nan Zothanpuia

Detection of biosynthetic gene and phytohormone production by endophytic actinobacteria associated with Solanum lycopersicum and their plant-growth-promoting effect

In the present study, fifteen endophytic actinobacterial isolates recovered from Solanum lycopersicum were studied for their antagonistic potential and plant-growth-promoting (PGP) traits. Among them, eight isolates showed significant antagonistic and PGP traits, identified by amplification of the 16S rRNA gene. Isolate number DBT204, identified as Streptomyces sp., showed multiple PGP traits tested in planta and improved a range of growth parameters in seedlings of chili (Capsicum annuum L.) and tomato (S. lycopersicum L.). Further, genes of indole acetic acid (iaaM) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase (acdS) were successively amplified from five strains. Six antibiotics (trimethoprim, fluconazole, chloramphenicol, nalidixic acid, rifampicin and streptomycin) and two phytohormones [indole acetic acid (IAA) and kinetin (KI)] were detected and quantified in Streptomyces sp. strain DBT204 using UPLC-ESI-MS/MS. The study indicates the potential of these PGP strains for production of phytohormones and shows the presence of biosynthetic genes responsible for production of secondary metabolites. It is the first report showing production of phytohormones (IAA and KI) by endophytic actinobacteria having PGP and biosynthetic potential. We propose Streptomyces sp. strain DBT204 for inoculums production and development of biofertilizers for enhancing growth of chili and tomato seedlings.

Production of Potent Antimicrobial Compounds from Streptomyces cyaneofuscatus Associated with Fresh Water Sediment

The genus Streptomyces under phylum actinobacteria has been recognized as a prolific source for the production of bioactive secondary metabolites. An actinobacterial strain designated as DST103 isolated from a wetland fresh water sediment of Tamdil Lake, Mizoram, Northeast, India was identified as Streptomyces cyaneofuscatus (KY287599) using 16SrRNA gene sequencing which shares 99.87% sequence similarity with Streptomyces cyaneofuscatus NRRL B-2570T. The strain showed broad spectrum antimicrobial activities against Gram negative bacteria (Escherichia coli MTCC 739 and Pseudomonas aeruginosa MTCC 2453), Gram positive bacteria (Micrococcus luteus NCIM 2170 and Staphylococcus aureus MTCC 96) and yeast pathogen Candida albicans MTCC 3017). The methanolic extract of the strain DST103 exhibited highest antimicrobial activity against E. coli (IC50 = 2.10 μg/mL) and minimum activity against S. aureus (IC50 = 43.63 μg/mL). Five antibiotics [trimethoprim (18 μg/g), fluconazole (6 μg/g), ketoconazole (18 μg/g), nalidixic acid (135 μg/g), and rifampicin (56 μg/g)] were detected and quantified using ultra-performance liquid chromatography (UPLC-ESI-MS/MS). Further, biosynthetic potential genes [polyketide synthases type II, non-ribosomal peptide synthetases, and aminodeoxyisochorismate synthase (phzE)] were also detected in strain DST103 which may possibly be responsible for the production of antimicrobial compounds. Additionally, gas chromatography-mass spectrometry analysis showed the presence of four volatile compounds which might be responsible for their diverse biological activity. The present study revealed the presence of bioactive compounds in strain DST103, which may be a promising resource for the discovery of novel bioactive metabolites against wide range of pathogens.

Detection of antibiotic-resistant bacteria endowed with antimicrobial activity from a freshwater lake and their phylogenetic affiliation

Antimicrobial resistance poses a serious challenge to global public health. In this study, fifty bacterial strains were isolated from the sediments of a freshwater lake and were screened for antibiotic resistance. Out of fifty isolates, thirty-three isolates showed resistance against at least two of the selected antibiotics. Analysis of 16S rDNA sequencing revealed that the isolates belonged to ten different genera, namely Staphylococcus(n = 8), Bacillus(n = 7), Lysinibacillus(n = 4), Achromobacter(n=3), bacterium(n = 3), Methylobacterium(n = 2), Bosea(n = 2), Aneurinibacillus(n = 2), Azospirillum(n = 1), Novosphingobium(n = 1). Enterobacterial repetitive intergenic consensus (ERIC) and BOX-PCR markers were used to study the genetic relatedness among the antibiotic resistant isolates. Further, the isolates were screened for their antimicrobial activity against bacterial pathogens viz., Staphylococcus aureus(MTCC-96), Pseudomonas aeruginosa(MTCC-2453) and Escherichia coli(MTCC-739), and pathogenic fungi viz., Fusarium proliferatum (MTCC-286), Fusarium oxysporum (CABI-293942) and Fusarium oxy. ciceri (MTCC-2791). In addition, biosynthetic genes (polyketide synthase II (PKS-II) and non-ribosomal peptide synthetase (NRPS)) were detected in six and seven isolates, respectively. This is the first report for the multifunctional analysis of the bacterial isolates from a wetland with biosynthetic potential, which could serve as potential source of useful biologically active metabolites.

Bioprospection of actinobacteria derived from freshwater sediments for their potential to produce antimicrobial compounds

BackgroundActinobacteria from freshwater habitats have been explored less than from other habitats in the search for compounds of pharmaceutical value. This study highlighted the abundance of actinobacteria from freshwater sediments of two rivers and one lake, and the isolates were studied for their ability to produce antimicrobial bioactive compounds.Results16S rRNA gene sequencing led to the identification of 84 actinobacterial isolates separated into a common genus (Streptomyces) and eight rare genera (Nocardiopsis, Saccharopolyspora, Rhodococcus, Prauserella, Amycolatopsis, Promicromonospora, Kocuria and Micrococcus). All strains that showed significant inhibition potentials were found against Gram-positive, Gram-negative and yeast pathogens. Further, three biosynthetic genes, polyketide synthases type II (PKS II), nonribosomal peptide synthetases (NRPS) and aminodeoxyisochorismate synthase (phzE), were detected in 38, 71 and 29% of the strains, respectively. Six isolates based on their antimicrobial potentials were selected for the detection and quantification of standard antibiotics using ultra performance liquid chromatography (UPLC–ESI–MS/MS) and volatile organic compounds (VOCs) using gas chromatography mass spectrometry (GC/MS). Four antibiotics (fluconazole, trimethoprim, ketoconazole and rifampicin) and 35 VOCs were quantified and determined from the methanolic crude extract of six selected Streptomyces strains.ConclusionInfectious diseases still remain one of the leading causes of death globally and bacterial infections caused millions of deaths annually. Culturable actinobacteria associated with freshwater lake and river sediments has the prospects for the production of bioactive secondary metabolites.

Phylogenetic affiliation and determination of bioactive compounds of bacterial population associated with organs of mud crab, Scylla olivacea

Mud crab belongs to the genus Scylla is an economically valuable and preferred species for costal aquaculture in Asian countries, including India. In recent years, there has been a tremendous expansion of Scylla farming, which has led to increasing research on its habit and habitats. However, there has been no study undertaken to understand the role of the bacterial population associated with the different organs of the mud crab, Scylla olivacea. In total, 43 isolates were recovered from four selected parts of the crab (carapace, nu202f=u202f18; abdomen nu202f=u202f11; leg, nu202f=u202f8; and hand, nu202f=u202f6), and the 16S rRNA gene was used to identify the bacterial isolates. The antimicrobial potential along with the detection of modular polyketide synthase (PKSI), cytochrome P450 hydroxylase (CYP) and non-ribosomal peptide synthetase (NRPS) gene clusters were investigated to show a relationship among the biosynthetic genes with their useful aspects. Additionally, the potential three strains (BPS_CRB12, BPS_CRB14 and BPS_CRB41), which showed significant antimicrobial activities, also showed the presence of twenty volatile compounds (VOCs) using GC–MS analysis. We conclude that the strain Aneurinibacillus aneurinilyticus BPS_CRB41 could be source for the production of bioactive compounds.

Molecular Markers Used for Identification and Genomic Profiling of Plant Associated Endophytic Actinobacteria

Abstract Molecular markers are defined as the fragments of DNA sequence associated with a genome that are used to identify a particular DNA sequence. There is great genetic diversity of microorganisms associated with various plant species around the world and these diverse genetic variations can be exploited to develop molecular markers. Thus, for this purpose, the identification, characterization, and documentation of the gene pool of endophytic actinobacteria are essential. Genomic study of endophytic actinobacterial species has developed rapidly in the past decade and specific regions of DNA (genetic markers) are used to identify up to species level as well as to study their evolutionary relationships. Hence, DNA based molecular markers such as 16S rRNA, RAPD, and REP-PCR (BOX-PCR & ERIC-PCR) have proved useful for identification of endophytic actinobacteria up to species level and for establishing genetic relatedness among the isolates. Moreover, they can be used in diversity analysis of endophytic actinobacteria on the basis of even a single nucleotide polymorphism. Here, we have explored various molecular markers for genomic profiling of endophytic actinobacteria, including genes of 16S rRNA, 16S rRNA-RFLP, RAPD, and REP-PCR (BOX-PCR & ERIC-PCR).

Freshwater Actinobacteria: Potential Source for Natural Product Search and Discovery

Abstract Actinobacteria isolated from freshwater has become an emerging area in the field of microbiology for its untapped bio-resources including secondary metabolites production. The phylum actinobacteria has been reported as prolific producers of thousands of bioactive secondary metabolites. Among the phylum, the genus Streptomyces is considered as one of the most dominant genus in freshwater, accounting for the production of more than 50% of the total known bioactive natural compounds. Since most of the researchers working on freshwater habitats are concerned with the diversity of actinobacteria, literature regarding the production of secondary metabolites from freshwater actinobacteria remains scarce and very little information is known about their ecological role in freshwater ecosystems. Freshwater with reference to actinobacteria has been relatively neglected and largely unexplored. So the search for actinobacteria in these regions is of significant interest for the discovery of novel compounds. This chapter highlights the significance of freshwater actinobacteria by evaluating the work done by various researchers on actinobacteria in various freshwater sources, which covers the isolation, media used for the isolation, their antimicrobial potential, and the metabolites synthesized. With the increase in multiple drug resistant diseases, there come greater demands for new biologically active compounds synthesized by actinobacteria from freshwater sources.

Actinobacteria: A Highly Potent Source for Holocellulose Degrading Enzymes

Abstract Actinobacteria are renowned for their secondary metabolites production, with numerous research areas and immense applications explored. The depletion of the fossil fuels and the quest for alternative energy or biofuels has brought forward plant biomasses that are particularly rich in holocellulose (cellulose+hemicelluloses) to the forefront. Given the capabilities of actinobacterial cultures to withstand harsher climatic conditions and growth in unique habitats, their possibility to produce holocellulose-degrading enzymes such as cellulases, xylanases, etc., makes them extremely important. This review thus intends to systematically analyze the diversity of actinobacterial cultures capable of hydrolyzing holocelluosic materials, and their methodology followed in screening, analyzing, and purifying the enzymes associated with them.

Correction to: Bioprospection of actinobacteria derived from freshwater sediments for their potential to produce antimicrobial compounds

Upon publication of this article [1], it was brought to our attention that Figs.xa03, 4 and 5 are incorrectly presented in the original version of the article. The figures were inadvertently swapped in the original submission and published. Figurexa03 should be treated as Fig.xa05; Fig.xa04 should be 3 and Fig.xa05 should be Fig.xa04.n

Biocontrol of Fusarium wilt of Capsicum annuum by rhizospheric bacteria isolated from turmeric endowed with plant growth promotion and disease suppression potential

In the present study, 129 rhizospheric bacteria isolated from Curcuma longa were screened for their antagonistic potential against six fungal phytopathogens. Among them, 32 isolates that showed significant antagonistic potential were screened for their in vitro plant growth promoting (PGP) traits. The identification of potential isolates was confirmed by 16S rRNA gene sequencing and results revealed Bacillus as the dominant genus followed by Staphylococcus, Pseudomonas, Sphingomonas and Achromobacter. Based on the antagonistic activity and PGP traits; two strains (BPSRB4 and BPSRB14), identified as Bacillus amyloliquefaciens, were further tested for their in vivo PGP and disease suppression potential on Capsicum annuum seedlings under greenhouse conditions. The results demonstrated that BPSRB4 and BPSR14 strains suppress fungal pathogen infection and promote plant growth. Further, the BPSRB4 strain was positive for the production of the phytohormone indole acetic acid (IAA) detected by thin layer chromatography (TLC). In addition, nitrogen fixation and plant growth promotion activity were also confirmed by amplification and sequencing of nitrogen fixation gene (nifH) and ACC (1-aminocyclopropane-1-carboxylate) deaminase (acdS) gene from strains BPSRB4 and BPSRB14. The present study demonstrated that the B. amyloliquefaciens strains BPSRB4 and BPSR14 possess antagonistic activity and PGP potential which could be explored for the development of biofertilizers and biocontrol agents for the growth of chilli seedlings.