B. Jasim

Plant growth promoting potential of endophytic bacteria isolated from Piper nigrum

Piper nigrum is an interesting plant to study the endophytic microbial factors affecting plant growth because of its unique features. Endophytic bacterial isolation from the plant resulted in the isolation of twelve bacterial isolates which were screened for various plant growth promoting properties like phosphate solubilization, ACC deaminase production, siderophore production etc. Interestingly, seven isolates were found to have IAA biosynthetic potential. Bacterial isolates with multiple plant growth promoting properties were studied for their growth promoting effect on Vigna radiata seedlings. This resulted in the identification of Klebsiella sp. (PnB 10) and Enterobacter sp. (PnB 11) as the isolates with excellent growth promoting properties. The results confirm promising applications of the endophytic bacterial isolates obtained in the study and also their possible growth promoting effect in P. nigrum.

Piperine production by endophytic fungus Colletotrichum gloeosporioides isolated from Piper nigrum

Many endophytic fungi have been reported with the biosynthetic potential to produce same or similar metabolites present in host plants. The adaptations that might have acquired by these fungi as a result of the long-term association with their host plants can be the possible basis of their biosynthetic potential. The bioactive compounds originated from endophytes are currently explored for their potential applications in pharmaceutical, agriculture and food industries. Piper nigrum, a plant of the Piperaceae is very remarkable because of the presence of the alkaloid piperine. Piperine has been reported to have broad bioactive properties ranging from antimicrobial, antidepressant, anti-inflammatory, antioxidative to anticancer activities. Interestingly, piperine also plays a vital role in increasing the bioavailability of many drugs which again is a promising property. The current study was carried out to identify piperine producing endophytic fungus from Piper nigrum L. By screening various endophytic fungi, the isolate which was identified as member of Colletotrichum gloeosporioides was found to have the ability to form piperine and was confirmed by HPLC and LCMS. Considering the broad bioactive potential of piperine, the piperine producing fungi identified in the study can expect to have much industrial potential.

Phenazine carboxylic acid production and rhizome protective effect of endophytic Pseudomonas aeruginosa isolated from Zingiber officinale

Abstract Ginger (Zingiber officinale) is cultivated commercially in most parts of the world especially in India for its culinary and medicinal applications. One of the major challenges that limit the yield of ginger is rhizome rot disease caused by organisms including Pythium myriotylum. A feasible ecofriendly method is yet to be devised to prevent the plant from this threatening disease. Recent studies on plant microbiome show the possibility of having endophytic organisms with plant protective characteristics associated with the plants. Because of the uniquely evolved underground nature of the ginger rhizome and its peculiar survival in soil for a long time, many interesting endophytic microbes with plant protective characters can be well expected from it. In the current study, previously isolated endophytic Pseudomonas aeruginosa from ginger was investigated in detail for its effect on Pythium myriotylum. The rhizome protective effect of the organism was also studied by co-inoculation studies, which confirmed that Pseudomonasaeruginosa has very potent inhibitory effect on Pythium myriotylum. On further studies, the active antifungal compound was identified as phenazine 1-carboxylic acid.

Identification of two strains of Paenibacillus sp. as indole 3 acetic acid-producing rhizome-associated endophytic bacteria from Curcuma longa

Curcuma longa is well known for its use as spice and medicine. The remarkable feature of the plant is the presence of rhizome, which provides an interesting habitat for association by various groups of bacteria. Some of these associated endophytic bacteria can have growth-promoting effects. In the current study, two species of endophytic Paenibacillus has been identified from the rhizome as indole 3 acetic acid producers. These isolates can thus have potential growth-regulating effect in rhizomes.

Studies on Plant Growth Promoting Properties of Fruit-Associated Bacteria from Elettaria cardamomum and Molecular Analysis of ACC Deaminase Gene

Endophytic microorganisms have been reported to have diverse plant growth promoting mechanisms including phosphate solubilization, N2 fixation, production of phyto-hormones and ACC (1-aminocyclopropane-1-carboxylate) deaminase and antiphyto-pathogenic properties. Among these, ACC deaminase production is very important because of its regulatory effect on ethylene which is a stress hormone with precise role in the control of fruit development and ripening. However, distribution of these properties among various endophytic bacteria associated with fruit tissue and its genetic basis is least investigated. In the current study, 11 endophytic bacteria were isolated and identified from the fruit tissue of Elettaria cardamomum and were studied in detail for various plant growth promoting properties especially ACC deaminase activity using both culture-based and PCR-based methods. PCR-based screening identified the isolates EcB 2 (Pantoea sp.), EcB 7 (Polaromonas sp.), EcB 9 (Pseudomonas sp.), EcB 10 (Pseudomonas sp.) and EcB 11 (Ralstonia sp.) as positive for ACC deaminase. The PCR products were further subjected to sequence analysis which proved the similarity of the sequences identified in the study with ACC deaminase sequences reported from other sources. The detailed bioinformatic analysis of the sequence including homology-based modelling and molecular docking confirmed the sequences to have ACC deaminase activity. The docking of the modelled proteins was done using patch dock, and the detailed scrutiny of the protein ligand interaction revealed conservation of key amino acids like Lys51, Ser78, Tyr268 and Tyr294 which play important role in the enzyme activity. These suggest the possible regulatory effect of these isolates on fruit physiology.

Identification of a novel endophytic Bacillus sp. from Capsicum annuum with highly efficient and broad spectrum plant probiotic effect

The study mainly aimed the isolation and characterization of plant probiotic endophytic bacteria from Capsicum annuum to explore its multipotent agricultural applications.

Identification of endophytic Bacillus mojavensis with highly specialized broad spectrum antibacterial activity

Biosynthetic adaptation of endophytic bacteria to chemically support host plant is very remarkable. Hence these organisms from medicinal plants are considered as highly valuable sources for natural products with diverse bioactivity. Their metabolite diversity and biosynthetic versatility have been increasingly explored for drug discovery. In this study, an endophytic Bacillus mojavensis with broad spectrum antibacterial properties has been analyzed for the chemical basis of its activity. By LC–MS/MS the organism was identified to have the biosynthetic ability to produce lipopeptides surfactin and fengycin. The impressive antibacterial activity of B. mojavensis as reported in the study indicates its broad antimicrobial applications.

Endophytic Phomopsis sp. colonization in Oryza sativa was found to result in plant growth promotion and piperine production

Endophytic fungi have been reported to have the acquired ability to synthesize host plant specific medicinal natural products. Many fungi with such properties have been characterized and optimized for the conditions which favor maximal production of desired products. However, the inherent plant colonization property of promising endophytic fungi is least studied. Exploiting the transgenome functioning of these fungi have immense applications to add beneficial features to nonhost plants. In the present study, the endophytic fungus Phomopsis sp. isolated from Piper nigrum was confirmed for piperine production by HPLC and LCMS/MS. Further, the fungal isolate was studied for its colonization ability in Oryza sativa. Interestingly, the fungi treated plants were found to have significant plant growth enhancement when compared to the control. Further screening of extract from treated plants by HPLC and LCMS/MS resulted in the confirmation of presence of piperine. The observed result is extremely significant as it opens up novel applications of endophytic fungal colonization in taxonomically diverse plants.

Metabolite and Mechanistic Basis of Antifungal Property Exhibited by Endophytic Bacillus amyloliquefaciens BmB 1

Plants are ubiquitously colonized by endophytic microorganisms which contribute significantly to plant health through production of plant growth regulators or disease suppression. In the present study, an endophytic bacterial isolate designated as BmB 1 with significant antifungal and plant growth promoting properties was isolated from the stem tissue of Bacopa monnieri (L.) Pennell. The isolate was studied in detail for the molecular and chemical basis of its bioactivity which proved it to have the presence of surfactin, iturin, and type I polyketide synthase (PKS) genes. For the analysis of the chemical basis of antifungal property, extract of the isolate was initially checked for its activity on test pathogens and LC-MS/MS based analysis further confirmed the presence of bacillomycin (m/z (M+H+) 1031.8) and surfactin (m/z (M+H+) 1008.6 and 1022.6) in the extract prepared. The light microscopic and SEM analysis of the treated and untreated mycelia of the pathogens clearly revealed the hypal destruction caused by the compounds produced by the selected isolate. This confirms the ability of the organism to directly inhibit the growth of the tested pathogens. The GC-MS analysis also confirmed the isolate to have the presence of volatile compounds with the expected role to induce induced systemic resistance (ISR) of the plant. Because of the multitargeted antifungal property, the isolate which was identified as Bacillus amyloliquefaciens can have potential biocontrol applications.

Epigenetic Modifier Based Enhancement of Piperine Production in Endophytic Diaporthe sp. PF20

Biodiversity and metabolite richness of endophytic fungi are highly fascinating. Some of them have even been reported to have the shared biosynthetic basis for the production of plant specific metabolites. However, only limited reports are there on enhancement of production of plant specific metabolites from endophytic fungi. In the study, endophytic Diaporthe sp. PF20 from Piper nigrum L. was identified to have the ability to produce piperine by liquid chromatography tandem mass spectroscopy. The isolate PF20 was further subjected to epigenetic treatment along with previously characterized piperine producing Colletotrichum sp. and Mycosphaerella sp. from the same plant. Very interestingly, use of histone deacetylase inhibitor suberohydroxamic acid enhanced the piperine production in PF20. Here, the epigenetic modulator mediated enhancement of phytochemical biosynthetic potential of endophytic fungi is novel in its approach. Hence the results of the study open up new avenues to maintain the biosynthetic competency of endophytic fungi, which is highly challenging. Even though piperine production has previously been reported from endophytic fungi, epigenetic modulator mediated multiplexing of this property as observed for PF20 is highly attractive. This is because, only this organism was found to be susceptible to epigenetic modulation based piperine enhancement among the selected isolates.