Optimization of Soilless Media for Alkaline Irrigation Water

High root zone pH reduces nutrient availability and high alkalinity water is strongly buffered around an alkaline pH. Soilless media can be altered to improve nutrient availability. This study was conducted to optimize the composition of soilless media for use with high alkalinity water. Mixes of peat and/or perlite or vermiculite in 50/50 and 33/33/33 volumetric ratios were tested. In some studies, mixes were also amended with up to 2.4 g/L of dolomite limestone to neutralize the initial acidity of the peat. Mixes containing vermiculite settled more, had higher water holding capacity (WHC) and percent plant available water (%PAW), and similar air filled porosity (AFP), compared to mixes containing perlite. Dry mass was measured in corn, peas, tomatoes, and soybeans, and chlorophyll content was measured in corn. The addition of dolomite increased pH and decreased dry mass in corn, soybean, and tomato, but peas were unaffected. Chlorophyll content in corn also declined with increased amounts of dolomite. After a week of daily irrigation, pH 7.8 nutrient solution neutralized the acidity of the peat, without the need for addition of dolomite. Mixes containing vermiculite improved growth and chlorophyll concentration compared to mixes with perlite. The higher cation exchange capacity (CEC) of vermiculite-containing mixes may have improved nutrient availability. A soilless mix of only peat and vermiculite, in approximately equal volumes, resulted in the greatest growth and chlorophyll content when watered with high alkalinity nutrient solution

Genetic and Biochemical Studies of Plasmid pIR52-1 in Lactobacillus helveticus

Lactobacillus helveticus is a species of lactic acid bacteria. These bacteria, which produce lactic acid as a major product of carbohydrate metabolism, are used industrially to produce cheese and other fermented dairy products (Ebringer et al., 2008). Many species of lactic acid bacteria also possess probiotic characteristics and when ingested potentially confer increased immune function, regulate gut microbiota, and improve digestion in the host (Reid, 2008). Genetic studies of these probiotic effects and other characteristics of L. helveticus and related species have been hindered by the lack of stably replicating plasmid vectors. Plasmid vectors for several Lactobacillus species have been constructed, but these are often derived from broad host range plasmids and may not be stably maintained over many generations (Fang et al., 2008; Thompson et al., 2001). In L. helveticus specifically, a small number of attempts have been made at adapting plasmid vectors for use in genetic studies, but as the source plasmids were not native to L. helveticus, they were either unable to replicate extrachromosomally or be maintained over many generations (Hagen et al., 2010; Thompson et al., 2001)