traits. According to the 16S rRNA gene sequence, these isolates were divided into six families and eight genera, where Streptomyces was most abundant (n=29, 56.86%), followed by Actinomadura, Nocardia, Nocardiopsis, Nocardioides, Pseudonocardia, Microbacterium, and Mycolicibacterium. Regarding PGP characteristics, 25 (49.01%) isolates demonstrated phosphate solubilization in the range of 61.1±4.4 - 289.7±11.9 µg/ml, whereas 27 (52.94%) isolates biosynthesized IAA in the range of 4.0 ± 0.08 - 43.8 ± 0.2 µg/ml, and 35 (68.62%) isolates generated ammonia in the range of 0.9 ± 0.1 - 5.9 ± 0.2 µmol/ml. These isolates also produced extracellular enzymes, viz. protease (43.13%), cellulase (23.52%), pectinase (21.56%), ACC deaminase (27.45%), and chitinase (37.25%). Out of 51 isolates, 27 (52.94%) showed antagonism against at least one test phytopathogen. In molecular screening, most isolates with antifungal and chitinase producing traits revealed the presence of 18 family chitinase genes. Two actinobacterial endophytes, Streptomyces sp. VCLA3 and Streptomyces sp. RVRA7 were ranked as the best strains based on PGP and antifungal activity on bonitur scale. GC-MS examination of ethyl acetate extract of these potent strains displayed antimicrobial compound phenol, 2,4-bis-(1,1-dimethylethyl) as the major metabolite along with other antifungal and plant growth beneficial bioactive chemicals. SEM analysis of fungal pathogen F. oxysporum (MTCC 4633) affected by Streptomyces sp. VCLA3 revealed significant destruction in the spore structure. An in vivo plant growth promotion experiment with VCLA3 and RVRA7 on chili plants exhibited statistically significant (p<0.05) improvements in all of the evaluated vegetative parameters compared to the control. Our research thus gives insight into the diversity, composition, and functional significance of endophytic actinobacteria associated with orchids. This research demonstrates that isolates with multiple plant development and broad-spectrum antifungal properties are beneficial for plant growth. They may provide a viable alternative to chemical fertilizers and pesticides and a sustainable solution for chemical inputs in agriculture.

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“…Phytohormones are involved in many physiological processes, they include auxins, gibberellins, cytokinins, ethylene, and abscisic acid, which are classified based on their function and structure composition. They are mainly produced by rhizospheric microorganisms, fungi, algae, and Actinobacteria (Mulani et al, 2021).…”

Section: Producing Phytohormones Like Auxins Cytokinins and Gibberellinsmentioning

confidence: 99%

“…Ethylene, which are the aging hormones of plants (Patel et al, 2018), are produced as a response to stress "stress ethylene, " meaning the development of the plant is slowed, to respond to this stress condition and promote plant growth, PGP bacteria produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase (Glick, 2005). This (ACC) deaminase delivered by PGPR, will metabolize ACC into alpha-ketobutyrate, methionine, and ammonia and thus will regulate ethylene production (Mulani et al, 2021). Inoculation of ACC deaminase-producing bacteria immediately enhances plant root elongation and promotes shoot growth (Onofre-Lemus et al, 2009).…”

Section: -Aminocyclopropane-1-carboxylate Deaminase (Acc Deaminase)mentioning

confidence: 99%

Plant Growth Promoting Actinobacteria, the Most Promising Candidates as Bioinoculants?

Boukhatem¹,

Merabet²,

Tsaki³

2022

Front. Agron.

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Plant Growth Promoting Bacteria (PGPBs) are a strong ally for sustainable agriculture. They offer an interesting alternative to chemical fertilizers and pesticides. Many microorganisms have been widely documented for their PGPR traits, but actinobacterial microbes which have been increasingly documented only these two past decades for their ability to promote plant growth. Their action on plant health and yield could be either direct, indirect or both. This review will cover articles that have been published on Actinobacteria PGP traits, highlighting the involved mechanisms to reveal their strong potential as microbial fertilizers. Possible strategies to encourage Actinobacteria use as bioinoculants are also discussed.

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Decoding the mojo of plant-growth-promoting microbiomes

Cited by 23 publications

References 133 publications

Generation of a high quality library of bioactive filamentous actinomycetes from extreme biomes using a culture-based bioprospecting strategy

Generation of a high quality library of bioactive filamentous actinomycetes from extreme biomes using a culture-based bioprospecting strategy

Phylogenetic affiliation of endophytic actinobacteria associated with selected orchid species and their role in growth promotion and suppression of phytopathogens

Plant Growth Promoting Actinobacteria, the Most Promising Candidates as Bioinoculants?

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