Research, Research Reports
Cellular cholesterol licenses Legionella pneumophila intracellular replication in macrophages
Edna Ondari1,#, Ashley Wilkins1,#, Brian Latimer3, Ana-Maria Dragoi2,3 and Stanimir S. Ivanov1
Host membranes are inherently critical for niche homeostasis of vacuolar pathogens such as Legionella. One membrane component that is often subverted by vacuolar bacteria is cholesterol. We provide experimental evidence that cellular cholesterol promotes L. pneumophila replication within a membrane bound organelle in infected macrophages.
DadY (PA5303) is required for fitness of Pseudomonas aeruginosa when growth is dependent on alanine catabolism
Ronnie L. Fulton1 and Diana M. Downs1
Pseudomonas aeruginosa inhabits diverse environmental niches that can have varying nutrient composition. The ubiquity of this organism is facilitated by a metabolic strategy that preferentially utilizes low-energy, non-fermentable organic acids, such as amino acids, rather than the high-energy sugars preferred by many other microbes. The amino acid alanine is among the preferred substrates of P. aeruginosa. The dad locus encodes the constituents of the alanine catabolic pathway of P. aeruginosa. Physiological roles for DadR (AsnC-type transcriptional activator), DadX (alanine racemase), and DadA (D-amino acid dehydrogenase) have been defined in this pathway. An additional protein, PA5303, is encoded in the dad locus in P. aeruginosa. PA5303 is a member of the ubiquitous Rid protein superfamily and is designated DadY based on the data presented herein. (...)
Multiple genome analysis of Candida glabrata clinical isolates renders new insights into genetic diversity and drug resistance determinants
Pedro Pais1,2,3,#, Mónica Galocha1,2,3,#, Azusa Takahashi-Nakaguchi4, Hiroji Chibana4 and Miguel C. Teixeira1,2,3
The emergence of drug resistance significantly hampers the treatment of human infections, including those caused by fungal pathogens such as Candida species. Candida glabrata ranks as the second most common cause of candidiasis worldwide, supported by rapid acquisition of resistance to azole and echinocandin antifungals frequently prompted by single nucleotide polymorphisms (SNPs) in resistance associated genes, such as PDR1 (azole resistance) or FKS1/2 (echinocandin resistance). To determine the frequency of polymorphisms and genome rearrangements as the possible genetic basis of C. glabrata drug resistance, we assessed genomic variation across 94 globally distributed isolates with distinct resistance phenotypes, whose sequence is deposited in GenBank. The(...)
Up-regulation of Osh6 boosts an anti-aging membrane trafficking pathway toward vacuoles
Ilham Kadhim1, Nazneen Begum1, William King1, Licheng Xu1 and Fusheng Tang1
Members of the family of oxysterol-binding proteins mediate non-vesicular lipid transport between membranes and contribute to longevity in different manners. We previously found that a 2-fold up-regulation of Osh6, one of seven yeast oxysterol-binding proteins, remedies vacuolar morphology defects in mid-aged cells, partly down-regulates the target of rapamycin complex 1 (TORC1), and increases the replicative lifespan. At the molecular level, Osh6 transports phosphatidylserine (PS) and phosphatidylinositol-4-phosphate (PI4P) between the endoplasmic reticulum (ER) and the plasma membrane (PM). To decipher how an ER-PM working protein controls vacuolar morphology, we tested genetic interactions between OSH6 and DRS2, whose protein flips PS from the lumen to the cytosolic side of the Golgi, the organelle between ER and vacuoles in many pathways. Up-regulated (...)
Investigating the role of G-quadruplexes at Saccharomyces cerevisiae telomeres
Sonia Stinus1, Fernando R. Rosas Bringas1, Lisa Wanders1, and Michael Chang1
In this study, the authors examine the in vivo relevance of telomeric G-quadruplexes in the budding yeast Saccharomyces cerevisiae by expressing a mutant telomerase RNA subunit (tlc1-tm) that introduces mutant telomeric repeats instead to the distal ends of telomeres. (...)
Air- and dustborne fungi in repositories of the National Archive of the Republic of Cuba
Sofia Borrego1, Isbel Vivar1 and Alian Molina1
This study has as objectives to determine the concentration and diversity of the air- and dustborne mycobiota in seven National Archive of the Republic of Cuba repositories, and to assess the potential risk of biodeterioration that iso-lated taxa may have. In the indoor and outdoor environmental microbiological samplings a SAS biocollector was used and the indoor/outdoor (I/O) ratio was determined for each repository. The settled dust was collected during six months. Sørensen's coefficient of similarity (QS) was calculated to compare the isolated taxa among the three studied niches (indoor air, dust, outdoor air). The biodegradation potential of the isolated taxa was determined by semi-quantitative tests. The concentrations in the air of repositories with natural cross-ventilation ranged from 225.2-750.3 CFU m-3, while in the Map library with air-conditioning (...)
Cleavage-defective Topoisomerase I mutants sharply increase G-quadruplex-associated genomic instability
Alexandra Berroyer1,2, Albino Bacolla3, John A. Tainer2,3,4 and Nayun Kim1,2
Topoisomerase 1 (Top1) removes transcription-associated helical stress to suppress G4-formation and its induced recombination at genomic loci containing guanine-run containing sequences. Interestingly, Top1 binds tightly to G4 structures, and its inhibition or depletion can cause elevated instability at these genomic loci. Top1 is targeted by the widely used anti-cancer chemotherapeutic camptothecin (CPT) and its derivatives, which stabilize Top1 covalently attached on a DNA nick and prevent the re-ligation step. Here we investigated how CPT-resistance conferring Top1 mutants, which emerge in cancer patients and cells treated with CPT, affect G4-induced genomic instability in S. cerevisiae. We found that Top1 mutants form stable complexes with G4 DNA and that expression of Top1 cleavage-defective mutants but not a DNA-binding-defective (...)
Chromosome-condensed G1 phase yeast cells are tolerant to desiccation stress
Zhaojie Zhang1 and Gracie R. Zhang2
The budding yeast Saccharomyces cerevisiae is capable of surviving extreme water loss for a long time. However, less is known about the mechanism of its desiccation tolerance. In this study, we revealed that in an exponential culture, all desiccation tolerant yeast cells were in G1 phase and had condensed chromosomes. (...)
Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its first variants in fourplex real-time quantitative reverse transcription-PCR assays
Mathieu Durand1, Philippe Thibault1, Simon Lévesque2,3, Ariane Brault4, Alex Carignan2, Louis Valiquette2, Philippe Martin2 and Simon Labbé4
The early diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections is required to identify and isolate contagious patients to prevent further transmission of SARS-CoV-2. In this study, we present a multitarget real-time TaqMan reverse transcription PCR (rRT-PCR) assay for the quantitative detection of SARS-CoV-2 and some of its circulating variants harboring mutations that give the virus a selective advantage. Seven different primer-probe sets that included probes containing locked nucleic acid (LNA) nucleotides were designed to amplify specific wild-type and mutant sequences in Orf1ab, Envelope (E), Spike (S), and Nucleocapsid (N) genes (...)
A time-resolved high-throughput screening of fission yeast deletion mutants for oxidative stress resistance
July 22, 2026
By capturing dynamic trajectories rather than static outcomes, this study exposes hidden layers of growth under oxidative stress and identifies new genetic determinants of cellular resilience in fission yeast.
Microwave-assisted preparation of yeast cells for ultrastructural analysis by electron microscopy
November 18, 2024
Budding yeast Saccharomyces cerevisiae is widely used as a model organism to study the biogenesis and architecture of organellar membranes, which can be visualized by transmission electron microscopy (TEM).
Direct detection of stringent alarmones (pp)pGpp using malachite green
August 5, 2024
In this study, we demonstrate the surprising discovery of a commercially available, low-cost malachite green (MG) detection kit, originally designed for orthophosphate (Pi) detection, for detecting (p)ppGpp and its analogues, especially pGpp
Unresolved mystery of cyclic nucleotide second messengers, periplasmic acid phosphatases and bacterial natural competence
July 18, 2024
In this study we aimed to identify the promotors responsible for the expression of the non-specific acid phosphatase AphA during different starvation conditions, to confirm the requirement of the cAMP-dependent CRP regulon for aphA expression, and to finally identify regulators of its expression.
Yeast gene KTI13 (alias DPH8) operates in the initiation step of diphthamide synthesis on elongation factor 2
August 8, 2023
We show here that apart from its effector role for Elongator-dependent tRNA modification in yeast, Kti13 alias Dph8 also operates in step one of the diphthamide modification pathway.
Atg1, a key regulator of autophagy, functions to promote MAPK activation and cell death upon calcium overload in fission yeast
May 10, 2023
Here, we provide evidence that the fission yeast Atg1 regulates cell death responses upon intracellular calcium load in addition to its role in promoting Pmk1 MAPK.
Investigating the role of G-quadruplexes at Saccharomyces cerevisiae telomeres
May 19, 2022
In this study, the authors examine the in vivo relevance of telomeric G-quadruplexes in the budding yeast Saccharomyces cerevisiae by expressing a mutant telomerase RNA subunit (tlc1-tm) that introduces mutant telomeric repeats instead to the distal ends of telomeres. (...)