scholarly journals Expanded roles of pyruvate-sensing PdhR in transcription regulation of the Escherichia coli K-12 genome: fatty acid catabolism and cell motility

2020 ◽  
Vol 6 (10) ◽  
Author(s):  
Takumi Anzai ◽  
Sousuke Imamura ◽  
Akira Ishihama ◽  
Tomohiro Shimada
Keyword(s):  
Escherichia Coli ◽  
Fatty Acid ◽  
Type Species ◽  
Metabolic Energy ◽  
Oxidative Decarboxylation ◽  
Fatty Acid Degradation ◽  
Content Type ◽  
Acid Degradation ◽  
Link Type ◽  
K 12

The transcription factor PdhR has been recognized as the master regulator of the pyruvate catabolism pathway in Escherichia coli , including both NAD-linked oxidative decarboxylation of pyruvate to acetyl-CoA by PDHc (pyruvate dehydrogenase complex) and respiratory electron transport of NADH to oxygen by Ndh-CyoABCD enzymes. To identify the whole set of regulatory targets under the control of pyruvate-sensing PdhR, we performed genomic SELEX (gSELEX) screening in vitro. A total of 35 PdhR-binding sites were identified along the E. coli K-12 genome, including previously identified targets. Possible involvement of PdhR in regulation of the newly identified target genes was analysed in detail by gel shift assay, RT-qPCR and Northern blot analysis. The results indicated the participation of PdhR in positive regulation of fatty acid degradation genes and negative regulation of cell mobility genes. In fact, GC analysis indicated an increase in free fatty acids in the mutant lacking PdhR. We propose that PdhR is a bifunctional global regulator for control of a total of 16–23 targets, including not only the genes involved in central carbon metabolism but also some genes for the surrounding pyruvate-sensing cellular pathways such as fatty acid degradation and flagella formation. The activity of PdhR is controlled by pyruvate, the key node between a wide variety of metabolic pathways, including generation of metabolic energy and cell building blocks.

scholarly journals Lipopolysaccharide core type diversity in the Escherichia coli species in association with phylogeny, virulence gene repertoire and distribution of type VI secretion systems

2021 ◽  
Vol 7 (9) ◽  
Author(s):  
Sébastien O. Leclercq ◽  
Maxime Branger ◽  
David G. E. Smith ◽  
Pierre Germon
Keyword(s):  
Escherichia Coli ◽  
Type Species ◽  
Virulence Gene ◽  
Uneven Distribution ◽  
Gene Repertoire ◽  
Content Type ◽  
E Coli ◽  
Link Type ◽  
Wide Range ◽  
K 12

Escherichia coli is a very versatile species for which diversity has been explored from various perspectives highlighting, for example, phylogenetic groupings and pathovars, as well as a wide range of O serotypes. The highly variable O-antigen, the most external part of the lipopolysaccharide (LPS) component of the outer membrane of E. coli , is linked to the innermost lipid A through the core region of LPS of which five different structures, denominated K-12, R1, R2, R3 and R4, have been characterized so far. The aim of the present study was to analyse the prevalence of these LPS core types in the E. coli species and explore their distribution in the different E. coli phylogenetic groups and in relationship with the virulence gene repertoire. Results indicated an uneven distribution of core types between the different phylogroups, with phylogroup A strains being the most diverse in terms of LPS core types, while phylogroups B1, D and E strains were dominated by the R3 type, and phylogroups B2 and C strains were dominated by the R1 type. Strains carrying the LEE virulence operon were mostly of the R3 type whatever the phylogroup while, within phylogroup B2, strains carrying a K-12 core all belonged to the complex STc131, one of the major clones of extraintestinal pathogenic E. coli (ExPEC) strains. The origin of this uneven distribution is discussed but remains to be fully explained, as well as the consequences of carrying a specific core type on the wider aspects of bacterial phenotype.

scholarly journals Whole set of constitutive promoters for RpoN sigma factor and the regulatory role of its enhancer protein NtrC in Escherichia coli K-12

2021 ◽  
Vol 7 (11) ◽  
Author(s):  
Tomohiro Shimada ◽  
Shun Furuhata ◽  
Akira Ishihama
Keyword(s):  
Escherichia Coli ◽  
Type Species ◽  
Promoter Activity ◽  
Content Type ◽  
E Coli ◽  
Link Type ◽  
Presence And Absence ◽  
K 12 ◽  
Sigma Subunit

The promoter selectivity of Escherichia coli RNA polymerase (RNAP) is determined by its promoter-recognition sigma subunit. The model prokaryote E. coli K-12 contains seven species of the sigma subunit, each recognizing a specific set of promoters. Using genomic SELEX (gSELEX) screening in vitro, we identified the whole set of ‘constitutive’ promoters recognized by the reconstituted RNAP holoenzyme alone, containing RpoD (σ70), RpoS (σ38), RpoH (σ32), RpoF (σ28) or RpoE (σ24), in the absence of other supporting regulatory factors. In contrast, RpoN sigma (σ54), involved in expression of nitrogen-related genes and also other cellular functions, requires an enhancer (or activator) protein, such as NtrC, for transcription initiation. In this study, a series of gSELEX screenings were performed to search for promoters recognized by the RpoN RNAP holoenzyme in the presence and absence of the major nitrogen response enhancer NtrC, the best-characterized enhancer. Based on the RpoN holoenzyme-binding sites, a total of 44 to 61 putative promoters were identified, which were recognized by the RpoN holoenzyme alone. In the presence of the enhancer NtrC, the recognition target increased to 61–81 promoters. Consensus sequences of promoters recognized by RpoN holoenzyme in the absence and presence of NtrC were determined. The promoter activity of a set of NtrC-dependent and -independent RpoN promoters was verified in vivo under nitrogen starvation, in the presence and absence of RpoN and/or NtrC. The promoter activity of some RpoN-recognized promoters increased in the absence of RpoN or NtrC, supporting the concept that the promoter-bound NtrC-enhanced RpoN holoenzyme functions as a repressor against RpoD holoenzyme. Based on our findings, we propose a model in which the RpoN holoenzyme fulfils the dual role of repressor and transcriptase for the same set of genes. We also propose that the promoter recognized by RpoN holoenzyme in the absence of enhancers is the ‘repressive’ promoter. The presence of high-level RpoN sigma in growing E. coli K-12 in rich medium may be related to the repression role of a set of genes needed for the utilization of ammonia as a nitrogen source in poor media. The list of newly identified regulatory targets of RpoN provides insight into E. coli survival under nitrogen-depleted conditions in nature.

TetR-family transcriptional repressor Thermus thermophilus FadR controls fatty acid degradation

Microbiology ◽  
2011 ◽  
Vol 157 (6) ◽  
pp. 1589-1601 ◽  
Author(s):  
Yoshihiro Agari ◽  
Kazuko Agari ◽  
Keiko Sakamoto ◽  
Seiki Kuramitsu ◽  
Akeo Shinkai
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Target Genes ◽  
Thermus Thermophilus ◽  
Acyl Chain ◽  
Metabolic Energy ◽  
Straight Chain ◽  
Fatty Acid Degradation ◽  
Acid Degradation

In the extremely thermophilic bacterium Thermus thermophilus HB8, one of the four TetR-family transcriptional regulators, which we named T. thermophilus FadR, negatively regulated the expression of several genes, including those involved in fatty acid degradation, both in vivo and in vitro. T. thermophilus FadR repressed the expression of the target genes by binding pseudopalindromic sequences covering the predicted −10 hexamers of their promoters, and medium-to-long straight-chain (C10–18) fatty acyl-CoA molecules were effective for transcriptional derepression. An X-ray crystal structure analysis revealed that T. thermophilus FadR bound one lauroyl (C12)-CoA molecule per FadR monomer, with its acyl chain moiety in the centre of the FadR molecule, enclosed within a tunnel-like substrate-binding pocket surrounded by hydrophobic residues, and the CoA moiety interacting with basic residues on the protein surface. The growth of T. thermophilus HB8, with palmitic acid as the sole carbon source, increased the expression of FadR-regulated genes. These results indicate that in T. thermophilus HB8, medium-to-long straight-chain fatty acids can be used for metabolic energy under the control of FadR, although the major fatty acids found in this strain are iso- and anteiso-branched-chain (C15 and 17) fatty acids.

PBP4 and PBP5 are involved in regulating exopolysaccharide synthesis during Escherichia coli biofilm formation

Microbiology ◽  
2021 ◽  
Vol 167 (3) ◽  
Author(s):  
Sathi Mallick ◽  
Shanti Kiran ◽  
Tapas Kumar Maiti ◽  
Anindya S. Ghosh
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Type Species ◽  
Pentose Phosphate ◽  
Bacterial Cells ◽  
Surface Adhesion ◽  
Content Type ◽  
Penicillin Binding Proteins ◽  
E Coli ◽  
Link Type

Escherichia coli low-molecular-mass (LMM) Penicillin-binding proteins (PBPs) help in hydrolysing the peptidoglycan fragments from their cell wall and recycling them back into the growing peptidoglycan matrix, in addition to their reported involvement in biofilm formation. Biofilms are external slime layers of extra-polymeric substances that sessile bacterial cells secrete to form a habitable niche for themselves. Here, we hypothesize the involvement of Escherichia coli LMM PBPs in regulating the nature of exopolysaccharides (EPS) prevailing in its extra-polymeric substances during biofilm formation. Therefore, this study includes the assessment of physiological characteristics of E. coli CS109 LMM PBP deletion mutants to address biofilm formation abilities, viability and surface adhesion. Finally, EPS from parent CS109 and its ΔPBP4 and ΔPBP5 mutants were purified and analysed for sugars present. Deletions of LMM PBP reduced biofilm formation, bacterial adhesion and their viability in biofilms. Deletions also diminished EPS production by ΔPBP4 and ΔPBP5 mutants, purification of which suggested an increased overall negative charge compared with their parent. Also, EPS analyses from both mutants revealed the appearance of an unusual sugar, xylose, that was absent in CS109. Accordingly, the reason for reduced biofilm formation in LMM PBP mutants may be speculated as the subsequent production of xylitol and a hindrance in the standard flow of the pentose phosphate pathway.

scholarly journals d-Serine induces distinct transcriptomes in diverse Escherichia coli pathotypes

Microbiology ◽  
2021 ◽  
Vol 167 (10) ◽  
Author(s):  
James P. R. Connolly ◽  
Natasha C. A. Turner ◽  
Jennifer C. Hallam ◽  
Patricia T. Rimbi ◽  
Tom Flett ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Type Species ◽  
Pathogenic Bacteria ◽  
Neonatal Meningitis ◽  
Published Data ◽  
Toxic Metabolite ◽  
Transcriptional Responses ◽  
Content Type ◽  
E Coli ◽  
Link Type

Appropriate interpretation of environmental signals facilitates niche specificity in pathogenic bacteria. However, the responses of niche-specific pathogens to common host signals are poorly understood. d-Serine (d-ser) is a toxic metabolite present in highly variable concentrations at different colonization sites within the human host that we previously found is capable of inducing changes in gene expression. In this study, we made the striking observation that the global transcriptional response of three Escherichia coli pathotypes – enterohaemorrhagic E. coli (EHEC), uropathogenic E. coli (UPEC) and neonatal meningitis-associated E. coli (NMEC) – to d-ser was highly distinct. In fact, we identified no single differentially expressed gene common to all three strains. We observed the induction of ribosome-associated genes in extraintestinal pathogens UPEC and NMEC only, and the induction of purine metabolism genes in gut-restricted EHEC, and UPEC indicating distinct transcriptional responses to a common signal. UPEC and NMEC encode dsdCXA – a genetic locus required for detoxification and hence normal growth in the presence of d-ser. Specific transcriptional responses were induced in strains accumulating d-ser (WT EHEC and UPEC/NMEC mutants lacking the d-ser-responsive transcriptional activator DsdC), corroborating the notion that d-ser is an unfavourable metabolite if not metabolized. Importantly, many of the UPEC-associated transcriptome alterations correlate with published data on the urinary transcriptome, supporting the hypothesis that d-ser sensing forms a key part of urinary niche adaptation in this pathotype. Collectively, our results demonstrate distinct pleiotropic responses to a common metabolite in diverse E. coli pathotypes, with important implications for niche selectivity.

Sphingomonas cynarae sp. nov., a proteobacterium that produces an unusual type of sphingan

2013 ◽  
Vol 63 (Pt_1) ◽  
pp. 72-79 ◽  
Author(s):  
Adelfia Talà ◽  
Marcello Lenucci ◽  
Antonio Gaballo ◽  
Miriana Durante ◽  
Salvatore M. Tredici ◽  
...  
Keyword(s):  
Fatty Acid ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Type Species ◽  
Sensu Stricto ◽  
Rrna Gene ◽  
Globe Artichoke ◽  
Native Plant ◽  
Content Type ◽  
Link Type

Strain SPC-1T was isolated from the phyllosphere of Cynara cardunculus L. var. sylvestris (Lamk) Fiori (wild cardoon), a Mediterranean native plant considered to be the wild ancestor of the globe artichoke and cultivated cardoon. This Gram-stain-negative, catalase-positive, oxidase-negative, non-spore-forming, rod-shaped and non-motile strain secreted copious amounts of an exopolysaccharide, formed slimy, viscous, orange-pigmented colonies and grew optimally at around pH 6.0–6.5 and 26–30 °C in the presence of 0–0.5 % NaCl. Phylogenetic analysis based on comparisons of 16S rRNA gene sequences demonstrated that SPC-1T clustered together with species of the genus Sphingomonas sensu stricto. The G+C content of the DNA (66.1 mol%), the presence of Q-10 as the predominant ubiquinone, sym-homospermidine as the predominant polyamine, 2-hydroxymyristic acid (C14 : 0 2-OH) as the major hydroxylated fatty acid, the absence of 3-hydroxy fatty acids and the presence of sphingoglycolipid supported this taxonomic position. 16S rRNA gene sequence analysis showed that SPC-1T was most closely related to Sphingomonas hankookensis ODN7T, Sphingomonas insulae DS-28T and Sphingomonas panni C52T (98.19, 97.91 and 97.11 % sequence similarities, respectively). However, DNA–DNA hybridization analysis did not reveal any relatedness at the species level. Further differences were apparent in biochemical traits, and fatty acid, quinone and polyamine profiles leading us to conclude that strain SPC-1T represents a novel species of the genus Sphingomonas , for which the name Sphingomonas cynarae sp. nov. is proposed; the type strain is SPC-1T ( = JCM 17498T = ITEM 13494T). A component analysis of the exopolysaccharide suggested that it represents a novel type of sphingan containing glucose, rhamnose, mannose and galactose, while glucuronic acid, which is commonly found in sphingans, was not detected.

Paracoccus huijuniae sp. nov., an amide pesticide-degrading bacterium isolated from activated sludge of a wastewater biotreatment system

2013 ◽  
Vol 63 (Pt_3) ◽  
pp. 1132-1137 ◽  
Author(s):  
Li-Na Sun ◽  
Jun Zhang ◽  
Soon-Wo Kwon ◽  
Jian He ◽  
Shun-Gui Zhou ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Fatty Acid ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Activated Sludge ◽  
Type Species ◽  
Amide Bond ◽  
Rrna Gene ◽  
Content Type ◽  
Link Type

A facultatively anaerobic, non-spore-forming, non-motile, catalase- and oxidase-positive, Gram-reaction-negative, coccoid to short rod-shaped strain, designated FLN-7T, was isolated from activated sludge of a wastewater biotreatment facility. The strain was able to hydrolyse amide pesticides (e.g. diflubenzuron, propanil, chlorpropham and dimethoate) through amide bond cleavage. Strain FLN-7T grew at 4–42 °C (optimum 28 °C), at pH 5.0–8.0 (optimum pH 7.0) and with 0–5.0 % (w/v) NaCl (optimum 1.0 %). The major respiratory quinone was ubiquinone-10. The major cellular fatty acid was C18 : 1ω7c. The genomic DNA G+C content of strain FLN-7T was 66.4±0.5 mol%. The major polar lipids were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylcholine and an unidentified glycolipid. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain FLN-7T was a member of the genus Paracoccus and showed highest 16S rRNA gene sequence similarities with Paracoccus aminovorans JCM 7685T (99.2 %), P. denitrificans DSM 413T (97.8 %), P. yeei CDC G1212T (97.3 %) and P. thiocyanatus THI 011T (97.1 %). Strain FLN-7T showed low DNA–DNA relatedness with P. aminovorans KACC 12261T (36.5±3.4 %), P. denitrificans KACC 12251T (30.5±2.6 %), P. yeei CCUG 46822T (26.2±2.4 %) and P. thiocyanatus KACC 13901T (15.5±0.9 %). Based on the phylogenetic analysis, DNA–DNA hybridization, whole-cell fatty acid composition and biochemical characteristics, strain FLN-7T was clearly distinguished from all recognized species of the genus Paracoccus and should be classified in a novel species, for which the name Paracoccus huijuniae sp. nov. is proposed. The type strain is FLN-7T ( = KACC 16242T  = ACCC 05690T).

scholarly journals Murimonas intestini gen. nov., sp. nov., an acetate-producing bacterium of the family Lachnospiraceae isolated from the mouse gut

2015 ◽  
Vol 65 (Pt_3) ◽  
pp. 870-878 ◽  
Author(s):  
Karoline Kläring ◽  
Sarah Just ◽  
Ilias Lagkouvardos ◽  
Laura Hanske ◽  
Dirk Haller ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Methyl Ester ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Type Strain ◽  
Type Species ◽  
Rrna Gene ◽  
Content Type ◽  
Link Type ◽  
The Family

Three strains of an anaerobic, Gram-stain-positive coccobacillus were isolated from the intestines of mice. These strains shared 100 % similarity in their 16S rRNA gene sequences, but were distantly related to any described members of the family Lachnospiraceae (<94 %). The most closely related species with names that have standing in nomenclature were Robinsoniella peoriensis , Ruminococcus gnavus , Blautia producta and Clostridium xylanolyticum . Phylogenetic relationships based on 16S rRNA gene sequence analysis were confirmed by partial sequencing of hsp60 genes. The use of an in-house database search pipeline revealed that the new isolates are most prevalent in bovine gut samples when compared with human and mouse samples for Ruminococcus gnavus and B. producta . All three isolated strains shared similar cellular fatty acid patterns dominated by C16 : 0 methyl ester. Differences in the proportions of C12 : 0 methyl ester, C14 : 0 methyl ester and C18 : 1 cis-11 dimethyl acetal were observed when compared with phylogenetically neighbouring species. The major short-chain fatty acid produced by strain SRB-530-5-HT was acetic acid. This strain tested positive for utilization of d-fructose, d-galacturonic acid, d-malic acid, l-alanyl l-threonine and l-glutamic acid but was negative for utilization of amygdalin, arbutin, α-d-glucose, 3-methyl d-glucose and salicin, in contrast to the type strain of the closest related species Robinsoniella peoriensis . The isolates were not able to use mannitol for growth. Based on genotypic, phenotypic and chemotaxonomic characteristics, we propose to create the new genus and species Murimonas intestini gen. nov., sp. nov. to accommodate the three strains SRB-530-5-HT ( = DSM 26524T = CCUG 63391T) (the type strain of Murimonas intestini), SRB-509-4-S-H ( = DSM 27577 = CCUG 64595) and SRB-524-4-S-H ( = DSM 27578 = CCUG 64594).

scholarly journals bla OXA-48-like genome architecture among carbapenemase-producing Escherichia coli and Klebsiella pneumoniae in the Netherlands

2021 ◽  
Vol 7 (5) ◽  
Author(s):  
Antoni P. A. Hendrickx ◽  
Fabian Landman ◽  
Angela de Haan ◽  
Sandra Witteveen ◽  
Marga G. van Santen-Verheuvel ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
The Netherlands ◽  
Resistance Genes ◽  
Type Species ◽  
Antibiotic Resistance Genes ◽  
Gene Content ◽  
Content Type ◽  
E Coli ◽  
Link Type

Carbapenem-hydrolysing enzymes belonging to the OXA-48-like group are encoded by bla OXA-48-like alleles and are abundant among Enterobacterales in the Netherlands. Therefore, the objective here was to investigate the characteristics, gene content and diversity of the bla OXA-48-like carrying plasmids and chromosomes of Escherichia coli and Klebsiella pneumoniae collected in the Dutch national surveillance from 2014 to 2019 in comparison with genome sequences from 29 countries. A combination of short-read genome sequencing with long-read sequencing enabled the reconstruction of 47 and 132 complete bla OXA-48-like plasmids for E. coli and K. pneumoniae , respectively. Seven distinct plasmid groups designated as pOXA-48-1 to pOXA-48-5, pOXA-181 and pOXA-232 were identified in the Netherlands which were similar to internationally reported plasmids obtained from countries from North and South America, Europe, Asia and Oceania. The seven plasmid groups varied in size, G+C content, presence of antibiotic resistance genes, replicon family and gene content. The pOXA-48-1 to pOXA-48-5 plasmids were variable, and the pOXA-181 and pOXA-232 plasmids were conserved. The pOXA-48-1, pOXA-48-2, pOXA-48-3 and pOXA-48-5 groups contained a putative conjugation system, but this was absent in the pOXA-48-4, pOXA-181 and pOXA-232 plasmid groups. pOXA-48 plasmids contained the PemI antitoxin, while the pOXA-181 and pOXA-232 plasmids did not. Furthermore, the pOXA-181 plasmids carried a virB2-virB3-virB9-virB10-virB11 type IV secretion system, while the pOXA-48 plasmids and pOXA-232 lacked this system. A group of non-related pOXA-48 plasmids from the Netherlands contained different resistance genes, non-IncL-type replicons or no replicons. Whole genome multilocus sequence typing revealed that the bla OXA-48-like plasmids were found in a wide variety of genetic backgrounds in contrast to chromosomally encoded bla OXA-48-like alleles. Chromosomally localized bla OXA-48 and bla OXA-244 alleles were located on genetic elements of variable sizes and comprised regions of pOXA-48 plasmids. The bla OXA-48-like genetic element was flanked by a direct repeat upstream of IS1R, and was found at multiple locations in the chromosomes of E. coli . Lastly, K. pneumoniae isolates carrying bla OXA-48 or bla OXA-232 were mostly resistant for meropenem, whereas E. coli bla OXA-48, bla OXA-181 and chromosomal bla OXA-48 or bla OXA-244 isolates were mostly sensitive. In conclusion, the overall bla OXA-48-like plasmid population in the Netherlands is conserved and similar to that reported for other countries, confirming global dissemination of bla OXA-48-like plasmids. Variations in size, presence of antibiotic resistance genes and gene content impacted pOXA-48, pOXA-181 and pOXA-232 plasmid architecture.

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