scholarly journals CYTOPLASMIC INHERITANCE OF CHLORAMPHENICOL RESISTANCE IN TETRAHYMENA

Genetics ◽  
1973 ◽  
Vol 73 (2) ◽  
pp. 259-272
Author(s):  
Charles T Roberts ◽  
Eduardo Orias
Keyword(s):  
Wild Type Strain ◽  
Genetic Determinant ◽  
Wild Type ◽  
Mitochondrial Localization ◽  
Chloramphenicol Resistance ◽  
Mitochondrial Structure ◽  
Ciliate Species ◽  
And Function ◽  
Cytoplasmic Determinant ◽  
Mutagenized Cell

ABSTRACT Chloramphenicol-resistant mutants of Tetrahymena pyriform's were obtained after mutagenesis with nitrosoguanidine at an estimated frequency of 10-3 mutants per mutagenized cell. The mutants are still partially sensitive to chloramphenicol and have a lowered growth rate, compared to the wild type strain, in rich medium without chloramphenicol. The genetic analysis described here indicates that chloramphenicol resistance is inherited as a cytoplasmic determinant that is not exchanged during conjugation. This represents the first simple cytoplasmic genetic determinant described in this species. A number of arguments favor a mitochondrial localization for this genetic determinant. In addition to the possible utility of such mutants for studies of mitochondrial structure and function in Tetrahymena, analogous mutations might serve as cytoplasmic "tags" in other ciliate species where the results of selfing need to be distinguished from those of outcrossing.

scholarly journals Mycothiol Import by Mycobacterium smegmatis and Function as a Resource for Metabolic Precursors and Energy Production

2007 ◽  
Vol 189 (19) ◽  
pp. 6796-6805 ◽  
Author(s):  
Krzysztof P. Bzymek ◽  
Gerald L. Newton ◽  
Philong Ta ◽  
Robert C. Fahey
Keyword(s):  
Stationary Phase ◽  
Mycobacterium Smegmatis ◽  
Type Strain ◽  
Energy Production ◽  
Wild Type Strain ◽  
Krebs Cycle ◽  
Wild Type ◽  
Suitable Target ◽  
Cysteine Desulfhydrase ◽  
And Function

ABSTRACT Mycothiol ([MSH] AcCys-GlcN-Ins, where Ac is acetyl) is the major thiol produced by Mycobacterium smegmatis and other actinomycetes. Mutants deficient in MshA (strain 49) or MshC (transposon mutant Tn1) of MSH biosynthesis produce no MSH. However, when stationary phase cultures of these mutants were incubated in medium containing MSH, they actively transported it to generate cellular levels of MSH comparable to or greater than the normal content of the wild-type strain. When these MSH-loaded mutants were transferred to MSH-free preconditioned medium, the cellular MSH was catabolized to generate GlcN-Ins and AcCys. The latter was rapidly converted to Cys by a high deacetylase activity assayed in extracts. The Cys could be converted to pyruvate by a cysteine desulfhydrase or used to regenerate MSH in cells with active MshC. Using MSH labeled with [U-14C]cysteine or with [6-3H]GlcN, it was shown that these residues are catabolized to generate radiolabeled products that are ultimately lost from the cell, indicating extensive catabolism via the glycolytic and Krebs cycle pathways. These findings, coupled with the fact the myo-inositol can serve as a sole carbon source for growth of M. smegmatis, indicate that MSH functions not only as a protective cofactor but also as a reservoir of readily available biosynthetic precursors and energy-generating metabolites potentially important under stress conditions. The half-life of MSH was determined in stationary phase cells to be ∼50 h in strains with active MshC and 16 ± 3 h in the MshC-deficient mutant, suggesting that MSH biosynthesis may be a suitable target for drugs to treat dormant tuberculosis.

scholarly journals Campylobacter fetus Uses Multiple Loci for DNA Inversion within the 5′ Conserved Regions ofsap Homologs

2001 ◽  
Vol 183 (22) ◽  
pp. 6654-6661 ◽  
Author(s):  
Zheng-Chao Tu ◽  
Kevin C. Ray ◽  
Stuart A. Thompson ◽  
Martin J. Blaser
Keyword(s):  
Wild Type Strain ◽  
Invertible Element ◽  
Kanamycin Resistance ◽  
Wild Type ◽  
Sequence Analyses ◽  
Chloramphenicol Resistance ◽  
Reading Frame ◽  
Dna Inversion ◽  
Multiple Loci ◽  
Campylobacter Fetus

ABSTRACT Campylobacter fetus cells possess multiple promoterless sap homologs, each capable of expressing a surface layer protein (SLP) by utilizing a unique promoter present on a 6.2-kb invertible element. Each sap homolog includes a 626-bp 5′ conserved region (FCR) with 74 bp upstream and 552 bp within the open reading frame. After DNA inversion, the splice is seamless because the FCRs are identical. In mutant strain 23D:ACA2K101, in whichsapA and sapA2 flanking the invertible element in opposite orientations were disrupted by promoterless chloramphenicol resistance (Cmr) and kanamycin resistance (Kmr) cassettes, respectively, the frequency of DNA inversion is 100-fold lower than that of wild-type strain 23D. To define the roles of a 15-bp inverted repeat (IR) and a Chi-like site (CLS) in the FCR, we mutagenized each upstream of sapA2in 23D:ACA2K101 by introducing NotI andKpnI sites to create strains 23D:ACA2K101N and 23D:ACA2K101K, respectively. Alternatively selecting colonies for Cmr or Kmr showed that mutagenizing the IR or CLS had no apparent effect on the frequency of the DNA inversion. However, mapping the unique NotI or KpnI site in relation to the Cmr or Kmr cassette in the cells that changed phenotype showed that splices occurred both upstream and downstream of the mutated sites. PCR and sequence analyses also showed that the splice could occur in the 425-bp portion of the FCR downstream of the cassettes. In total, these data indicate that C.fetus can use multiple sites within the FCR for itssap-related DNA inversion.

scholarly journals Differential Localization and Function of PB1-F2 Derived from Different Strains of Influenza A Virus

2010 ◽  
Vol 84 (19) ◽  
pp. 10051-10062 ◽  
Author(s):  
Chi-Jene Chen ◽  
Guang-Wu Chen ◽  
Ching-Ho Wang ◽  
Chih-Heng Huang ◽  
Yeau-Ching Wang ◽  
...  
Keyword(s):  
Amino Acid ◽  
Influenza A Virus ◽  
Influenza A ◽  
Amino Acid Sequences ◽  
Wild Type ◽  
Mitochondrial Localization ◽  
Sequence Context ◽  
C Terminus ◽  
Different Strains ◽  
And Function

ABSTRACT PB1-F2 is a viral protein that is encoded by the PB1 gene of influenza A virus by alternative translation. It varies in length and sequence context among different strains. The present study examines the functions of PB1-F2 proteins derived from various human and avian viruses. While H1N1 PB1-F2 was found to target mitochondria and enhance apoptosis, H5N1 PB1-F2, surprisingly, did not localize specifically to mitochondria and displayed no ability to enhance apoptosis. Introducing Leu into positions 69 (Q69L) and 75 (H75L) in the C terminus of H5N1 PB1-F2 drove 40.7% of the protein to localize to mitochondria compared with the level of mitochondrial localization of wild-type H5N1 PB1-F2, suggesting that a Leu-rich sequence in the C terminus is important for targeting of mitochondria. However, H5N1 PB1-F2 contributes to viral RNP activity, which is responsible for viral RNA replication. Lastly, although the swine-origin influenza virus (S-OIV) contained a truncated form of PB1-F2 (12 amino acids [aa]), potential mutation in the future may enable it to contain a full-length product. Therefore, the functions of this putative S-OIV PB1-F2 (87 aa) were also investigated. Although this PB1-F2 from the mutated S-OIV shares only 54% amino acid sequence identity with that of seasonal H1N1 virus, it also increased viral RNP activity. The plaque size and growth curve of the viruses with and without S-OIV PB1-F2 differed greatly. The PB1-F2 protein has various lengths, amino acid sequences, cellular localizations, and functions in different strains, which result in strain-specific pathogenicity. Such genetic and functional diversities make it flexible and adaptable in maintaining the optimal replication efficiency and virulence for various strains of influenza A virus.

scholarly journals Myc Stimulates Nuclearly Encoded Mitochondrial Genes and Mitochondrial Biogenesis

2005 ◽  
Vol 25 (14) ◽  
pp. 6225-6234 ◽  
Author(s):  
Feng Li ◽  
Yunyue Wang ◽  
Karen I. Zeller ◽  
James J. Potter ◽  
Diane R. Wonsey ◽  
...  
Keyword(s):  
Mitochondrial Biogenesis ◽  
Structure And Function ◽  
Wild Type ◽  
Primary Hepatocytes ◽  
Mitochondrial Mass ◽  
Mitochondrial Structure ◽  
Direct Binding ◽  
Rat Fibroblasts ◽  
And Function

ABSTRACT Although several genes involved in mitochondrial function are direct Myc targets, the role of Myc in mitochondrial biogenesis has not been directly established. We determined the effects of ectopic Myc expression or the loss of Myc on mitochondrial biogenesis. Induction of Myc in P493-6 cells resulted in increased oxygen consumption and mitochondrial mass and function. Conversely, compared to wild-type Myc fibroblasts, Myc null rat fibroblasts have diminished mitochondrial mass and decreased number of normal mitochondria. Reconstitution of Myc expression in Myc null fibroblasts partially restored mitochondrial mass and function and normal-appearing mitochondria. Concordantly, we also observed in primary hepatocytes that acute deletion of floxed murine Myc by Cre recombinase resulted in diminished mitochondrial mass in primary hepatocytes. Our microarray analysis of genes responsive to Myc in human P493-6 B lymphocytes supports a role for Myc in mitochondrial biogenesis, since genes involved in mitochondrial structure and function are overrepresented among the Myc-induced genes. In addition to the known direct binding of Myc to many genes involved in mitochondrial structure and function, we found that Myc binds the TFAM gene, which encodes a key transcriptional regulator and mitochondrial DNA replication factor, both in P493-6 lymphocytes with high ectopic MYC expression and in serum-stimulated primary human 2091 fibroblasts with induced endogenous MYC. These observations support a pivotal role for Myc in regulating mitochondrial biogenesis.

scholarly journals THE EFFECTS OF ERYTHROMYCIN AND CHLORAMPHENICOL ON THE ULTRASTRUCTURE OF MITOCHONDRIA IN SENSITIVE AND RESISTANT STRAINS OF PARAMECIUM

1972 ◽  
Vol 54 (1) ◽  
pp. 8-19 ◽  
Author(s):  
A. Adoutte ◽  
M. Balmefrézol ◽  
J. Beisson ◽  
J. André
Keyword(s):  
Wild Type Strain ◽  
Cell Structure ◽  
Mitochondrial Protein ◽  
Wild Type ◽  
Resistance Mutations ◽  
Mitochondrial Structure ◽  
Mutant Strains ◽  
Resistant Strains ◽  
Inherited Mutations ◽  
Good Agreement

The effects on cell structure of 12 hr to 6 days of exposure to erythromycin or chloramphenicol, two antibiotics known to inhibit specifically the mitochondrial protein synthesizing system, have been studied in the ciliate Paramecium aurelia. A wild type strain (sensitive to both antibiotics) and three mutant strains carrying cytoplasmically inherited mutations conferring resistance to one or the other antibiotic have been used In sensitive cells both antibiotics lead to a progressive and profound alteration of mitochondrial structure evidenced by an elongation of the organelle, a considerable decrease in the number of cristae, and the appearance of some abnormal lamellar cristae and of rigid plates of periodic structure. The modifications of cell structure, then, are mainly restricted to mitochondrial cristae. The three resistant mutants studied, on the contrary, retain normal or nearly normal mitochondrial structure in the presence of the antibiotic to which they are resistant. This fact is in good agreement with the postulated location in the mitochondrial DNA of the resistance mutations studied. The results are discussed in the light of present knowledge concerning the function of the mitochondrial protein-synthesizing system.

scholarly journals Secretion and Function of Salmonella SPI-2 Effector SseF Require Its Chaperone, SscB

2004 ◽  
Vol 186 (15) ◽  
pp. 5078-5086 ◽  
Author(s):  
Shipan Dai ◽  
Daoguo Zhou
Keyword(s):  
Type Iii Secretion ◽  
Type Strain ◽  
Wild Type Strain ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Transcriptional Analysis ◽  
Transcriptional Level ◽  
Wild Type ◽  
And Function

ABSTRACT Salmonella strains utilize a type III secretion system for their successful survival and replications inside host cells. SseF is one of the several effector proteins that are required for conferring this survival ability by altering the trafficking of the Salmonella-containing vacuoles. These effector proteins often require appropriate chaperones to maintain their stabilities inside the bacteria. These chaperones are also known to assist the subsequent secretion and translocation of their substrates. We report here that SscB acts as the chaperone for SseF, an effector for the Salmonella pathogenicity island 2 (SPI-2). We found that the sscB gene is required for the formation of Salmonella sp.-induced continuous filaments in epithelial cells. Efficient Salmonella replication in macrophages requires SscB function. Intracellular and secretion levels of SseF are greatly reduced in an sscB mutant strain compared to the wild-type strain. A protein stability assay demonstrated that the half-life of SseF is significantly shortened in the absence of SscB. Transcriptional analysis of the sseF gene showed that the effect of SscB on the SseF level is not at the transcriptional level. A coprecipitation experiment indicated that SscB interacts with SseF. In summary, our results indicate that SscB is a chaperone for SPI-2 effector SseF to facilitate its secretion and function inside the host cells.

scholarly journals Role of EspB in Experimental Human EnteropathogenicEscherichia coli Infection

2000 ◽  
Vol 68 (6) ◽  
pp. 3689-3695 ◽  
Author(s):  
Carol O. Tacket ◽  
Marcelo B. Sztein ◽  
Genevieve Losonsky ◽  
Akio Abe ◽  
B. Brett Finlay ◽  
...  
Keyword(s):  
Host Cell ◽  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Cell Structure ◽  
Wild Type ◽  
Double Blind ◽  
Host Cytoplasm ◽  
And Function

ABSTRACT Enteropathogenic Escherichia coli (EPEC), a leading cause of diarrhea among infants in developing countries, induces dramatic alterations in host cell architecture that depend on a type III secretion system. EspB, one of the proteins secreted and translocated to the host cytoplasm via this system, is required for numerous alterations in host cell structure and function. To determine the role of EspB in virulence, we conducted a randomized, double-blind trial comparing the ability of wild-type EPEC and an isogenic ΔespB mutant strain to cause diarrhea in adult volunteers. Diarrhea developed in 9 of 10 volunteers who ingested the wild-type strain but in only 1 of 10 volunteers who ingested the ΔespB mutant strain. Marked destruction of the microvillous brush border adjacent to adherent organisms was observed in a jejunal biopsy from a volunteer who ingested the wild-type strain but not from two volunteers who ingested the ΔespB mutant strain. Humoral and cell-mediated immune responses to EPEC antigens were stronger among recipients of the wild-type strain. In addition, four of the volunteers who ingested the wild-type strain had lymphoproliferative responses to EspB. These results demonstrate that EspB is a critical virulence determinant of EPEC infections and suggest that EspB contributes to an immune response.

Molecular characterization of protein O-mannosyltransferase and its involvement in cell-wall synthesis in Aspergillus nidulans

Microbiology ◽  
2004 ◽  
Vol 150 (6) ◽  
pp. 1973-1982 ◽  
Author(s):  
Takuji Oka ◽  
Tetsu Hamaguchi ◽  
Yuka Sameshima ◽  
Masatoshi Goto ◽  
Kensuke Furukawa
Keyword(s):  
Cell Wall ◽  
Aspergillus Nidulans ◽  
Protein Modification ◽  
Wild Type Strain ◽  
Wild Type ◽  
Gene Encoding ◽  
And Function ◽  
Encoding Protein

Protein O-glycosylation is essential for protein modification and plays important roles in eukaryotic cells. O-Mannosylation of proteins occurs in the filamentous fungus Aspergillus. The structure and function of the pmtA gene, encoding protein O-d-mannosyltransferase, which is responsible for the initial O-mannosylation reaction in Aspergillus nidulans, was characterized. Disruption of the pmtA gene resulted in the reduction of in vitro protein O-d-mannosyltransferase activity to 6 % of that of the wild-type strain and led to underglycosylation of an extracellular glucoamylase. The pmtA disruptant exhibited abnormal cell morphology and alteration in carbohydrate composition, particularly reduction in the skeletal polysaccharides in the cell wall. The results indicate that PmtA is required for the formation of a normal cell wall in A. nidulans.

scholarly journals Nuclear mutations affecting mitochondrial structure and function in Chlamydomonas.

1977 ◽  
Vol 73 (1) ◽  
pp. 56-77 ◽  
Author(s):  
A Wiseman ◽  
N W Gillham ◽  
J E Boynton
Keyword(s):  
Cytochrome Oxidase ◽  
Oxidase Activity ◽  
Structure And Function ◽  
Class Iii ◽  
Wild Type ◽  
Mitochondrial Ultrastructure ◽  
Cytochrome Oxidase Activity ◽  
Mitochondrial Structure ◽  
Nadh Cytochrome ◽  
And Function

Wild type cells of the green alga Chlamydomonas reinhardtii can grow in the in the dark by taking up and respiring exogenously supplied acetate. Obligate photoautotrophic (dark dier, dk) mutants of this alga have been selected which grow at near wild type rates in the light, but rapidly die when transferred to darkness because of defects in mitochondrial structure and function. In crosses of the dk mutants to wild type, the majority of the mutants are inherited in a mendelian fashion, although two have been isolated which are inherited in a clearly nonmendelian fashion. Nine mendelian dk mutants have been analyzed in detail, and belong to eight different complementation groups representing eight gene loci. These mutants have been tentatively grouped into three classes on the basis of the pleiotropic nature of their phenotypic defects. Mutants in Class I have gross alterations in the ultrastructure of their mitochondrial inner membranes together with deficiencies in cytochrome oxidase and antimycin/rotenone-sensitive NADH-cytochrome c reductase activities. Mutants in Class II have a variety of less severe alterations in mitochondrial ultrastructure and deficiencies in cytochrome oxidase activity. Mutants in Class III have normal or near normal mitochondrial ultrastructure and reduced cytochrome oxidase activity. Eight of the nine mutants show corresponding reductions in cyanide-sensitive respiration.

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