Vol. 03, 2016

Bacterial genotoxin functions as immune-modulator and promotes host survival

R. Guidi¹, L. Del Bell Belluz², T. Frisan²

This article comments on work published by Del Bel Belluz et al. (PLoS Pathog, 2016), which demonstrated that the typhoid toxin of Salmonella enterica serovar Typhi esembles an immune-modulatory molecule rather than a toxic agent.

Functions and regulation of the MRX complex at DNA double-strand breaks

Elisa Gobbini¹, Corinne Cassani¹, Matteo Villa¹, Diego Bonetti² and Maria Pia Longhese¹

DNA double-strand breaks (DSBs) pose a serious threat to genome stability and cell survival. Cells possess mechanisms that recognize DSBs and promote their repair through either homologous recombination (HR) or non-homologous end joining (NHEJ). The present review focuses mainly on recent works in the budding yeast Saccharomyces cerevisiae to highlight structure and regulation of the evolutionary conserved Mre11-Rad50-Xrs2 (MRX) complex as well as its interplays with Tel1.

Attenuation of polyglutamine-induced toxicity by enhancement of mitochondrial OXPHOS in yeast and fly models of aging

Andrea L. Ruetenik^1,2,3, Alejandro Ocampo^1,2,3,¶, Kai Ruan^4,5,#, Yi Zhu^4,5, Chong Li^4,6, R. Grace Zhai^1,4,5,6 and Antoni Barrientos^1,2,3,5

Defects in mitochondrial biogenesis and function are common in many neurodegenerative disorders, including Huntington’s disease (HD). We could shown that enhancement of mitochondrial biogenesis protects against neurodegeneration in HD yeast and fly models. Our results suggest that therapeutic interventions aiming at the enhancement of mitochondrial respiration and OXPHOS could reduce polyQ toxicity and delay disease onset.

Cox1 mutation abrogates need for Cox23 in cytochrome c oxidase biogenesis

Richard Dela Cruz^1,2, Mi-Young Jeong¹ and Dennis R. Winge¹

Cox23 is a known conserved assembly factor for cytochrome c oxidase, although its role in cytochrome c oxidase (CcO) biogenesis remains unresolved. To gain additional insights into its role, we isolated spontaneous suppressors of the respiratory growth defect in cox23∆ yeast cells. In this report, we describe the isolation of a robust suppressor of the respiratory defect in cox23∆ cells that mapped to the mitochondrial-encoded Cox1 subunit.

Inhibition of Zika virus by Wolbachia in Aedes aegypti

Eric Pearce Caragata, Heverton Leandro Carneiro Dutra and Luciano Andrade Moreira

This article comments on work published by Dutra et al. (Cell Host Microbe, 2016), which investigated the potential of Wolbachia infections in Aedes aegypti to restrict infection and transmission of Zika virus.

Syphilis: Re-emergence of an old foe

Lola V. Stamm

Syphilis is caused by infection with Treponema pallidum subsp. pallidum, a not-yet-cultivable spiral-shaped bacterium that is usually transmitted by sexual contact with an infected partner or by an infected pregnant woman to her fetus. This review provides insights into the etiology, epidemiology, clinical manifestation, diagnosis, treatment and prevention of syphilis.

Genital Herpes: Insights into Sexually Transmitted Infectious Disease

Dinesh Jaishankar^1,2,4 and Deepak Shukla^1,2,3

Genital herpes is one of the most common, persistent and highly infectious sexually transmitted viral infections. This review provides an insight into the epidemiology, pathology, our current understanding of the molecular mechanisms of infection and the currently available and upcoming treatments for genital herpes.

Trichomoniasis – are we giving the deserved attention to the most common non-viral sexually transmitted disease worldwide?

Camila Braz Menezes, Amanda Piccoli Frasson, Tiana Tasca

Trichomonas vaginalis is the etiologic agent of trichomoniasis, the most common non-viral sexually transmitted disease (STD) in the world. This article contributes to claim the attention of public health policies to control this STD.

House of cellulose – a new hideout for drug tolerant Mycobacterium tuberculosis

Ashwani Kumar

This article comments on work published by Trivedi et al. (Nat Commun, 2016), which shows that Mycobacterium tuberculosis cells organise themselves into biofilms in response to intracellular thiol reductive stress.

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Yeast screening platform identifies FDA-approved drugs that reduce Aβ oligomerization

Triana Amen^1,2 and Daniel Kaganovich¹

This article comments on work published by Park et al. (Microbial Cell, 2016), which discovered a number of small molecules capable of modulating Aβ aggregation in a yeast model.

Differentiated cytoplasmic granule formation in quiescent and non-quiescent cells upon chronological aging

Hsin-Yi Lee^1,3,†, Kuo-Yu Cheng^2,3,†, Jung-Chi Chao³ and Jun-Yi Leu³

Stationary phase cultures represent a complicated cell population comprising at least two different cell types, quiescent (Q) and non-quiescent (NQ) cells. The authors show that the cell fate of NQ cells is largely irreversible even if they are allowed to reenter mitosis. Their results reveal that the formation of different granule structures may represent the early stage of cell type differentiation in yeast stationary phase cultures.

Mitochondrial regulation of cell death: a phylogenetically conserved control

Lorenzo Galluzzi^1,2,3,4,5, Oliver Kepp^1,2,3,4,6and Guido Kroemer^{1,2,3,4,6,7,8}

Mitochondria are fundamental for eukaryotic cells as they participate in critical catabolic and anabolic pathways. Moreover, mitochondria play a key role in the signal transduction cascades that precipitate many (but not all) regulated variants of cellular demise. In this short review, the authors discuss the differential implication of mitochondria in the major forms of regulated cell death.

Mek1/Mre4 is a master regulator of meiotic recombination in budding yeast

Nancy M. Hollingsworth

This article comments on work published by Chen et al. (PLoS BIol, 2015), showing that the meiosis specific kinase Mek1 indirectly regulates the crossover/non-crossover decision between homologs as well as genetic interference and suggests Mek1 to be a "master regulator" of meiotic recombination in budding yeast.

Shaping meiotic chromosomes with SUMO: a feedback loop controls the assembly of the synaptonemal complex in budding yeast

Hideo Tsubouchi¹, Bilge Argunhan¹ and Tomomi Tsubouchi²

This article comments on work published by Leung et al. (J Cell Biol, 2015), which shows that the formation of the meiosis-specific synaptonemal complex is controlled through SUMOylation of a regulator required for the assembly of transverse filaments, implicating the involvement of a positive feedback loop in the control of synaptonemal complex assembly.

Towards understanding the gliotoxin detoxification mechanism: in vivo thiomethylation protects yeast from gliotoxin cytotoxicity

Elizabeth B. Smith, Stephen K. Dolan, David A. Fitzpatrick, Sean Doyle and Gary W. Jones

Gliotoxin is a mycotoxin produced by some species of ascomycete fungi including the opportunistic human pathogen Aspergillus fumigatus. In order to produce gliotoxin the host organism needs to have evolved a self-protection mechanism. The authors demonstrate that the activity of a novel thiomethyltransferase is requiered for protection against exogenous gliotoxin and provide implications for understanding the evolution of gliotoxin self-protection mechanisms.

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Mek1/Mre4 is a master regulator of meiotic recombination in budding yeast

Nancy M. Hollingsworth

Shaping meiotic chromosomes with SUMO: a feedback loop controls the assembly of the synaptonemal complex in budding yeast

Hideo Tsubouchi¹, Bilge Argunhan¹ and Tomomi Tsubouchi²

Learning epigenetic regulation from mycobacteria

Sanjeev Khosla¹, Garima Sharma^1,2 and Imtiyaz Yaseen^1,2

This article comments on work published by Koshla et al. (Nat Commun, 2015), which shows that pathogenic Mycobacterium tuberculosis has evolved strategies to hijack the epigenetic regulation of host transcripton for its own survival.

Location, location, location. Salmonella senses ethanolamine to gauge distinct host environments and coordinate gene expression

Christopher J. Anderson and Melissa M. Kendall

This article comments on work published by Anderson and Kendell (PLoS Pathog, 2015), which demonstrates that Salmonella enterica serovar Typhimurium (Salmonella) exploits ethanolamine signaling to adapt to distinct host environments to precisely coordinate expression of genes encoding metabolism and virulence.

Biofilm assembly becomes crystal clear – filamentous bacteriophage organize the Pseudomonas aeruginosa biofilm matrix into a liquid crystal

Patrick R. Secor¹, Laura K. Jennings¹, Lia A. Michaels¹, Johanna M. Sweere², Pradeep K. Singh¹, William C. Parks³, Paul L. Bollyky²

This article comments on work published by Secor et al. (Host Cell & Microbe, 2015), which highlights a previously unknown role for filamentous Pf phage in organizing the P. aeruginosa biofilm matrix into a liquid crystalline structure. These findings help ground our understanding of biofilm formation within established paradigms of soft matter physics

Histone modifications as regulators of life and death in Saccharomyces cerevisiae

Birthe Fahrenkrog

The mechanism by which chromosomes restructure during apoptosis is still poorly understood, but it is becoming increasingly clear that altered epigenetic histone modifications are fundamental parameters that influence the chromatin state and the nuclear rearrangements within apoptotic cells. This review highlights recent work on the epigenetic regulation of programmed cell death in budding yeast.

Spermidine cures yeast of prions

Shaun H. Speldewinde, and Chris M. Grant

This article comments on work published by Speldewinde and Grant (Mol Biol Cell, 2015), which found that spermidine, a polyamine that has been used to increase autophagic flux, acts as a protective agent which prevents spontaneous prion formation in yeast.

Autophagy: one more Nobel Prize for yeast

Andreas Zimmermann¹, Katharina Kainz¹, Aleksandra Andryushkova¹, Sebastian Hofer¹, Frank Madeo^1,2 and Didac Carmona-Gutierrez¹

The recent announcement of the 2016 Nobel Prize in Physiology or Medicine, awarded to Yoshinori Ohsumifor the discoveries of mechanisms governing autophagy, underscores the importance of intracellular degradation and recycling. Here we provide a quick historical overview that mirrors both the importance of autophagy as a conserved and essential process for cellular life and death as well as the crucial role of yeast in its mechanistic characterization.

Physiology, phylogeny, and LUCA

William F. Martin^1,2, Madeline C. Weiss¹, Sinje Neukirchen³, Shijulal Nelson-Sathi⁴, Filipa L. Sousa³

Genomes record their own history. But if we want to look all the way back to life's beginnings some 4 billion years ago, the record of microbial evolution that is preserved in prokaryotic genomes is not easy to read. The classical approach has been to look for genes that are universally distributed. Another approach is to make all trees for all genes, and sift out the trees where signals have been overwritten by lateral gene transfer. What is left ought to be ancient. If we do that, what do we find?

The curious case of vanishing mitochondria

Anna Karnkowska¹ and Vladimír Hampl²

Due to their involvement in the energy metabolism, mitochondria are essential for most eukaryotic cells. Microbial eukaryotes living in low oxygen environments possess reduced forms of mitochondria, namely mitochondrion-related organelles (MROs). Recently, the first microbial eukaryote with neither mitochondrion nor MRO was characterized – Monocercomonoides sp. The discovery of such bona fide amitochondriate eukaryote broadens our knowledge about the diversity and plasticity of eukaryotic cells and provides a substantial contribution to our understanding of eukaryotic cell evolution.

Accumulation of metabolic side products might favor the production of ethanol in Pho13 knockout strains

Guido T. Bommer, Francesca Baldin & Emile Van Schaftingen

This article comments on work published by Collard et al. (Nat Chem Biol, 2016), which describes the discovery of a striking example illustrating the metabolite repair concept.

Sexually transmitted infections: old foes on the rise

Didac Carmona-Gutierrez^1,*, Katharina Kainz¹ and Frank Madeo^1,2,*

Sexually transmitted infections (STIs) are commonly spread via sexual contact. It is estimated that one million STIs are acquired every day worldwide. Besides their impact on sexual, reproductive and neonatal health, they can cause disastrous and life-threatening complications if left untreated. In addition to this personal burden, STIs also represent a socioeconomic problem, deriving in treatment costs of tremendous proportions. Despite a substantial progress in diagnosis, treatment and prevention, the incidence of many common STIs is increasing, and STIs continue to represent a global public health problem and a major cause for morbidity and mortality. With this Special Issue, Microbial Cell provides an in-depth overview of the eight major STIs, covering all relevant features of each infection.

Similar environments but diverse fates: Responses of budding yeast to nutrient deprivation.

Saul M. Honigberg

Diploid budding yeast (Saccharomyces cerevisiae) can adopt one of several alternative differentiation fates in response to nutrient limitation, and each of these fates provides distinct biological functions. When different strain backgrounds are taken into account, these various fates occur in response to similar environmental cues, are regulated by the same signal transduction pathways, and share many of the same master regulators. I propose that the relationships between fate choice, environmental cues and signaling pathways are not Boolean, but involve graded levels of signals, pathway activation and master-regulator activity.

Non-genetic impact factors on chronological lifespan and stress resistance of baker’s yeast

Michael Sauer and Diethard Mattanovich

This article comments on work published by Bisschops et al. (Microbial Cell, 2015), which illustrates how important the choice of the experimental setup is and how culture conditions influcence cellular aging and survival in biotechnological processes.

The complexities of bacterial-fungal interactions in the mammalian gastrointestinal tract

Eduardo Lopez-Medina¹ and Andrew Y. Koh²

This article comments on work published by Lopez-Medina et al. (PLoS Pathog, 2015) and Fan et al. (Nat Med, 2015), which utilize an “artificial” niche, the antibiotic-treated gut with concomitant pathogenic microbe expansion, to gain insight in bacterial-fungal interactions in clinically common scenarios.

Gearing up for survival – HSP-containing granules accumulate in quiescent cells and promote survival

Ruofan Yu and Weiwei Dang

This article comments on work published by Lee et al. (Microbial Cell, 2016), which reports that distinct granules are formed in quiescent and non-quiescent cells, which determines their respective cell fates.

Recent Insights into the HIV/AIDS Pandemic

September 4, 2016

Acquired immunodeficiency syndrome (AIDS), caused by chronic infection with the human immunodeficiency virus1 (HIV-1), is one of the most devastating pandemics ever recorded in human history. In this review, we assemble new details on the molecular events from the attachment of the virus, to the assembly and release of the viral progeny.

Gonorrhea – an evolving disease of the new millennium

September 4, 2016

Neisseria gonorrhoeae (the gonococcus) is a Gram-negative diplococcus, an obligate human pathogen, and the etiologic agent of the sexually transmitted disease, gonorrhea. This review provides insight into the molecular epidemiology, virulence mechanisms, pathogenesis and therapeutic options.

Phylogenetic profiles of all membrane transport proteins of the malaria parasite highlight new drug targets

August 30, 2016

In order to combat the on-going malaria epidemic, discovery of new drug targets remains vital. Proteins that are essential to survival and specific to malaria parasites are key candidates. Here, we present a comprehensive orthology assignment of all Plasmodium falciparum putative membrane transport proteins and provide a detailed overview of the associated essential gene functions obtained through experimental genetics studies in human and murine model parasites.

VDAC regulates AAC-mediated apoptosis and cytochrome c release in yeast

August 25, 2016

Mitochondrial outer membrane permeabilization is a key event in apoptosis processes leading to the release of lethal factors. In this study, we sought to determine whether Por1p functionally interacts with ADP/ATP carrier (AAC) proteins, as well as its contribution to cytochrome c release and yeast apoptosis induced by acetic acid treatment. Our data indicate that Por1p may regulate cell survival by acting as a negative regulator of AAC proteins in the apoptotic cascade.

Cryptococcus flips its lid – membrane phospholipid asymmetry modulates antifungal drug resistance and virulence

August 1, 2016

This article comments on work published by Huang et al. (MBio, 2016), which reported that in the pathogenic fungus Cryptococcus neoformans loss of lipid flippase activity sensitized cryptococcal cells to multiple classes of antifungal drugs and abolished fungal virulence in murine models.