Urokinase enhances the growth of Pseudomonas spp. in vitro under nonshaking (oxygen limited) conditions

Urokinase is a proteinase that normally functions as a plasminogen activator. It is detected in a number of tissues and can be expressed by inflammatory cells such as macrophages and polymorphonuclear leucocytes. Addition of human urokinase to cultures of mucoid or nonmucoid variants of Pseudomonas aeruginosa (strain PAO and clinical isolates from patients with cystic fibrosis) or Pseudomonas cepacia incubated in a minimal medium under nonshaking (oxygen limited) conditions led to dose-dependent enhancement of bacterial growth. The enzyme exhibited a minimal effect on the growth of bacteria when cultured under more intense aeration conditions. This enhancement of bacterial growth by urokinase required the presence of active enzyme and was not detected with inactivated enzyme or noncatalytic domains of the enzyme. Enhancement of bacterial growth was not observed following incubation of P. aeruginosa with other proteinases including thrombin, neutrophil elastase, trypsin, chymotrypsin, or pseudomonas elastase and pseudomonas alkaline proteinase. Therefore, the observed effect of urokinase was relatively specific for this enzyme. As urokinase is a natural constituent of the lung, this enzyme could contribute to bacterial growth during pulmonary infections, particularly in an inflammatory environment in which the oxygen tension may be reduced.Key words: plasminogen activators, Pseudomonas aeruginosa, bacterial growth, urokinase, host proteinases.

Effects of oxygen tension on the lipid composition of Azotobacter chroococcum

Lipid content and composition were determined in Azotobacter chroococcum grown, under nitrogen-fixing conditions, in continuous culture with intense aeration under atmospheres containing between 5 and 40% O2. Total lipid content remained almost constant at approximately 9% of dry weight.Phospholipid content was maximal at 20% O2 where it accounted for 92% of total lipid, and was minimal at 40% O2. Phosphatidylethanolamine was the only species of phosphatide detected in this fraction. Neutral lipid content was minimal at 20% O2 and maximal at 40% O2 where it represented approximately 30% of the total lipid. Glycolipid remained between 2 and 13% of total lipid throughout. The principal fatty acids of A. chroococcum were hexadecanoic (C16:0), hexadecenoic (C16:1), and octadecenoic acid (C18:1) at all O2 tensions, but C18:1 increased at the expense of C16:1 at higher O2 tensions, particularly in free fatty acid and phospholipid fractions. [U-14C]acetate was readily incorporated into lipid at both 20 and 40% O2 but total incorporation was much greater at 20% O2.

The growth of nitrogen-fixing Azotobacter chroococcum in continuous culture under intense aeration

Azotobacter chroococcum (ATCC 7493) was grown in continuous culture with intense vortex aeration (stirring rate 1750 rpm) with up to 50% O2 in the gas phase. Under these conditions the dissolved O2 generally remained at zero while the cell growth rose to about twice the normally accepted value. The meaning of the term "O2-limitation" in N2-fixing A. chroococcum cultures is critically examined.

The metabolic activity of the protoplasts and normal cells of Saccharomyces cerevisiae and the effect of inhibitors

Protoplasts of Saccharomyces cerevisiae obtained after 1 hours treatment with digestive enzymes of snail are, under the specified conditions, most suitable for metabolic experiments. By estimating the kinetics of the incorporation of leucine-14C, adenine-14C, uracil-14C, respiration, and anaerobic fermentation in protoplasts in a synthetic medium ((NH4)2SO4 used as source of nitrogen, glucose as source of carbon, five vitamins, and KCl as osmotic stabilizer) under intense aeration it was found that the incorporation of all the above-mentioned 14C-compounds and the rate of respiration rise with the increase in the size of the protoplasts. Thymidine-14C is not incorporated in cells or protoplasts. Comparative studies on the effects of the antibiotics chloramphenicol, oxytetracycline, cyanein, and isothiocyanates characterized by large molecules supplied data showing no differences in the action of these compounds on the cells and protoplasts of S. cerevisiae.

THE INTERMEDIATE METABOLISM OF PSEUDOMONAS AERUGINOSA: II. LIMITATIONS OF SIMULTANEOUS ADAPTATION AS APPLIED TO THE IDENTIFICATION OF ACETIC ACID, AN INTERMEDIATE IN GLUCOSE OXIDATION

Acetic acid has been isolated as an intermediate compound in the oxidation of glucose or α-ketoglutaric acid by Pseudomonas aeruginosa. Cells of this organism produced under conditions of intense aeration were found to have lost the ability to oxidize acetic acid and this compound was found in large quantities in the growth medium. When these cells were used to carry out the oxidation of glucose, it was found that the oxygen consumed was the amount needed to convert glucose to acetic acid, thus confirming the role of acetate as an intermediate in glucose oxidation. In contrast to the above-mentioned criteria the technique of simultaneous adaptation ruled out acetic acid as a possible intermediate in the oxidation of either glucose or α-ketoglutaric acid. The status of the theory of simultaneous adaptation is discussed in relation to the data obtained.