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

A cooperativity between virus and bacteria during respiratory infections

Respiratory tract infections remain the leading cause of morbidity and mortality worldwide. The burden is further increased by polymicrobial infection or viral and bacterial co-infection, often exacerbating the existing condition. Way back in 1918, high morbidity due to secondary pneumonia caused by bacterial infection was known, and a similar phenomenon was observed during the recent COVID-19 pandemic in which secondary bacterial infection worsens the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) condition. It has been observed that viruses paved the way for subsequent bacterial infection; similarly, bacteria have also been found to aid in viral infection. Viruses elevate bacterial infection by impairing the host’s immune response, disrupting epithelial barrier integrity, expression of surface receptors and adhesion proteins, direct binding of virus to bacteria, altering nutritional immunity, and effecting the bacterial biofilm. Similarly, the bacteria enhance viral infection by altering the host’s immune response, up-regulation of adhesion proteins, and activation of viral proteins. During co-infection, respiratory bacterial and viral pathogens were found to adapt and co-exist in the airways of their survival and to benefit from each other, i.e., there is a cooperative existence between the two. This review comprehensively reviews the mechanisms involved in the synergistic/cooperativity relationship between viruses and bacteria and their interaction in clinically relevant respiratory infections

PHYTOCHEMICAL SCREENING AND DETERMINATION OF ANTIOXIDANT ACTIVITY OF Helicia nilagirica Bedd., AN ETHNOMEDICINAL PLANT OF MIZORAM, INDIA

  Objectives: The present study was undertaken to screen the phytochemical constituents and determine the antioxidant activity of Helicia nilagirica Bedd., an ethnomedicinal plant of Mizoram, India.Methods: Phytochemical screening was carried out according to standard procedures on the methanolic bark extract of the plant. The methanolic extract was subjected to in-vitro screening models such as DPPH radical scavenging assay, hydroxyl scavenging activity assay and reducing power assay using BHA and ascorbic acid respectively as standards. The total phenolic and total flavonoid content were determined using Gallic acid and Quercetin respectively as standards.Results: The presence of flavonoids, glycosides, steroids and carbohydrates was indicated by the tests conducted. The methanol extract exhibited IC50 values of 3.92 μg/ml and 6.86 μg/ml respectively in DPPH and hydroxyl radical scavenging activity assay. The reducing power of the extract was lower than that of the standard ascorbic acid. The total phenolic content and flavonoid content was 62.75 mg/g and 56 mg/g of gallic acid and quercetin equivalent respectively.Conclusion: The results of the present study concluded that the methanolic extract of the bark of Helicia nilagirica Bedd. possess antioxidant activity.Keywords: Helicia nilagirica, Phytochemicals, Antioxidant activity, Diphenyl-1-picrylhydrazyl, Phenol and flavonoid

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

<em>In vitro</em> evaluation of antimicrobial activities and antibiotic susceptibility profiling of culturable actinobacteria from fresh water streams

665-673Actinobacteria are major producers of antibiotics, industrially significant enzymes and many pharmaceutically important biologically active compounds. Twenty two actinobacterial strains were isolated from fresh water stream sediment samples of Murlen National Park, Mizoram, India. The actinobacterial strains were screened against antifungal pathogens (Fusarium oxysporum, Fusarium udum, Fusarium proliferatum, Fusarium oxysporum ciceri and Fusarium graminearum), and antibacterial activities against five bacterial pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, Micrococcus luteus, Bacillus subtilis and Escherichia coli) and a yeast pathogen Candida albicans. All strains showed antibacterial activity against E. coli and F. proliferatum. Based on the results of antagonistic, antibacterial and anti-yeast, two most potent strains Kocuria sp. and Streptomyces intermidus were further evaluated for their antibiotics susceptibility activity against 21 different antibiotics. Kocuria sp. showed resistance to 10 antibiotics whereas Streptomyces intermidus was resistance to 15 antibiotics. Modular genes Polyketide Synthase (PKS II) and Nonribosomal Peptide Synthetase (NRPS) were also detected in these two strains, which might be responsible for the production of secondary metabolites. Two volatile compounds, Di-N-octyl phthalate and 1-Bromo-3, 7-Dimethyloctane were identified from the extract of Streptomyces intermidus BPSWAC29 strain using Gas chromatography Mass spectrometry (GC-MS). This study highlights the promise of discovering novel actinobacteria with antimicrobial activity from underexplored niche biotopes such as fresh water stream sediments

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. 3, 4 and 5 are incorrectly presented in the original version of the article. The figures were inadvertently swapped in the original submission and published. Figure 3 should be treated as Fig. 5; Fig. 4 should be 3 and Fig. 5 should be Fig. 4

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, n = 18; abdomen n = 11; leg, n = 8; and hand, n = 6), 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 (BPSCRB12, BPSCRB14 and BPSCRB41), 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 BPSCRB41 could be source for the production of bioactive compounds

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

Abstract Background Actinobacteria 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. Results 16S 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. Conclusion Infectious 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