Physiological and biochemical changes accompanying the loss of mucoidy by Pseudomonas aeruginosa

Improving the Growth and Productivity of Macrotyloma uniflorum Medicinal Plant by the Co-inoculation of P, Zn and K-Solubilizing Fungi Under Field Conditions

The presence of small amount of soluble forms of Phosphorus (P), Potassium (K) and Zinc (Zn) in most soils is one of the limiting factors for agronomic crop production. The current study focuses on Macrotyloma uniflorum (horse gram or gahat), the most commonly cultivated crop in Uttarakhand. The current initiative and study were started, because there is a little information available on the impact of co-inoculation of beneficial fungi on crops in agricultural fields. Aspergillus niger K7 and Penicillium chrysogenum K4 were isolated and selected for the study on the basis of in vitro P, K and Zn-solubilizing activity. The solubilizing efficiency of K4 strain was 140% and K7 was 173.9% for P. However, the solubilizing efficiencies of K4 and K7 were 160% and 138.46% for Zn and 160% and 466% for K, respectively. The field trials were performed for two consecutive years, and growth and yield related parameters were measured for evaluation of the effect of P, K and Zn-solubilizing fungal strains on the crop. All the treatments showed a significant (P < 0.05) increase in growth and yield of M. uniflorum plants over uninoculated control; however, the best treatment was found to be soil inoculated with P. chrysogenum K4 + A. niger K7 in which the yield was enhanced by 71% over control. Thus, the co-inoculation of K4 and K7 strains showed a great potential to improve the growth and yield of plants. Both the fungal strains simultaneously solubilized three important nutritional elements in soil, which is a rare trait. Moreover, the capacity of these fungal strains to enhance the plant root nodulation and microbial count in soil makes the co-inoculation practice quite beneficial for sustainable agriculture.

Decolorization of Distillery Spent Wash Using Biopolymer Synthesized by Pseudomonas aeruginosa Isolated from Tannery Effluent

A bacterial strain was isolated from tannery effluent which can tolerate high concentrations of potassium dichromate up to 1000 ppm. The isolated microorganism was identified as Pseudomonas aeruginosa by performing biochemical tests and molecular characterization. In the presence of excess of carbohydrate source, which is a physiological stress, this strain produces Polyhydroxybutyrate (PHB). This intracellular polymer, which is synthesized, is primarily a product of carbon assimilation and is employed by microorganisms as an energy storage molecule to be metabolized when other common energy sources are limitedly available. Efforts were taken to check whether the PHB has any positive effect on spent wash decolorization. When a combination of PHB and the isolated bacterial culture was added to spent wash, a maximum color removal of 92.77% was found which was comparatively higher than the color removed when the spent wash was treated individually with the PHB and Pseudomonas aeruginosa. PHB behaved as a support material for the bacteria to bind to it and thus develops biofilm, which is one of the natural physiological growth forms of microorganisms. The bacterial growth in the biofilm and the polymer together acted in synergy, adsorbing and coagulating the pollutants in the form of color pigments.

Physiology of poly-3-hydroxybutyrate (PHB) production by Alcaligenes eutrophus growing in continuous culture

Summary: Alcaligenes eutrophus was grown in continuous culture (34 °C, pH 6.8) under various conditions with respect to dilution rate, nutrient limitation and carbon substrate. Poly-3-hydroxybutyrate (PHB) content, the rate of PHB production (q PHB) and the rate of carbon substrate utilization (q s) during growth on glucose were maximum at low dilution rate under ammonia limitation (ammonia limitation > potassium/oxygen limitation > glucose limitation). PHB content decreased in a linear manner as a function of dilution rate, from approximately 80% at D 0-025 h−1 during ammonia-limited growth to approximately 5% during growth at the maximum specific growth rate (μmax) in batch culture. PHB content, q PHB and qs varied with the nature of the carbon substrate during ammonia-limited growth at fixed dilution rate, and were maximum during growth on lactate [lactate>pyruvate>glucose/gluconate>fructose; highest q PHB 0.38 g PHB (g non-PHB biomass)−1 h−1]. qPHB was related in an approximately linear manner to the q s in excess of that required solely for the production of non-PHB biomass. This surplus q s was higher during growth on lactate than on glucose because q s was approximately equal to the maximum rate of carbon substrate utilization (q smax) during growth on lactate, but much lower than q smax during growth on glucose. The relationship between q PHB and surplus q s was confirmed by the effect of adding formate (as an additional source of NADH and/or ATP) and the uncoupling agent carbonyl cyanide-m-chlorophenylhydrazone (CCCP) to ammonia-limited cultures. It is concluded that A. eutrophus is unable to regulate the rate at which it takes up excess carbon substrate to match that required solely for growth, particularly during growth on lactate at low dilution rate, and thus produces PHB as a means of avoiding the potentially deleterious effects of generating high concentrations of intracellular metabolites. Possible ways of further increasing PHB production are discussed.