What am I reading today?

An article from 1972. Characterization of the Oxidized and Reduced Zones in Flooded Soil. I can't believe you still need a subscription to view this article. How long do copyright protections exist for articles published prior to 1978?

The oxidized and reduced layers in flooded soil were characterized by vertical distribution of the oxidation-reduction (redox) potential and concentrations of manganous manganese, ferrous iron, sulfide, nitrate, and ammonium. Redox potential was measured with a special motor-driven assembly which advanced a platinum electrode at a rate of 2 mm/hour through the flooded soil profile. Vertical distribution of reduced forms of manganese, iron, and sulfur and of nitrate and ammonium was determined by freezing and slicing the flooded soil into segments 1 or 2 mm thick. The apparent thickness of the oxidized layer was different when evaluated by the distribution of the various components in the profile, with the sulfide profile indicating the thickest oxidized zone, the manganese profile indicating the thinnest oxidized zone, and the iron profile showing an intermediate thickness. The thickness of the oxidized layer increased with duration of flooding.

Weekend Reading

Effects of Medium Composition on the Growth of Chlorella vulgaris During Photobioreactor Batch Cultivations

A promising alternative to petroleum-derived fuels lies in microalgae-produced biodiesel. Compared to major terrestrial crops, microalgae have higher rates of oil and biomass production and appear to be the only source of renewable biodiesel that can meet global demand for transport fuels. Chlorella vulgaris may be suitable for biodiesel production due to its faster growth and easier cultivation compared to other strains. Lipid production is achieved in two steps: a biomass production phase, and a lipid production phase, in which the lipid content of algal cells is increased by submitting them to environmental stress such as nitrogen starvation. As a preliminary step towards the optimization of the biomass production step, the effect of different nutrient concentrations in TAP medium on the photobioreactor cultivation of C. vulgaris was studied. The results showed good growth of Chlorella vulgaris in 2X TAP, reaching a biomass concentration of 6.0 g/liter. Growth inhibition was observed at concentrations of the nitrogen source, NH4Cl, between 500 and 1000 mg/liter in the medium. Varying the concentration of the phosphorus source, K2HPO4 in the medium had no effect on cell growth within the range studied, provided phosphorus sufficiency is ensured. Other medium components are non-limiting at the levels studied.

Link.

... and ...

Semi-continuous Cultivation of Chlorella vulgaris for Treating Undigested and Digested Dairy Manures

The present study, based on a previous batch-wise experiment, investigated a lab-scale semi-continuous cultivation of green microalgae Chlorella vulgaris (UTEX 2714), as a useful means for nutrient reduction as well as production of algal biomass which can be used as potential feedstock for the production of biofuel and other commodities, on 20x diluted dairy manures. Both undigested and digested samples were applied in parallel experiments for comparison regarding the requirements of hydraulic retention times (HRTs), removal efficiencies of nitrogen, phosphorus, and chemical oxygen demand (COD), biomass productivities, and CO(2) sequestration abilities. It was demonstrated that algae grown in undigested dairy manure achieved removal rates of 99.7%, 89.5%, 92.0%, and 75.5% for NH (4) (+) -N, TN, TP, and COD, respectively, under a 5-day HRT, while the HRT had to extend to 20 days in order to achieve 100.0% removal of NH (4) (+) -N in digested one with simultaneous removals of 93.6% of TN, 89.2% of TP, and 55.4% of COD. The higher organic carbon contained in undigested dairy manure helped boost the growth of mixotrophic Chlorella, thus resulting in a much shorter HRT needed for complete removal of NH (4) (+) -N. Moreover, algae grown in digested dairy manure provided more penitential than those grown in undigested one in CO(2) sequestration per milligram of harvested dried biomass (1.68 mg CO(2)/mg dry weight (DW) vs 0.99 mg CO(2)/mg DW), but did not surpass in total the amount of CO(2) sequestered on a 15-day period basis because of the better productivity gained in undigested dairy manure.

Link.

Guess I'm going to be interested in algae this weekend. What about everyone else?

What are you reading?

Effects of plant and influent C:N:P ratio on microbial diversity in pilot-scale constructed wetlands (pdf, 9 pages)

Abstract
Microbial processes within the rhizosphere of constructed wetlands are crucial to wastewater treatment, but the relation between microbial community diversity in rhizosphere, plant growth and water quality are unclear at present. The effects of plant growth, water C:N:P ratio and their interaction on microbial diversity in the rhizosphere were studied in synthetic wastewater in planted and unplanted wetlands during three different seasons. The physiological profile of microbial community-level in each wetland was assessed using substrate utilization patterns gathered via BIOLOGTM ECOplates. Plant had a significant effect on AWCD parameter, since the planted wetlands usually had a higher the total microbial activity than the unplanted over the study period. The Shannon, Simpson and McIntosh indices in the planted wetlands were apparently higher than those in the unplanted wetlands under any C:N:P ratio influent condition especially in summer. It was also shown that the unplanted wetlands have a greater shift of the interstitial microbial community than the planted at different seasons, since plant rhizospheres produce a more ecologically stable system in order to resist against shifts in microbial community composition in response to C:N:P ratio change in wastewater. Principal component analysis and clustering analysis indicated that influent C:N:P ratio would induce similar microbial species in the planted wetlands and detach them from the unplanted wetlands.

What are you reading?

Today I'm reading the following:
A widely distributed bacterial pathway for siderophore biosynthesis independent of nonribosomal peptide synthetases.
by: Gregory L. Challis

There is no abstract for this article (published in ChemBioChem). As you can surmise from the title though, it deals with iron acquisition and siderophore biosynthesis. I have a side-project I am working on in which I'm taking some techniques I used in graduate school, studying pathogens, and employing them in the area of soil microbial ecology. We'll see, eventually, how successful I am. I'm doing all the DNA preps now.

What are you reading?

Today, I'm reading the following: Induction of purple sulfur bacterial growth in dairy wastewater lagoons by circulation (PDF, 7 pages).

Abstract
Aims: To determine whether circulation of dairy wastewater induces the growth of phototrophic purple sulfur bacteria (PSB).

Methods and Results: Two dairy wastewater lagoons that were similar in size, geographic location, number and type of cattle loading the lagoons were chosen. The only obvious visual difference between them was that one was stagnant and the water was brown in colour (Farm 1), and the other was circulated and the water was red in colour because of the presence of PSB that contained carotenoid pigments (Farm 2). Both wastewaters were sampled monthly for 3 months and assayed for PSB and extractable carotenoid pigments (ECP). After this point, circulators were placed in the wastewater lagoon on Farm 1, and samples were taken monthly for 9 months and assayed for PSB and ECP. Before the installation of circulators, no PSB-like 16S rRNA sequences or ECP were observed in the wastewater from Farm 1; however, both were observed in the wastewater from Farm 2. After the installation of circulators, statistically greater levels of PSB and extractable carotenoid pigments were observed in the wastewater from Farm 1.

Conclusions: Circulation enhances the growth of PSB in dairy wastewater. Significance and Impact of this Study: Because PSB utilize H2S and volatile organic acids (VOA) as an electron source for photosynthesis, and VOA and alcohols as a carbon source for growth, the increase in these bacteria should reduce H2S, volatile organic compounds and alcohol emissions from the lagoons, enhancing the air quality in dairy farming areas.