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The development of microbial biofilms increases the survival of microorganisms in the extreme conditions of ecosystems contaminated with components of liquid radioactive waste (LRW) and may contribute to the successful bioremediation of groundwater. The purpose of this work was to compare the composition of the microorganisms and the exopolysaccharide matrix of the biofilms formed on sandy loams collected at the aquifer from a clean zone and from a zone with nitrate and radionuclide contamination. The aquifer is polluted from the nearby surface repository for liquid radioactive waste (Russia). The phylogenetic diversity of prokaryotes forming biofilms on the sandy loams' surface was determined during 100 days using high-throughput sequencing of the V4 region of the 16S rRNA genes. Scanning electron microscopy was used to study the development of microbial biofilms on the sandy loams. The ratio of proteins and carbohydrates in the biofilms changed in the course of their development, and the diversity of monosaccharides decreased, depending on the contamination of the sites from which the rocks were selected. The presence of pollution affects biofilm formation and EPS composition along with the dominant taxa of microorganisms and their activity. Biofilms establish a concentration gradient of the pollutant and allow the microorganisms involved to effectively participate in the reduction of nitrate and sulfate; they decrease the risk of nitrite accumulation during denitrification and suppress the migration of radionuclides. These biofilms can serve as an important barrier in underground water sources, preventing the spread of pollution. Pure cultures of microorganisms capable of forming a polysaccharide matrix and reducing nitrate, chromate, uranyl, and pertechnetate ions were isolated from the biofilms, which confirmed the possibility of their participation in the bioremediation of the aquifer from nonradioactive waste components and the decrease in the radionuclides' migration. [ABSTRACT FROM AUTHOR]

Urinary tract infection (UTI) is a major infectious disease commonly induced by uropathogenic Escherichia coli (UPEC), of which a prevalent serogroup is the mostly antibiotic-resistant O4. Therefore, protective vaccines against UPEC infection, especially serogroup O4, are needed. Polysaccharide-based glycoproteins are promising candidates for development of anti-bacterial vaccines; however, current chemical and chemoenzymatic syntheses are costly and environmentally unfriendly, because of the complex ligation strategies and chemical reagents required. Development of efficient microbial cell factories, using cheap, renewable feedstocks and avoiding the use of toxic reagents would reduce toxic waste generation and environmental concerns. An O-glycosylation Escherichia coli chassis was developed to install the O-antigen gene cluster to biosynthesize a polysaccharide-based glycoprotein, by co-utilization of a glucose/glycerol mixture with high synergistic metabolic efficiency. Towards this goal, 32 genes related to competing pathways were deleted from E. coli MG1655 and 28 genes relevant to the biosynthesis of the glycoprotein were introduced, resulting in the successful production of the target recombinant glycoprotein. Subsequently, the availability of the intracellular sugar derivative precursors dTDP- L -Rha and UDP- L -FucNAc was optimized by tuning the expression of the corresponding enzymes. Further optimization of fermentation conditions resulted in a glycoprotein titre of 27.71 mg L−1. MS and EMR confirmed the precise biosynthesis of the target glycoprotein and highly efficient glycosylation. Finally, vaccination with the glycoprotein stimulated a strong immune response in mice, which markedly reduced the bacterial burden in the bladder and kidneys after UPEC challenge. This study provides guidance for the development of a sustainable and environmentally friendly manufacturing platform for specific high-value therapeutic glycoproteins. [ABSTRACT FROM AUTHOR]

Capsule polysaccharide (CPS) plays an important role in the virulence of Streptococcus pneumoniae and is usually used as the pneumococcal vaccine target. Glycerol-2-phosphate is found in the CPS of S. pneumoniae types 15A and 23F and is rarely found in the polysaccharides of other bacteria. The biosynthetic pathway of the nucleotide-activated form of glycerol-2-phosphate (NDP-2-glycerol) has never been identified. In this study, three genes (gtpl, gtp2, and gtp3) from S. pneumoniae 23F that have been proposed to be involved in the synthesis of NDP-2-glycerol were cloned and the enzyme products were expressed, purified, and assayed for their respective activities. Capillary electrophoresis was used to detect novel products from the enzymesubstrate reactions, and the structure of the product was elucidated using electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. Gtp1 was identified as a reductase that catalyzes the conversion of 1,3-dihydroxyacetone to glycerol, Gtp3 was identified as a glycerol-2-phosphotransferase that catalyzes the conversion of glycerol to glycerol-2-phosphate, and Gtp2 was identified as a cytidylyltransferase that transfers CTP to glycerol-2-phosphate to form CDP-2-glycerol as the final product. The kinetic parameters of Gtpl and Gtp2 were characterized in depth, and the effects of temperature, pH, and cations on these two enzymes were analyzed. This is the first time that the biosynthetic pathway of CDP-2-glycerol has been identified biochemically; this pathway provides a method to enzymatically synthesize this compound. doi: 10.1128/JB.00561-10

O-antigen is a component of the outer membrane of Gram-negative bacteria and is one of the most variable cell surface constituents, leading to major antigenic variability. The O-antigen forms the basis for bacterial serotyping. In this study, the O-antigen structure of Salmonella 066 was established, which differs from the known O-antigen structure of Escherichia coil O166 only in one linkage (most likely the linkage between the O-units) and O-acetylation. The O-antigen gene clusters of Salmonella 066 and E. coil O166 were found to have similar organizations, the only exception being that in Salmonella 066, the wzy gene is replaced by a non-coding region. The function of the wzy gene in E. coil O166 was confirmed by the construction and analysis of deletion and trans-complementation mutants. It is proposed that a functional wzy gene located outside the O-antigen gene cluster is involved in Salmonella 066 O-antigen biosynthesis, as has been reported previously in Salmonella serogroups A, B and D1. The sequence identity for the corresponding genes between the O-antigen gene clusters of Salmonella 066 and E. coil O166 ranges from 64 to 70 %, indicating that they may originate from a common ancestor. It is likely that after the species divergence, Salmonella 066 got its specific O-antigen form by inactivation of the wzy gene located in the O-antigen gene cluster and acquisition of two new genes (a wzy gene and a prophage gene for Q-acetyl modification) both residing outside the O-antigen gene cluster. DOI 10.1099/mic.0.037325-0

O-antigen variation due to the presence of different types of sugars and sugar linkages is important for the survival of bacteria threatened by host immune systems. The O antigens of Shigella dysenteriae type 7 and Escherichia coli O7 contain 4-(N-acetylglycyl)amino-4,6-dideoxy-D-glucose (D-Qui4NGlyAc) and 4-acetamido-4,6-dideoxy-D-glucose (D-Qui4NAc), respectively, which are sugars not often found in studied polysaccharides. In this study, we characterized the biosynthetic pathways for dTDP-D-Qui4N and dTDP-D-Qui4Nac (the nucleotide-activated precursors of D-Qui4NGlyAc and D-Qui4NAc in O antigens). Predicted genes involved in the synthesis of the two sugars were cloned, and the gene products were overexpressed and purified as His-tagged fusion proteins. In vitro enzymatic reactions were carried out using the purified proteins, and the reaction products were analyzed by capillary electrophoresis, electrospray ionization-mass spectrometry, and nuclear magnetic resonance spectroscopy. It is shown that in S. dysenteriae type 7 and E. coli O7, dTDP-D-Qui4N is synthesized from [alpha]-D-glucose-l-phosphate in three reaction steps catalyzed by glucose-1-phosphate thymidyltransferase (RmlA), dTDP-D-glucose 4,6-dehydratase (RmlB), and dTDP-4-keto-6-deoxy-D-glucose aminotransferase (VioA). An additional acetyltransferase (VioB) catalyzes the conversion of dTDP-D-Qui4N into dTDP-D-Qui4NAc in E. coli O7. Kinetic parameters and some other properties of VioA and VioB are described and differences between VioA proteins from S. dysenteriae type 7 (Vio[A.sub.D7]) and E. coil O7 (Vio[A.sub.O7]) discussed. To our knowledge, this is the first time that functions of VioA and VioB have been biochemically characterized. This study provides valuable enzyme sources for the production of dTDP-D-Qui4N and dTDP-D-Qui4NAc, which are potentially useful in the pharmaceutical industry for drug development.

The O-antigen moiety of the LPS is one of the most variable cell surface components of the Gram-negative bacterial outer membrane. Variation is due to the presence of different sugars and sugar linkages. Here, it is reported that a group of Escherichia coli O serogroups (017, 044, 073, 077 and 0106), and the Salmonella enterica serogroup 0:6,14 (H), share a common four-sugar backbone O-subunit structure, and possess almost identical O-antigen gene clusters. Whereas the E. coli 077 antigen does not have any substitutions, the other O antigens in this group differ by the addition of one or two glucose side branches at various positions of the backbone. The O-antigen gene clusters for all members of the group encode only the proteins required for biosynthesis of the common four-sugar backbone. The identification of three genes within a putative prophage in the E. coli 044 genome is also reported; these genes are presumably involved in the glucosylation of the basic tetrasaccharide unit. This was confirmed by deletion of one of the genes, which encodes a putative glucosyltransferase. Structural analysis of the O antigen produced by the mutant strain demonstrated the absence of glucosylation. An O-antigen structure shared by five E. coli and one S. enterica serogroups, all of which have a long evolutionary history, suggests that the common backbone may be important for the survival of E. coli strains in the environment, or for their pathogenicity.

Shigella dysenteriae type 1 is the most virulent serotype of Shigella. Enterotoxigenic Escherichia coli O148 is pathogenic and can cause diarrhoea. The following structure was established for the tetrasaccharide repeating unit of the E. coli O148 O antigen: [right arrow] 3)-[alpha](-L-Rhap-(1 [right arrow] 3)-[alpha](-L-Rhap-(1 [right arrow] 2)-[alpha]-D-Glcp-(1[right arrow] 3)-[alpha]-D-GlcpNAc-(1 [right arrow]. This differs from the structure reported earlier for S. dysenteriae type 1 by having a glucose (GIc) residue in place of a galactose (Gal) residue. The two bacteria also have the same genes for O antigen synthesis, with the same organization and high level of DNA identity, except that in S. dysenteriae type 1 wbbG is interrupted by a deletion, and a galactosyltransferase gene wbbP located on a plasmid is responsible for the transfer of galactose to make a novel antigenic epitope of the O antigen. The S. dysenteriae type 10 antigen was reconstructed by replacing the E. coli O148 wbbG gene with the wbbP gene, and it had the LPS structure and antigenic properties of S. dysenteriae type 1, indicating that the S. dysenteriae type 1 O antigen evolved from that of E. coli O148. It was also confirmed that wbbG of E. coli O148 is a glucosyltransferase gene, and two serotype-specific genes of E. coli O148 and S. dysenteriae type 1 were identified.