Aminopolycarboxylic acids (APCAs) have the ability to form stable, water-soluble complexes with di- and trivalent metal ions. For that reason, synthetic APCAs are used in a broad range of domestic products and industrial applications to control solubility and precipitation of metal ions. Because most of these applications are water-based, APCAs are disposed of in wastewater and reach thus sewage treatment plants and the environment, where they undergo abiotic and/or biotic degradation processes. Recently, also natural APCAs have been described which are produced by plants or micro-organisms and are involved in the metal uptake by these organisms. For the two most widely used APCAs, nitrilotriacetate (NTA) and ethylenediaminetetraacetate (EDTA), transformation and mineralisation processes have been studied rather well, while for other xenobiotic APCAs and for the naturally occurring APCAs little is known on their fate in the environment. Whereas NTA is mainly degraded by bacteria under both oxic and anoxic conditions, biodegradation is apparently of minor importance for the environmental fate of EDTA. Photodegradation of iron(III)-complexed EDTA is supposed to be mostly responsible for its elimination. Isolation of a number of NTA- and EDTA-utilising bacterial strains has been reported and the spectrum of APCAs utilised by the different isolates indicates that some of them are able to utilise a range of different APCAs whereas others seem to be restricted to one compound. The two best characterised obligately aerobic NTA-utilising genera (Chelatobacter and Chelatococcus) are members of the alpha-subgroup of Proteobacteria. There is good evidence that they are present in fairly high numbers in surface waters, soils and sewage treatment plants. The key enzymes involved in NTA degradation in Chelatobacter and Chelatococcus have been isolated and characterised. The two first catabolic steps are catalysed by a monooxygenase (NTA MO) and a membrane-bound iminodiacetate dehydrogenase. NTA MO has been cloned and sequenced and its regulation as a function of growth conditions has been studied. Under denitrifying conditions, NTA catabolism is catalysed by a NTA dehydrogenase. EDTA breakdown was found to be initiated by a MO also which shares many characteristics with NTA MO from strictly aerobic NTA-degrading bacteria. In contrast, degradation of [S,S]-ethylenediaminedisuccinate ([S,S]-EDDS), a structural isomer of EDTA, was shown to be catalysed by an EDDS lyase in both an EDTA degrader and in a NTA-utilising Chelatococcus strain. So far, transport of APCAs into cells has only been studied for EDTA and the results obtained give strong evidence for an energy-dependent carrier system and Ca(2+) seems to be co-transported with EDTA. Due to their metal-complexing capacities, APCAs occur in the environment mostly in the metal-complexed form. Hence, the influence of metal speciation on various degradation processes is of utmost importance to understand the environmental behaviour of these compounds. In case of biodegradation, th...

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An in situ mesocosm system was designed to monitor the in situ dynamics of the microbial community in polluted aquifers. The mesocosm system consists of a permeable membrane pocket filled with aquifer material and placed within a polypropylene holder, which is inserted below groundwater level in a monitoring well. After a specific time period, the microcosm is recovered from the well and its bacterial community is analyzed. Using this system, we examined the effect of benzene, toluene, ethylbenzene, and xylene (BTEX) contamination on the response of an aquifer bacterial community by denaturing gradient gel electrophoresis analysis of PCRamplified 16S rRNA genes and PCR detection of BTEX degradation genes. Mesocosms were filled with nonsterile or sterile aquifer material derived from an uncontaminated area and positioned in a well located in either the uncontaminated area or a nearby contaminated area. In the contaminated area, the bacterial community in the microcosms rapidly evolved into a stable community identical to that in the adjacent aquifer but different from that in the uncontaminated area. At the contaminated location, bacteria with tmoA-and xylM/xylE1-like BTEX catabolic genotypes colonized the aquifer, while at the uncontaminated location only tmoA-like genotypes were detected. The communities in the mesocosms and in the aquifer adjacent to the wells in the contaminated area consisted mainly of Proteobacteria. At the uncontaminated location, Actinobacteria and Proteobacteria were found. Our results indicate that communities with long-term stability in their structures follow the contamination plume and rapidly colonize downstream areas upon contamination.

Aims: The objective was to analyse the impact of growth conditions, in particular of the specific growth rate, on the resistance of Escherichia coli towards UV-C irradiation. Methods and Results: Escherichia coli K12 wild-type bacteria (and in some experiments also a mutant not expressing RpoS, the global regulator of the general stress response; rpoS ) mutant) were cultivated either in batch culture

Three protein factors IF1, IF2 and IF3 are involved in the initiation of translation in prokaryotes. No clear function has been assigned to the smallest of these three factors, IF1. Therefore, to investigate the role of this protein in the initiation process in Escherichia coli we have mutated the corresponding gene infA. Because IF1 is essential for cell viability and no mutant selection has so far been described, the infA gene in a plasmid was mutated by site-directed mutagenesis in a strain with a chromosomal infA + gene, followed by deletion of this infA + gene. Using this approach, the six arginine residues of IF1 were altered to leucine or aspartate. Another set of plasmid-encoded IF1 mutants with a cold-sensitive phenotype was collected using localized random mutagenesis. All mutants with a mutated infA gene on a plasmid and a deletion of the chromosomal infA copy were viable, except for an R65D alteration. Differences in growth phenotypes of the mutants were observed in both minimal and rich media. Some of the mutated infA genes were successfully recombined into the chromosome thereby replacing the wild-type infA + allele. Several of these recombinants showed reduced growth rate and a partial coldsensitive phenotype. This paper presents a collection of IF1 mutants designed for in vivo and in vitro studies on the function of IF1.Keywords: initiation factor IF1; mutagenesis; translation initiation.Translation initiation is the first step in protein synthesis and comprises several steps: (a) the 70S ribosome dissociates into 30S and 50S subunits; (b) a 30S initiation complex is formed in which initiator fMet-tRNA interacts with the initiation codon of an mRNA bound to the 30S ribosomal subunit; (c) finally, the 50S subunit joins to form the 70S initiation complex that then enters the elongation phase of translation. These reactions, in particular the formation of the 30S initiation complex, are promoted by the three initiation factors IF1, IF2 and IF3 [1]. In contrast to IF2 and IF3, the role of IF1 is uncertain and so far no clear specific function has been assigned to this protein [2,3] even though IF1 is essential for cell viability in Escherichia coli [4]. Apart from this latter in vivo study most other available data on IF1 have been gathered by in vitro investigations (for an overview see Sette et al.IF1 is a small protein consisting of 71 amino acids [6] and its structure contains an oligomer-binding motif which binds to oligonucleotides or oligosaccharides [5]. The oligomer-binding motif is also present in other nucleicacid binding proteins such as cold shock protein A or aspartyl-tRNA-synthetase. For several of these proteins it has been demonstrated that basic and aromatic amino acids are involved in the binding to RNA or DNA. Moreover, previous NMR studies have suggested that the arginine and lysine residues of IF1 are involved in binding to the 30S ribosomal subunit [7]. IF1 binds to the 30S subunit in a 1 : 1 ratio [8,9] and this interaction is enhanced in the presence of IF2 and IF3. This effe...

Two previously isolated strains (DSM 9103 T and LPM-4 T ) able to grow with EDTA (facultatively and obligately, respectively) as the source of carbon, nitrogen and energy were investigated in order to clarify their taxonomic positions. The strains were strictly aerobic, Gram-negative, asporogenous and non-motile rods that required biotin for growth. Reproduction occurred by binary fission. The strains were mesophilic and neutrophilic. Their major fatty acids were summed feature 7 (consisting of C 18 : 1 v7c, C 18 : 1 v9t and/or C 18 : 1 v12t) and C 19 : 0 cyclo v8c. The polyamine pattern revealed homospermidine as a major polyamine. Predominant polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, phosphatidyldimethylethanolamine, phosphatidylmonomethylethanolamine and diphosphatidylglycerol. Mesorhizobium-specific ornithine lipid was absent. The predominant isoprenoid quinone was Q-10. The DNA G+C values were 60.8 and 63.1 mol% (T m ) for strains LPM-4 T and DSM 9103 T , respectively. The level of 16S rRNA gene sequence similarity between these EDTA-utilizers was 99.3 % while the DNA-DNA hybridization value was only 37 %. Both strains were phylogenetically related to members of the genera Aminobacter and Mesorhizobium (95-97 % sequence similarity). However, DNA-DNA hybridization values between the novel EDTAdegrading strains and Aminobacter aminovorans DSM 7048 T and Mesorhizobium loti DSM 2626 T were low (10-11 %). Based on their genomic and phenotypic properties, the new alphaproteobacterial strains are assigned to a novel genus, Chelativorans gen. nov., with the names Chelativorans multitrophicus sp. nov. (type strain DSM 9103 T 5VKM B-2394 T ) and Chelativorans oligotrophicus sp. nov. (type strain LPM-4 T 5VKM B-2395 T 5DSM 19276 T ).EDTA is a chelating agent from the group of aminopolycarboxylic acids that are able to form stable, water-soluble complexes with many metal ions. At present, the amount of EDTA utilized worldwide amounts to some 103 000 tonnes per year. It is used in many diverse fields including the photographic and galvanic industries, in textile and paper manufacturing, for decontamination of nuclear power installations, as a component of industrial cleaners, as an additive in cosmetics and food products, in gas scrubbing for the removal of hydrogen sulfide from waste gases and in agricultural applications to improve the uptake of micronutrients to correct trace metal deficiencies in plants (Potthoff-Karl et al., 1996;Weilenmann et al., 2004). The predominantly water-based use of EDTA and the recalcitrance of EDTA to biodegradation have resulted in high concentrations of this agent in surface waters. The extensive environmental EDTA pollution that has been observed in Abbreviations: APL, aminophospholipid; DPG, diphosphatidylglycerol; PC, phosphatidylcholine; PDE, phosphatidyldimethylethanolamine; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; PHB, poly-bhydroxybutyrate; PL, phospholipids; PME, phosphatidylmonomethylethanolamine.The GenBank/EMBL/DDBJ...

Edited by Lev KisselevAbstract The influence in vivo of mutated forms of translation initiation factor (IF1) on the expression of the lacZ or 3A 0 reporter genes, with different initiation and/or +2 codons, has been investigated. Reporter gene expression in these infA(IF1) mutants is similar to the wild-type strain. The results do not support the longstanding hypothesis that IF1 could perform discriminatory functions while blocking the aminoacyl-tRNA acceptor site (A-site) of the ribosome. One cold-sensitive IF1 mutant shows a general overexpression, in particular at low temperatures, of both reporter genes at the protein but not mRNA level.