scholarly journals Ornithine capture by a translating ribosome controls bacterial polyamine synthesis

2019 ◽  
Author(s):  
Alba Herrero del Valle ◽  
Britta Seip ◽  
Iñaki Cervera-Marzal ◽  
Guénaël Sacheau ◽  
A. Carolin Seefeldt ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Binding Pocket ◽  
Growth Stress ◽  
Release Factor ◽  
Human Pathogens ◽  
Polyamine Synthesis ◽  
E Coli ◽  
Ribosome Stalling ◽  
Nascent Peptide ◽  
Transcription Antitermination

ABSTRACTPolyamines are essential metabolites that play an important role in cell growth, stress adaptation, and microbial virulence1–3. In order to survive and multiply within a human host, pathogenic bacteria adjust the expression and activity of polyamine biosynthetic enzymes in response to different environmental stresses and metabolic cues2. Here, we show that ornithine capture by the ribosome and the nascent peptide SpeFL controls polyamine synthesis in γ-proteobacteria by inducing the expression of the ornithine decarboxylase SpeF4, via a mechanism involving ribosome stalling and transcription antitermination. In addition, we present the cryo-EM structure of an Escherichia coli (E. coli) ribosome stalled during translation of speFL in the presence of ornithine. The structure shows how the ribosome and the SpeFL sensor domain form a highly selective binding pocket that accommodates a single ornithine molecule but excludes near-cognate ligands. Ornithine pre-associates with the ribosome and is then held in place by the sensor domain, leading to the compaction of the SpeFL effector domain and blocking the action of release factor RF1. Thus, our study not only reveals basic strategies by which nascent peptides assist the ribosome in detecting a specific metabolite, but also provides a framework for assessing how ornithine promotes virulence in several human pathogens.

scholarly journals Fitness Cost and Interference of Arm/Rmt Aminoglycoside Resistance with the RsmF Housekeeping Methyltransferases

2012 ◽  
Vol 56 (5) ◽  
pp. 2335-2341 ◽  
Author(s):  
Belen Gutierrez ◽  
Jose A. Escudero ◽  
Alvaro San Millan ◽  
Laura Hidalgo ◽  
Laura Carrilero ◽  
...  
Keyword(s):  
16S Rrna ◽  
Pathogenic Bacteria ◽  
Binding Pocket ◽  
Maldi Mass Spectrometry ◽  
Fitness Cost ◽  
Resistance Pattern ◽  
Aminoglycoside Resistance ◽  
Content Type ◽  
E Coli ◽  
High Level

ABSTRACTArm/Rmt methyltransferases have emerged recently in pathogenic bacteria as enzymes that confer high-level resistance to 4,6-disubstituted aminoglycosides through methylation of the G1405 residue in the 16S rRNA (like ArmA and RmtA to -E). In prokaryotes, nucleotide methylations are the most common type of rRNA modification, and they are introduced posttranscriptionally by a variety of site-specific housekeeping enzymes to optimize ribosomal function. Here we show that while the aminoglycoside resistance methyltransferase RmtC methylates G1405, it impedes methylation of the housekeeping methyltransferase RsmF at position C1407, a nucleotide that, like G1405, forms part of the aminoglycoside binding pocket of the 16S rRNA. To understand the origin and consequences of this phenomenon, we constructed a series of in-frame knockout and knock-in mutants ofEscherichia coli, corresponding to the genotypesrsmF+, ΔrsmF,rsmF+rmtC+, and ΔrsmF rmtC+. When analyzed for the antimicrobial resistance pattern, the ΔrsmFbacteria had a decreased susceptibility to aminoglycosides, including 4,6- and 4,5-deoxystreptamine aminoglycosides, showing that the housekeeping methylation at C1407 is involved in intrinsic aminoglycoside susceptibility inE. coli. Competition experiments between the isogenicE. colistrains showed that, contrary to expectation, acquisition ofrmtCdoes not entail a fitness cost for the bacterium. Finally, matrix-assisted laser desorption ionization (MALDI) mass spectrometry allowed us to determine that RmtC methylates the G1405 residue not only in presence but also in the absence of aminoglycoside antibiotics. Thus, the coupling between housekeeping and acquired methyltransferases subverts the methylation architecture of the 16S rRNA but elicits Arm/Rmt methyltransferases to be selected and retained, posing an important threat to the usefulness of aminoglycosides worldwide.

scholarly journals Widespread Distribution in Pathogenic Bacteria of Di-Iron Proteins That Repair Oxidative and Nitrosative Damage to Iron-Sulfur Centers

2008 ◽  
Vol 190 (6) ◽  
pp. 2004-2013 ◽  
Author(s):  
Tim W. Overton ◽  
Marta C. Justino ◽  
Ying Li ◽  
Joana M. Baptista ◽  
Ana M. P. Melo ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pathogenic Bacteria ◽  
Nitrosative Stress ◽  
Human Pathogens ◽  
Paramagnetic Resonance ◽  
Widespread Distribution ◽  
Iron Proteins ◽  
E Coli

ABSTRACT Expression of two genes of unknown function, Staphylococcus aureus scdA and Neisseria gonorrhoeae dnrN, is induced by exposure to oxidative or nitrosative stress. We show that DnrN and ScdA are di-iron proteins that protect their hosts from damage caused by exposure to nitric oxide and to hydrogen peroxide. Loss of FNR-dependent activation of aniA expression and NsrR-dependent repression of norB and dnrN expression on exposure to NO was restored in the gonococcal parent strain but not in a dnrN mutant, suggesting that DnrN is necessary for the repair of NO damage to the gonococcal transcription factors, FNR and NsrR. Restoration of aconitase activity destroyed by exposure of S. aureus to NO or H2O2 required a functional scdA gene. Electron paramagnetic resonance spectra of recombinant ScdA purified from Escherichia coli confirmed the presence of a di-iron center. The recombinant scdA plasmid, but not recombinant plasmids encoding the complete Escherichia coli sufABCDSE or iscRSUAhscBAfdx operons, complemented repair defects of an E. coli ytfE mutant. Analysis of the protein sequence database revealed the importance of the two proteins based on the widespread distribution of highly conserved homologues in both gram-positive and gram-negative bacteria that are human pathogens. We provide in vivo and in vitro evidence that Fe-S clusters damaged by exposure to NO and H2O2 can be repaired by this new protein family, for which we propose the name repair of iron centers, or RIC, proteins.

scholarly journals Isolation, characterization, and molecular identification of soil bacteria showing antibacterial activity against human pathogenic bacteria

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
R. Prashanthi ◽  
Shreevatsa G.K. ◽  
Krupalini S. ◽  
Manoj L.
Keyword(s):  
Antibacterial Activity ◽  
Soil Bacteria ◽  
Pathogenic Bacteria ◽  
Nitrogen Sources ◽  
Proteinase K ◽  
Human Pathogens ◽  
E Coli ◽  
Carbon And Nitrogen ◽  
Culture Filtrates ◽  
Proteinase K Treatment

Abstract Background The present study dealt with the screening of soil bacteria with antibacterial activity from different locations in Bangalore, India. Antibiotics play the role of self-defense mechanism for the bacteria and are produced as secondary metabolites to protect themselves from other competitive microorganisms. The need for new antibiotics arose as the pathogenic bacteria acquire resistance to various antibiotics meant for treating human diseases. Given the importance of antibiotics of bacterial origin, standard techniques have been used to isolate and characterize the soil bacteria which showed antibacterial activity. Results The isolated bacteria were tested against human pathogenic bacteria like Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae by primary and secondary screening methods. The isolates PR1, PR2, and PR3 were confirmed to have antibacterial activity against S. aureus, E. coli, P. aeruginosa, and K. pneumoniae by both methods. Studies on the effect of filter sterilization, autoclaving, and proteinase K treatment on culture filtrates showed filter sterilization as the best method. The effect of different carbon and nitrogen sources on the antibacterial activity showed that preference by each isolate differed for carbon and nitrogen requirements. The isolates PR1, PR2, and PR3 were identified as Bacillus aryabhattai strain PR-D07, Arthrobacter humicola strain PR-F07, and Neomicrococcus lactis strain PR-F11 through 16S rRNA sequencing. Conclusion Findings from this research work are encouraging and could proceed further to applied aspects. Only 3 bacterial isolates out of 263 isolates from soil samples displayed antibacterial activity against human pathogens S. aureus, E. coli, P. aeruginosa, and K. pneumoniae. They were identified as B. aryabhattai, A. humicola, and N. lactis by 16S rRNA studies and all of them are Gram-positive. Each isolate preferred different carbon and nitrogen sources for their enhanced antibacterial activity. Efficacy of the culture filtrates of these isolates was tested by filter sterilization, autoclaving, and proteinase K treatment. Filter-sterilized culture filtrates showed higher antibacterial activity than other treatments. A comparison of the antibacterial activity of culture filtrates and antibiotic streptomycin produced an inhibition zone of 18.5 mm and 15.5 mm respectively. This is the first report on the antibacterial activity of all the 3 bacterial strains (B. aryabhattai strain PR-D07, A. humicola strain PR-F07, and N. lactis strain PR-F11), against all the human pathogens, mentioned earlier. It is also found that the antibiotic factor is proteinaceous as proteinase K considerably reduced the antibacterial activity of the culture filtrates. With the above significant results, these 3 bacteria are considered to be promising candidates for the isolation of new antibacterial agents.

Antimicrobial activity of Commercial essential oils on human pathogens

2021 ◽  
pp. 4440-4444
Author(s):  
B. R. Malathy ◽  
Sweetlin Ajitha P ◽  
Sangeetha K. S ◽  
Swetha Thampy ◽  
Kamala G
Keyword(s):  
Antimicrobial Activity ◽  
Essential Oils ◽  
Pathogenic Bacteria ◽  
Steam Distillation ◽  
Diffusion Method ◽  
Human Pathogens ◽  
Aromatic Plants ◽  
Zone Of Inhibition ◽  
E Coli ◽  
Development Of Resistance

Essential oils (EOs) are natural extracts from the seeds, stems, roots, flowers, bark and other parts of the plant prepared by steam distillation. They are complex, volatile, natural compounds formed by aromatic plants as secondary metabolites. They are known for their bactericidal, virucidal, fungicidal, sedative, anti-inflammatory, analgesic, spasmolytic and locally anesthetic properties. They are generally composed of a combination of substances like terpenes, phenolics, aldehydes or alcohols. The complex composition and different mechanisms of action of EOs may be an advantage over other antimicrobials to prevent the development of resistance of pathogenic bacteria. With this background, the aim of this study was to evaluate the antimicrobial activity of five essential oils like basil, lime, rosemary, thyme and canada balsam against 14 microbes. The effects of essential oil on the selected microbes were determined by agar well diffusion method. The zone of inhibition was observed and measured in millimeter. Essential oils which showed inhibitory diameter >15 mm were further tested to determine the minimum inhibitory concentration (MIC). S. aureus, E. coli, S. mutans, S. sanguinis, C. albicans and M. furfur were inhibited by all essential oils. K. pneumoniae, P. aeruginosa and E .faecalis were inhibited only by thyme and not by other essential oils. The MIC values ranged from 50% to 0.10%. The least MIC value of 0.10% was shown by thyme and basil to S. aureus, thyme to E.coli and all essential oils against C. albicans except lime.

scholarly journals Transfer of Escherichia coli O157:H7 to Spinach by House Flies, Musca domestica (Diptera: Muscidae)

2013 ◽  
Vol 103 (4) ◽  
pp. 373-380 ◽  
Author(s):  
Lakmini Wasala ◽  
Justin L. Talley ◽  
Udaya DeSilva ◽  
Jacqueline Fletcher ◽  
Astri Wayadande
Keyword(s):  
Escherichia Coli ◽  
Pathogenic Bacteria ◽  
Quantitative Polymerase Chain Reaction ◽  
Escherichia Coli O157 ◽  
Human Pathogens ◽  
House Flies ◽  
E Coli ◽  
Filth Flies ◽  
Microscopy Techniques ◽  
Nutrition Source

Filth flies are known mechanical vectors of pathogenic bacteria in hospital and restaurant settings, but their role as vectors for disseminating microbes to plants has not been demonstrated. Escherichia coli O157:H7 deposition by flies onto spinach was studied using molecular, microbiological, and microscopy techniques. Relative quantitative polymerase chain reaction studies showed that bacteria acquired by flies from contaminated cattle manure and deposited in regurgitation spots on leaves survived and multiplied. Scanning electron microscopy of the regurgitation spots of flies exposed to manure inoculated with E. coli suggested the multiplication of bacteria-like organisms within the spots. This finding implies that the bacteria were active and is consistent with a hypothesis that regurgitation spots serve as a nutrition source allowing E. coli O157:H7 to survive on the spinach phylloplane. E. coli O157:H7 persisted on fly body surfaces up to 13 days after exposure to acquisition sources, suggesting that fly cuticular surfaces are conducive to the growth of this pathogen. These results are consistent with the hypothesis of bioenhanced transmission of human pathogens by house flies and suggest that filth flies may affect the microbial safety of fresh produce.

Comparison of Quality in Aquacultured Fresh Catfish Fillets II. Pathogens E. coli O157:H7, Campylobacter, Vibrio, Plesiomonas, and Klebsiella†

1997 ◽  
Vol 60 (10) ◽  
pp. 1182-1188 ◽  
Author(s):  
CUSTY F. FERNANDES ◽  
GEORGE J. FLICK ◽  
JUAN L. SILVA ◽  
THOMAS A. McCASKEY
Keyword(s):  
Ictalurus Punctatus ◽  
Channel Catfish ◽  
Pathogenic Bacteria ◽  
Escherichia Coli O157 ◽  
Human Pathogens ◽  
E Coli ◽  
Warm Weather ◽  
Significant Difference ◽  
Catfish Fillets ◽  
Plate Counts

Aquacultured channel catfish (Ictalurus punctatus) were evaluated for the presence of human pathogenic bacteria. Fresh catfish fillets procured from three catfish processors in the southeastern United States during the four annual seasons (e.g., summer, fall, winter, and fall) were screened for selected human pathogens. At each sampling time point, 20 freshly processed catfish fillets were randomly selected from each processor during each season. Five catfish fillets were randomly selected for aerobic plate counts and all 20 fillets were screened for five pathogenic bacteria viz. Campylobacter jejuni/coli, Escherichia coli O157:H7, Klebsiella pneumoniae subsp. pneumoniae, Plesiomonas shigelloides, and Vibrio cholerae. There was a significant difference (P < 0.05) in the aerobic plate counts due to differences in unit processing operations and processing season. C. jejuni/coli, E. coli O157:H7 and K. pneumoniae subsp. pneumoniae were not isolated. Only P. shigelloides and V. cholerae were isolated during the warm weather.

scholarly journals Structural basis for the tryptophan sensitivity of TnaC-mediated ribosome stalling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Anne-Xander van der Stel ◽  
Emily R. Gordon ◽  
Arnab Sengupta ◽  
Allyson K. Martínez ◽  
Dorota Klepacki ◽  
...  
Keyword(s):  
Structural Basis ◽  
Leader Peptide ◽  
Release Factor ◽  
Active Conformation ◽  
Peptidyl Transferase ◽  
Peptidyl Transferase Center ◽  
Ribosome Stalling ◽  
Enhanced Sensitivity ◽  
Nascent Peptide ◽  
Recognition And Response

AbstractFree L-tryptophan (L-Trp) stalls ribosomes engaged in the synthesis of TnaC, a leader peptide controlling the expression of the Escherichia coli tryptophanase operon. Despite extensive characterization, the molecular mechanism underlying the recognition and response to L-Trp by the TnaC-ribosome complex remains unknown. Here, we use a combined biochemical and structural approach to characterize a TnaC variant (R23F) with greatly enhanced sensitivity for L-Trp. We show that the TnaC–ribosome complex captures a single L-Trp molecule to undergo termination arrest and that nascent TnaC prevents the catalytic GGQ loop of release factor 2 from adopting an active conformation at the peptidyl transferase center. Importantly, the L-Trp binding site is not altered by the R23F mutation, suggesting that the relative rates of L-Trp binding and peptidyl-tRNA cleavage determine the tryptophan sensitivity of each variant. Thus, our study reveals a strategy whereby a nascent peptide assists the ribosome in detecting a small metabolite.

scholarly journals Inhibitory Effect of Bacteriophages Isolated from Sewage Water in the City of Kirkuk on some Types of Human Pathogenic Bacteria

2017 ◽  
Vol 14 (4) ◽  
pp. 727-734 ◽  
Author(s):  
Baghdad Science Journal
Keyword(s):  
Pathogenic Bacteria ◽  
Inhibitory Effect ◽  
Sewage Water ◽  
Resistant Bacteria ◽  
Human Pathogens ◽  
Salmonella Spp ◽  
Antibiotic Resistant ◽  
E Coli ◽  
New Antibiotics ◽  
The City

Most approaches to combat antibiotic resistant bacteria concentrate on discovering new antibiotics or modifying existing ones. However, one of the most promising alternatives is the use of bacteriophages. This study was focused on the isolation of bacteriophages that are specific to some of commonly human pathogens namely E. coli, Streptococcus pyogenes, Staphylococcus aureus, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella spp. and Klebsiella pneumoniae. These bacteriophages were isolated from sewages that were collected from four different locations in Kirkuk City. Apart from S. pyogenes, bacteriophages specific to all tested bacteria were successfully isolated and tested for their effectiveness by spot test. The most effective bacteriophages that were isolated from sewages and sewage water of Al-Jumhori Hospital compared to other sites. It is concluded that the sewage water of hospitals represents a perfect environment for these bacteriophages.

scholarly journals Modulation of antibacterial activity of actinomycetes by co-culture with pathogenic bacteria

2015 ◽  
Vol 18 (1) ◽  
pp. 61-65 ◽  
Author(s):  
Md Uzzal Haque ◽  
Md Ajijur Rahman ◽  
Md Anwarul Haque ◽  
Ashish Kumar Sarker ◽  
Md Anwar Ul Islam
Keyword(s):  
Staphylococcus Aureus ◽  
Antibacterial Activity ◽  
Pathogenic Bacteria ◽  
High Specificity ◽  
Inhibition Zone ◽  
Pharmaceutical Journal ◽  
Human Pathogens ◽  
Microbial Competition ◽  
E Coli ◽  
Diffusion Assay

In this study, we investigated the effect of pathogenic bacteria on the production of antibiotics by actinomycetes. We used four strains of actinomycetes-ANAM-5, ANAM-39, AIAH-10 and ANTS-1, which were isolated from the soils of Sundrabans, Bangladesh. All the strains were cultured in absence or presence of either alive or heatkilled human pathogens (Staphylococcus aureus and E. coli). The antibacterial activity of cultured cell-free supernatant fluid was analyzed by disc diffusion assay against the inducer strains. Three out of the four marine actinomycetes tested showed enhanced antibacterial activity against Staphylococcus aureus and E. coli. ANAM-5 and AIAH-10 showed enhanced antibacterial activity when co-cultured with Staphylococcus aureus whereas ANAM-5 and ANAM-39 showed enhanced antibacterial activity when co-cultured with E. coli. The highest enhancement of antibacterial activity was exhibited by the strain ANAM-5 against Staphylococcus aureus (from 9 mm to 18 mm inhibition zone). The study has important ecological and biotechnological implications in case of microbial competition in the natural environment and may become helpful to discover novel classes of antibiotics with high specificity and huge production.Bangladesh Pharmaceutical Journal 18(1): 61-65, 2015

The Bacillus subtilis PriA winged helix domain is critical for surviving DNA damage

2022 ◽  
Author(s):  
Lindsay A. Matthews ◽  
Lyle A. Simmons
Keyword(s):  
Dna Damage ◽  
Dna Binding ◽  
Replication Fork ◽  
Pathogenic Bacteria ◽  
Replication Forks ◽  
Human Pathogens ◽  
Winged Helix ◽  
E Coli ◽  
Stalled Replication Forks

DNA replication forks regularly encounter lesions or other impediments that result in a blockage to fork progression. PriA is one of the key proteins used by virtually all eubacteria to survive conditions that result in a blockage to replication fork movement. PriA directly binds stalled replication forks and initiates fork restart allowing for chromosomes to be fully duplicated under stressful conditions. We used a CRISPR-Cas gene editing approach to map PriA residues critical for surviving DNA damage induced by several antibiotics in B. subtilis . We find that the winged helix (WH) domain in B. subtilis PriA is critical for surviving DNA damage and participates in DNA binding. The critical in vivo function of the WH domain mapped to distinct surfaces that were also conserved among several Gram-positive human pathogens. In addition, we identified an amino acid linker neighboring the WH domain that is greatly extended in B. subtilis due to an insertion. Shortening this linker induced a hypersensitive phenotype to DNA damage, suggesting that its extended length is critical for efficient replication fork restart in vivo . Because the WH domain is dispensable in E. coli PriA, our findings demonstrate an important difference in the contribution of the WH domain during fork restart in B. subtilis . Further, with our results we suggest that this highly variable region in PriA could provide different functions across diverse bacterial organisms. IMPORTANCE PriA is an important protein found in virtually all bacteria that recognizes stalled replication forks orchestrating fork restart. PriA homologs contain a winged helix (WH) domain which is dispensable in E. coli and functions in a fork restart pathway that is not conserved outside of E. coli and closely related proteobacteria. We analyzed the importance of the WH domain and an associated linker in B. subtilis and found that both are critical for surviving DNA damage. This function mapped to a small motif at the C-terminal end of the WH domain, which is also conserved in pathogenic bacteria. The motif was not required for DNA binding and therefore may perform a novel function in the replication fork restart pathway.

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