Proceedings of the National Academy of Sciences

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Wed, 02/26/2014 - 03:20
The intracellular pathogen Salmonella enterica serovar Typhimurium requires the mgtC gene to cause disease. The mgtC transcript includes a long leader region that harbors a short proline codon-rich ORF—termed mgtP—the translation of which is predicted to favor formation of one of two alternative stem-loop structures. We now report that the...
Tue, 01/07/2014 - 14:58
Proceedings of the National Academy of Sciences
Antibiotic-resistant isolates of Salmonella enterica were selected on plates containing lethal concentrations of rifampicin, kanamycin, and nalidixic acid. The stability of the resistance phenotype was scored after nonselective growth. Rifampicin-resistant (Rifr) isolates were stable, suggesting that they had...
Tue, 01/07/2014 - 14:58
Proceedings of the National Academy of Sciences
The nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 12 (NLRP12) plays a protective role in intestinal inflammation and carcinogenesis, but the physiological function of this NLR during microbial infection is largely unexplored. Salmonella enterica serovar...
Tue, 12/17/2013 - 15:17
Proceedings of the National Academy of Sciences
Capsular polysaccharides (CPSs) are high-molecular-mass cell-surface polysaccharides, that act as important virulence factors for many pathogenic bacteria. Several clinically important Gram-negative pathogens share similar systems for CPS biosynthesis and export; examples include Escherichia coli,...
Tue, 12/17/2013 - 15:17
Proceedings of the National Academy of Sciences
MICROBIOLOGY Correction for “Intracellular Shigella remodels its LPS to dampen the innate immune recognition and evade inflammasome activation,” by Ida Paciello, Alba Silipo, Luigi Lembo-Fazio, Laura Curcurù, Anna Zumsteg, Gaëlle Noël, Valeria Ciancarella, Luisa Sturiale, Antonio Molinaro, and Maria Lina...
Tue, 12/10/2013 - 14:13
Proceedings of the National Academy of Sciences
Genome-scale models (GEMs) of metabolism were constructed for 55 fully sequenced Escherichia coli and Shigella strains. The GEMs enable a systems approach to characterizing the pan and core metabolic capabilities of the E. coli species. The majority of pan metabolic content was found to consist of alternate...
Tue, 12/03/2013 - 14:58
Proceedings of the National Academy of Sciences
Successful macrophage colonization by Coxiella burnetii, the cause of human Q fever, requires pathogen-directed biogenesis of a large, growth-permissive parasitophorous vacuole (PV) with phagolysosomal characteristics. The vesicular trafficking pathways co-opted by C. burnetii for PV development are poorly...
Tue, 11/26/2013 - 16:13
Proceedings of the National Academy of Sciences
We appreciate the interest taken in our recent work (1) by Blair et al. (2), who are “perplexed” that we did not observe induction of ramA expression in Salmonella typhimurium treated with 50–125 μM indole. It is important to note, however, that induction of the Salmonella typhimurium ramA gene by.....
Tue, 11/12/2013 - 14:35
Proceedings of the National Academy of Sciences
LPS is a potent bacterial effector triggering the activation of the innate immune system following binding with the complex CD14, myeloid differentiation protein 2, and Toll-like receptor 4. The LPS of the enteropathogen Shigella flexneri is a hexa-acylated isoform possessing an optimal inflammatory activity...
Tue, 11/12/2013 - 14:35
Proceedings of the National Academy of Sciences
Efflux pumps belonging to the ubiquitous resistance–nodulation–cell division (RND) superfamily transport substrates out of cells by coupling proton conduction across the membrane to a conformationally driven pumping cycle. The heavy metal-resistant bacteria Cupriavidus metallidurans CH34 relies notably on as...
Tue, 10/22/2013 - 13:48
Proceedings of the National Academy of Sciences
Shigella sonnei is a human-adapted pathogen that is emerging globally as the dominant agent of bacterial dysentery. To investigate local establishment, we sequenced the genomes of 263 Vietnamese S. sonnei isolated over 15 y. Our data show that S. sonnei was introduced into Vietnam in the 1980s and has...
Tue, 10/01/2013 - 14:59
Proceedings of the National Academy of Sciences
Identifying the major sources of risk in disease transmission is key to designing effective controls. However, understanding of transmission dynamics across species boundaries is typically poor, making the design and evaluation of controls particularly challenging for zoonotic pathogens. One such global...
Tue, 10/01/2013 - 14:59
Proceedings of the National Academy of Sciences
We recently showed that infection by Listeria monocytogenes causes mitochondrial network fragmentation through the secreted pore-forming toxin listeriolysin O (LLO). Here, we examine factors involved in canonical fusion and fission. Strikingly, LLO-induced mitochondrial fragmentation does not require the...
Tue, 09/10/2013 - 13:57
Proceedings of the National Academy of Sciences
Robust cytotoxic CD8+ T-cell response is important for immunity to intracellular pathogens. Here, we show that the transcription factor IFN Regulatory Factor 4 (IRF4) is crucial for the protective CD8+ T-cell response to the intracellular bacterium Listeria monocytogenes. IRF4-deficient (Irf4−/−) mice could...
Tue, 08/27/2013 - 13:57
Proceedings of the National Academy of Sciences
Inflammasome mediated by central nucleotide-binding and oligomerization domain (NOD)-like receptor (NLR) protein is critical for defense against bacterial infection. Here we show that type III secretion system (T3SS) needle proteins from several bacterial pathogens, including Salmonella typhimurium,...
Tue, 08/06/2013 - 14:12
Proceedings of the National Academy of Sciences
Riboswitches are ligand-binding elements located in 5′ untranslated regions of messenger RNAs, which regulate expression of downstream genes. In Listeria monocytogenes, a vitamin B12-binding (B12) riboswitch was identified, not upstream of a gene but downstream, and antisense to the adjacent gene, pocR,...
Tue, 07/30/2013 - 13:57
Proceedings of the National Academy of Sciences
The attaching and effacing Escherichia coli (AEEC) are characterized by the presence of a type III secretion system encoded by the locus of enterocyte effacement (LEE). Enterohemorrhagic E. coli (EHEC) are often identified as isolates that are LEE+ and carry the Shiga toxin (stx)-encoding phage, which are...
Tue, 07/16/2013 - 13:42
Proceedings of the National Academy of Sciences
Genome-wide association studies have the potential to identify causal genetic factors underlying important phenotypes but have rarely been performed in bacteria. We present an association mapping method that takes into account the clonal population structure of bacteria and is applicable to both core and...
Tue, 07/16/2013 - 13:42
Proceedings of the National Academy of Sciences
Oral feed-based passive immunization can be a promising strategy to prolong maternal lactogenic immunity against postweaning infections. Enterotoxigenic Escherichia coli (ETEC)-caused postweaning diarrhea in piglets is one such infection that may be prevented by oral passive immunization and might avert...
Tue, 07/16/2013 - 13:42
Proceedings of the National Academy of Sciences
The efficacy of antibiotics and host defenses has been linked to the metabolic and redox states of bacteria. In this study we report that a stress-induced export pump belonging to the major facilitator superfamily effluxes citrate and iron from the enteric pathogen Salmonella Typhimurium to arrest growth and...
Tue, 07/09/2013 - 14:27
Proceedings of the National Academy of Sciences
Caseinolytic proteases (ClpPs) are large oligomeric protein complexes that contribute to cell homeostasis as well as virulence regulation in bacteria. Although most organisms possess a single ClpP protein, some organisms encode two or more ClpP isoforms. Here, we elucidated the crystal structures of ClpP1 and...
Tue, 07/09/2013 - 14:27
Proceedings of the National Academy of Sciences
Defects in normal autophagic pathways are implicated in numerous human diseases—such as neurodegenerative diseases, cancer, and cardiomyopathy—highlighting the importance of autophagy and its proper regulation. Herein we show that Vibrio parahaemolyticus uses the type III effector VopQ (Vibrio outer protein Q...