Characteristics of carbohydrate metabolism of R-, S- i M-dissociants of Pseudomonas aeruginosa]

R and S dissociants of the hydrocarbon-oxidizing strain Pseudomonas aeruginosa K-2 differed but little in their growth in a minimal defined medium with glucose as the source of carbon and energy. At the same time, the number of cells of M dissociant in the late exponential phase was five orders of magnitude less than that of R and S dissociants. The growth of M dissociant was accompanied by the accumulation of formate in the culture liquid and a concurrent decrease in pH. All three dissociants contained the key enzymes of the Entner-Doudoroff pathway of glucose oxidation; however, the activities of these enzymes, especially 6-phosphogluconate dehydrogenase, were low in M dissociant. Conversely, the activity of formate dehydrogenase in cells of M dissociant was higher than in other dissociants. The activity of 6-phosphogluconate dehydrogenase, a key enzyme of the pentosephosphate pathway of glucose oxidation, was detected only in S dissociant. The peculiarities of the carbohydrate metabolism of M dissociant are probably responsible for its poor growth on glucose and determine the more pronounced anaerobic type of its metabolism.     

Effect of carbon, nitrogen and phosphorus nutrition on the R, S, and M dissociants of Pseudomonas aeruginosa in mixed cultures

The effect of glucose, nitrate, and phosphate on the stationary-phase growth characteristics of R, S, and M dissociants of the hydrocarbon-oxidizing strain P. aeruginosa K-2 was studied. The optimal concentrations of glucose and phosphate providing for at least 90% of the maximal culture density were found to be 2-7% glucose and 0.02-0.12% phosphate. The main factor that determined the proportion of dissociants in bacterial populations was the initial concentration of phosphate. The fraction of R dissociant in populations increased linearly with the concentration of glucose and varied nonlinearly with the concentration of phosphate in the growth medium. The fraction of M dissociant depended solely on the concentration of phosphate in a manner inverse to that typical of R dissociant. In glucose-deficient media containing sufficient amounts of phosphorus, S dissociant prevailed over R dissociant.     

The requirements of Pseudomonas aeruginosa dissociants for carbon, nitrogen, and phosphorus

Quantitative data on the nutritional requirements of microorganisms are necessary to predict the behavior of bacterial populations and to control their cultivation. The requirements of the R, S, and M dissociants of Pseudomonas aeruginosa for carbon, nitrogen, and phosphorus were derived from the results of 88 cultivation experiments. For each of the dissociants, we derived a coefficient that relates the optical density and the number of cells in the dissociant culture, determined the time when the cultures entered the stationary growth phase, studied cultural changes induced by transfer to the stationary phase, and determined what nutrients limit the growth of particular dissociants. The nutritional requirements of the dissociants are discussed in relation to our earlier data.     

Effect of nitrogen sources on the kinetic growth parameters of a Pseudomonas aeruginosa culture oxidizing quinoline

The object of the work was to study the kinetic parameters of Pseudomonas aeruginosa P1 growth. Quinoline could be used as a sole nitrogen source during growth of the organism in a mineral medium. Reduced nitrogen forms were shown to be preferable for the growth.     

Effect of carbon and nitrogen sources on neutral proteinase production byPseudomonas aeruginosa

A strain ofPseudomonas aeruginosa from soil produced large quantitaties of extracellular neutral proteinase and could utilize several organic substances as carbon and nitrogen sources for enzyme production. The growth media required the presence of a high amount of phosphate when glucose was the carbon source. The intermediates of citric-acid cycle acids supported the proteinase production more than any other carbon sources. However, complex nitrogenous substances supported enzyme production more efficiently. Higher concentration of casamino acids suppressed the proteinase synthesis.     

Interaction of nitrogen and phosphorus nutrition in determining growth

In this paper we discuss the differences and similarities in the growth response of tomato plants to N and P limitation, and to their interaction. Two detailed growth experiments, with varied N or P supply, were conducted in order to unravel the effects of N and P limitation on growth of young tomato plants (Lycopersicon esculentum Mill.). Relative growth rate (RGR) initially increased sharply with increasing plant P concentration but leveled off at higher plant P concentrations. In contrast, RGR increased gradually with increasing plant N concentration before it leveled off at higher plant N concentrations. The relationship of RGR with organic leaf N and P showed the same shape as with total N and P concentrations, respectively. The difference in response is most likely due to the different roles of N and P in the machinery of the plant's energy metabolism (e.g., photosynthesis, respiration). Plant N concentration decreased with increasing P limitation. We show that this decrease cannot be explained by a shift in dry-mass partitioning. Our results suggest that the decrease in N concentration with increasing P limitation may be mediated by a decrease in leaf cytokinin levels and is less likely due to decreased energy availability at low P conditions. Dry-mass partitioning to the roots was closely linearly related to the leaf reduced-N concentration. However, treatments that were severely P limited deviated from this relationship.     

Efficient phosphorus solubilization by mutant strain of Xanthomonas campestris using different carbon, nitrogen and phosphorus sources

The phosphate solubilization activity of Xanthomonas campestris was measured in both the wild type and mutant strains using various carbon and nitrogen sources. Glucose was found to be the best in both (wild 39.9%; mutant 67.1%) strains followed by sucrose (46.8%) in the mutant and molasses (36.0%) in the wild type. Ammonium sulphate was the best nitrogen source for both the strains, followed by ammonium nitrate and urea. Dicalcium phosphate (DCP) was solubilized maximally by both the strains followed by tricalcium phosphate (TCP) and rock phosphate (RP) when various concentrations of different phosphate sources were tested.     

Effect of chromium on growth of Pseudomonas aeruginosa

Tolerance level to trivalent chromium-Cr(salen)(H2O)2+ and hexavalent chromium-K2Cr2O7 was assessed in P. aeruginosa isolated from tannery effluent soil. It could tolerate 80 and 100 ppm in liquid cultures and up to 100 and 200 ppm in plate count agar in the presence of trivalent and hexavalent chromium respectively. Unadapted cells took a longer time to grow than adapted cells in the presence of K2Cr2O7. Chromium influenced the cellular contents, morphology and respiration of P. aeruginosa. The chosen trivalent salt of chromium was more toxic than the hexavalent one.     

Effect of different nitrogen and carbon sources on the proteolytic activity

Two-three fold increases in the levels of proteolytic activities in one strain of Bacillus licheniformis (R1-8) were obtained when changes in the nature of the nitrogen source (food and fodder yeast instead of soybean meal) and in the amount of invert sugars in the culture medium were performed.     

Effect of carbon and nitrogen sources on growth and biological efficacy of Pseudomonas fluorescens and Bacillus subtilis against Rhizoctonia solani, the causal agent of bean damping-off

One of the most important environmental factors that regulate the growth and antagonistic efficacy of biocontrol agents is the medium. The aim of this paper was to find the nitrogen and carbon sources that provide maximum biomass production of strains P-5 and P-6 (Pseudomonas fluorescens), B-3 and B-16 (Bacillus subtilis) and minimum cost of media, whilst maintaining biocontrol efficacy. All of the strains were grown in seven liquid media (pH=6.9) including: sucrose + yeast extract, molasses of sugar beet + yeast extract in 2:1 and 1:1 w/w ratios, molasses of sugar beet + urea, nutrient broth, molasses and malt extract, at an initial inoculation of 1 x 10(5) CFU ml(-1). Cells from over night cultures used to inoculate soil at 1 x 10(9) CFU cm(-3) soil. At the same time, fungal inoculum (infected millet seed with Rhizoctonia solani) was added to soil at the rate of 2 g kg(-1) soil. Results indicated that growth of P-6, B-3 and B-16 in molasses + yeast extract (1:1 w/w) medium was significantly higher than in the other media. Molasses + yeast extract (1:1 and 2:1 w/w) media supported rapid growth and high cell yields in P-5. In greenhouse condition, results indicated that the influence of the media on the biocontrol efficacy of P-5, P-6, B-3 and B-16 was the same and Pseudomonas fluorescens P-5 in molasses and malt extract media reduced the severity of disease up to 72.8 percent. On the other hand, there were observed significant differences on bean growth after one month in greenhouse. P-5 in molasses + yeast extract (1:1 w/w) medium had the most effects on bean growth promotion. In this study molasses media showed good yield efficacy in all of the strains. The high sucrose concentration in molasses justifies the high biomass in all of the strains. Also, the low cost of molasses allows its concentration to be increased in media. On the other hand, yeast extract was the best organic nitrogen source for antagonist bacteria but it is expensive for an industrial process. So it should be replaced by another industrial product instead of yeast extract, which confirm by an economic and technological study. The results obtained in this study could be used to provide a reliable basis to increase the population of biocontrol agents in fermentation process.     

Influence of carbon and nitrogen sources on growth, nitrogenase activity, and carbon metabolism of Gluconacetobacter diazotrophicus

The effects of different carbon and nitrogen sources on the growth, nitrogenase activity, and carbon metabolism of Gluconacetobacter diazotrophicus were investigated. The amino acids asparagine, aspartic acid, and glutamic acid affected microbial growth and nitrogenase activity. Several enzymatic activities involved in the tricarboxylic acid cycle were affected by the carbon source used. In addition, glucose and gluconate significantly increased the oxygen consumption (respiration rate) of whole cells of G. diazotrophicus grown under aerobic conditions. Enzymes responsible for direct oxidation of glucose and gluconate were especially active in cells grown with sucrose and gluconate. The presence of amino acids in the apoplastic and symplastic sap of sugarcane stems suggests that these compounds might be of importance in the regulation of growth and nitrogenase activity during the symbiotic association. The information obtained from the plant-bacterium association together with the results of other biochemical studies could contribute to the development of biotechnological applications of G. diazotrophicus.     

The effect of nitrogen and carbon sources on proteinase production by Pseudomonas fluorescens

Some factors influencing the production of an extracellular proteinase by Pseudomonas fluorescens NCDO 2085 were studied. Proteinase production was optimal at 20C and pH 69 in static culture when calcium was included in the medium. Proteinase was not detectable in basal medium but could be induced by organic nitrogen compounds. The proteinase was produced in the exponential phase of growth on protein substrates but not until early stationary phase during growth on amino acids. The organism did not utilize lactose, the most abundant carbohydrate in milk. Citrate was readily utilized as an energy source but had a strong repressive effect on proteinase production. A medium containing sodium caseinate and pyruvate supported good growth and enzyme production. All the amino acids utilized as a sole carbon source, with the exception of serine, could induce proteinase production. Asparagine was the most effective amino acid inducer. Particular combinations of amino acids could induce or repress proteinase production. The regulation of proteinase production by Ps. fluorescens NCDO 2085 appears to be based on a balance between induction by low concentrations of low molecular weight degradation products and sensitivity to end product catabolite repression. The results suggest that the function of the proteinase is to ensure a supply of carbon rather than amino acids for protein synthesis.     

The effect of nitrogen and carbon sources on proteinase production by Pseudomonas fluorescens

Some factors influencing the production of an extracellular proteinase by Pseudomonas fluorescens NCDO 2085 were studied. Proteinase production was optimal at 20 degrees C and pH 6.9 in static culture when calcium was included in the medium. Proteinase was not detectable in basal medium but could be induced by organic nitrogen compounds. The proteinase was produced in the exponential phase of growth on protein substrates but not until early stationary phase during growth on amino acids. The organism did not utilize lactose, the most abundant carbohydrate in milk. Citrate was readily utilized as an energy source but had a strong repressive effect on proteinase production. A medium containing sodium caseinate and pyruvate supported good growth and enzyme production. All the amino acids utilized as a sole carbon source, with the exception of serine, could induce proteinase production. Asparagine was the most effective amino acid inducer. Particular combinations of amino acids could induce or repress proteinase production. The regulation of proteinase production by Ps. fluorescens NCDO 2085 appears to be based on a balance between induction by low concentrations of low molecular weight degradation products and sensitivity to end product catabolite repression. The results suggest that the function of the proteinase is to ensure a supply of carbon rather than amino acids for protein synthesis.     

Effect of Pseudomonas aeruginosa melanin on antibiotic activity]

The properties of microbial melanines are very diverse. Melanine of P. aeruginosa is little studied. The pigment was isolated from a strain of P. aeruginosa possessing all characteristic properties of the species. Interaction of P. aeruginosa melanine with various antibiotics was determined by the method of serial dilutions in beaf-peptone broth, using Staph. aureus 209 as a test-microbe, which was added to the medium in an amount of 10(6) cells to each tube. It was found that P. aeruginosa melanine differed from DOPA-melanine in a concentration of 1 mg/ml and did not change the activity of penicillin, tetracycline, oleandomycin, kanamycin and gentamicin with respect to Staph. aureus.     

Effect of carbon and nitrogen sources on glucoamylase production inLactobacillus brevis

A strain ofLactobacillus brevis produced extracellular glucoamylase. Induction of the glucoamylase occurred when saccharides such as starch, dextrin, maltose, mannitol and sucrose were employed as sole carbon sources. Synthesis of the amylase also occurred when soybean extract and peptone were used as sole nitrogen sources. The organism could be employed as a starter culture for local food fermentation.