Electron microscope study of the intracellular development of the Pseudomonas aeruginosa bacteriophage phi KZ

The study of the ultrathin sections of cells infected with virulent phage phi KZ has confirmed the presence of a specific cylindrical formation, an inner body, in the head of this phage and revealed the spiral structure of this inner body. The formation of DNA condensates whose structure resembles a spring wound around the core (the inner body) has been shown to occur in the cells in the process of the ultracellular development of phage phi KZ. This development leads to characteristic changes in the cellular structure, and in particular in the cell walls and the nucleoid.     

Prediction of GTP interacting residues,dipeptides and tripeptides in a protein from its evolutionary information

Background  

Guanosine triphosphate (GTP)-binding proteins play an important role in regulation of G-protein. Thus prediction of GTP interacting residues in a protein is one of the major challenges in the field of the computational biology. In this study, an attempt has been made to develop a computational method for predicting GTP interacting residues in a protein with high accuracy (Acc), precision (Prec) and recall (Rc).     

Construction of the new <Emphasis Type="Italic">Escherichia coli</Emphasis> K-12 MG 1655 novel strain with improved growth characteristics for application in metabolic engineering

MG1655 of Escherichia coli K-12 is frequently used in metabolic engineering as the wild-type strain. However, its two mutations, ilvG and rph-1 provide a negative effect on culture growth. The “polar effect” of rph-1 decreases the level of pyrE expression, causing partial auxotrophy for pyrimidines. Mutation ilvG leading to the appearance of Val^S phenotype causes retardation of cell growth rate on media containing amino acids. In this work, the substitution of two loci in the genome of MG1655 with the recovery of the wild-type phenotype was accomplished. Gene rph ^wt from the chromosome of E. coli TG1 was marked via Red-dependent integration of DNA fragment carrying λattL-Cm^R-λattR and transduced with phage P1 into MG1655; later, the Cm^R marker was removed with the use of λXis/Int recombinase. Parallel to this procedure, a spontaneous Val^R mutant of E. coli MG1655 yielding colonies of maximal size on M9 medium with glucose in the presence of L-Val (50 μg/ml) was isolated. It was shown that a nucleotide deletion in the isolated Val^R strain had been generated in the region of the identified ilvG mutation, which led to the recovery of the reading frame and active protein synthesis. This mutation named ilvG-15, which is the only reason for the Val^R phenotype in the obtained strain, was transferred to MG1655-rph ^wt using cotransduction, by analogy to the transfer of rph ^wt. Evaluation of rates of aerobically growing cells (μ, hour-1) on M9 medium with glucose produced the following values: 0.56, 0.69, and 0.73 for strains MG1655,MG1655-rph ^wt, and MG1655-(rph ^wt, ilvG-15), respectively.     

Expression of Pseudomonas aeruginosa transposable phages in Pseudomonas putida cells. I. The establishment of a lysogenic state and the effectiveness of lytic development

Expression of transposable phages (TP) of Pseudomonas aeruginosa in the cells of P. putida was studied. The high efficiency of phage lytic development was shown both as a consequence of zygotic induction after transfer of the RP4::TPc+ plasmid into nonlysogenic recipients, and as a result of heat induction of lysogens PpG1 (D3112cts15). The high phage yield (20-25 particles of D3112cts phage per one cell of P. putida) is an evidence for a high level of transposition in the cells of this bacterial species. Plasmids RP4::TP are transferred into cells of PpG1 and PAO1 with similar frequency. However, the efficiency of establishment of the lysogenic state is lower in PpG1. Transposable phages of P. aeruginosa can integrate into the chromosome of PpG1 producing stable inducible lysogens. The presence of RP4 in the P. putida cells is not necessary for expression of transposable phages. The transposable phage D3112cts15 can be used in experiments of interspecies transduction of plasmids and chromosomal genes.