Endothermic microbial growth. A calorimetric investigation of an extreme case of entropy-driven microbial growth

Life is almost always associated with the generation of heat. Thus far, all chemotrophic life forms that have been studied in calorimeters were found to be exothermic. Certain literature reports have even cast doubt on the existence of endothermic growth, even though thermodynamic principles do not rule it out. The present report describes the first experiments demonstrating the actual existence of chemotrophic life forms that take up heat rather than produce i

Influence of residual ethanol concentration on the growth of Gluconacetobacter xylinus I2281

The influence of residual ethanol on metabolism of food grade Gluconacetobacter xylinus I2281 was investigated during controlled cultivations on 35g/l glucose and 5g/l ethanol. Bacterial growth was strongly reduced in the presence of ethanol, which is unusual for acetic acid bacteria. Biomass accumulated only after complete oxidation of ethanol to acetate and carbon dioxide. In contrast, bacterial growth initiated without delay on 35g/l glucose and 5g/l acetate. It was found that acetyl CoA was activated by the acetyl coenzyme A synthetase (Acs) pathway in parallel with the phosphotransacetylase (Pta)-acetate kinase (Ack) pathway. The presence of ethanol in the culture medium strongly reduced Pta activity while Acs and Ack remained active. A carbon balance calculation showed that the overall catabolism could be divided into two independent parts: upper glycolysis linked to glucose catabolism and lower glycolysis liked to ethanol catabolism. This calculation showed that the carbon flux through the tricarboxylic cycle is lower on ethanol than on acetate. This corroborated the diminution of carbon flux through the Pta-Ack pathway due to the inhibition of Pta activity on ethano

Influence of residual ethanol concentration on the growth of Gluconacetobacter xylinus I 2281

The influence of residual ethanol on metab. of food grade Gluconacetobacter xylinum I 2281 was investigated during controlled cultivations on 35 g/l glucose and 5 g/l ethanol. Bacterial growth was strongly reduced in the presence of ethanol, which is unusual for acetic acid bacteria. Biomass accumulated only after complete oxidn. of ethanol to acetate and carbon dioxide. In contrast, bacterial growth initiated without delay on 35 g/l glucose and 5 g/l acetate. It was found that acetyl CoA was activated by the acetyl CoA synthetase (Acs) pathway in parallel with the phosphotransacetylase (Pta)-acetate kinase (Ack) pathway. The presence of ethanol in the culture medium strongly reduced Pta activity while Acs and Ack remained active. A carbon balance calcn. showed that the overall catabolism could be divided into two independent parts: upper glycolysis linked to glucose catabolism and lower glycolysis linked to ethanol catabolism. This calcn. showed that the carbon flux through the tricarboxylic cycle is lower on ethanol than on acetate. This corroborated the diminution of carbon flux through the Pta-Ack pathway due to the inhibition of Pta activity on ethanol. [on SciFinder (R)

ACCELERATED PUBLICATION Expression of a Plant-Derived Peptide Harboring Water-Cleaning and Antimicrobial Activities

Abstract: Drinking water is currently a scarce world resource, the preparation of which requires complex treatments that include clarification of suspended particles and disinfection. Seed extracts of Moringa oleifera Lam., a tropical tree, have been proposed as an environmentfriendly alternative, due to their traditional use for the clarification of drinking water. However, the precise nature of the active components of the extract and whether they may be produced in recombinant form are unknown. Here we show that recombinant or synthetic forms of a cationic seed polypeptide mediate efficient sedimentation of suspended mineral particles and bacteria. Unexpectedly, the polypeptide was also found to possesses a bactericidal activity capable of disinfecting heavily contaminated water. Furthermore, the polypeptide has been shown to efficiently kill several pathogenic bacteria, including antibiotic-resistant isolates of Staphylococcus, Streptococcus, and Legionella species. Thus, this polypeptide displays the unprecedented feature of combining water purification and disinfectant properties. Identification of an active principle derived from the seed extracts points to a range of potential for drinking water treatment or skin and mucosal disinfection in clinical settings

Large-scale calorimetry and biotechnology

A review with 75 refs. of calorimetric techniques used and results obtained in calorimetric expts. aimed at developing quant. relation between heat release and other important process parameters for potential use in monitoring and controlling tech. bioprocesses. [on SciFinder (R)

Physiology of Saccharomyces cerevisiae during cell cycle oscillations

Synchronized populations of Saccharomyces cerevisiae CBS 426 are characterized by autonomous oscillations of process variables. CO2 evolution rate, O2 uptake rate and heat prodn. rate varied by a factor of 2 for a continuous culture grown at a diln. rate of 0.10 h-1. Elemental anal. showed that the carbon mass fraction of biomass did not change. Since the reactor is not at steady state, the elemental and energy balances were calcd. on cumulated quantities, i.e., the integral of the reaction rates. It was possible to show that carbon, degree of redn. and energy balances matched. Application of simple mass balance principles for non-steady state systems indicated that oscillations were basically characterized by changes in biomass prodn. rate. In addn., the amt. of intermediates, e.g., ethanol or acetate, produced or consumed was negligible. Growth rate was low during the S-phase (0.075 h-1) and high during the G2, M and G1 phases (0.125 h-1) for a const. diln. rate of 0.10 h-1. However, nitrogen, ash, sulfur and potassium content showed systematic increases during the S-phase (bud initiation). Cell component analyses showed that changes in cellular fractions during oscillations (storage carbohydrate content decreased during the S-phase) were due to changes in prodn. rates, particularly for protein and carbohydrates. Nevertheless, using the data evaluation techniques for dynamic systems presented here, it was shown that storage carbohydrates are not consumed during the S-phase. Only the synthesis rate of the different cell components changed depending on position in cell cycle. The growth process may be divided into two phenomena: the formation of new cells during mitosis with a low yield, and size increase of newborn cells with high yield. Both kinetic and stoichiometric coeffs. varied with the position in the oscillation. The results showed that biomass structure changed and that specific growth rate, as well as biomass yield, varied by +-25% during the oscillation. [on SciFinder (R)