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Concept: Agar


The requirements of micronutrients for biomass and hydrocarbon production in Botryococcus braunii UTEX 572 were studied using response surface methodology. The concentrations of four micronutrients (iron, manganese, molybdenum, and nickel) were manipulated to achieve the best performance of B. braunii in laboratory conditions. The responses of algal biomass and hydrocarbon to the concentration variations of the four micronutrients were estimated by a second order quadratic regression model. Genetic algorithm calculations showed that the optimal level of micronutrients for algal biomass were 0.266 µM iron, 0.707 µM manganese, 0.624 µM molybdenum and 3.38 µM nickel. The maximum hydrocarbon content could be achieved when the culture media contained 10.43 µM iron, 6.53 µM manganese, 0.012 µM molybdenum and 1.73 µM nickel. The validation through an independent test in a photobioreactor suggests that the modified media with optimised concentrations of trace elements can increase algal biomass by 34.5% and hydrocarbon by 27.4%. This study indicates that micronutrients play significant roles in regulating algal growth and hydrocarbon production, and the response surface methodology can be used to optimise the composition of culture medium in algal culture.

Concepts: Algae, Photosynthesis, Metal, Agar, Mathematical optimization, Algae fuel, Algaculture, Botryococcus braunii


The aim of this study was to develop novel anaerobic media using gellan gum for the isolation of previously uncultured rumen bacteria. Four anaerobic media, a basal liquid medium (BM) with agar (A-BM), a modified BM (MBM) with agar (A-MBM), an MBM with phytagel (P-MBM) and an MBM with gelrite (G-MBM) were used for the isolation of rumen bacteria and evaluated for the growth of previously uncultured rumen bacteria. Of the 214 isolates composed of 144 OTUs, 103 isolates (83 OTUs) were previously uncultured rumen bacteria. Most of the previously uncultured strains were obtained from A-MBM, G-MBM and P-MBM, but the predominant cultural members, isolated from each medium, differed. A-MBM and G-MBM showed significantly higher numbers of different OTUs derived from isolates than A-BM (P < 0·05). The Shannon index indicated that the isolates of A-MBM showed the highest diversity (H' = 3·89) compared with those of G-MBM, P-MBM and A-BM (H' = 3·59, 3·23 and 3·39, respectively). Although previously uncultured rumen bacteria were isolated from all media used, the ratio of previously uncultured bacteria to total isolates was increased in A-MBM, P-MBM and G-MBM.

Concepts: Ratio, Agar, E number, Diversity index, Shannon index, Gellan gum, Sphingomonas


Elements of micropropagation include establishment of shoot tip cultures, proliferation, rooting, and acclimatization of the resulting plantlets. The wide genetic variation in Pyrus makes micropropagation challenging for many genotypes. Initiation of shoots is most successful from forced dormant shoots or from scions grafted onto seedling rootstocks to impose juvenility. Clean shoots are recovered after testing for contaminants at the initiation stage on ½ strength Murashige and Skoog 1962 medium (MS), at pH 6.9 for 1 week or by streaking on nutrient agar. Although pear species and cultivars are cultured on several well-known media, MS is the most commonly used. Our studies showed that multiplication and growth of shoots are best on Pear Medium with higher concentrations of calcium chloride, potassium phosphate, and magnesium sulfate than MS medium and 4.4 μM N(6) benzyladenine. Pear shoots are often recalcitrant to rooting; however, a 5 s dip in 10 mM indole-3-butyric acid or naphthalene acetic acid before planting on basal medium without plant growth regulators is effective for many genotypes. Pear shoots store well at 1-4°C, and can hold for as long as 4 years without reculture. Cryopreservation protocols are available for long-term storage of pear shoot tips. Acclimation of in vitro-rooted or micrografted shoots in a mist bed follows standard procedures.

Concepts: Grafting, Agar, Plant hormone, Salt, Plant reproduction, Shoot, Rootstock, Plant propagation


The large-scale production of nematophagous fungi as agents of biological control is one of the main challenges to be commercially used. In order to improve growth of microorganism in a culture medium, the addition of growth inducer is common. At the moment, the action of their addition in the mycelia growth and sporulation rate of nematophagous fungi is not known. The purpose of this trial was to evaluate the sporulation rate of Duddingtonia flagrans by adding two growth inducers, meso-inositol and Tween 80, both at 0.5 % in a traditional culture medium Sabouraud glucose agar (SGA) and also in a traditional culture medium enriched with wheat flour and milk powder. From a traditional sterile culture of D. flagrans, four groups were made: SGA; Sabouraud glucose agar-meso-inositol 0.5 %; Sabouraud glucose agar-Tween 80 0.5 %; and Sabouraud glucose agar-enriched (SGA-E). These media were placed at a constant temperature of 27 °C for 4 weeks. Following this, chlamydospores were gently rinsed off with sterile water and counted using a Neubauer haematocytometer to estimate the number of chlamydospores per millilitre of water. The addition of meso-inositol 0.5 % to SGA promoted a significant increase (p < 0.05) in chlamydospore production obtaining an average of 51,715,000 chlamydospores per Petri dish. The highest chlamydospore concentration was observed in the SGA-E in comparison with SGA (p < 0.01) obtaining an average of 208,760,000 chlamydospores. The aim of this study was to obtain basic knowledge regarding the effect of enriched culture medium and growth-inducing meso-inositol and Tween 80 on mycelial growth and production of chlamydospores.

Concepts: Bacteria, Fungus, Milk, Agar, Mycelium, Agar plate, Petri dish, Nematophagous fungus


Tetrazolium salts (TTZ), such as tetrazolium violet (TV), have been widely used for microbiological studies. The formation of the colored formazan product due to bacterial reduction of the uncolored reagent is extensively exploited to stain cells or colonies in agar or on filters. But an important toxic effect of tetrazolium salts on bacteria exists that limits their use at high concentrations, impairing the efficient staining of the colonies. This is especially the case for Salmonella spp. where we observed, using a classic photometric approach and mathematical modeling of the growth, an important impact of tetrazolium violet on the apparent growth rate below the inhibitory concentration. In this study, we demonstrate that adding magnesium to the medium in the presence of TV leads to a significant increase in the apparent growth rate. Moreover, when higher TV concentrations are used which lead to total inhibition of Salmonella strains, magnesium addition to the culture media allows growth and TV reduction. This effect of magnesium may allow the use of higher TTZ concentrations in liquid growth media and enhance bacteria detection capabilities.

Concepts: Bacteria, Microbiology, Yeast, Agar, Agar plate, Growth medium, Formazan, Neutral red


Endemic brucellosis threatens wild herds of wood bison (Bison bison athabascae) in and around Wood Buffalo National Park, the largest genetic reserve of wood bison in the world. The overall goal of our project was to produce and preserve disease-free embryos for the purpose of conserving the genetic diversity of this species. The aim of the present experiment was to determine the effectiveness of washing procedures for removing Brucella bacteria from in vivo-derived wood bison embryos exposed in vitro to the pathogen. Wood bison cows were given 300mg im of Folltropin diluted in 0.5% hyaluronan on the day of follicle wave emergence (Day 0) and 100mg im of hyaluronan on Day 2, and then given 2500IU im of hCG on Day 5 and inseminated 12 and 24h later. Embryos were collected on Day 13. The experiment was done in 6 replicates (n=4 bison/replicate) and an average of 9 embryos/replicate were collected. Zona pellucida-intact embryos were kept in holding medium (PBS+2% fetal calf serum) and transported to a Biosafety Level 3 laboratory at the International Vaccine Centre, University of Saskatchewan. Embryos were transferred through 5 aliquots of holding medium to remove any contaminant before exposure to Brucella. Embryos were divided equally into 2 Petri dishes (representing later wash groups with v. without antibiotics) containing 2.7mL of holding medium (n=2 to 7 embryos per dish/replicate). In a Class II biosafety cabinet, Brucella abortus biovar 1 (1×10(7) to 1×10(9)CFUmL(-1) in 0.3mL) was added to each Petri dish and incubated for 2h at 37°C in 8% CO2. A sample of holding medium was taken before exposure and after incubation for culture as negative and positive controls, respectively. After incubation, embryos in each Petri dish were subjected to a 10-step washing procedure (according to the IETS Manual, 2010) using wash medium (PBS+0.4% BSA) without antibiotics or with antibiotics (100IUmL(-1) of penicillin+100μgmL(-1) of streptomycin). The embryo wash medium was cultured at wash steps 1, 3, 6, and 9. After the tenth wash, the zona pellucida of each embryo was ruptured mechanically using a glass pipette and embryos were cultured individually. Culturing of samples was done on sheep blood agar and specific identification of Brucella organisms was done by PCR. Brucella abortus was detected in 3 embryos from the group washed in medium without antibiotics (3/27), whereas all embryos washed in medium with antibiotics were culture negative (0/27). Brucella abortus was not detected in wash media after the third wash in either group (with or without antibiotics). In summary, Brucella abortus was removed from 89% of in vitro-exposed wood bison embryos using the washing procedure without antibiotics, and from 100% using the washing procedure with antibiotics. Results validate the embryo washing technique for producing Brucella-free wood bison embryos.

Concepts: Fetus, Brucellosis, Agar, Agar plate, American Bison, Bison, Petri dish, Wood Bison


The research described here was focused on the effect on human intestinal epithelial cell monolayers of sulphated red algal polysaccharides (κ-, λ-, and κ/β-carrageenans) alone and in combination with casein or lipopolysaccharide (LPS). HT-29 cells were investigated under normal and stress conditions; stress was induced by exposure to ethanol. Cell viability was monitored with a real-time system. The change in binding properties of negatively sulphated red algal polysaccharides assessed by the measurement of free carrageenans in mixtures with casein or McCoy’s 5A culture medium by means of toluidine blue O. Low sulphate content and the presence of 3,6-anhydogalactose are prerequisites for the recovery of ethanol-exposed HT-29 cells by carrageenans. Analysis of carrageenan binding ability confirmed that casein and LPS should affect carrageenan activity. Whether the combined action of the mucin-containing layer and carrageenans or the action of carrageenans alone was responsible for enhanced cell viability under stress conditions induced by ethanol is a subject for further research. This article is protected by copyright. All rights reserved.

Concepts: Bacteria, Glucose, Epithelium, Lipopolysaccharide, Agar, All rights reserved, Intestinal epithelium, Copyright


Microbiologists have been using agar growth medium for over 120 years. It revolutionized microbiology in the 1890’s when microbiologists were seeking effective methods to isolate microorganisms, which led to the successful cultivation of microorganisms as single clones. But there has been a disparity between total cell counts and cultivable cell counts on plates, often referred to as the “great plate count anomaly”, that has long been a phenomenon that still remains unsolved. Here we report that a common practice microbiologists have been employing to prepare agar medium has a hidden pitfall: when phosphate was autoclaved together with agar to prepare solid growth media (PT medium), total colony counts were remarkably lower when compared with those grown on agar plates in which phosphate and agar were separately autoclaved and mixed right before solidification (PS medium). We used a pure culture Gemmatimonas aurantiaca T-27(T) and three representative sources of environmental samples, soil, sediment and water, as inocula and compared colony counts between PT and PS agar plates. There were higher numbers of colony forming units (CFUs) on PS medium compared to PT medium using G. aurantiaca or any of the environmental samples. Chemical analysis of PT agar plates suggested that hydrogen peroxide was contributing to growth inhibition. Comparison of 454 pyrosequences of the environmental samples to the isolates revealed that taxa grown on PS medium were more reflective of the original community structure than those grown on PT medium. Moreover, more hitherto-uncultivated microbes grew on PS than on PT medium.

Concepts: Bacteria, Metabolism, Microbiology, Agar, Agar plate, XLD agar, Growth medium, Petri dish


We describe a novel protocol to quantitatively and simultaneously compare the chemotactic responses of cells towards different chemokines. In this protocol, droplets of agarose gel containing different chemokines are applied onto the surface of a Petri dish, and then immersed under culture medium in which cells are suspended. As chemokine molecules diffuse away from the spot, a transient chemoattractant gradient is established across the spots. Cells expressing the corresponding cognate chemokine receptors migrate against this gradient by crawling under the agarose spots towards their centre. We show that this migration is chemokine-specific; meaning that only cells that express the cognate chemokine cell surface receptor, migrate under the spot containing its corresponding chemokine ligand. Furthermore, we show that migration under the agarose spot can be modulated by selective small molecule antagonists present in the cell culture medium.

Concepts: Protein, Bacteria, Signal transduction, Chemotaxis, Cell biology, Receptor antagonist, Chemokine, Agar


Living color: Fluorescent pH-sensitive nanoparticles 12 nm in diameter were prepared and incorporated into agarose gel in a Petri dish to image pH changes during bacterial growth and metabolism.

Concepts: Molecular biology, Enzyme, Agar, Agarose gel electrophoresis, Petri dish