Vol. 09, 2022

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. (...)

Breaking the clip for cargo unloading from motor proteins: mechanism and significance

Keisuke Obara¹, and Takumi Kamura¹

The mitochondrion is an essential organelle involved in ATP generation, lipid metabolism, regulation of calcium ions, etc. Therefore, it should be inherited properly by newly generated cells. In the budding yeast Saccharomyces cerevisiae, mitochondria are passed on to daughter cells by the motor protein, Myo2, on the actin cable. The mitochondria and Myo2 are connected via the adaptor protein Mmr1. After reaching daughter cells, mitochondria are released from the actin-myosin machinery and move dynamically. In our recent paper (Obara K et al. (2022), Nat Commun, doi:10.1038/s41467-022-29704-8), we demonstrated that the regulated proteolysis of Mmr1 is required for the unloading of mitochondria from Myo2 in daughter cells. Sequential post-translational modifications of Mmr1, i.e., phosphorylation followed by ubiquitination, are essential for Mmr1 degradation and mitochondrial release from Myo2. Defects in Mmr1 degradation cause stacking and deformation of mitochondria at the bud-tip and bud-neck, where Myo2 accumulates. Compared to wild-type cells, mutant cells with defects in Mmr1 degradation possess an elevated mitochondrial membrane potential and produce higher levels of reactive oxygen species (ROS), along with hypersensitivity to oxidative stress.

A hundred spotlights on microbiology: how microorganisms shape our lives

Didac Carmona-Gutierrez¹, Katharina Kainz¹, Andreas Zimmermann¹, Sebastian J. Hofer¹, Maria A. Bauer¹, Christoph Ruckenstuhl¹, Guido Kroemer^2-4 and Frank Madeo^1,5,6

Viral, bacterial, fungal and protozoal biology is of cardinal importance for the evolutionary history of life, ecology, biotechnology and infectious diseases. Various microbiological model systems have fundamentally contributed to the understanding of molecular and cellular processes, including the cell cycle, cell death, mitochondrial biogenesis, vesicular fusion and autophagy, among many others. Microbial interactions within the environment have profound effects on many fields of biology, from ecological diversity to the highly complex and multifaceted impact of the microbiome on human health. Also, biotechnological innovation and corresponding industrial operations strongly depend on microbial engineering. With this wide range of impact in mind, the peer-reviewed (...)

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 (...)

Yeast goes viral: probing SARS-CoV-2 biology using S. cerevisiae

Brandon Ho¹, Raphael Loll-Krippleber¹ and Grant W. Brown¹

The budding yeast Saccharomyces cerevisiae has long been an outstanding platform for understanding the biology of eukaryotic cells. Robust genetics, cell biology, molecular biology, and biochemistry complement deep and detailed genome annotation, a multitude of genome-scale strain collections for functional genomics, and substantial gene conservation with Metazoa to comprise a powerful model for modern biological research. Recently, the yeast model has demonstrated its utility in a perhaps unexpected area, that of eukaryotic virology. Here we discuss three innovative applications of the yeast model system to reveal functions and investigate variants of proteins encoded by the SARS-CoV-2 virus.

Fatty acid metabolism of Mycobacterium tuberculosis: A double-edged sword

Camila G. Quinonez^1,2, Jae Jin Lee¹, Juhyeon Lim¹, Mark Odell³, Christopher P. Lawson⁴, Amarachukwu Anyogu⁵, Saki Raheem² and Hyungjin Eoh¹

Unlike other heterotrophic bacteria, Mycobacterium tuberculosis (Mtb) can co-catabolize a range of carbon sources simultaneously. Evolution of Mtb within host nutrient environment allows Mtb to consume the host’s fatty acids as a main carbon source during infection. The fatty acid-induced metabolic advantage greatly contributes to Mtb’s pathogenicity and virulence. Thus, the identification of key enzymes involved in Mtb’s fatty acid metabolism is urgently needed to aid new drug development. Two fatty acid metabolism enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and isocitrate lyase (ICL) have been intensively studied as promising drug targets, but recently, Quinonez et al. (mBio, doi: 10.1128/mbio.03559-21) highlighted a link between the fatty acid-induced dormancy-like state and drug tolerance. (...)

Pirates of the haemoglobin

Daniel Akinbosede¹, Robert Chizea¹ and Stephen A. Hare^1,†

Not all treasure is silver and gold; for pathogenic bacteria, iron is the most precious and the most pillaged of metallic elements. Iron is essential for the survival and growth of all life; however free iron is scarce for bacteria inside human hosts. As a mechanism of defence, humans have evolved ways to store iron so as to render it inaccessible for invading pathogens, such as keeping the metal bound to iron-carrying proteins. For bacteria to survive within humans, they must therefore evolve counters to this defence to compete with these proteins for iron binding, or directly steal iron from them. (...)

An ionophore breaks the multi-drug-resistance of Acinetobacter baumannii

David M.P. De Oliveira¹ and Mark J. Walker¹

Within intensive care units, multi-drug resistant Acinetobacter baumannii outbreaks are a frequent cause of ventilator-associated pneumonia. During the on-going COVID-19 pandemic, patients who receive ventilator support experience a 2-fold increased risk of mortality when they contract a secondary A. baumannii pulmonary infection. In our recent paper (De Oliveira et al. (2022), Mbio, doi: 10.1128/mbio.03517-21), we demonstrate that the 8-hydroxquinoline ionophore, PBT2 breaks the resistance of A. baumannii to tetracycline class antibiotics. In vitro, the combination of PBT2 and zinc with either tetracycline, doxycycline, or tigecycline was shown to be bactericidal against multi-drug-resistant A. baumannii, (...)

Cleavage-defective Topoisomerase I mutants sharply increase G-quadruplex-associated genomic instability

Alexandra Berroyer^1,2, Albino Bacolla³, John A. Tainer^2,3,4 and Nayun Kim^1,2

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 (...)

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Endomembrane remodeling and dynamics in Salmonella infection

Ziyan Fang¹ and Stéphane Méresse¹

Salmonellae are bacteria that cause moderate to severe infections in humans, depending on the strain and the immune status of the infected host. These pathogens have the particularity of residing in the cells of the infected host. They are usually found in a vacuolar compartment that the bacteria shape with the help of effector proteins. Following invasion of a eukaryotic cell, the bacterial vacuole undergoes maturation characterized by changes in localization, composition and morphology. In particular, membrane tubules stretching over the microtubule cytoskeleton are formed from the bacterial vacuole. Although these tubules do not occur in all infected cells, they are functionally important and promote intracellular replication. This review focuses on the role and significance of membrane compartment remodeling observed in infected cells and the bacterial and host cell pathways involved.

The small bowel microbiome changes significantly with age and aspects of the ageing process

Gabriela Leite¹, Mark Pimentel^1,2, Gillian M. Barlow¹ and Ruchi Mathur^1,3

Gut microbiome changes have been associated with human ageing and implicated in age-related diseases including Alzheimer’s disease and Parkinson’s disease. However, studies to date have used stool samples, which do not represent the entire gut. Although more challenging to access, the small intestine plays critical roles in host metabolism and immune function. In this paper (Leite et al. (2021), Cell Reports, doi: 10.1016/j.celrep.2021.109765), we demonstrate significant differences in the small intestinal microbiome in older subjects, (...)

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 Lévesque^2,3, 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 (...)

The small bowel microbiome changes significantly with age and aspects of the ageing process

Gabriela Leite¹, Mark Pimentel^1,2, Gillian M. Barlow¹ and Ruchi Mathur^1,3

Flagellated bacterial porter for in situ tumor vaccine

Haiheng Xu¹, Yiqiao Hu^{1, 2} and Jinhui Wu^{1, 2, 3}

Cancer immunotherapy, which use the own immune system to attack tumors, are increasingly popular treatments. But, due to the tumor immunosuppressive microenvironment, the antigen presentation in the tumor is limited. Recently, a growing number of people use bacteria to stimulate the body's immunity for tumor treatment due to bacteria themselves have a variety of elements that activate Toll-like receptors. Here, we discuss the use of motility of flagellate bacteria to transport antigens to the tumor periphery to activate peritumoral dendritic cells to enhance the effect of in situ tumor vaccines.

The rise of Candida auris: from unique traits to co-infection potential

Nadine B. Egger^1,§, Katharina Kainz^1,§, Adina Schulze¹, Maria A. Bauer¹, Frank Madeo^1-3 and Didac Carmona-Gutierrez¹

Candida auris is a multidrug resistant (MDR) fungal pathogen with a crude mortality rate of 30-60%. First identified in 2009, C. auris has been rapidly rising to become a global risk in clinical settings and was declared an urgent health threat by the Centers for Disease Control and Prevention (CDC). A concerted global action is thus needed to successfully tackle the challenges created by this emerging fungal pathogen. In this brief article, we underline the importance of unique virulence traits, including its easy transformation, its persistence outside the host and its resilience against multiple cellular stresses, as well as of environmental factors that have mainly contributed to the rise of this superbug.

Detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its first variants in fourplex real-time quantitative reverse transcription-PCR assays

November 25, 2021