Tarun C. Bora

A microwave promoted solvent-free approach to steroidal quinolines and their in vitro evaluation for antimicrobial activities.

The preparation of A-ring and D-ring fused steroidal quinolines is described from one-pot reaction of steroidal β-bromovinylaldehydes and arylamines in solvent-free and catalyst-free condition under microwave irradiation. The antimicrobial activities of the compounds were tested by agar diffusion assay and broth macro dilution method. Compounds 7a, 7e and 7g-h showed promising in vitro activity when tested against fungal pathogen Aspergillus niger whereas compounds 7e-h and 7j showed promising activity when tested against fungal pathogen Candida albicans. Compounds 7c and 7f showed potent inhibition against the growth of Gram negative bacteria Pseudomonas aeruginosa and compounds 7e, 7g-h and 7j inhibited the growth of tested Gram positive bacteria Bacillus subtilis and Staphylococcus aureus.

Brevibacillus laterosporus strain BPM3, a potential biocontrol agent isolated from a natural hot water spring of Assam, India

A bacterial strain designated as BPM3 isolated from mud of a natural hot water spring of Nambar Wild Life Sanctuary, Assam, India, strongly inhibited growth of phytopathogenic fungi (Fusarium oxysporum f. sp. ciceri, F. semitectum, Magnaporthe grisea and Rhizoctonia oryzae) and gram-positive bacterium (Staphylococcus aureus). The maximum growth and antagonistic activity was recorded at 30°C, pH 8.5 when starch and peptone were amended as carbon and nitrogen sources, respectively. In greenhouse experiment, this bacterium (BPM3) suppressed blast disease of rice by 30-67% and protected the weight loss by 35-56.5%. The maximum disease protection (67%) and weight loss protection (56.5%) were recorded when the bacterium was applied before 2 days of the pathogen inoculation. Antifungal and antibacterial compounds were isolated from the bacterium which also inhibited the growth of these targeted pathogens. The compounds were purified and on spectroscopic analysis of a purified fraction having R(f) 0.22 which showed strong antifungal and antibacterial activity indicated the presence of C-H, carbonyl group, dimethyl group, -CH(2) and methyl group. The bacterium was characterized by morphological, biochemical and molecular approaches and confirmed that the strain BPM3 is Brevibacillus laterosporus.

Possible involvement of plasmids in degradation of malathion and chlorpyriphos by Micrococcus sp.

Two plasmid-harboring strains ofMicrococcus sp. (M-36 and AG-43) degrade malathion and chlorpyriphos. Derivatives of the strains (SDS-36 and AO-43) treated with acridine orange and sodium dodecyl sulfate could not utilize malathion and chlorpyriphos for growth as the sole carbon source. Agarose gel electrophoresis of cell extracts of M-36 and AG-43 revealed the presence of a plasmid which was absent in SDS-36 and AO-43—suggesting probable involvement of plasmids in the degradation of malathion and chlorpyriphos by M-36 and AG-43. Nalidixic acid resistance in M-36 was also lost upon elimination of plasmids.

Experimental biofilm and its application in malathion degradation.

Mixed bacterial culture consisting of three different strains ofMicrococcus sp. (AG 36, AG 94 and AG 98) and two strains ofPseudomonas sp. (AG 7 and AG 52) and its individual components was passed through a sand column and 25.5–92% of cell dry mass was found to be retained (adsorbed) on it. Incubation of sand soaked in mineral medium containing glucose as a sole carbon source resulted in formation of a biofilm with 1.2–2.5-fold increase in biomass. A 61% degradation of malathion by the mixed culture biofilm could be achieved in 4 d.

Complete genome sequence analysis of Pseudomonas aeruginosa N002 reveals its genetic adaptation for crude oil degradation.

The present research work reports the whole genome sequence analysis of Pseudomonas aeruginosa strain N002 isolated from crude oil contaminated soil of Assam, India having high crude oil degradation ability. The whole genome of the strain N002 was sequenced by shotgun sequencing using Ion Torrent method and complete genome sequence analysis was done. It was found that the strain N002 revealed versatility for degradation, emulsification and metabolizing of crude oil. Analysis of cluster of orthologous group (COG) revealed that N002 has significantly higher gene abundance for cell motility, lipid transport and metabolism, intracellular trafficking, secretion and vesicular transport, secondary metabolite biosynthesis, transport and catabolism, signal transduction mechanism and transcription than average levels found in other genome sequences of the same bacterial species. However, lower gene abundance for carbohydrate transport and metabolism, replication, recombination and repair, translation, ribosomal structure, biogenesis was observed in N002 than average levels of other bacterial species.

Genetic and Functional Diversity Among the Antagonistic Potential Fluorescent Pseudomonads Isolated from Tea Rhizosphere

Twenty-five fluorescent pseudomonads from rhizospheric soil of six tea gardens in four district of Upper Assam, India were isolated and screened for antagonistic activity against fungal pathogens such as Fusariumoxysporum f. sp. raphani (For), Fusarium oxysporum f. sp. ciceri (Foc), Fusarium semitectum (Fs), and Rhizoctonia solani (Rs); and bacterial pathogens—Staphylococcus aureus (Sa), Escherichia coli (Ec), and Klebsiellapneumoniae (Kp). Most of the isolates exhibited strong antagonistic activity against the fungal pathogens and gram-positive bacterium i.e. Staphylococcus aureus. Productions of siderophore, salicylic acid (SA), hydrogen cyanide (HCN), and cell wall-degrading enzyme (chitinase) were studied to observe the possible mechanisms of antagonistic activity of the isolates. Correlation between the antagonistic potentiality of some isolates and their levels of production of siderophore, salicylic acid, and hydrogen cyanide was observed. Out of the 25 isolates, antibiotic-coding genes, 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) were detected in the isolates, Pf12 and Pf373, respectively. Genetic diversity of these fluorescent pseudomonads were analyzed with reference to four strains of Pseudomonas fluorescens NICM 2099T, P. aeruginosa MTCC 2582T, P. aureofaciens NICM 2026T, and P. syringae MTCC 673T. 16S rDNA-RFLP analysis of these isolates using three tetra cutter restriction enzymes (HaeIII, AluI and MspI) revealed two distinct clusters. Cluster A comprised only two isolates Pf141 and 24-PfM3, and cluster B comprised 23 isolates along with four reference strains.

Bio-transformation of artemisinin using soil microbe: Direct C-acetoxylation of artemisinin at C-9 by Penicillium simplissimum

Potent antimalarial compound artemisinin, 1 was bio-transformed to C-9 acetoxy artemisinin, 2 using soil microbe Penicillium simplissimum along with C-9 hydroxy derivative 3. The products were characterized using high field NMR and MS-MS data. The absolute stereochemistry of the newly generated chiral centers has been ascertained by COSY and 1D NOESY experiments. This is the first Letter of direct C-acetoxylation of artemisinin using microbial strains.

Bioprospecting Micromonospora from Kaziranga National Park of India and their anti-infective potential

Large number of strains was isolated from soils of Kaziranga National Park of North-East India using selective isolation procedure. They were assigned to the genus Micromonospora on the basis of their typical colonial and pigmentation features. The taxonomic identities of the isolates were confirmed on the basis of their molecular characters (16SrDNA). A total of one hundred Micromonospora strains were isolated during the present investigation. The diagnostic cell wall sugar and amino acids were determined from these Micromonospora strains. After preliminary screening most of the isolates exhibited excellent anti-infective activity against human bacterial pathogens Staphylococcus aureas, Bacillus subtilis, Proteus vulgaris, Echerichia coli, Pseudomonas aeroginosa and fungal pathogens Aspergillus niger, Fusarium oxysporum and Candida albicans. Among these isolates one strain designated as HK-10 showed promising activity against human pathogens S. aureas, B. subtilis, P. vulgaris and P. aeroginosa.

Complete genome sequencing and comparative analyses of broad-spectrum antimicrobial-producing Micromonospora sp. HK10.

Micromonospora genus produces >700 bioactive compounds of medical relevance. In spite of its ability to produce high number of bioactive compounds, no genome sequence is available with comprehensive secondary metabolite gene clusters analysis for anti-microbial producing Micromonospora strains. Thus, here we contribute the full genome sequence of Micromonospora sp. HK10 strain, which has high antibacterial activity against several important human pathogens like, Mycobacterium abscessus, Mycobacterium smegmatis, Bacillus subtillis, Staphylococcus aureus, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella and Escherichia coli. We have generated whole genome sequence data of Micromonospora sp. HK10 strain using Illumina NexSeq 500 sequencing platform (2×150bp paired end library) and assembled it de novo. The sequencing of HK10 genome enables identification of various genetic clusters associated with known- and probably unknown- antimicrobial compounds, which can pave the way for new antimicrobial scaffolds.

Community profiling of culturable fluorescent pseudomonads in the rhizosphere of green gram (Vigna radiata L.).

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. 16S rRNA partial sequencing analysis of 85 distantly related fluorescent pseudomonads depicted Pseudomonas aeruginosa 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. Pseudomonas aeruginosa 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., acdS, KatA and gbsA and elevated production efficiency of different PGP traits could promote GGRJ21 as a potent plant growth regulator.