Biosequestration of carbon dioxide using carbonic anhydrase from novel Streptomyces kunmingensis.

The increase in the atmospheric concentrations of carbon dioxide due to anthropogenic interventions has led to several undesirable consequences, notably global warming and related changes. Avoidance of and/or removal of carbon dioxide will result in the reduction of global warming. Biosequestration of carbon by using carbonic anhydrase (CA) as biocatalyst is one of most effective approaches. In the present study, actinobacterial cultures isolated from bamboo (Bambusa vulgaris) rhizosphere were screened for the production of carbonic anhydrase enzyme. The strain BS19 which showed promising CA production was selected as the potential strain. Strain BS19 was identified as Streptomyces kunmingensis based on the phenotypic and molecular characteristics. In submerged fermentation, strain BS19 produced 214.21 IU/ml of CA enzyme. The molecular mass of the CA was determined as 45 ± 2 kDa. The production of CA was found to be optimal at pH 7.0 and at temperature of 28 °C. The full length periplasmic CA gene was successfully amplified from S. kunmingensis BS19. Biomimetic sequestration of carbon was detected and quantified through CaCO3 precipitation method. Further, the CA of BS 19 was successfully used to mineralize CO2 present in motorbike exhaust, which has a similar composition to that of flue gas. The well-defined rhombohedral calcite crystals formed in the mineral carbonation reaction was observed through SEM analysis. The findings of this study clearly indicated that Streptomyces kunmingensis BS19 isolated from bamboo rhizosphere is a promising candidate for the production of carbonic anhydrase which deserves the potential for CO2 sequestration.

Impacts of global warming on marine microbial communities.

Global warming in ocean ecosystems alters temperature, acidification, oxygen content, circulation, stratification, and nutrient inputs. Microorganisms play a dominant role in global biogeochemical cycles crucial for a planet's sustainability. Since microbial communities are highly dependent on the temperature factor, fluctuations in the same will lead to adverse effects on the microbial community organization. Throughout the Ocean, increase in evaporation rates causes the surface mixed layer to become shallower. This intensified stratification inhibits vertical transport of nutrient supplies. Such density driven processes will decrease oxygen solubility in surface waters leading to significant decrease of oxygen from future Ocean. Metabolism and diversity of microbes along with ocean biogeochemistry will be at great risk due to global warming and its related effects. As a response to the changes in temperature, alteration in the distribution of phytoplankta communities is observed all over the planet, creating changes in the primary production of the ocean causing massive impact on the biosphere. Marine microbial communities try to adapt to the changing ocean environmental conditions by responding with biogeographic range shifts, community structure modifications, and adaptive evolution. Persistence of this climate change on ocean ecosystems, in future, will pose serious threat to the metabolism and distribution of marine microbes leading to fluctuations in the biogeochemical cycles thereby affecting the overall ecosystem functioning. Genomics plays an important role in marine microbial research by providing tools to study the association between environment and organisms. The ecological and genomic perspectives of marine microbes are being investigated to design effective models to understand their physiology and evolution in a changing ocean. Mesocosm/microcosm experimental studies and field studies are in the need of the hour to evaluate the impact of climate shifts on microbial genesis.

Microbial degradation, spectral analysis and toxicological assessment of malachite green by Streptomyces chrestomyceticus S20.

Malachite green (MG), a triphenylmethane dye is extensively used for coloring silk, aquaculture and textile industries, it has also has been reported toxic to life forms. This study aimed to investigate the biodegradation potential of MG by actinobacteria. The potent actinobacterial strain S20 used in this study was isolated from forest soil (Sabarimala, Kerala, India) and identified as Streptomyces chrestomyceticus based on phenotype and molecular features. Strain S20 degraded MG up to 59.65 ± 0.68% was studied in MSM medium and MG (300 mg l-1) and degradation was increased (90-99%) by additions of 1% glucose and yeast extract into the medium at pH 7. The treated metabolites from MG by S20 characterized by FT-IR and GC-MS. The results showed MG has been degraded into nontoxic compounds evaluated by (1) phytotoxic assay on Vigna radiata, (2) microbial toxicity on Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Streptococcus sp. and Escherichia coli, (3) cytotoxicity assay in a human cell line (MCF 7). The toxicity studies demonstrated that the byproducts from MG degradation by S. chrestomyceticus S20 were no toxic to plants and microbes and less toxic to human cells as compared to the parent MG. Perhaps this is the first work reported on biodegradation of MG by S. chrestomyceticus which could be a potential candidate for the removal of MG from various environments.

Actinobacterial-Mediated Fabrication of Silver Nanoparticles and Their Broad Spectrum Antibacterial Activity Against Clinical Pathogens.

The aim of this study is to fabricate silver nanoparticles (AgNPs) using actinobacterial strain isolated from lawn soil. Among six isolates, one isolate named AS-3 was potent in AgNPs production; hence it was identified deployed on gene sequence (16S rRNA) as Streptomyces spongiicola AS-3 (99.8% similarity). Actinobacteria mediated synthesized AgNPs were analyzed using UV-visible spectroscopy (UV-Vis), which showed a Surface Plasmon Resonance (SPR) at around λ = 443 nm. Scanning electron microscopy (SEM) analyses revealed the occurrence of predominant spherical AgNPs with polydispersed, with an average size of 22 nm. Energy-dispersive X-ray spectroscopy (EDS) established the existence of silver component. While the Fourier transforms infrared spectroscopy (FTIR) evidenced the occurrence of proteins as the bio reduction and topping agents over the AgNPs. X-ray diffraction (XRD) examination confirmed the obtained AgNPs were in crystalline planes of the face centric cubic. The S. spongiicola AgNPs antibacterial activity showed a broad spectrum antibacterial action against Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Vibrio cholera, Shigella sp., and Salmonella typhi were confirmed by disc diffusion test and MIC analysis.

Isolation, characterization and identification of antibiofouling metabolite from mangrove derived Streptomyces sampsonii PM33.

In this study, we report the production, bioassay guided isolation and identification of antibiofouling metabolite from mangrove derived actinobacterium, Streptomyces sampsonii (PM33). The actinobacterial strain PM33 yields maximum amount of antifouling compounds through agar surface fermentation. In optimization, carbohydrates such as glucose, fructose and xylose, are suitable for maximum production of the active compound. In addition, other compounds such as malt extract, glutamine, and sodium chloride concentrations (2.5, 5 and 7.5%) and parameters such as pH 7.0 and temperature range 30 °C to 40 °C enhanced the production of antifouling metabolite. The antifouling metabolite was extracted in ethyl acetate. TLC and bioautography was used to separate and detect the antifouling metabolite present in the crude extract. The physico chemical features revealed that the antifouling metabolite PM33 - B as taxifolin (C15H12O7). The purified taxifolin was found to be active against biofouling bacteria, algal spore germination and mollusc foot adherence, respectively. Toxicity nature of taxifolin was also determined by adopting zebrafish embryos. The taxifolin isolated from mangrove-derived Streptomyces sampsonii PM33 is a promising candidate for the development of eco-friendly antifouling preparation.

Potential applications of lactic acid bacteria and bacteriocins in anti-mycobacterial therapy

Tuberculosis (TB) is a communicable disease caused by Mycobacterium tuberculosis (M. tuberculosis). WHO estimated that 10.4 million new (incident) TB cases worldwide in year 2016. The increased prevalence of drug resistant strains and side effects associated with the current anti-tubercular drugs make the treatment options more complicated. Hence, there are necessities to identify new drug candidates to fight against various sub-populations of M. tuberculosis with less or no toxicity/side effects and shorter treatment duration. Bacteriocins produced by lactic acid bacteria (LAB) attract attention of researchers because of its 'Generally recognized as safe' status. LAB and its bacteriocins possess an effective antimicrobial activity against various bacteria and fungi. Interestingly bacteriocins such as nisin and lacticin 3147 have shown antimycobacterial activity in vitro. As probiotics, LAB plays a vital role in promoting various health benefits including ability to modulate immune response against various infectious diseases. LAB and its metabolic products activate immune system and thereby limiting the M. tuberculosis pathogenesis. The protein and peptide engineering techniques paved the ways to obtain hybrid bacteriocin derivatives from the known peptide sequence of existing bacteriocin. In this review, we focus on the antimycobacterial property and immunomodulatory role of LAB and its metabolic products. Techniques for large scale synthesis of potential bacteriocin with multifunctional activity and enhanced stability are also discussed.

Biocompatible silver, gold and silver/gold alloy nanoparticles for enhanced cancer therapy: in vitro and in vivo perspectives.

The aims of nano oncology are to detect, target and treat cancer cells without any side effects. The present study describes the microbial synthesis of biocompatible nanoparticles of silver (AgNPs), gold (AuNPs) and their alloy (Ag/AuNPs) for hepatoprotective activity against diethylnitrosamine (DEN)-induced liver cancer in a Sprague Dawley (SD) rat model. The crystalline nature and physicochemical features of the nanoparticles were identified by Fourier transform infra-red (FT-IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analysis. Based on the instrumental analysis, the synthesised nanomaterials were found to be spherical in shape and have an average size in the nano region. Nitrate reductase was characterized after partial purification of the culture filtrate via polyacrylamide gel electrophoresis and its molecular weight was determined as ∼45 kDa. Furthermore, the IC50 values of the AgNPs, AuNPs and Ag/AuNPs on HepG2 cells were determined as 38.42 µg ml-1, 43.25 µg ml-1 and 39.20 µg ml-1, respectively, and the antioxidant potential of the nanoparticles was also systematically analyzed. The No-Observed-Adverse-Effect-Level (NOAEL) for the AgNPs was determined to be 2000 mg per kg of body weight (bw) from an acute toxicity test. Similarly, the NOAEL of AuNPs and Ag/AuNPs were calculated as 1000 mg per kg bw. Based on the in vivo studies, a significant tumour reduction (∼45 to 65%) was observed in the nanoparticle-treated animals, which was further confirmed by hematological, biochemical, TEM and histopathological analysis. Immunohistochemistry analysis confirmed the presence of BAX antibodies, up to immunoreactive (3+) level in treated animals. These results strongly suggest the potential anticancer activities of AgNPs, AuNPs and Ag/AuNPs against DEN-induced liver cancer and they could be potential candidates for effective nano drug development.

Terpenoid bioactive compound from Streptomyces rochei (M32): taxonomy, fermentation and biological activities.

The present study emphasized the production of biologically active terpenoid compound from Streptomyces rochei M32, which was isolated from Western Ghats ecosystem, South India. The presence of resistant genes like mecA, vanA of Staphylococcus aureus and bla SHV, bla TEM of Pseudomonas aeruginosa was confirmed by molecular studies. The isolated compound from Streptomyces rochei M32 inhibited wide range of standard and clinical drug resistant pathogens and enteric pathogens. The rice bran supplemented basal medium influenced the active compound production on 8th day of fermentation and yielded 1875 mg of crude extract from 10 g of rice bran substrate. Purification and characterization of crude ethyl acetate extract was achieved by preparative thin layer chromatography. The active fraction was identified as terpenoid class compound by chemical screening. Based on the results of spectral studies (NMR, LC-MS, FTIR, etc.), the active compound was tentatively identified as 1, 19-bis (3-hydroxyazetidin-1-yl) nonadeca-5, 14-diene-1, 8, 12, 19-tetraone with molecular weight 462.41 g/mol. Minimum inhibitory concentration value ranges between 7.6 and 31.2 µg/mL against test organisms was observed. The cytotoxicity results on cervical cancer (HeLa) cell line showed IC50 value of 2.034 µg/mL. The corresponding compound is not previously reported from any microbial resources.

Antibiofouling potential of quercetin compound from marine-derived actinobacterium, Streptomyces fradiae PE7 and its characterization.

An attempt has been made to isolate, purify and characterize antifouling compound from Streptomyces fradiae PE7 isolated from Vellar estuarine sediment, Parangipettai, South India. The microbial identification was done at species level based on its phenotypic, cell wall and molecular characteristics. Strain PE7 produced high quantity of antifouling compounds in agar surface fermentation when compared to submerged fermentation. In fermentation optimization, wide range of sugars, amino acids, minerals, pH, temperature and NaCl concentration was found to influence the antifouling compound production from the strain PE7. Antifouling compound PE7-C was purified from the crude extract by preparative TLC, and its activity against biofouling bacteria was confirmed by bioautography. Based on the physico-chemical characteristics, the chemical structure of the antifouling compound PE7-C was identified as quercetin (C15H10O7), a flavonoid class of compound with the molecular weight 302.23 g/mol. The purified quercetin was active against 18 biofouling bacteria with MIC range between 1.6 and 25 µg/ml, algal spore germination and mollusc foot adherence found at 100 µg/ml and 306 ± 19.6 µg ml(-1) respectively. The present study, for the first time, reported quercetin from marine-derived Streptomyces sp. PE7 with antifouling activity. This also leads to the repurposing of quercetin for the development of antifouling agent.

A study of the bactericidal, anti-biofouling, cytotoxic and antioxidant properties of actinobacterially synthesised silver nanoparticles.

Actinobacteria- mediated synthesis of silver nanoparticles (AgNPs) is a reliable, eco-friendly and important aspect of nanobiotechnology. In this study, aqueous silver ions, which were exposed to an actinobacterial biomass of Streptomyces naganishii (MA7), were reduced to form stable AgNPs under optimised conditions. The microbially synthesised AgNPs were characterised by UV-Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), atomic force microscopy (AFM) and high- resolution transmission electron microscopy (HR-TEM). The size (5-50 nm) and shape (spherical) of the AgNPs were determined. The biosynthesised AgNPs exhibited good bactericidal, anti-biofouling, antioxidant and cytotoxic effects with regards to the HeLa cell line. A single protein band with a molecular weight of 44 kDa was obtained after partial purification of the culture filtrate via polyacrylamide gel electrophoresis. The potent actinobacterial strain was identified by its molecular (16s rRNA sequencing), phenotypic and cultural characteristics. The current study demonstrated the potential use of the extremophilic actinobacterial strain of S. naganishii (MA7) as a novel source for AgNPs synthesis with improved biomedical applications.

Characterization and phylogenetic analysis of antituberculous compound producing actinomycete strain D25 isolated from Thar Desert soil, Rajasthan.

During the course of the anti-infective drug discovery programme, actinomycete strain D25 was recovered from the Thar Desert soil, Rajasthan, India. Actinomycin type of compound isolated from the strain D25 showed promising activity against multi drug resistant and extensively drug resistant M. tuberculosis isolates. The present study reports the characteristics and phylogenetic status of the actinomycete strain D25. Phenotypic and cell wall characteristics revealed that the strain belongs to the genus Streptomyces. Further 16s rRNA analysis confined the genus Streptomyces with 97% similarity to the closely related species Streptomyces althioticus KCTC 9752. The 16s rRNA sequence was submitted to GenBank with the accession number JN604533.1. According to Bossard et al. (2003) strain D25 was found to be a novel species of the genus Streptomyces from Thar Desert soil, Rajasthan.