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https://www.readbyqxmd.com/read/29043249/interactions-between-bacteria-and-bile-salts-in-the-gastrointestinal-and-hepatobiliary-tracts
#1
REVIEW
Verónica Urdaneta, Josep Casadesús
Bile salts and bacteria have intricate relationships. The composition of the intestinal pool of bile salts is shaped by bacterial metabolism. In turn, bile salts play a role in intestinal homeostasis by controlling the size and the composition of the intestinal microbiota. As a consequence, alteration of the microbiome-bile salt homeostasis can play a role in hepatic and gastrointestinal pathological conditions. Intestinal bacteria use bile salts as environmental signals and in certain cases as nutrients and electron acceptors...
2017: Frontiers in Medicine
https://www.readbyqxmd.com/read/29022867/response-to-photo-oxidative-stress-of-pseudomonas-aeruginosa-pao1-mutants-impaired-in-different-functions
#2
Viviana Teresa Orlandi, Fabrizio Bolognese, Eleonora Martegani, Vincenzo Cantaluppi, Claudio Medana, Paola Barbieri
Clinicians often have to deal with infections that are difficult to control because they are caused by superbugs resistant to many antibiotics. Alternatives to antibiotic treatment include antimicrobial photodynamic therapy (aPDT). The photodynamic process causes bacterial death, inducing oxidative stress through the photoactivation of photosensitizer molecules in the presence of oxygen. No PDT-resistant bacteria have been selected to date, thus the response to photo-oxidative stress in non-phototrophic bacteria needs further investigation...
October 12, 2017: Microbiology
https://www.readbyqxmd.com/read/28925518/chemistry-of-peptidoglycan-in-mycobacterium-tuberculosis-life-style-an-off-the-wall-balance-of-synthesis-and-degradation
#3
Flavia Squeglia, Alessia Ruggiero, Rita Berisio
The cell wall envelope of mycobacteria is structurally distinct from that of both Gram-positive and Gram-negative bacteria. In Mycobacterium tuberculosis, this cell wall has unique structural features and plays a crucial role in drug resistance and macrophage survival under stress conditions. Peptidoglycan is the major constituent of this cell wall, with an important structural role, giving structural strength, and counteracting the osmotic pressure of the cytoplasm. Synthesis of this complex polymer takes place in three stages that occur at three different locations in the cell, from the cytoplasm to the external side of the cell membrane, where polymerization occurs...
September 19, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28922502/the-three-component-system-esrisr-regulates-a-cell-envelope-stress-response-in-corynebacterium-glutamicum
#4
Britta Kleine, Ava Chattopadhyay, Tino Polen, Daniela Pinto, Thorsten Mascher, Michael Bott, Melanie Brocker, Roland Freudl
When the cell envelope integrity is compromised, bacteria trigger signaling cascades resulting in the production of proteins that counteract these extracytoplasmic stresses. Here, we show that the two-component system EsrSR regulates a cell envelope stress response in the Actinobacterium Corynebacterium glutamicum. The sensor kinase EsrS possesses an amino-terminal phage shock protein C (PspC) domain, a property that sets EsrSR apart from all other two-component systems characterized so far. An integral membrane protein, EsrI, whose gene is divergently transcribed to the esrSR gene locus and which interestingly also possesses a PspC domain, acts as an inhibitor of EsrSR under non-stress conditions...
September 18, 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28807687/influence-of-tween-80-on-the-production-and-structure-of-water-insoluble-curdlan-from-agrobacterium-sp
#5
Ying Liang, Li Zhu, Minjie Gao, Zhiyong Zheng, Jianrong Wu, Xiaobei Zhan
In order to explore the mechanism by which Tween-80 enhances the production of curdlan produced by Agrobacterium sp., the effects of Tween-80 on the production and structure of curdlan and Agrobacterium sp. were evaluated. Maximum curdlan production (51.94g/L) was achieved when 16g/L Tween-80 was added at the beginning of the cell growth stage. The addition of Tween-80 at higher concentration inhibited cell growth. However, the addition of 16g/L Tween-80 enhanced the production of curdlan with a looser ultrastructure, significantly weakened the envelopment of curdlan on Agrobacterium sp...
August 11, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28760851/a-bacterial-stress-response-regulates-respiratory-protein-complexes-to-control-envelope-stress-adaptation
#6
Randi L Guest, Junshu Wang, Julia L Wong, Tracy L Raivio
The Cpx envelope stress response mediates adaptation to stresses that affect protein folding within the envelope of Gram-negative bacteria. Recent transcriptome analyses revealed that the Cpx response impacts genes that affect multiple cellular functions predominantly associated with the cytoplasmic membrane. In this study, we examined the connection between the Cpx response and the respiratory complexes NADH dehydrogenase I and cytochrome bo3 in enteropathogenic Escherichia coli We found that the Cpx response directly represses the transcription of the nuo and cyo operons and that Cpx-mediated repression of these complexes confers adaptation to stresses that compromise envelope integrity...
October 15, 2017: Journal of Bacteriology
https://www.readbyqxmd.com/read/28741415/gram-negative-bacterial-membrane-vesicle-release-in-response-to-the-host-environment-different-threats-same-trick
#7
Charlotte Volgers, Paul H M Savelkoul, Frank R M Stassen
Bacteria are confronted with a multitude of stressors when occupying niches within the host. These stressors originate from host defense mechanisms, other bacteria during niche competition or result from physiological challenges such as nutrient limitation. To counteract these stressors, bacteria have developed a stress-induced network to mount the adaptations required for survival. These stress-induced adaptations include the release of membrane vesicles from the bacterial envelope. Membrane vesicles can provide bacteria with a plethora of immediate and ultimate benefits for coping with environmental stressors...
July 25, 2017: Critical Reviews in Microbiology
https://www.readbyqxmd.com/read/28674071/major-tom-to-ground-control-how-lipoproteins-communicate-extracytoplasmic-stress-to-the-decision-center-of-the-cell
#8
REVIEW
Géraldine Laloux, Jean-François Collet
The envelope of bacteria is a complex multilayered shield that ensures multiple essential functions, including protecting the cell from external assaults. Hence, bacterial cells have evolved intricate mechanisms called envelope stress response systems (ESRS) to monitor all kinds of perturbations affecting the integrity of their envelope and to mount an appropriate response to contain or repair the damage. In the model bacterium Escherichia coli, several ESRS are built around a two-component system, in which envelope stress triggers a phosphotransfer between a sensor protein in the inner membrane of the envelope and a response regulator in the cytoplasm...
November 1, 2017: Journal of Bacteriology
https://www.readbyqxmd.com/read/28588134/the-rcs-regulated-colanic-acid-capsule-maintains-membrane-potential-in-salmonella-enterica-serovar-typhimurium
#9
Jasmine M Pando, Joyce E Karlinsey, Jimmie C Lara, Stephen J Libby, Ferric C Fang
The Rcs phosphorelay and Psp (phage shock protein) systems are envelope stress responses that are highly conserved in gammaproteobacteria. The Rcs regulon was found to be strongly induced during metal deprivation of Salmonella enterica serovar Typhimurium lacking the Psp response. Nineteen genes activated by the RcsA-RcsB response regulator make up an operon responsible for the production of colanic acid capsular polysaccharide, which promotes biofilm development. Despite more than half a century of research, the physiological function of colanic acid has remained elusive...
June 6, 2017: MBio
https://www.readbyqxmd.com/read/28513097/evidence-for-a-peptidoglycan-like-structure-in-orientia-tsutsugamushi
#10
Sharanjeet Atwal, Suparat Giengkam, Suwittra Chaemchuen, Jack Dorling, Nont Kosaisawe, Michael VanNieuwenhze, Somponnat Sampattavanich, Peter Schumann, Jeanne Salje
Bacterial cell walls are composed of the large cross-linked macromolecule peptidoglycan, which maintains cell shape and is responsible for resisting osmotic stresses. This is a highly conserved structure and the target of numerous antibiotics. Obligate intracellular bacteria are an unusual group of organisms that have evolved to replicate exclusively within the cytoplasm or vacuole of a eukaryotic cell. They tend to have reduced amounts of peptidoglycan, likely due to the fact that their growth and division takes place within an osmotically protected environment, and also due to a drive to reduce activation of the host immune response...
August 2017: Molecular Microbiology
https://www.readbyqxmd.com/read/28467057/conditional-chaperone-client-interactions-revealed-by-genetically-encoded-photo-cross-linkers
#11
Shuai Zhang, Dan He, Zhi Lin, Yi Yang, Haiping Song, Peng R Chen
The cell envelope is an integral and essential component of Gram-negative bacteria. As the front line during host-pathogen interactions, it is directly challenged by host immune responses as well as other harsh extracellular stimuli. The high permeability of the outer-membrane and the lack of ATP energy system render it difficult to maintain important biological activities within the periplasmic space under stress conditions. The HdeA/B chaperone machinery is the only known acid resistant system found in bacterial periplasm, enabling enteric pathogens to survive through the highly acidic human stomach and establish infections in the intestine...
May 3, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28439041/cues-from-the-membrane-bacterial-glycerophospholipids
#12
Zachary D Dalebroux
In this issue of the Journal of Bacteriology, V. W. Rowlett et al. unveil new Escherichia coli circuitry linking membrane glycerophospholipid (GPL) homeostasis to bacterial stress response and adaptation mechanisms (J Bacteriol 199:e00849-16, 2017, https://doi.org/10.1128/JB.00849-16). Glycerophospholipids comprise critical components of the dual-membrane envelope of Gram-negative bacteria and participate in many processes. The new evidence suggests that, in some instances, distinct E. coli GPL molecules function for distinct biochemistry and bacteria sense perturbations in membrane GPL concentrations to coordinate survival strategies...
July 1, 2017: Journal of Bacteriology
https://www.readbyqxmd.com/read/28439040/impact-of-membrane-phospholipid-alterations-in-escherichia-coli-on-cellular-function-and-bacterial-stress-adaptation
#13
Veronica W Rowlett, Venkata K P S Mallampalli, Anja Karlstaedt, William Dowhan, Heinrich Taegtmeyer, William Margolin, Heidi Vitrac
Bacteria have evolved multiple strategies to sense and rapidly adapt to challenging and ever-changing environmental conditions. The ability to alter membrane lipid composition, a key component of the cellular envelope, is crucial for bacterial survival and adaptation in response to environmental stress. However, the precise roles played by membrane phospholipids in bacterial physiology and stress adaptation are not fully elucidated. The goal of this study was to define the role of membrane phospholipids in adaptation to stress and maintenance of bacterial cell fitness...
July 1, 2017: Journal of Bacteriology
https://www.readbyqxmd.com/read/28416660/redefining-the-essential-trafficking-pathway-for-outer-membrane-lipoproteins
#14
Marcin Grabowicz, Thomas J Silhavy
The outer membrane (OM) of Gram-negative bacteria is a permeability barrier and an intrinsic antibiotic resistance factor. Lipoproteins are OM components that function in cell wall synthesis, diverse secretion systems, and antibiotic efflux pumps. Moreover, each of the essential OM machines that assemble the barrier requires one or more lipoproteins. This dependence is thought to explain the essentiality of the periplasmic chaperone LolA and its OM receptor LolB that traffic lipoproteins to the OM. However, we show that in strains lacking substrates that are toxic when mislocalized, both LolA and LolB can be completely bypassed by activating an envelope stress response without compromising trafficking of essential lipoproteins...
May 2, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28408482/small-regulatory-bacterial-rnas-regulating-the-envelope-stress-response
#15
REVIEW
Gracjana Klein, Satish Raina
Most bacteria encode a large repertoire of RNA-based regulatory mechanisms. Recent discoveries have revealed that the expression of many genes is controlled by a plethora of base-pairing noncoding small regulatory RNAs (sRNAs), regulatory RNA-binding proteins and RNA-degrading enzymes. Some of these RNA-based regulated processes respond to stress conditions and are involved in the maintenance of cellular homeostasis. They achieve it by either direct posttranscriptional repression of several mRNAs, including blocking access to ribosome and/or directing them to RNA degradation when the synthesis of their cognate proteins is unwanted, or by enhanced translation of some key stress-regulated transcriptional factors...
April 15, 2017: Biochemical Society Transactions
https://www.readbyqxmd.com/read/28030630/system-wide-adaptations-of-desulfovibrio-alaskensis-g20-to-phosphate-limited-conditions
#16
Tanja Bosak, Florence Schubotz, Ana de Santiago-Torio, Jennifer V Kuehl, Hans K Carlson, Nicki Watson, Mirna Daye, Roger E Summons, Adam P Arkin, Adam M Deutschbauer
The prevalence of lipids devoid of phosphorus suggests that the availability of phosphorus limits microbial growth and activity in many anoxic, stratified environments. To better understand the response of anaerobic bacteria to phosphate limitation and starvation, this study combines microscopic and lipid analyses with the measurements of fitness of pooled barcoded transposon mutants of the model sulfate reducing bacterium Desulfovibrio alaskensis G20. Phosphate-limited G20 has lower growth rates and replaces more than 90% of its membrane phospholipids by a mixture of monoglycosyl diacylglycerol (MGDG), glycuronic acid diacylglycerol (GADG) and ornithine lipids, lacks polyphosphate granules, and synthesizes other cellular inclusions...
2016: PloS One
https://www.readbyqxmd.com/read/27865622/protecting-from-envelope-stress-variations-on-the-phage-shock-protein-theme
#17
REVIEW
Riccardo Manganelli, Maria Laura Gennaro
During envelope stress, critical inner-membrane functions are preserved by the phage-shock-protein (Psp) system, a stress response that emerged from work with Escherichia coli and other Gram-negative bacteria. Reciprocal regulatory interactions and multiple effector functions are well documented in these organisms. Searches for the Psp system across phyla reveal conservation of only one protein, PspA. However, examination of Firmicutes and Actinobacteria reveals that PspA orthologs associate with non-orthologous regulatory and effector proteins retaining functions similar to those in Gram-negative counterparts...
March 2017: Trends in Microbiology
https://www.readbyqxmd.com/read/27821607/novel-rpos-dependent-mechanisms-strengthen-the-envelope-permeability-barrier-during-stationary-phase
#18
Angela M Mitchell, Wei Wang, Thomas J Silhavy
Gram-negative bacteria have effective methods of excluding toxic compounds, including a largely impermeable outer membrane (OM) and a range of efflux pumps. Furthermore, when cells become nutrient limited, RpoS enacts a global expression change providing cross-protection against many stresses. Here, we utilized sensitivity to an anionic detergent (sodium dodecyl sulfate [SDS]) to probe changes occurring to the cell's permeability barrier during nutrient limitation. Escherichia coli is resistant to SDS whether cells are actively growing, carbon limited, or nitrogen limited...
January 15, 2017: Journal of Bacteriology
https://www.readbyqxmd.com/read/27790614/antimicrobial-activity-of-cationic-antimicrobial-peptides-against-gram-positives-current-progress-made-in-understanding-the-mode-of-action-and-the-response-of-bacteria
#19
REVIEW
Soraya Omardien, Stanley Brul, Sebastian A J Zaat
Antimicrobial peptides (AMPs) have been proposed as a novel class of antimicrobials that could aid the fight against antibiotic resistant bacteria. The mode of action of AMPs as acting on the bacterial cytoplasmic membrane has often been presented as an enigma and there are doubts whether the membrane is the sole target of AMPs. Progress has been made in clarifying the possible targets of these peptides, which is reported in this review with as focus gram-positive vegetative cells and spores. Numerical estimates are discussed to evaluate the possibility that targets, other than the membrane, could play a role in susceptibility to AMPs...
2016: Frontiers in Cell and Developmental Biology
https://www.readbyqxmd.com/read/27720009/the-journey-of-lipoproteins-through-the-cell-one-birthplace-multiple-destinations
#20
REVIEW
J Szewczyk, J-F Collet
Bacterial lipoproteins are a very diverse group of proteins characterized by the presence of an N-terminal lipid moiety that serves as a membrane anchor. Lipoproteins have a wide variety of crucial functions, ranging from envelope biogenesis to stress response. In Gram-negative bacteria, lipoproteins can be targeted to various destinations in the cell, including the periplasmic side of the cytoplasmic or outer membrane, the cell surface or the external milieu. The sorting mechanisms have been studied in detail in Escherichia coli, but exceptions to the rules established in this model bacterium exist in other bacteria...
2016: Advances in Microbial Physiology
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