Sirvi Autor "Tamman, Hedvig" järgi

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The GraTA toxin-antitoxin system of Pseudomonas putida: regulation and role in stress tolerance
(2016-09-19) Tamman, Hedvig; Hõrak, Rita, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond.
Elu on stressirohke, eriti üheraksetel organismidel nagu bakterid. Sageli tundub, et parim viis stressiga toimetulekuks on rahulikult oodata tingimuste paranemist. Selline käitumismall on kasutust leidnud ka mikroobide maailmas. Bakteritel on palju erinevaid kasvu reguleerimise võimalusi, mille hulka on viimasel ajal arvatud ka toksiin-antitoksiin (TA) süsteemid. TA-süsteemid koosnevad kahest komponendist: rakule eluliselt olulisi protsesse või rakukesta kahjustavast toksiinist ja teda neutraliseerivast antitoksiinist. Selliste geenide olemasolu bakterite genoomis on esmapilgul mõistatuslik, sest miks peaks bakter tootma iseendale toksilist valku? Hiljutised uuringud mikroobide mudelorganismis Escherichia coli on näidanud, et toksiinid põhjustavad bakterite üleminekut uinuvasse olekusse, mida iseloomustab bakterite ainevahetuse aeglustumine ja peatunud kasv. Sellised mikroobid tekitavad suuri probleeme meditsiinis, kuna on väga paljude stressiolukordade, kaasa arvatud paljude antibiootikumide toime suhtes tundetumad ja võimelised üle elama tingimusi, mis kiirelt kasvavaid baktereid tapaks. Kui mudelorganismis E. coli on TA süsteemide osalus bakteri stressitaluvuses hästi kirjeldatud, siis teistes bakteriliikides ei ole neid potentsiaalselt toksilisi süsteeme nii süstemaatiliselt uuritud. Seetõttu ei ole ka selge, kas erinevates bakterites toimivad TA süsteemid erinevalt või mingi üldise mehhanismi alusel. Käesolev töö kirjeldab keskkonnabakteri Pseudomonas putida kasvukiirust mõjutavat GraTA süsteemi. Tavaliselt takistab antitoksiin GraA väga efektiivselt toksiini GraT aktiivsust, kuid antitoksiinist vabanenult suudab toksiin mõjutada selle bakteri stressitaluvust. Toksiini mõju on kahetine, sest olenevalt stressi tüübist võib toksiin nii suurendada kui ka vähendada bakteri stressitaluvust. Seetõttu on bakterile väga oluline, et potentsiaalselt kahjulik TA süsteem aktiveeruks vaid kindlatel stressitingimustel.
Isolation and characterization of a phage collection against Pseudomonas putida
(2024-06-11) Brauer, Age; Rosendahl, Sirli; Kängsep, Anu; Lewańczyk, Alicja Cecylia; Rikberg, Roger; Hõrak, Rita; Tamman, Hedvig
The environmental bacterium, Pseudomonas putida, possesses a broad spectrum of metabolic pathways. This makes it highly promising for use in biotechnological production as a cell factory, as well as in bioremediation strategies to degrade various aromatic pollutants. For P. putida to flourish in its environment, it must withstand the continuous threats posed by bacteriophages. Interestingly, until now, only a handful of phages have been isolated for the commonly used laboratory strain, P. putida KT2440, and no phage defence mechanisms have been characterized. In this study, we present a new Collection of Environmental P. putida Phages from Estonia, or CEPEST. This collection comprises 67 double-stranded DNA phages, which belong to 22 phage species and 9 phage genera. Our findings reveal that most phages in the CEPEST collection are more infectious at lower temperatures, have a narrow host range, and require an intact lipopolysaccharide for P. putida infection. Furthermore, we show that cryptic prophages present in the P. putida chromosome provide strong protection against the infection of many phages. However, the chromosomal toxin–antitoxin systems do not play a role in the phage defence of P. putida. This research provides valuable insights into the interactions between P. putida and bacteriophages, which could have significant implications for biotechnological and environmental applications.
Prophage-encoded RexAB-type phage defense system in Pseudomonas putida
(2026-01-21) Rosendahl, Sirli; Kängsep, Anu; Ainelo, Andres; Lipu, Anita; Tamman, Hedvig; Hõrak, Rita
Pseudomonas putida kasvukiirust vähendav toksiin GraT supresseerib colR mutandi glükoossõltuvat lüüsi
(2012) Tamman, Hedvig
RelA-SpoT Homolog toxins pyrophosphorylate the CCA end of tRNA to inhibit protein synthesis
(Cell Press, 2021-08) Brodiazhenko, Tetiana; Alves Oliveira, Sofia Raquel; Roghanian, Mohammad; Sakaguchi, Yuriko; Turnbull, Kathryn Jane; Bulvas, Ondrej; Takada, Hiraku; Tamman, Hedvig; Ainelo, Andres; Pohl, Radek; Rejman, Dominik; Tenson, Tanel; Suzuki, Tsutomu; Garcia-Pino, Abel; Atkinson, Gemma C; Haurilyiuk, Vasili; Kurata, Tatsuki
RelA-SpoT Homolog (RSH) enzymes control bacterial physiology through synthesis and degradation of the nucleotide alarmone (p)ppGpp. We recently discovered multiple families of small alarmone synthetase (SAS) RSH acting as toxins of toxin-antitoxin (TA) modules, with the FaRel subfamily of toxSAS abrogating bacterial growth by producing an analog of (p)ppGpp, (pp)pApp. Here we probe the mechanism of growth arrest used by four experimentally unexplored subfamilies of toxSAS: FaRel2, PhRel, PhRel2, and CapRel. Surprisingly, all these toxins specifically inhibit protein synthesis. To do so, they transfer a pyrophosphate moiety from ATP to the tRNA 3′ CCA. The modification inhibits both tRNA aminoacylation and the sensing of cellular amino acid starvation by the ribosome-associated RSH RelA. Conversely, we show that some small alarmone hydrolase (SAH) RSH enzymes can reverse the pyrophosphorylation of tRNA to counter the growth inhibition by toxSAS. Collectively, we establish RSHs as RNA-modifying enzymes.
The opposite effects of stringent response on phage infection of Pseudomonas putida
(2026-01-02) Lewańczyk, Alicja Cecylia; Hinnu, Mariliis; Mägi, Elise; Rikberg, Roger; Brauer, Age; Tamman, Hedvig
Guanosine tetra- and pentaphosphate ((p)ppGpp) are one of the key players in the stress response of bacteria. Accumulation of these alarmones activates the stringent response, usually triggered by different nutritional stresses. For Pseudomonas putida, there is only limited data available on the importance of the stringent response in stress situations. Also, in recent years, different specific phage defence systems have received much attention, but little is known about the involvement of stringent response in phage infection. Here, we show that P. putida PaW85 (p)ppGpp0 is prototrophic and tolerates chemical stress well. However, in the stationary phase P. putida cells deprived of (p)ppGpp have impaired membrane integrity. In addition, we conducted a large-scale screening of stringent response effects on phage infections using the CEPEST phage collection. We tested 67 phages of 22 different species and revealed that the lack of (p)ppGpp has opposing effects on phage infection with nearly half of the tested phages showing higher infection efficiency on the (p)ppGpp0 cells, whereas the other half shows reduced infection. We show that the differences in phage infection efficiency for phages Aura and Amme-3 are not caused by adsorption rate differences, but alterations in downstream steps of the infection cycle—prolonged latent period in the absence of (p)ppGpp or unproductive infection in the presence of (p)ppGpp. Altogether, results indicate that the role of stringent response in phage infection is highly diverse, and over half of the times the presence of (p)ppGpp facilitates phage infections rather than protects the cells.
Uute Pseudomonas putida ColRS kahekomponentse regulatsioonisüsteemi märklaudgeenide tuvastamine
(2010) Tamman, Hedvig