SEARCH · PubMed Health

Results for “microbial eukaryotes”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed1982

Perspectives in molecular mutagenesis.

The models and paradigms that underlie a vigorously developing science may tend to stifle progress or may serve to sharpen the knife edge of paradox. Working out mutagenic mechanisms is a conceptually and technologically demanding task, and we are accumulating an increasingly uncomfortable number of experimental and theoretical inconsistencies. First, there continue to be widespread difficulties in specifying the chemical nature of mutagenic DNA alterations, both because of the multitude of DNA reaction products induced by many mutagens and because of the intrinsic rarity of most mutational responses. For instance, alkylation of the 0(6) position of guanine to generate adducts of modest dimensions is widely believed to form the basis for the mutagenic and carcinogenic actions of numerous chemicals. However, while this scheme is supported by in vitro evidence, it has failed to explain why bacteriophages can be thus alkylated in vitro by N-methyl-N'-nitro-N-nitrosoguanidine without the production of mutations, or why microbial eukaryotes alkylated by ethyl methanesulfonate or N-methyl-N'-nitro-N-nitrosoguanidine display no mutagenic response when their "error-prone repair systems" are mutationally inactivated. Second, a base pair is typically mutated at vastly different rates, and with different directional specificities, when it resides at different positions within a gene; whereas very little of this variability is explained by current theories that aim to describe the determinants of fidelity in DNA replication. (Some sizable portion of this variation now appears to depend not only upon neighboring base-pair influences but also upon much more subtle and distant effects). Third, experimental modifications of enzymatic fidelity by means of amino acid substitutions, and perhaps also cation replacements, lead to such a diversity of modified mutation rates as to seriously challenge the ability of any simple theory to organize the experimental observations into a coherent and predictive network.

Alkylation↗

PubMed1979

Yeast chromosomal DNA molecules have strands which are cross-linked at their termini.

The microbial eukaryote Saccharomyces cerevisiae has 18 chromosomes, each consisting of a DNA molecule of 1 x 15 x 10(8) daltons (150 to 2,300 kilobase pairs). Interstand cross-links have now been found in molecules of all sizes by examining the ability of high molecular weight DNA to snap back, i.e., to rapidly renature after denaturation. Experiments in which snap back was assessed for molecules broken by shearing indicate that there are probably two cross-links in each chromosome. Evidence that the cross-links occur at specific sites in the genome was obtained by treating total chromosomal DNA with the endonuclease EcoRI which cleaves the yeast genome into approximately 2,000 discrete fragments. Cross-link containing fragments were separated from fragments without cross-links. This purification resulted in enrichment for about 18 specific fragments. To determine whether the cross-links are terminal or at internal sites in chromosomal DNA, large shear-produced fragments were examined by electron microsopy. With complete denaturation few fragments exhibit the X-shaped single strand configuration expected for internal cross-links. When partially denatured fragments were examined some ends had single strand loops as expected for (AT-rich) cross-linked termini. We propose that a duplex chromosomal DNA molecules have cross-linked termini. We propose that a duplex chromosomal DNA molecule in this eukaryote consists of a continuous, single, self-complementary strand of DNA. This structure has implications for the mechanism of chromosome replication and may be the basis of telomere behavior.

Chromosomes↗

PubMed2005

Computational and comparative analyses of 150 full-length cDNA sequences from the oomycete plant pathogen Phytophthora infestans.

Phytophthora infestans is a devastating phytopathogenic oomycete that causes late blight on tomato and potato. Recent genome sequencing efforts of P. infestans and other Phytophthora species are generating vast amounts of sequence data providing opportunities to unlock the complex nature of pathogenesis. However, accurate annotation of Phytophthora genomes will be a significant challenge. Most of the information about gene structure in these species was gathered from a handful of genes resulting in significant limitations for development of ab initio gene-calling programs. In this study, we collected a total of 150 bioinformatically determined near full-length cDNA (FLcDNA) sequences of P. infestans that were predicted to contain full open reading frame sequences. We performed detailed computational analyses of these FLcDNA sequences to obtain a snapshot of P. infestans gene structure, gauge the degree of sequence conservation between P. infestans genes and those of Phytophthora sojae and Phytophthora ramorum, and identify patterns of gene conservation between P. infestans and various eukaryotes, particularly fungi, for which genome-wide translated protein sequences are available. These analyses helped us to define the structural characteristics of P. infestans genes using a validated data set. We also determined the degree of sequence conservation within the genus Phytophthora and identified a set of fast evolving genes. Finally, we identified a set of genes that are shared between Phytophthora and fungal phytopathogens but absent in animal fungal pathogens. These results confirm that plant pathogenic oomycetes and fungi share virulence components, and suggest that eukaryotic microbial pathogens that share similar lifestyles also share a similar set of genes independently of their phylogenetic relatedness.

Base Composition↗

PubMed2003

Structure of the micronuclear alpha-tubulin gene in the phyllopharyngean ciliate Chilodonella uncinata: implications for the evolution of chromosomal processing.

Ciliates are a group of microbial eukaryotes defined by the presence of dimorphic nuclei-each cell contains both a transcriptionally active macronucleus and a germline micronucleus. During the development of the macronucleus, germline chromosomes are rearranged through extensive fragmentation, removal of internally excised sequences (IESs) and DNA amplification. We have characterized three IESs in the gene that encodes alpha-tubulin in the phyllopharyngean ciliate Chilodonella uncinata. The IESs are located within the coding domain, range in size from 81 to 107 bp, and are flanked by direct repeats that vary in length from 6 to 8 bp. All three IESs are moderately AT-rich and each contains two copies of a conserved sequence motif. These data provide evidence for the existence of IESs in phyllopharyngean ciliates and suggest that IES processing in C. uncinata may rely on a novel cis-acting sequence. Comparisons of the IESs in C. uncinata with those of 'model' ciliates-Paramecium, Tetrahymena, Euplotes, Oxytricha and Stylonychia-reveal considerable variation in chromosomal processing among ciliates.

Animals↗

PubMed2005

Using the transcriptome to annotate the genome revisited: application of massively parallel signature sequencing (MPSS).

Transcriptome analysis can provide useful data for refining genome sequence annotation. Application of massively parallel signature sequencing (MPSS) revealed reproducible transcription, in multiple MPSS cycles, from 73% of computationally predicted genes in the Theileria parva schizont lifecycle stage. Signatures spanning consecutive exons confirmed 142 predicted introns. MPSS identified 83 putative genes, >100 codons overlooked by annotation software, and 139 potentially incorrect gene models (with either truncated ORFs or overlooked exons) by interfacing signature locations with stop codon maps. Twenty representative models were confirmed as likely to be incorrect using reverse transcription PCR amplification from independent schizont cDNA preparations. More than 50% of the 60 putative single copy genes in T. parva that were absent from the genome of the closely related T. annulata had MPSS signatures. This study illustrates the utility of MPSS for improving annotation of small, gene-rich microbial eukaryotic genomes.

Animals↗

PubMed2006

Hydrogenosomal succinyl-CoA synthetase from the rumen-dwelling fungus Neocallimastix patriciarum; an energy-producing enzyme of mitochondrial origin.

Hydrogenosomes are hydrogen-producing organelles that are related to mitochondria and found in a variety of evolutionarily unrelated anaerobic microbial eukaryotes. Similar to classic mitochondria, hydrogenosomes contain the enzyme catalyzing the only reaction of the citric acid cycle directly producing energy; succinyl-CoA synthetase. We have isolated and characterized the genes encoding both subunits of this enzyme from the anaerobic chytrid fungus Neocallimastix patriciarum, a model organism in hydrogenosome research. Both subunits contain all characteristic features of this enzyme, including predicted hydrogenosomal targeting signals. Phylogenetic analyses of succinyl-CoA synthetase clearly indicate its mitochondrial ancestry, both by affiliation with mitochondrially localized fungal homologues and by the sisterhood of the eukaryotic succinyl-CoA synthetase clade with alpha-proteobacteria. Our analyses of the Trichomonas vaginalis SCS sequences also confirmed the mitochondrial affiliation of these hydrogenosomal enzymes, in contrast to previous results. While both hydrogenosomal and mitochondrial succinyl-CoA synthetase homologues have been identified, no succinyl-CoA synthetase proteins were identifiable in taxa possessing another mitochondrially derived organelle, the mitosome. Our analyses further confirm the mitochondrial ancestry of the Neocallimastix hydrogenosome and sheds light upon the stepwise process by which mitochondria evolve into alternate forms of the organelle.

Amino Acid Sequence↗

PubMed2006

A multiple PCR-primer approach to access the microeukaryotic diversity in environmental samples.

The Cariaco Basin off the Venezuelan coast in the Caribbean Sea is the world's largest truly marine body of anoxic water. The first rRNA survey of microbial eukaryotes in this environment revealed a number of novel lineages, but sampled only a fraction of the entire diversity. The goal of this study was to significantly improve recovery of protistan rRNA from the Basin. This was achieved by a systematic application of multiple PCR primer sets and substantially larger sequencing efforts. We focused on the most diverse habitat in the basin, anoxic waters approximately 100m below the oxic-anoxic interface, and detected novel lineages that escaped the single PCR primer approach. All clones obtained proved unique. A 99% sequence similarity cut-off value combined these clones into operational taxonomic units (OTUs), over 75% of which proved novel. Some of these OTUs form deep branches within established protistan groups. Others signify discovery of novel protistan lineages that appear unrelated to any known microeukaryote. Surprisingly, even this large-scale multi-primer rRNA approach still missed a substantial part of the samples' rRNA diversity. The overlap between the species lists obtained with different primers is low, with only 4% of OTUs shared by all three libraries, and the number of species detected only once is large (55%). This strongly indicates that, at least in anoxic environments, protistan diversity may be much larger than is commonly thought. A single sample appears to contain thousands of largely novel protistan species. Multiple PCR primer combinations may be needed to capture these species.

Animals↗

PubMed2003

Crystal structure of shikimate 5-dehydrogenase (SDH) bound to NADP: insights into function and evolution.

The crystal structure of Methanococcus jannaschii shikimate 5-dehydrogenase (MjSDH) bound to the cofactor nicotinamide adenine dinucleotide phosphate (NADP) has been determined at 2.35 A resolution. Shikimate 5-dehydrogenase (SDH) is responsible for NADP-dependent catalysis of the fourth step in shikimate biosynthesis, which is essential for aromatic amino acid metabolism in bacteria, microbial eukaryotes, and plants. The structure of MjSDH is a compact alpha/beta sandwich with two distinct domains, responsible for binding substrate and the NADP cofactor, respectively. A phylogenetically conserved deep cleft on the protein surface corresponds to the enzyme active site. The structure reveals a topologically new domain fold within the N-terminal segment of the polypeptide chain, which binds substrate and supports dimerization. Insights gained from homology modeling and sequence/structure comparisons suggest that the SDHs represent a unique class of dehydrogenases. The structure provides a framework for further investigation to discover and develop novel inhibitors targeting this essential enzyme.

Alcohol Oxidoreductases↗

PubMed1998

Structure of dehydroquinate synthase reveals an active site capable of multistep catalysis.

Dehydroquinate synthase (DHQS) has long been regarded as a catalytic marvel because of its ability to perform several consecutive chemical reactions in one active site. There has been considerable debate as to whether DHQS is actively involved in all these steps, or whether several steps occur spontaneously, making DHQS a spectator in its own mechanism. DHQS performs the second step in the shikimate pathway, which is required for the synthesis of aromatic compounds in bacteria, microbial eukaryotes and plants. This enzyme is a potential target for new antifungal and antibacterial drugs as the shikimate pathway is absent from mammals and DHQS is required for pathogen virulence. Here we report the crystal structure of DHQS, which has several unexpected features, including a previously unobserved mode for NAD+-binding and an active-site organization that is surprisingly similar to that of alcohol dehydrogenase, in a new protein fold. The structure reveals interactions between the active site and a substrate-analogue inhibitor, which indicate how DHQS can perform multistep catalysis without the formation of unwanted by-products.

Alcohol Oxidoreductases↗

PubMed1996

Comparative analysis of the QUTR transcription repressor protein and the three C-terminal domains of the pentafunctional AROM enzyme.

The AROM protein is a pentadomain protein catalysing steps two to six in the prechorismate section of the shikimate pathway in microbial eukaryotes. On the basis of amino acid sequence alignments and the properties of mutants unable to utilize quinic acid as a carbon source, the AROM protein has been proposed to be homologous throughout its length with the proteins regulating transcription of the genes necessary for quinate catabolism. The QUTR transcription repressor protein has been proposed to be homologous with the three C-terminal domains of the AROM protein and one-fifth of the penultimate N-terminal domain. We report here the results of experiments designed to overproduce the QUTR and AROM proteins and their constituent domains in Escherichia coli, the purpose being to facilitate domain purification and (in the case of AROM), complementation of E. coli aro- mutations in order to probe the degree to which individual domains are stable and functional. The 3-dehydroquinate dehydratase domain of the AROM protein and the 3-dehydroquinate dehydratase-like domain of the QUTR spectroscopy and fluorescence emission spectroscopy. The CD spectra were found to be virtually superimposable. The fluorescence emission spectra of both domains had the signal from the tryptophan residues almost completely quenched, giving a tyrosine-dominated spectrum for both the AROM- and QUTR-derived domains. This unexpected observation was demonstrated to be due to a highly unusual environment provided by the tertiary structure, as addition of the denaturant guanidine hydrochloride gave a typical tryptophan-dominated spectrum for both domains. The spectroscopy experiments had the potential to refute the biologically-based proposal for a common origin for the AROM and QUTR proteins; however, the combined biophysical data are consistent with the hypothesis. We have previously reported that the AROM dehydroquinate synthase and 3-dehydroquinate dehydratase are stable and functional as individual domains, but that the 5-enol-pyruvylshikimate-3-phosphate synthase is only active as part of the complete AROM protein or as a bi-domain fragment with dehydroquinate synthase. Here we report that the aromA gene (encoding the AROM protein) of Aspergillus nidulans contains a 53 nt intron in the extreme C-terminus of the shikimate dehydrogenase domain. This finding accounts for the previously reported observation that the AROM protein was unable to complement aroE- (lacking shikimate dehydrogenase) mutations in E. coli. When the intron is removed the correctly translated AROM protein is able to complement the E. coli aroE- mutation. An AROM-derived shikimate dehydrogenase domain is, however, non-functional, but function is restored in a bi-domain protein with e-dehydroquinate dehydratase. This interaction is not entirely specific, as substitution of the 3-dehydroquinate dehydratase domain with the glutathione S-transferase protein partially restores enzyme activity. Similarly an AROM-derived shikimate kinase domain is non-functional, but is functional as part of the complete AROM protein, or as a bi-domain protein with 3-dehydroquinate dehydratase.

Alcohol Oxidoreductases↗

PubMed2002

Promiscuity in ligand-binding: The three-dimensional structure of a Piromyces carbohydrate-binding module, CBM29-2, in complex with cello- and mannohexaose.

Carbohydrate-protein recognition is central to many biological processes. Enzymes that act on polysaccharide substrates frequently contain noncatalytic domains, "carbohydrate-binding modules" (CBMs), that target the enzyme to the appropriate substrate. CBMs that recognize specific plant structural polysaccharides are often able to accommodate both the variable backbone and the side-chain decorations of heterogeneous ligands. "CBM29" modules, derived from a noncatalytic component of the Piromyces equi cellulase/hemicellulase complex, provide an example of this selective yet flexible recognition. They discriminate strongly against some polysaccharides while remaining relatively promiscuous toward both beta-1,4-linked manno- and cello-oligosaccharides. This feature may reflect preferential, but flexible, targeting toward glucomannans in the plant cell wall. The three-dimensional structure of CBM29-2 and its complexes with cello- and mannohexaose reveal a beta-jelly-roll topology, with an extended binding groove on the concave surface. The orientation of the aromatic residues complements the conformation of the target sugar polymer while accommodation of both manno- and gluco-configured oligo- and polysaccharides is conferred by virtue of the plasticity of the direct interactions from their axial and equatorial 2-hydroxyls, respectively. Such flexible ligand recognition targets the anaerobic fungal complex to a range of different components in the plant cell wall and thus plays a pivotal role in the highly efficient degradation of this composite structure by the microbial eukaryote.

Binding Sites↗

PubMed2025

Unisexual reproduction in the global human fungal pathogen Cryptococcus neoformans.

The human fungal pathogen Cryptococcus species complex (encompassing Cryptococcus neoformans, Cryptococcus deneoformans, and the Cryptococcus gattii species complexes) exhibits diversity in sexual reproduction, including α-a mating, pseudosexual reproduction, as well as unisexual reproduction initiated from a single isolate or between isolates of the same mating type. A central conundrum is that while most Cryptococcus natural populations exhibit significant α mating-type bias, genetic and genomic analyses show recombination occurs in nature. The discovery of unisexual reproduction in C. deneoformans provided insight; however, thus far, unisexual reproduction has never been directly observed in the predominant global pathogenic species C. neoformans. Here, we provide evidence that mutating the RIC8 gene, which encodes a conserved guanine nucleotide exchange factor (GEF) involved in both chaperoning and activating Gα proteins, enables unisexual reproduction in C. neoformans. Additionally, we show that genetic variation in the natural population promotes unisexual reproduction, and unisexual reproduction in C. neoformans involves canonical meiotic recombination. Finally, we found that deletion of both GPA2 and GPA3 in the MATα background leads to self-filamentation without sporulation, suggesting that differential modulation of the Gα proteins, likely involving Ric8, could underlie the switch between different modes of sexual reproduction in Cryptococcus. Our study further highlights that the highly conserved Ric8 GEF can act as an important regulator of cellular development in response to environmental stimuli and could modulate sexual reproduction in nature. We hypothesize that unisexual reproduction occurs much more frequently in nature than currently appreciated, and possibly in other fungi and microbial eukaryotes as well.

Cryptococcus neoformans↗

PubMed2005

Mitogen activated protein kinases of Aspergillus fumigatus.

In microbial eukaryotes, mitogen activated protein kinase (MAPK) pathways play a pivotal role in regulating cellular physiology. In fungi MAPK pathways have established functions in mating-pheromone responses, maintaining cell wall integrity, responding to changes in osmolarity and nutrient sensing. We have been studying MAPK functions in the human pathogenic fungus Aspergillus fumigatus. The genome of A. fumigatus has four MAPK genes, sakA/hogA, mpkA, mpkB and mpkC. Deletion of the sakA gene produces a strain that does not correctly regulate conidial germination, sense environmental nitrogen or responds to hypertonic stress. The function of the remaining MAPK genes is still under investigation, but by analogy to work in other filamentous fungi, we speculate as to their possible functions in A. fumigatus.

Aspergillus fumigatus↗

PubMed2004

Characterization of the Saccharomyces cerevisiae Fol1 protein: starvation for C1 carrier induces pseudohyphal growth.

Tetrahydrofolate (vitamin B9) and its folate derivatives are essential cofactors in one-carbon (C1) transfer reactions and absolutely required for the synthesis of a variety of different compounds including methionine and purines. Most plants, microbial eukaryotes, and prokaryotes synthesize folate de novo. We have characterized an important enzyme in this pathway, the Saccharomyces cerevisiae FOL1 gene. Expression of the budding yeast gene FOL1 in Escherichia coli identified the folate biosynthetic enzyme activities dihydroneopterin aldolase (DHNA), 7,8-dihydro-6-hydroxymethylpterin-pyrophosphokinase (HPPK), and dihydropteroate synthase (DHPS). All three enzyme activities were also detected in wild-type yeast strains, whereas fol1Delta deletion strains only showed background activities, thus demonstrating that Fol1p catalyzes three sequential steps of the tetrahydrofolate biosynthetic pathway and thus is the central enzyme of this pathway, which starting from GTP consists of seven enzymatic reactions in total. Fol1p is exclusively localized to mitochondria as shown by fluorescence microscopy and immune electronmicroscopy. FOL1 is an essential gene and the nongrowth phenotype of the fol1 deletion leads to a recessive auxotrophy for folinic acid (5'-formyltetrahydrofolate). Growth of the fol1Delta deletion strain on folinic acid-supplemented rich media induced a dimorphic switch with haploid invasive and filamentous pseudohyphal growth in the presence of glucose and ammonium, which are known suppressors of filamentous and invasive growth. The invasive growth phenotype induced by the depletion of C1 carrier is dependent on the transcription factor Ste12p and the flocullin/adhesin Flo11p, whereas the filamentation phenotype is independent of Ste12p, Tec1p, Phd1p, and Flo11p, suggesting other signaling pathways as well as other adhesion proteins.

Aldehyde-Lyases↗

PubMed2026

Biocontrol potential and molecular basis of predation in a marine raptorial ciliate.

Predator-prey interactions are widespread across organisms and are key drivers of morphological and behavioral evolution. Despite this, predation remains poorly understood among microbial eukaryotes, mostly due to the absence of a tractable experimental system that allows quantitative, reproducible investigation. This study establishes the marine raptorial ciliate Chaenea vorax as a highly efficient predator, with Rosenzweig-MacArthur model simulations based on predation data showing that only a few dozen individuals can eliminate the vast majority of the facultatively pathogenic ciliate Uronema marinum within 1-2 days, providing a quantitative basis for developing predator-based biocontrol strategies in aquaculture. Genomic analysis shows that C. vorax possesses a highly fragmented macronuclear genome enriched with predation-related pathways, including calcium-mediated contractility, cellular proteolysis, toxin expulsion systems, among others. Transcriptomic profiling during predation events further demonstrates significant upregulation of genes involved in cytoskeletal remodeling, proteolytic activity, and cellular detoxification. Evolutionary analyses suggest that C. vorax has an extremely long evolutionary history, exceptionally high nucleotide diversity even among ciliates, and gene family expansions linked to predatory adaptation. Although the prey possesses certain defensive mechanisms (e.g. trichocysts), these are largely ineffective against short-term predation in closed aquatic environments. These findings provide fundamental insights into the molecular basis of predation in ciliates and suggest the potential utility of C. vorax in biocontrol applications targeting pathogenic ciliates.

Ciliophora↗

PubMed2004

A functional screen identifies lateral transfer of beta-glucuronidase (gus) from bacteria to fungi.

Lateral gene transfer (LGT) from prokaryotes to microbial eukaryotes is usually detected by chance through genome-sequencing projects. Here, we explore a different, hypothesis-driven approach. We show that the fitness advantage associated with the transferred gene, typically invoked only in retrospect, can be used to design a functional screen capable of identifying postulated LGT cases. We hypothesized that beta-glucuronidase (gus) genes may be prone to LGT from bacteria to fungi (thought to lack gus) because this would enable fungi to utilize glucuronides in vertebrate urine as a carbon source. Using an enrichment procedure based on a glucose-releasing glucuronide analog (cellobiouronic acid), we isolated two gus(+) ascomycete fungi from soils (Penicillium canescens and Scopulariopsis sp.). A phylogenetic analysis suggested that their gus genes, as well as the gus genes identified in genomic sequences of the ascomycetes Aspergillus nidulans and Gibberella zeae, had been introgressed laterally from high-GC gram(+) bacteria. Two such bacteria (Arthrobacter spp.), isolated together with the gus(+) fungi, appeared to be the descendants of a bacterial donor organism from which gus had been transferred to fungi. This scenario was independently supported by similar substrate affinities of the encoded beta-glucuronidases, the absence of introns from fungal gus genes, and the similarity between the signal peptide-encoding 5' extensions of some fungal gus genes and the Arthrobacter sequences upstream of gus. Differences in the sequences of the fungal 5' extensions suggested at least two separate introgression events after the divergence of the two main Euascomycete classes. We suggest that deposition of glucuronides on soils as a result of the colonization of land by vertebrates may have favored LGT of gus from bacteria to fungi in soils.

Amino Acid Sequence↗

PubMed2006

Genome architecture drives protein evolution in ciliates.

Studies of microbial eukaryotes have been pivotal in the discovery of biological phenomena, including RNA editing, self-splicing RNA, and telomere addition. Here we extend this list by demonstrating that genome architecture, namely the extensive processing of somatic (macronuclear) genomes in some ciliate lineages, is associated with elevated rates of protein evolution. Using newly developed likelihood-based procedures for studying molecular evolution, we investigate 6 genes to compare 1) ciliate protein evolution to that of 3 other clades of eukaryotes (plants, animals, and fungi) and 2) protein evolution in ciliates with extensively processed macronuclear genomes to that of other ciliate lineages. In 5 of the 6 genes, ciliates are estimated to have a higher ratio of nonsynonymous/synonymous substitution rates, consistent with an increase in the rate of protein diversification in ciliates relative to other eukaryotes. Even more striking, there is a significant effect of genome architecture within ciliates as the most divergent proteins are consistently found in those lineages with the most highly processed macronuclear genomes. We propose a model whereby genome architecture-specifically chromosomal processing, amitosis within macronuclei, and epigenetics-allows ciliates to explore protein space in a novel manner. Further, we predict that examination of diverse eukaryotes will reveal additional evidence of the impact of genome architecture on molecular evolution.

Animals↗

PubMed1989

Factors influencing the haematoporphyrin-sensitized photoinactivation of Candida albicans.

Photosensitizing activity of haematoporphyrin (Hp) on Candida albicans cells is mainly promoted by unbound dye molecules in the bulk aqueous medium. Moreover, the death of photosensitized cells is dependent on the dye concentration, irradiation time, irradiation temperature, and the composition of the growth media. Morphological and biochemical studies indicate that the photoprocess involves an initial limited alteration of the cytoplasmic membrane, which allows the penetration of the dye into the cell with consequent photodamage of intracellular targets. In this respect, the Hp-sensitized photoinactivation of eukaryotic microbial cells differs from that in prokaryotic cells.

Candida albicans↗