scholarly journals Le monoxyde d’azote: Une arme du système immunitaire pour brouiller les communications entre bactéries

2020 ◽  
Vol 36 (11) ◽  
pp. 1074-1077
Author(s):  
Merlin Després ◽  
Simon Gaudin

Le dossier thématique suivant a été rédigé par les étudiantes et étudiants de Master 1 de Biologie de l’École Normale Supérieure de Lyon à l’issue de l’UE Microbiologie Moléculaire et Structurale (2019-2020). Le Master de Biologie de l’ENS de Lyon, cohabilité par l’université Claude Bernard Lyon 1, accueille chaque année environ 50 étudiants en M1 et en M2 et propose une formation de haut niveau à la recherche en biosciences. Chaque étudiant y construit son parcours à la carte, en choisissant ses options parmi un large panel de modules, favorisant ainsi une approche pluridisciplinaire des sciences du vivant, et ce en relation étroite avec les laboratoires de recherche du tissu local, national et international. En participant à diverses activités scientifiques connexes aux UE de leur formation, les étudiants préparent également l’obtention du Diplôme de l’ENS de Lyon, qui valide leur scolarité à l’ENS. La rédaction du présent dossier, qui vise à transmettre de façon claire les messages issus d’une sélection d’articles scientifiques publiés récemment dans le domaine de la microbiologie, constitue l’une de ces activités connexes proposées aux étudiants. Les bactéries peuvent vivre en communautés dont la structure est régulée par de nombreuses interactions abiotiques et biotiques. Les interactions biotiques reposent sur des communications inter-bactériennes qui participent à la mise en place de relations de collaboration, de compétition ou de prédation. Ces communautés bactériennes peuvent en outre être en interaction avec des hôtes animaux, dans le cas des bactéries du microbiote ou des bactéries pathogènes par exemple, ou avec des virus parasites, les bactériophages. Le présent dossier illustre quelques aspects nouveaux de cette communication bactérienne, et de la façon dont les interactions bactéries/hôte ou bactéries/phages peuvent impacter cette communication. Deux nouvelles s’attardent sur des découvertes récentes autour du quorum sensing, une modalité de communication bactérienne permettant l’expression coordonnée des gènes à l’échelle de la population, en fonction de la densité de la population. La nouvelle intitulée « Le monoxyde d’azote : une arme du système immunitaire pour brouiller les communications entre bactéries » illustre comment le quorum sensing chez Staphylococcus aureus, une bactérie opportuniste, peut être affecté par un médiateur du système immunitaire de la souris. La nouvelle intitulée « Un bactériophage exploite le système de communication de son hôte bactérien pour entrer en cycle lytique » montre une stratégie étonnante par laquelle le phage VP882 décrypte des signaux issus du quorum sensing de la bactérie qu’il infecte pour réguler son propre cycle de réplication. Au-delà du quorum sensing, deux nouvelles décrivent de nouvelles modalités de communication inter-bactérienne. La nouvelle intitulée « Les nanotubes bactériens, acteurs de la compétition entre Bacillus subtilis et Bacillus megaterium » met en lumière le rôle des nanotubes, des structures de communication intercellulaire insoupçonnées jusque récemment chez les bactéries. La nouvelle intitulée « La bactérie Vibrio cholerae lyse les bactéries environnantes et assimile leur ADN qu’elle intègre dans son propre génome » illustre comment un système de sécrétion, qui permet l’injection d’effecteurs bactériens dans des cellules cibles, peut être exploité pour faciliter les transferts horizontaux de gènes chez les bactéries. Enfin, pour élargir la réflexion au monde des virus eucaryotes, deux nouvelles montrent comment l’infection virale peut interférer avec la communication entre cellules eucaryotes, sur l’exemple de la communication s’effectuant par l’intermédiaire de vésicules extracellulaires. La nouvelle intitulée « La sécrétion de vésicules extracellulaires par les plaquettes activées à l’origine de la létalité de la dengue ? » discute des mécanismes par lesquels le virus de la dengue déclenche la sécrétion de vésicules extracellulaires par les plaquettes, et des conséquences que cela peut avoir sur l’inflammation et le déclenchement de chocs hémorragiques. La nouvelle intitulée « Le coccolithovirus et Emiliania huxleyi : le détournement viral des vésicules extracellulaires » montre enfin comment ce virus d’algue unicellulaire exploite la communication intercellulaire de son hôte pour augmenter son pouvoir de diffusion au sein de la population, et des conséquences écologiques et géochimiques que cela peut entraîner à grande échelle.

Author(s):  
Umeh Odera Richard ◽  
E. I. Chukwura ◽  
Ibo Eziafakaego Mercy

A fish pond with recommended water quality will produce healthy fishes. Fish ponds with poor water quality will cause fish mortality and outbreak of diseases to fish consumers. Physicochemical analysis was done using standard analytical methods, the total bacterial count was determined by dilution and membrane filtration techniques. Parasitological analysis was done using the centrifugation method. A total of fifteen well waters were sampled during wet season. Results showed that the temperature ranged from 27°C to 29°C, pH, 6.21 to 8.15; dissolved oxygen, 4.28 mg/l to 5.78 mg/l, electrical conductivity, 166.36 µs/cm to 394.00 µs/cm; total dissolved solids, 41 mg/l to 121 mg/l; total suspended solids, 1.00 mg/l to 19.40 mg/l; total solids, 42.00 mg/l to 140.4 mg/l; turbidity values, 7.01 NTU to 10.36 NTU; nitrate, 3.10 mg/l to 28.00 mg/l; total alkalinity, 36 mg/l to 91 mg/l; phosphate, 1.26 mg/l to 13.11 mg/l; sulphate, 0.39 mg/l to 4.37 mg/l; total chloride, 7.08 mg/l to 14.19 mg/l; carbonates, 1.33 mg/l to 2.35 mg/l; bicarbonates, 34.59 mg/l to 89.38 mg/l; total hardness, 25.31 mg/l to 53.04 mg/l; calcium hardness, 23.94 mg/l to 51.96 mg/l; magnesium hardness, 1.08 mg/l to 4.20 mg/l; total acidity, 2 mg/l to 22 mg/l; potassium, 0.04 mg/l to 2.23 mg/l; cadmium, 0.00 mg/l to 0.04 mg/l; lead, 0.01 mg/l - 0.16 mg/l; chromium, 0.00 mg/l - 0.03 mg/l; mercury was not detected, copper, 0.00 mg/l - 0.04 mg/l; arsenic, 0.00 mg/l - 0.02 mg/l; zinc, 0.00 mg/l to 0.02 mg/l; iron, 0.01 mg/l - 1.19 mg/l. The total bacterial counts ranged from 3.60-4.12 log cfu/ml; total coliforms, 14-46 cfu/100ml, Vibrio cholerae, 0-11 cfu/100ml; Vibrio parahaemolyticus, 0-15 cfu/100ml; faecal coliform, 1-9 cfu/100 ml; Acinetobacter calcoaceticus, 0-8 cfu/100 ml; Bacillus subtilis, 0-9 cfu/ml; Staphylococcus aureus, 0-5 cfu/ml; Pseudomonas aeruginosa, 0-12 cfu/100 ml; Pseudomonas fluorescens, 0-12 cfu/100 ml and Clostridium perfringens were not detected in any of the samples. Twelve bacterial species namely Klebsiella pneumoniae, Acinetobacter calcoaceticus, Escherichia coli, Staphylococcus aureus, Vibrio cholerae, Pseudomonas fluorescens, Pseudomonas aeruginosa, Proteus mirabilis, Vibrio parahaemolyticus, Bacillus subtilis, Shigella flexineri and Salmonella typhi were isolated and identified using standard analytical and molecular procedures. Parasites identified were Ichthyobodo species, Diplostomum species, Myxobolus species, Chilodonella species, Bothriocephalus species, Ambiphrya species and Leech species. Salmonella typhi had the highest frequency of isolation (20.63%) while Acinetobacter calcoaceticus and Staphylococcus aureus had the lowest frequency of isolation (2.83%). Ichthyobodo species had the highest frequency of isolation (21.43%) while Leech species had the lowest frequency of isolation (5.71%). Some of the physicochemical, bacteriological and parasitological parameters had values above World Health Organization admissible limits and therefore proper sanitary practices and water treatments must be employed to prevent epidemic among fish consumers.


Author(s):  
Masteria Yunovilsa Putra ◽  
Ahmad Saparhadi ◽  
Firmansyah Karim ◽  
Tutik Murniasih ◽  
Respati Tri Swasono

With the aim of searching for new antibacterial compound from marine soft corals, the investigation had been conducted on antibacterial activity of an extract from soft corals Sarcophyton trocheliophorum in the n-hexane, ethyl acetate, n-butanol, and aqueous fractions. The antibacterial activity was tested against two Gram-positive bacteria, viz. Bacillus subtilis (ATCC 6633) and Staphylococcus aureus (ATCC 25923), and two Gram-negative bacteria, viz. Escherichia coli (ATCC 25922) and Vibrio cholerae (ATCC 14035) using the agar disc diffusion assay. Among them, the n-hexane fraction was the most active against three tested bacteria, viz. Bacillus subtilis, Staphylococcus aureus and Vibrio cholerae at the concentration 125 µg/ml, with inhibition zone 14.2, 18.2, 13.8 mm, respectively. Isolation and purification of the active component from the n-hexane fraction led to a known cembranoid-type diterpene, sarcophytoxide. The chemical structure of the isolated compound was determined by IR, MS and NMR, as well as compared to data from the literature. Sarcophytoxide showed moderate activity against B. subtilis, S. aureus and V. cholerae, with a minimum inhibitory concentration (MIC) of 125, 100, 125 mg/ml, respectively.


1994 ◽  
Vol 57 (1) ◽  
pp. 59-61 ◽  
Author(s):  
GERHARD J. HAAS ◽  
RAFFI BARSOUMIAN

The antimicrobial activity of hop resins against Streptococcus salivarius, Staphylococcus aureus (two strains), Bacillus megaterium, Escherichia coli B, and Bacillus subtilis was investigated. However, resistance development was carried out on Streptococcus salivarius, Staphylococcus aureus (two strains), and Bacillus megaterium. The two hop resins used were iso-alpha resin and beta resin. Prior to resistance development, S. salivarius, S. aureus, and B. megaterium were all inhibited by the iso-alpha-hop resin in the 0.01 to 0.03% range. The beta-hop resin which, according to the literature, is more active than the iso-alpha resin initially inhibited these organisms at the 0.003 to 0.01% concentrations. The ease of resistance development varied between the different microbes, B. megaterium being the least prone to develop resistance.


2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Fan Zhang ◽  
Bowei Wang ◽  
Shiluan Liu ◽  
Yuhui Chen ◽  
Yihuang Lin ◽  
...  

AbstractAs treatment of Staphylococcus aureus (S. aureus) osteomyelitis is often hindered by the development of antibiotic tolerance, novel antibacterial therapeutics are required. Here we found that the cell-free supernatant of Bacillus subtilis (B. subtilis CFS) killed planktonic and biofilm S. aureus, and increased S. aureus susceptibility to penicillin and gentamicin as well. Further study showed that B. subtilis CFS suppressed the expression of the genes involved in adhesive molecules (Cna and ClfA), virulence factor Hla, quorum sensing (argA, argB and RNAIII) and biofilm formation (Ica and sarA) in S. aureus. Additionally, our data showed that B. subtilis CFS changed the membrane components and increased membrane permeabilization of S. aureus. Finally, we demonstrated that B. subtilis CFS increased considerably the susceptibility of S. aureus to penicillin and effectively reduced S. aureus burdens in a mouse model of implant-associated osteomyelitis. These findings support that B. subtilis CFS may be a potential resistance-modifying agent for β-lactam antibiotics against S. aureus.


2021 ◽  
Author(s):  
Cameron Habib ◽  
Anna Mueller ◽  
Ming Liu ◽  
Jun Zhu ◽  
Tanja Schneider ◽  
...  

AbstractBacterial galactosemia or “galactose death,” triggered by incomplete galactose metabolism, was first discovered in Escherichia coli and Salmonella six decades ago, and later in many other microorganisms, yet the mechanism for the toxicity and subsequent cell death remains unclear. In Bacillus subtilis, galactosemia is manifested by a buildup of uridine-diphosphate-galactose (UDP-Gal) and a strong toxicity phenotype characterized by cell shape abnormality and rapid cell lysis. Here we present evidence that in B. subtilis, the toxicity is due to inhibition of cell wall biosynthesis through interference of the essential glycosyltransferase MurG that carries out lipid II synthesis from lipid I and uridine-diphosphate-N-acetyl-glucosamine (UDP-GlcNAc). Single-molecule imaging reveals real-time inhibition of cell wall biosynthesis and MurG activities in cells exhibiting toxicity. We further show that in vitro, MurG is able to utilize UDP-Gal as a substrate generating a “toxic” lipid II, causing a potential poisoning effect on peptidoglycan crosslinking. Evidence also suggests a similar mechanism in Vibrio cholerae and Staphylococcus aureus. Lastly, a strong synergistic lethality was seen in S. aureus wild-type cells treated with both galactose and sub-lethal doses of cell-wall antibiotics. Our study provides mechanistic explanation of the toxicity associated with bacterial galactosemia and its potential application in antibacterial solutions.SignificanceGalactosemia is a potentially fatal genetic disorder due to incomplete galactose metabolism, found in both eukaryotic and prokaryotic organisms. The molecular mechanisms of galactosemia-associated toxicity remain unclear in all cases. Here we present evidence that in the bacterium Bacillus subtilis, the toxicity is due to interference of an essential glycosyltransferase, MurG, which concerts lipid I to lipid II during peptidoglycan biosynthesis, by a nucleotide sugar derived from galactose metabolism. This interference leads to a halt of cell wall biosynthesis and structural defects causing rapid cell lysis. Our evidence also suggests a similar mechanism in other bacteria such as Staphylococcus aureus and Vibrio cholerae. Our study may help solve the long-time puzzle of bacterial galactosemia first uncovered six decades ago.


2021 ◽  
Author(s):  
Fan Zhang ◽  
Bowei Wang ◽  
Shiluan Liu ◽  
Yihuang Lin ◽  
Zixian Liu ◽  
...  

Abstract As treatment of Staphylococcus aureus osteomyelitis is often hindered by the development of antibiotic tolerance, novel antibacterial therapeutics are required. Here we found that the cell-free supernatant of Bacillus subtilis (B. subtilis CFS) killed planktonic and biofilm S. aureus, and increased S. aureus susceptibility to penicillin and gentamicin as well. Further study showed that B. subtilis CFS suppressed the expression of the genes involved in adhesive molecules (Cna and ClfA), virulence factor Hla, quorum sensing (argA, argB and RNAIII) and biofilm formation (Ica and sarA) in S. aureus. Additionally, our data showed that B. subtilis CFS changed the membrane components and increased membrane permeabilization of S. aureus. Finally, we demonstrated that B. subtilis CFS increased considerably the susceptibility of S. aureus to penicillin and effectively reduced S. aureus burdens in a mouse model of implant-associated osteomyelitis. These findings support that B. subtilis CFS may be a potential resistance-modifying agent against S. aureus osteomyelitis.


2019 ◽  
Vol 1 (1) ◽  
pp. 8-11
Author(s):  
Ni Komang Tri Dharmayani

Aktivitas antibakteri dari ekstrak aseton kulit batang Swietenia macrophylla telah dilakukan. dengan metode mikrodilusi. Hasilnya menunjukkan bahwa ekstrak aseton kulit batang S. macrophylla aktif sebagai antibakteri terhadap lima bakteri patogen yaitu Gram positif (Bacillus subtilis dan Staphylococcus aureus ) serta tiga bakteri Gram negatif antara (Escherichia coli, Salmonella thypii, dan  Vibrio cholerae) pada konsentrasi 12,5 ppm.


2019 ◽  
Vol 9 (02) ◽  
Author(s):  
Hussein A Kadhum ◽  
Thualfakar H Hasan2

The study involved the selection of two isolates from Bacillus subtilis to investigate their inhibitory activity against some bacterial pathogens. B sub-bacteria were found to have a broad spectrum against test bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa. They were about 23-30 mm and less against Klebsiella sp. The sensitivity of some antibodies was tested on the test samples. The results showed that the inhibitory ability of bacterial growth in the test samples using B. subtilis extract was more effective than the antibiotics used.


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