Self-restoration as fundamental property of CES providing their sustainability.

Sustainability is one of the most important criteria in the creation and evaluation of human life support systems intended for use during long space flights. The common feature of biological and physicochemical life support systems is that basically they are both catalytic. But there are two fundamental properties distinguishing biological systems: 1) they are auto-catalytic: their catalysts--enzymes of protein nature--are continuously reproduced when the system functions; 2) the program of every process performed by enzymes and the program of their reproduction are inherent in the biological system itself--in the totality of genomes of the species involved in the functioning of the ecosystem. Actually, one cell with the genome capable of the phenotypic realization is enough for the self-restoration of the function performed by the cells of this species in the ecosystem. The continuous microalgal culture of Chlorella vulgaris was taken to investigate quantitatively the process of self-restoration in unicellular algae population. Based on the data obtained, we proposed a mathematical model of the restoration process in a cell population that has suffered an acute radiation damage.

A new experimental approach to the search for chemical density factors in the regulation of monoculture growth.

In monocultures of micro-organisms, growth is controlled by feedback mechanisms involving chemical factors such as limiting substrates and inhibitory metabolic products. The role of such feedback in the growth regulation of Escherichia coli O-124 was investigated by growing cells in batch culture using a medium containing glucose and mineral salts. In various phases of growth, portions of the native culture were diluted with culture filtrate, so that although cell density decreased, the chemical composition of the growth medium was unaltered. As the diluted cultures grew, variations in growth acceleration were calculated and compared with those of native (undiluted) cultures. Towards the end of the exponential phase and in the growth deceleration phase, the specific feedback level (FBL) was between -20 and -200 (h g l-1)-1. The feedback components resulting from changes in glucose concentrations were calculated using experimentally determined values of mu max (0.55 +/- 0.05 h-1) and Ks (2.5 +/- 0.7 mg l-1). Only 0.1-40% of FBL could be accounted for by changes in glucose concentration, indicating the presence of additional growth regulators. The method developed may become a new tool for determination of growth-regulating cell-density factors in microbial cultures.