Biomimetic of hydroxyapatite with Tridax procumbens leaf extract and investigation of antibiofilm potential in Staphylococcus aureus and Escherichia coli

In the last few decades, hydroxyapatite (HA) has become one of the most highly prized biominerals in the biomedical industry for orthopedic and dental applications. The focus of this research was to synthesize biomimetic HA from Tridax procumbens (TP) leaf extract and investigate their antibiofilm properties. The HA was made using the sol-gel method and the HA-TP biocomposite was made by precipitation method. The d.nm size of HA and HA-TP biocomposite was determined as 193.28 and 258.14 d.nm, respectively. The zeta potential of HA and HA-TP biocomposite was determined as ?21.2 and ?18.3 mV, respectively, and found highly stable. The FTIR study revealed that phytochemicals of TP were successfully impregnated into HA-TP biocomposite. The HA and HA-TP biocomposite were found spherical and agglomerated from SEM analysis. In HR-TEM analysis, the average diameter of the HA and HA-TP biocomposite were 16.57 – 64.22 nm and 51.71 – 138.68 nm, respectively. According to the EDX analysis, HA is primarily composed of calcium, oxygen, and phosphate, whereas, HA-TP biocomposite is primarily composed of calcium, phosphate, oxygen, and carbon. In the antioxidant assay, the IC50 value (concentration required to scavenge 50% of free radicals) of HA-TP biocomposite was determined as 156.69 ± 14.02 and 180.21 ± 12.84 µg/mL in DPPH and ABTS free radical scavenging assays, respectively. The MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) of as-synthesized HA-TP biocomposite against Staphylococcus aureus – ATCC 13565 and Escherichia coli – MTCC 41 were observed as 181.09 ± 21.47 and 317.30 ± 41.03, and 157.59 ± 32.18 and 264.03 ± 21.58 µg/mL, respectively. The as-synthesized HA-TP biocomposite has detrimentally affected the biofilm formation of both the tested bacteria S. aureus – ATCC 13565 and E. coli – MTCC 41. The study concluded that the as-synthesized HA-TP biocomposite could be highly helpful in the biomedical field for alleviating oxidative-stress-related disorders and inhibiting microbial biofilm formation.

Antimicrobial profile of Arthrobacter kerguelensis VL-RK_09 isolated from Mango orchards

Abstract An actinobacterial strain VL-RK_09 having potential antimicrobial activities was isolated from a mango orchard in Krishna District, Andhra Pradesh (India) and was identified as Arthrobacter kerguelensis. The strain A. kerguelensis VL-RK_09 exhibited a broad spectrum of in vitro antimicrobial activity against bacteria and fungi. Production of bioactive metabolites by the strain was the highest in modified yeast extract malt extract dextrose broth, as compared to other media tested. Lactose (1%) and peptone (0.5%) were found to be the most suitable carbon and nitrogen sources, respectively, for the optimum production of the bioactive metabolites. The maximum production of the bioactive metabolites was detected in the culture medium with an initial pH of 7, in which the strain was incubated for five days at 30 °C under shaking conditions. Screening of secondary metabolites obtained from the culture broth led to the isolation of a compound active against a wide variety of Gram-positive and negative bacteria and fungi. The structure of the first active fraction was elucidated using Fourier transform infrared spectroscopy, electrospray ionization mass spectrometry, 1H and 13C nuclear magnetic resonance spectroscopy. The compound was identified as S,S-dipropyl carbonodithioate. This study is the first report of the occurrence of this compound in the genus Arthrobacter.

Optimization of the Cultural Parameters for Improved Production of Antimicrobial Metabolites by Streptomyces gulbargensis DAS 131.

Aims: To investigate the influence of appropriate culture medium by optimizing the cultural conditions affecting the growth and bioactive metabolite production by Streptomyces gulbargensis DAS 131 under submerged culture conditions in order to reduce the cost of fermentation process to improve the formation of antimicrobial compounds. Place and Duration of Study: Department of Botany and Microbiology, January 2012 to May 2012. Methodology: The impact of environmental parameters such as incubation period, pH, temperature and salt concentration and effect of various nutrients such as carbon and nitrogen sources and minerals on the antimicrobial metabolite production by Streptomyces gulbargensis DAS 131 was evaluated by employing agar well diffusion assay. Growth was measured in the form of dry mycelial weight. Results: The optimum pH and temperature for bioactive metabolite production were 7 and 35°C respectively. Highest antimicrobial metabolite production was found when the strain was inoculated into the medium amended with glucose at the concentration of 2%, soya peptone at the rate of 1% and NaCl at the concentration of 5% and incubated for six days under shaking conditions. The metabolites showed good antimicrobial activity against Gram positive and Gram negative bacteria, as well as unicellular and multicellular fungi. Conclusion: S. gulbargensis DAS 131 isolated from the semi-arid soils of Gulbarga, Northern Karnataka province, India exhibited broad spectrum antimicrobial activity. It was found that the antimicrobial metabolite production by the strain was positively influenced by carbohydrates, nitrogen sources and minerals.

Optimization of Process Parameters for Improved Production of Bioactive Metabolites by Streptomyces tritolerans DAS 165T.

Aims: To optimize the process parameters for enhanced production of bioactive metabolites by Streptomyces tritolerans DAS 165T. Place and Duration of Study: Department of Botany and Microbiology, April 2012 to August 2012. Methodology: Agar well diffusion assay was employed to study the effect of environmental parameters such as incubation period, pH, temperature and salt concentration and influence of various nutrients such as carbon and nitrogen sources and minerals on the bioactive metabolite production by Streptomyces tritolerans DAS 165T.  Results: The production of antimicrobial metabolite was high when the strain was cultured for six days at 35ºC in medium (pH 7.5) with sucrose at the concentration of 2% (carbon source), soya peptone at the concentration of 1% (nitrogen source) and sodium chloride at the concentration of 5%.  Conclusion: This is the first report on the optimization of bioactive metabolite production by Streptomyces tritolerans DAS 165T. As the strain exhibited potent antimicrobial activity, it may be explored for biotechnological purposes.

Exploration of Actinobacteria from Mangrove Ecosystems of Nizampatnam and Coringa for Antimicrobial Compounds and Industrial Enzymes.

Aim: A study was made to examine the kinship between the seasonal distribution of actinobacteria and the physico-chemical properties of the mangrove sediments of Nizampatnam and Coringa located along the South East coast of Andhra Pradesh, India. Place and Duration of Study: Department of Botany and Microbiology, between April 2010 to February 2011. Methodology: Seasonal enumeration of actinobacteria from two different stations 1 (Nizampatnam) and 2 (Coringa) accorded by four different pre-treatments of soil sediments followed by plating onto three different media showed high incidence of actinobacteria in the month of February and least in December. Pretreatment with calcium carbonate and plating on starch casein agar yielded maximum number of actinobacteria. The strains were identified based on the morphological characteristics such as aerial mycelium, substrate mycelium, diffusible pigments and micro morphological features. Results: The present investigation revealed that majority of the mangrove actinobacteria 69%) belongs to Streptomyces spp. Among the 55 isolates screened for antimicrobial compounds, 28 were found to be potential producers. The isolates could also produce commercially important enzymes such as L-asparaginase, cellulase and amylase. In addition the statistical study also revealed that positive correlation between the distribution of the actinomycetes and influence of physico-chemical parameters and the organic matter of the soil. Conclusion: Our study revealed that the unexplored regions like Nizampatnam and Coringa mangrove ecosystems are proved as potential sites for antimicrobial and industrial enzyme producing actinobacteria.

Optimization of Culture Conditions for Enhanced Antimicrobial Activity of Rhodococcus erythropolis VLK-12 Isolated from South Coast of Andhra Pradesh, India.

Aims: To Isolate and characterize the antimicrobial actinomycetes from the marine habitats of south coast of Andhra Pradesh, India. Place and Duration of the Study: Marine habitats of south coast of Andhra Pradesh, India, between June 2011 and July 2012. Methodology: The soil samples were collected, pre-treated and plated on yeast extractmalt extract dextrose agar medium. Identification of the strain was carried out by employing the polyphasic taxonomical studies including the 16S rRNA sequence based analysis. Phylogenetic tree was constructed using the Molecular Evolutionary Genetic Analysis (MEGA) version 5. The influence of culture conditions and the effect of environmental factors on the biomass and antimicrobial activy\ity of the strain was the focus of this study. Results: A total of 20 actinobacteria were isolated from the marine habitats of south coast of Andhra Pradesh, India, and screened for antimicrobial activity against test bacteria and fungi. The potent bioactive metabolite producing strain was designated as VLK-12. Further polyphasic studies revealed that the Isolate VLK-12 belongs to the genera Rhodococcus. Phylogenetic analysis of 16S rRNA sequencing studies revealed that the strain is closely related to Rhodococcus erythropolis. The crude ethyl acetate extract obtained by culturing the strain on YMD inhibited Gram positive and Gram negative bacteria along with fungi. Conclusion: Rhodococcus erythropolis isolated from the marine habitats of south coast of Andhra Pradesh exhibited antimicrobial activity against pathogens.

Optimization of Culturing Conditions for Improved Production of Bioactive Metabolites by Pseudonocardia sp. VUK-10

The purpose of the present study was to investigate the influence of cultural and environmental parameters affecting the growth and bioactive metabolite production of the rare strain VUK-10 of actinomycete Pseudonocardia, which exhibits a broad spectrum of in vitro antimicrobial activity against bacteria and fungi. Production of bioactive metabolites by the strain was high the in modified yeast extract-malt extract-dextrose (ISP-2) broth, as compared to other tested media. Glucose (1%) and tryptone (0.25%) were found to be the most suitable carbon and nitrogen sources, respectively, for optimum production of growth and bioactive metabolites. Maximum production of bioactive metabolites was found in the culture medium with initial pH 7 incubated with the strain for four days at 30degrees C, under shaking conditions. This is the first report on the optimization of bioactive metabolites by Pseudonocardia sp. VUK-10.