scholarly journals Anoxia-induced mitophagy in the yeast Kluyveromyces marxianus

2020 ◽  
Vol 20 (7) ◽  
Author(s):  
Hisashi Hoshida ◽  
Shota Kagawa ◽  
Kentaro Ogami ◽  
Rinji Akada
Keyword(s):  
Kluyveromyces Marxianus ◽  
Nitrogen Starvation ◽  
Glucose Consumption ◽  
Growth Conditions ◽  
Mitochondrial Morphology ◽  
Wild Type ◽  
Aerobic Growth ◽  
Anaerobic Conditions ◽  
Quantitative Analyses ◽  
Membrane Components

ABSTRACT Kluyveromyces marxianus is a thermotolerant, ethanol-producing yeast that requires oxygen for efficient ethanol fermentation. Under anaerobic conditions, glucose consumption and ethanol production are retarded, suggesting that oxygen affects the metabolic state of K. marxianus. Mitochondria require oxygen to function, and their forms and number vary according to environmental conditions. In this study, the effect of anoxia on mitochondrial behavior in K. marxianus was examined. Under aerobic growth conditions, mitochondria-targeted GFP exhibited a tubular and dotted localization, representing a typical mitochondrial morphology, but under anaerobic conditions, GFP localized in vacuoles, suggesting that mitophagy occurs under anaerobic conditions. To confirm mitophagy induction, the ATG32, ATG8, ATG11 and ATG19 genes were disrupted. Vacuolar localization of mitochondria-targeted GFP under anaerobic conditions was interrupted in the Δatg32 and Δatg8 strains but not the Δatg11 and Δatg19 strains. Electron microscopy revealed mitochondria-like membrane components in the vacuoles of wild-type cells grown under anaerobic conditions. Quantitative analyses using mitochondria-targeted Pho8 demonstrated that mitophagy was induced in K. marxianus by anoxia but not nitrogen starvation. To the best of our knowledge, this is the first demonstration of anoxia-induced mitophagy in yeasts.

scholarly journals Comparison of genes required for H2O2 resistance in Streptococcus gordonii and Streptococcus sanguinis

Microbiology ◽  
2014 ◽  
Vol 160 (12) ◽  
pp. 2627-2638 ◽  
Author(s):  
Yifan Xu ◽  
Andreas Itzek ◽  
Jens Kreth
Keyword(s):  
Growth Conditions ◽  
Streptococcus Gordonii ◽  
Aerobic Growth ◽  
Anaerobic Conditions ◽  
Oral Biofilm ◽  
Streptococcus Sanguinis ◽  
Functional Studies ◽  
Stress Protection ◽  
H2o2 Resistance

Hydrogen peroxide (H2O2) is produced by several members of the genus Streptococcus mainly through the pyruvate oxidase SpxB under aerobic growth conditions. The acute toxic nature of H2O2 raises the interesting question of how streptococci cope with intrinsically produced H2O2, which subsequently accumulates in the microenvironment and threatens the closely surrounding population. Here, we investigate the H2O2 susceptibility of oral Streptococcus gordonii and Streptococcus sanguinis and elucidate potential mechanisms of how they protect themselves from the deleterious effect of H2O2. Both organisms are considered primary colonizers and occupy the same intraoral niche making them potential targets for H2O2 produced by other species. We demonstrate that S. gordonii produces relatively more H2O2 and has a greater ability for resistance to H2O2 stress. Functional studies show that, unlike in Streptococcus pneumoniae, H2O2 resistance is not dependent on a functional SpxB and confirms the important role of the ferritin-like DNA-binding protein Dps. However, the observed increased H2O2 resistance of S. gordonii over S. sanguinis is likely to be caused by an oxidative stress protection machinery present even under anaerobic conditions, while S. sanguinis requires a longer period of time for adaptation. The ability to produce more H2O2 and be more resistant to H2O2 might aid S. gordonii in the competitive oral biofilm environment, since it is lower in abundance yet manages to survive quite efficiently in the oral biofilm.

scholarly journals One Pathway Can Incorporate either Adenine or Dimethylbenzimidazole as an α-Axial Ligand of B12 Cofactors in Salmonella enterica

2007 ◽  
Vol 190 (4) ◽  
pp. 1160-1171 ◽  
Author(s):  
Peter J. Anderson ◽  
Jozsef Lango ◽  
Colleen Carkeet ◽  
Audrey Britten ◽  
Bernhard Kräutler ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Axial Ligand ◽  
Vitamin B ◽  
Wild Type ◽  
Aerobic Growth ◽  
Anaerobic Conditions ◽  
Aerobic Conditions ◽  
Axial Ligands ◽  
And Control ◽  
Coenzyme B

ABSTRACT Corrinoid (vitamin B12-like) cofactors contain various α-axial ligands, including 5,6-dimethylbenzimidazole (DMB) or adenine. The bacterium Salmonella enterica produces the corrin ring only under anaerobic conditions, but it can form “complete” corrinoids aerobically by importing an “incomplete” corrinoid, such as cobinamide (Cbi), and adding appropriate α- and β-axial ligands. Under aerobic conditions, S. enterica performs the corrinoid-dependent degradation of ethanolamine if given vitamin B12, but it can make B12 from exogenous Cbi only if DMB is also provided. Mutants isolated for their ability to degrade ethanolamine without added DMB converted Cbi to pseudo-B12 cofactors (having adenine as an α-axial ligand). The mutations cause an increase in the level of free adenine and install adenine (instead of DMB) as an α-ligand. When DMB is provided to these mutants, synthesis of pseudo-B12 cofactors ceases and B12 cofactors are produced, suggesting that DMB regulates production or incorporation of free adenine as an α-ligand. Wild-type cells make pseudo-B12 cofactors during aerobic growth on propanediol plus Cbi and can use pseudo-vitamin B12 for all of their corrinoid-dependent enzymes. Synthesis of coenzyme pseudo-B12 cofactors requires the same enzymes (CobT, CobU, CobS, and CobC) that install DMB in the formation of coenzyme B12. Models are described for the mechanism and control of α-axial ligand installation.

scholarly journals Mapping the genetic landscape of biomineralization in Magnetospirillum magneticum AMB-1 with RB-Tnseq

2021 ◽  
Author(s):  
Hayley C McCausland ◽  
Kelly M Wetmore ◽  
Adam P. Arkin ◽  
Arash Komeili
Keyword(s):  
Essential Gene ◽  
Growth Conditions ◽  
Wild Type ◽  
Anaerobic Conditions ◽  
High Iron ◽  
Genetic Landscape ◽  
Transposon Insertions ◽  
Magnetospirillum Magneticum ◽  
Markerless Deletion

Magnetotactic bacteria (MTB) are a phylogenetically diverse group of bacteria remarkable for their ability to biomineralize magnetite (Fe3O4) or greigite (Fe3S4) in organelles called magnetosomes. The majority of genes required for magnetosome formation are encoded by a magnetosome gene island (MAI). Here, we conducted random barcoded transposon mutagenesis (RB-TnSeq) in Magnetospirillum magneticum AMB-1 to identify the global genetic requirements for magnetosome formation under different growth conditions. We generated a library of 184,710 unique strains in a wild-type background, generating ~34 mutant strains for each gene. RB-TnSeq also allowed us to determine the essential gene set of AMB-1 under standard laboratory growth conditions. To pinpoint novel genes that are important for magnetosome formation, we subjected the library to magnetic selection screens in varied growth conditions. We compared biomineralization in standard growth conditions to biomineralization in high iron and anaerobic conditions, respectively. Strains with transposon insertions in the MAI gene mamT had an exacerbated biomineralization defect under both high iron and anerobic conditions compared to standard conditions, adding to our knowledge of the role of MamT in magnetosome formation. Mutants in amb4151, a gene outside of the MAI, are more magnetic than wild-type cells under anaerobic conditions. All three of these phenotypes were validated by creating a markerless deletion strain of the gene and evaluating with TEM imaging. Overall, our results indicate that growth conditions affect which genes are required for biomineralization and that some MAI genes may have more nuanced functions than was previously understood.

scholarly journals The cobY Gene of the Archaeon Halobacterium sp. Strain NRC-1 Is Required for De Novo Cobamide Synthesis

2003 ◽  
Vol 185 (1) ◽  
pp. 311-316 ◽  
Author(s):  
J. D. Woodson ◽  
R. F. Peck ◽  
M. P. Krebs ◽  
J. C. Escalante-Semerena
Keyword(s):  
Null Allele ◽  
De Novo ◽  
Growth Conditions ◽  
Wild Type ◽  
Aerobic Growth ◽  
Reading Frame ◽  
Nutritional Analysis ◽  
Extremely Halophilic Archaeon ◽  
Primary Amino ◽  
Auxotrophic Requirement

ABSTRACT Genetic and nutritional analyses of mutants of the extremely halophilic archaeon Halobacterium sp. strain NRC-1 showed that open reading frame (ORF) Vng1581C encodes a protein with nucleoside triphosphate:adenosylcobinamide-phosphate nucleotidyltransferase enzyme activity. This activity was previously associated with the cobY gene of the methanogenic archaeon Methanobacterium thermoautotrophicum strain ΔH, but no evidence was obtained to demonstrate the direct involvement of this protein in cobamide biosynthesis in archaea. Computer analysis of the Halobacterium sp. strain NRC-1 ORF Vng1581C gene and the cobY gene of M. thermoautotrophicum strain ΔH showed the primary amino acid sequence of the proteins encoded by these two genes to be 35% identical and 48% similar. A strain of Halobacterium sp. strain NRC-1 carrying a null allele of the cobY gene was auxotrophic for cobinamide-GDP, a known intermediate of the late steps of cobamide biosynthesis. The auxotrophic requirement for cobinamide-GDP was corrected when a wild-type allele of cobY was introduced into the mutant strain, demonstrating that the lack of cobY function was solely responsible for the observed block in cobamide biosynthesis in this archaeon. The data also show that Halobacterium sp. strain NRC-1 possesses a high-affinity transport system for corrinoids and that this archaeon can synthesize cobamides de novo under aerobic growth conditions. To the best of our knowledge this is the first genetic and nutritional analysis of cobalamin biosynthetic mutants in archaea.

scholarly journals Regulation of early enzymes of ergosterol biosynthesis in Saccharomyces cerevisiae

1986 ◽  
Vol 240 (2) ◽  
pp. 541-547 ◽  
Author(s):  
M Servouse ◽  
F Karst
Keyword(s):  
Enzyme Activities ◽  
Auxotrophic Mutant ◽  
Growth Conditions ◽  
Ergosterol Biosynthesis ◽  
Wild Type ◽  
Aerobic Growth ◽  
Hmg Coa Reductase ◽  
Mutant Strains ◽  
Coa Reductase ◽  
Mutant Cells

In order to determine the regulation mechanisms of ergosterol biosynthesis in yeast, we developed growth conditions leading to high or limiting ergosterol levels in wild type and sterol-auxotrophic mutant strains. An excess of sterol is obtained in anaerobic sterol-supplemented cultures of mutant and wild type strains. A low sterol level is obtained in aerobic growth conditions in mutant strains cultured with optimal sterol supplementation and in wild type strain deprived of pantothenic acid, as well as in anaerobic cultures without sterol supplementation. Measurements of the specific activities of acetoacetyl-CoA thiolase, HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) synthase and HMG-CoA reductase (the first three enzymes of the pathway), show that in cells deprived of ergosterol, acetoacetyl-CoA thiolase and HMG-CoA synthase are generally increased. In an excess of ergosterol, in anaerobiosis, the same enzymes are strongly decreased. A 5-10-fold decrease is observed for acetoacetyl-CoA thiolase and HMG-CoA synthase. In contrast, HMG-CoA reductase is only slightly affected by these conditions. These results show that ergosterol could regulate its own synthesis, at least partially, by repression of the first two enzymes of the pathway. Our results also show that exogenous sterols, even if strongly incorporated by auxotrophic mutant cells, cannot suppress enzyme activities in aerobic growth conditions. Measurement of specific enzyme activities in mutant cells also revealed that farnesyl pyrophosphate thwarts the enhancement of the activities of the two first enzymes.

scholarly journals Starvation Response of Saccharomyces cerevisiae Grown in Anaerobic Nitrogen- or Carbon-Limited Chemostat Cultures

2005 ◽  
Vol 71 (6) ◽  
pp. 3007-3013 ◽  
Author(s):  
Elisabeth Thomsson ◽  
Lena Gustafsson ◽  
Christer Larsson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nitrogen Starvation ◽  
Growth Conditions ◽  
Carbon Starvation ◽  
Atp Content ◽  
Anaerobic Conditions ◽  
Uptake Capacity ◽  
Starvation Response ◽  
Fermentative Capacity ◽  
Chemostat Cultures

ABSTRACT Anaerobic starvation conditions are frequent in industrial fermentation and can affect the performance of the cells. In this study, the anaerobic carbon or nitrogen starvation response of Saccharomyces cerevisiae was investigated for cells grown in anaerobic carbon or nitrogen-limited chemostat cultures at a dilution rate of 0.1 h−1 at pH 3.25 or 5. Lactic or benzoic acid was present in the growth medium at different concentrations, resulting in 16 different growth conditions. At steady state, cells were harvested and then starved for either carbon or nitrogen for 24 h under anaerobic conditions. We measured fermentative capacity, glucose uptake capacity, intracellular ATP content, and reserve carbohydrates and found that the carbon, but not the nitrogen, starvation response was dependent upon the previous growth conditions. All cells subjected to nitrogen starvation retained a large portion of their initial fermentative capacity, independently of previous growth conditions. However, nitrogen-limited cells that were starved for carbon lost almost all their fermentative capacity, while carbon-limited cells managed to preserve a larger portion of their fermentative capacity during carbon starvation. There was a positive correlation between the amount of glycogen before carbon starvation and the fermentative capacity and ATP content of the cells after carbon starvation. Fermentative capacity and glucose uptake capacity were not correlated under any of the conditions tested. Thus, the successful adaptation to sudden carbon starvation requires energy and, under anaerobic conditions, fermentable endogenous resources. In an industrial setting, carbon starvation in anaerobic fermentations should be avoided to maintain a productive yeast population.

scholarly journals Genomic Analyses of Anaerobically Induced Genes in Saccharomyces cerevisiae: Functional Roles of Rox1 and Other Factors in Mediating the Anoxic Response

2002 ◽  
Vol 184 (1) ◽  
pp. 250-265 ◽  
Author(s):  
Kurt E. Kwast ◽  
Liang-Chuan Lai ◽  
Nina Menda ◽  
David T. James ◽  
Susanne Aref ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Large Fraction ◽  
Growth Conditions ◽  
Oxygen Availability ◽  
Dna Arrays ◽  
Wild Type ◽  
Anaerobic Conditions ◽  
Induced Genes

ABSTRACT DNA arrays were used to investigate the functional role of Rox1 in mediating acclimatization to anaerobic conditions in Saccharomyces cerevisiae. Multiple growth conditions for wild-type and rox1 null strains were used to identify open reading frames with a statistically robust response to this repressor. These results were compared to those obtained for a wild-type strain in response to oxygen availability. Transcripts of nearly one-sixth of the genome were differentially expressed (P < 0.05) with respect to oxygen availability, the majority (>65%) being down-regulated under anoxia. Of the anaerobically induced genes, about one-third (106) contain putative Rox1-binding sites in their promoters and were significantly (P < 0.05) up-regulated in the rox1 null strains under aerobiosis. Additional promoter searches revealed that nearly one-third of the anaerobically induced genes contain an AR1 site(s) for the Upc2 transcription factor, suggesting that Upc2 and Rox1 regulate the majority of anaerobically induced genes in S. cerevisiae. Functional analyses indicate that a large fraction of the anaerobically induced genes are involved in cell stress (∼1/3), cell wall maintenance (∼1/8), carbohydrate metabolism (∼1/10), and lipid metabolism (∼1/12), with both Rox1 and Upc2 predominating in the regulation of this latter group and Upc2 predominating in cell wall maintenance. Mapping the changes in expression of functional regulons onto metabolic pathways has provided novel insight into the role of Rox1 and other trans-acting factors in mediating the physiological response of S. cerevisiae to anaerobic conditions.

scholarly journals Alteration of a yeast SH3 protein leads to conditional viability with defects in cytoskeletal and budding patterns.

1993 ◽  
Vol 13 (8) ◽  
pp. 5070-5084 ◽  
Author(s):  
F Bauer ◽  
M Urdaci ◽  
M Aigle ◽  
M Crouzet
Keyword(s):  
Site Selection ◽  
Nitrogen Starvation ◽  
Growth Conditions ◽  
Selection Mechanism ◽  
Wild Type ◽  
Carbon And Nitrogen ◽  
Nutritional Deprivation ◽  
Significant Homology ◽  
Mutant Strains ◽  
Product Displays

Mutations in genes necessary for survival in stationary phase were isolated to understand the ability of wild-type Saccharomyces cerevisiae to remain viable during prolonged periods of nutritional deprivation. Here we report results concerning one of these mutants, rvs167, which shows reduced viability and abnormal cell morphology upon carbon and nitrogen starvation. The mutant exhibits the same response when cells are grown in high salt concentrations and other unfavorable growth conditions. The RVS167 gene product displays significant homology with the Rvs161 protein and contains a SH3 domain at the C-terminal end. Abnormal actin distribution is associated with the mutant phenotype. In addition, while the budding pattern of haploid strains remains axial in standard growth conditions, the budding pattern of diploid mutant strains is random. The gene RVS167 therefore could be implicated in cytoskeletal reorganization in response to environmental stresses and could act in the budding site selection mechanism.

New highly efficient coulometric cell with homogenous potential distribution on the working electrode

1986 ◽  
Vol 51 (3) ◽  
pp. 636-642
Author(s):  
Michal Németh ◽  
Ján Mocák
Keyword(s):  
Chemical Reactions ◽  
Potential Distribution ◽  
Anaerobic Conditions ◽  
Highly Efficient ◽  
Working Electrode ◽  
Constant Potential ◽  
Quantitative Analyses ◽  
Mechanism And Kinetics ◽  
Kinetics Of

A highly efficient coulometric cell was designed and constructed, ensuring a constant potential over the whole surface of the working electrode and suitable for very rapid electrolysis. It consists of concentric cylindrical Teflon parts; also the working and auxiliary electrodes are cylindrical and concentric. Electrolysis can be carried out under anaerobic conditions. Functioning of the cell was tested on the oxidation of hexacyanoferrate(II) and chlorpromazine and reduction of hexacyanoferrate(III). The new cell is suitable for routine quantitative analyses and in studying the mechanism and kinetics of moderately rapid chemical reactions.

scholarly journals The Lipid Lysyl-Phosphatidylglycerol Is Present in Membranes of Rhizobium tropici CIAT899 and Confers Increased Resistance to Polymyxin B Under Acidic Growth Conditions

2007 ◽  
Vol 20 (11) ◽  
pp. 1421-1430 ◽  
Author(s):  
Christian Sohlenkamp ◽  
Kanaan A. Galindo-Lagunas ◽  
Ziqiang Guan ◽  
Pablo Vinuesa ◽  
Sally Robinson ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Minimal Medium ◽  
Polymyxin B ◽  
Growth Conditions ◽  
Membrane Lipid ◽  
Low Ph ◽  
Wild Type ◽  
Rhizobium Tropici ◽  
Gram Negative ◽  
Inducible Genes

Lysyl-phosphatidylglycerol (LPG) is a well-known membrane lipid in several gram-positive bacteria but is almost unheard of in gram-negative bacteria. In Staphylococcus aureus, the gene product of mprF is responsible for LPG formation. Low pH-inducible genes, termed lpiA, have been identified in the gram-negative α-proteobacteria Rhizobium tropici and Sinorhizobium medicae in screens for acid-sensitive mutants and they encode homologs of MprF. An analysis of the sequenced bacterial genomes reveals that genes coding for homologs of MprF from S. aureus are present in several classes of organisms throughout the bacterial kingdom. In this study, we show that the expression of lpiA from R. tropici in the heterologous hosts Escherichia coli and Sinorhizobium meliloti causes formation of LPG. A wild-type strain of R. tropici forms LPG (about 1% of the total lipids) when the cells are grown in minimal medium at pH 4.5 but not when grown in minimal medium at neutral pH or in complex tryptone yeast (TY) medium at either pH. LPG biosynthesis does not occur when lpiA is deleted and is restored upon complementation of lpiA-deficient mutants with a functional copy of the lpiA gene. When grown in the low-pH medium, lpiA-deficient rhizobial mutants are over four times more susceptible to the cationic peptide polymyxin B than the wild type.

Sign in / Sign up

Export Citation Format

Share Document