[The selection and properties of Penicillium verruculosum mutants with enhanced production of cellulases and xylanases].

The paper describes three Penicillium verruculosum 28K mutants with about threefold enhanced production of five industrially important carbohydrases. The two-stage fermentation process that we developed provided a further two- to threefold increase in the production of carbohydrases. Physiological and biochemical studies showed that the synthesis of all five carbohydrases is inducible.

[Adaptive mutagenesis accelerates microorganism evolution only while competing for resources: mathematic modeling].

Mathematical simulation of adaptive mutagenesis was carried out. The results obtained indicate that adaptive mutagenesis can play an essential role in the survival of microbial populations. We show that the competition for natural resources is a necessary factor of adaptive mutagenesis.

[New insights into the molecular mechanisms of evolution: stress increases genetic diversity].

The mechanisms of stress-induced mutagenesis in prokaryotes and realization of reserved (preaccumulated) genetic variation in eukaryotes are considered. In prokaryotes, replication becomes error-prone in stress because of the induction of the SOS response and the inactivation of the mismatch repair system; stress also increases the transposition rate and the efficiency of interspecific gene transfer. In eukaryotes, chaperone HSP90, which restores the native folding of mutant proteins (e.

[Biochemical response of recombinant Hansenula polymorpha strains to oversynthesis of homologous dioxyacetone kinase and bacterial beta-galactosidase].

Changes in the activities of key enzymes responsible for utilization of methanol by recombinant strains of methylotrophic yeasts H. polymorpha R22-2B and H. polymorpha LAC-56 grown in a chemostat are described.

[Study of the stability of hybrid plasmids replicating in Saccharomyces cerevisiae due to DNA fragments from polyoma virus].

Hybrid plasmid pSP97 carrying the entire genome of polyoma virus (PY), inserted into bacterial vector psV3, transforms yeast cells with the frequency 1 x 10(-2). Plasmid pSP97 is capable of autonomous replication in S. cerevisiae, while its structure remains unaltered, the stability of hybrid plasmid in transformants is 44%--100%.

[Instability of recombinant molecules].

The regions and mechanisms of recombinant DNAs instability are reviewed, in particular, the mechanisms of the replication instability expressed as elimination of recombinant DNA from cells and the mechanisms of structural instability revealed as spontaneous alteration of the chemical structure of these DNAs. The replication instability is subdivided into that induced by ineffective replication systems, and that induced by disturbances in the process of correct partitioning of the plasmids between dividing cells. The structural instability is subdivided into topological one occurring due to formation in the hybrid plasmids of the anomalous elements of the secondary structure-"loops", the regulatory instability caused by nonbalanced transcription streams and metabolic instability induced because of the protein superproduction which is energy capacious and not necessary for normal cell growth.

[Gene amplification in prokaryote and eukaryote systems].

The studied cases of gene amplification in bacteriophages, bacteria, yeasts, Drosophila, animal viruses and animal cells are reviewed. It is suggested that gene amplification is the mechanism universal for all classes of organisms and necessary for: 1) rendering the needed overhigh level of gene expression provided that the efficiency of the given gene transcription reaches in maximum (adaptive amplification), 2) preferential genome replication in case the efficiency of replication initiation reaches its maximum (competitive amplification), 3) rendering the essential stable DNA-protein interaction, if this interaction is damaged by DNA deletion (compensatory amplification). Molecular mechanisms for gene amplifications are: a) multiple sequential gene duplications, b) differential overreplication, excision, extrareplication and reintegration.

[Instability of hybrid plasmids containing Drosophila melanogaster DNA in rec+ and rec- Escherichia coli K-12 strains].

The stability of hybrid plasmids, constructed on the basis of vector pCV20(AprTcr) and containing HindIII fragments of Drosophila melanogaster DNA (pDm6, pDm9) and PstI fragments of D. melanogaster DNA (pDm39, pDm187, pDm189) was studied. After the transformation of E.