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Arabidopsis thaliana proteome contains 667 proteases; some tens of them are chloroplast-targeted proteins, encoded by genes orthologous to the ones coding for bacterial proteolytic enzymes. It is thought that chloroplast proteases are involved in chloroplasts' proteins turnover and quality control (maturation of nucleus-encoded proteins and removal of nonfunctional ones). Some ATP-dependent chloroplast proteases belonging to FtsH family (especially FtsH2 and FtsH5) are considered to be involved in numerous aspects of chloroplast and whole plant maintenance under non-stressing as well as stressing conditions. This notion is supported by severe phenotype appearance of mutants deficient in these proteases. In contrast to seemingly high physiological importance of chloroplast members of FtsH protease family, only a few individual proteins have been identified so far as their physiological targets (i.e. Lhcb1, Lhcb3, PsbA and Rieske protein). Our knowledge regarding structure and molecular mechanisms of these enzymes' action is limited when compared with what is known about FtsHs of bacterial origin. Equally limited is the knowledge about ATP-dependent Lon4 protease being the single known chloroplast-targeted ortholog of Lon protease of Escherichia coli.

The group of 96 strains ofEscherichia coli isolated from children with diarrhea were investigated towards the presence and polymorphism of genes encoding autotransporters that belong to the group of proteins named SPATE (Serine Protease Autotransporters ofEnterobacteriaceae). Based on the results of restriction analysis of the products of PCR reaction 8 different types of genes encoding SPATE were detected. It was found that 39 strains contained one gene of SPATE, 15 strains contained two different genes and 3 different genes were detected in the case of 3 strains. The analysis of combination of presence of genes encoding SPATE let us divide the investigated group of strains into 17 different genotypes. The analysis of polymorphism of genes encoding SPATE seems to be very promising tool for exploring the genetic diversity among pathogenic E. coli.

Methylating agents belong to mutagens occurring most frequently in our environment. They methylate mainly the nitrogen bases in DNA and RNA, affecting their functions. In E. coli the alkylated bases are repaired by proteins and enzymes either permanently present in the cells (Ogt, Ada) or produced transiently (Ada, AlkB, AlkA, Aid), after induction of the Ada defence system. Alkylating agents induce also the SOS system, which enhances the synthesis of about 40 proteins, including those participating in recombination, replication and mutagenesis of DNA. All DNA interactions, modifications and repairs constitute an amazing and highly efficiently functioning cellular system. Among the repair proteins there are some which affect the alkylated bases in a non-conventional way, very rarely occurring in nature. Especially amazing is the mechanism of action of dioxogenase AlkB, which combines the repair of methyl-, ethyl- and etheno-base derivatives with oxidation and dissociation of the modified groups, leading to direct recovery of natural bases. This review attempts to elucidate the role of the individual proteins involved in the repair processes.

The formation of proper structural disulfide bonds is one of the key steps during the folding of many secretory proteins and occurs both in prokaryotes and eukaryotes. In Gram negative bacterium Escherichia coli this process is catalyzed by a set of periplasmic oxidoreductases, termed Dsb. These proteins function in two separate pathways: (1) oxidizing (DsbA/DsbB system), responsible for introducing S-S bonds, and (2) reducing (DsbC/DsbD system, DsbG, CcmG and CcmH) which acts to isomerase wrongly formed disulfide bonds and participates in maturation of cytochrome c. The first system acts in connection with the inner membrane electron transfer system, using quinone molecules as electron acceptors, whereas reducing pathway relies on constant supply of electrons provided by the cytoplasmic thioredoxin system. Majority of Dsb proteins belongs to the thioredoxin superfamily and they contain the conserved Cys-X-X-Cys motif in their active site. The redox properties of Dsb proteins with the particular focus on structure-function dependence are in this review discussed.

All living organisms respond to environmental stresses, such as heat or ethanol by increasing the synthesis of a specific group of proteins termed heat shock proteins (Hsps) or stress proteins. Major Hsps are molecular chaperones and proteases. Molecular chaperones facilitate the proper folding of polypeptides, protect other proteins from inactivation, and reactivate aggregated proteins. Heat shock proteases eliminate proteins irreversibly damaged by stress. This review describes the role of heat shock proteins of the model bacterial cell, E. coli in the protection of other proteins against aggregation and in the mechanism of removal of protein aggregates from the cell. This mechanism remains unclear and it is believed to involve substrate renaturation and proteolysis by molecular chaperones and heat shock proteases. Recently, many studies have been focused on the disaggregation and reactivation of proteins by a bi-chaperone system consisting of DnaK/DnaJ/GrpE and ClpB, an ATPase from the AAA superfamily of proteins.

The aim of this study was to compare the effectiveness of E-test and two disc methods applied for the detection of extended spectrum beta-lactamases. All strains were tested by E-test, by double-disc synergy test (DDST) according to Jarlier (cefotaxim, ceftazidim, aztreonam and clavulanic acid) and also by disc test according to Appleton (cefpodoxime and cefpodoxime with clavulanic acid, CPD and CD01 disc). We tested 148 clinical strains of E. coli and 78 strains of K. Pneumoniae. In case of K. pneumoniae, the activity of the ESBLs was detected among 30 strains--both in E-test, Jarlier test and Appleton test. Among E. coli, four strains were found ESBL-positive in the test according to Jarlier but only three strain of these when E-test and Appleton test was used. The results of investigations performed suggest, that E-test and disc methods according both Jarlier and Appleton have the same effectiveness in detection ESBLs among K. pneumoniae strains. However, in case of E. coli, interpretation of results may present a problem.

The purpose of the study was to characterize fermentation of sucrose by Escherichia coli strains and to answer why some of these strains doesn't utilize this disaccharide. Investigations included 16 E. coli strains. Only 5 of these strains utilized sucrose. Genotypic analysis demonstrated the presence of cscB gene (encoding the sucrase permease which catalyzes transport of sucrose through the plasma membrane of the cell) in 5 strains of E. coli and cscA gene (encoding an enzyme sucrase that catalyzes the utilization of sucrose) in 6 strains of E. coli. These 5 of E. coli strains which possessed a chromosomally encoded sucrose metabolic pathway utilized sucrose with a different time. 3 of them destroyed this disaccharide after 24 h and 2 of them destroyed it after 48 h. Ten of E. coli strains hadn't cscA gene and 11 of them had not cscB genes. The lack of these genes can be the prove that it is not possible for 11 of E. coli strains to synthesize sucrose permease and for 10 of them to synthesize sucrase and it may be the reason of not utilize disaccharide sucrose by these bacteria.

Enteroaggregative Escherichia coli (EAEC) are responsible for infant's persistent secretory diarrhea, traveler's diarrhea and outbreaks. Since isolated all over the world EAEC strains show a low to high level of resistance to antimicrobial agents, the aim of the study was to determine antimicrobial susceptibility and beta-lactamases extended spectrum (ESBL) production in vitro among 55 enteroaggregative E. coli strains isolated from children with diarrhea. Among the 17 antimicrobial agents tested, most of them showed good in vitro activity against EAEC isolates examined, apart from ampicylin and piperacylin (about 30% resistant EAEC strains). Three of 55 examined EAEC isolates were ESBL--producing strains. Because of the presence of ESBL--producing as well as resistant to antimicrobial agents EAEC isolates among enteroaggregative E. coli strains examined, treatment with antibiotics should be undertaken according to antibiogram.

Investigations concerned Escherichia coli nitroreductase in creation of mutagens from non-mutagenic pesticides-derivatives of urea. Three new compounds were studied: N-phenyl-N'-methylurea (IPO 4328), N-methyl,N-(2-hydroxyethyl)-N'phenylurea (IPO 2363), N-(2-hydroxyethyl), N-methyl-N'-(3,4 dichloroethyl) urea, and diurone-3-(3,4 dichlorophenyl)-1,1 dimethylurea. These compounds were incubated in anaerobic conditions with cells of E. coli K-12 (KF) strain and nitrate or nitrite. Using Ames test, mutagenicity of resulting metabolites was investigated. It was found that during incubation of herbicide IPO 4328 with cells of E. coli K-12 (KF) and nitrate, mutagenic product for strain of S. typhimurium TA 1537 is created. Very weak mutagenic metabolite for the same strain was appearing during incubation of herbicide IPO 2363 with cells of E. coli K-12 (KF) in presence of nitrite. Incubation of investigated compounds with E. coli K-12 (KF) cells alone did not result in appearance of mutagenic substances. Thus, role of Escherichia coli in creation of mutagenic compounds from non-mutagenic derivatives of urea consisted of nitrite from nitrate production with participation of nitroreductase, which afterwards in absence of bacteria or action of their enzymes reacted with investigated pesticides.