Fast screening of bacteria for plant growth promoting traits

Plant Growth Promoting Bacteria (PGPB) are a group of beneficial microorganisms that can positively influence plant fitness and development by improving nutrient acquisition, influencing global plant hormone levels (direct effect), or by reducing the detrimental effects of various pathogens on plant development (indirect effect). The use of PGPB in agriculture as formulated bioinoculants is a potential approach to reduce the negative environmental impacts caused by the continuous application of chemical fertilizers and pesticides. The evaluation of a great number of bacteria in the laboratory for key traits involved in the improvement of plant fitness is a suitable strategy to find prospective candidates for bioinoculants. This chapter presents the main methods described in the literature to quickly screen potential candidates from a bacterial collection to directly and indirectly promote the plant growth

Ubiquitous broad-line emission and the relation between ionized gas outflows and Lyman continuum escape in Green Pea galaxies

We report observational evidence of highly turbulent ionized gas kinematics in a sample of 20 Lyman continuum (LyC) emitters (LCEs) at low redshift (z ~ 0:3). Detailed Gaussian modeling of optical emission line profiles in high-dispersion spectra consistently shows that both bright recombination and collisionally excited lines can be fitted as one or two narrow components with intrinsic velocity dispersion of s ~ 40-100 km s-1, in addition to a broader component with s ~ 100-300 km s-1, which contributes up to ~40% of the total flux and is preferentially blueshifted from the systemic velocity. We interpret the narrow emission as highly ionized gas close to the young massive star clusters and the broader emission as a signpost of unresolved ionized outflows, resulting from massive stars and supernova feedback. We find a significant correlation between the width of the broad emission and the LyC escape fraction, with strong LCEs exhibiting more complex and broader line profiles than galaxies with weaker or undetected LyC emission. We provide new observational evidence supporting predictions from models and simulations; our findings suggest that gas turbulence and outflows resulting from strong radiative and mechanical feedback play a key role in clearing channels through which LyC photons escape from galaxies. We propose that the detection of blueshifted broad emission in the nebular lines of compact extreme emission-line galaxies can provide a new indirect diagnostic of Lyman photon escape, which could be useful to identify potential LyC leakers in the epoch of reionization with the JWST.</p

Optimization of cultivation conditions for combined nutrient removal and CO2 fixation in a batch photobioreactor

BACKGROUND The application of Chlorella vulgaris for simultaneous CO2 biofixation and nutrient removal has been optimised using response surface methodology (RSM) based on Box Behnken design (BBD). Experimental conditions employed comprised CO2 concentrations (Cc,g) of 0.03–22% CO2, irradiation intensities (I) of 100–400 μE, temperatures of 20–30 °C and nutrient concentrations of 0–56 and 0–19 mg L−1 nitrogen and phosphorus, respectively, the response parameters being specific growth rate μ, CO2 uptake rate Rc and %nutrient removal. RESULTS Over 10 days the biomass concentration reached almost 3 g L−1 for Cc,g of 5% CO2, with corresponding values of 0.74 g L−1 day−1 and 1.17 day−1 for Rc and μ, respectively, and 100% nutrient (N and P) removals. At 22% CO2 the Rc and μ decreased by around an order of magnitude, and nutrient removal also decreased to 79% and 50% for N and P, respectively. CONCLUSION Optimum values 5% CO2, 100 μE and 22 °C were identified for Cc,g, I and T, respectively, with μ and Rc reaching 1.53 day−1 and 1 g L−1 day−1, respectively, along with associated nutrient removal of 100%. Regression analysis indicated a good fit between experimental and model data. © 2016 Society of Chemical Industr