Observations on the theca of the motile phase of free-living and symbiotic isolates of Zooxanthella microadriatica (Freudenthal) comb.nov.

1979 ◽  
Vol 59 (1) ◽  
pp. 195-205 ◽  
Author(s):  
Alfred R. Loeblich ◽  
James L. Sherley
Keyword(s):  
Cell Cycle ◽  
Aqueous Medium ◽  
Chondrus Crispus ◽  
Free Living

A strain of Zooxanthella microadriatica (Freudenthal) comb.nov. has been isolated from decaying Chondrus crispus (L.) Stackh. The ultrastructure of this isolate has been compared to that of Z. microadriatica inhabiting Cassiopea Peron and Lesueur, 1809, sp. In an aqueous medium the cell cycle of both isolates consists of a coccoid non-motile phase alternating with a thecate motile phase.

scholarly journals Phylogenetic analysis of cell-cycle regulatory proteins within the Symbiodiniaceae

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Lucy M. Gorman ◽  
Shaun P. Wilkinson ◽  
Sheila A. Kitchen ◽  
Clinton A. Oakley ◽  
Arthur R. Grossman ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Phylogenetic Position ◽  
Cellular Mechanisms ◽  
Free Living ◽  
Cycle Progression ◽  
Altered Expression ◽  
Cyclin Dependent Kinases ◽  
Cell Cycle Regulatory Proteins ◽  
Cyclin Gene

AbstractIn oligotrophic waters, cnidarian hosts rely on symbiosis with their photosynthetic dinoflagellate partners (family Symbiodiniaceae) to obtain the nutrients they need to grow, reproduce and survive. For this symbiosis to persist, the host must regulate the growth and proliferation of its symbionts. One of the proposed regulatory mechanisms is arrest of the symbiont cell cycle in the G1 phase, though the cellular mechanisms involved remain unknown. Cell-cycle progression in eukaryotes is controlled by the conserved family of cyclin-dependent kinases (CDKs) and their partner cyclins. We identified CDKs and cyclins in different Symbiodiniaceae species and examined their relationship to homologs in other eukaryotes. Cyclin proteins related to eumetazoan cell-cycle-related cyclins A, B, D, G/I and Y, and transcriptional cyclin L, were identified in the Symbiodiniaceae, alongside several alveolate-specific cyclin A/B proteins, and proteins related to protist P/U-type cyclins and apicomplexan cyclins. The largest expansion of Symbiodiniaceae cyclins was in the P/U-type cyclin groups. Proteins related to eumetazoan cell-cycle-related CDKs (CDK1) were identified as well as transcription-related CDKs. The largest expansion of CDK groups was, however, in alveolate-specific groups which comprised 11 distinct CDK groups (CDKA-J) with CDKB being the most widely distributed CDK protein. As a result of its phylogenetic position, conservation across Symbiodiniaceae species, and the presence of the canonical CDK motif, CDKB emerged as a likely candidate for a Saccharomyces cerevisiae Cdc28/Pho85-like homolog in Symbiodiniaceae. Similar to cyclins, two CDK-groups found in Symbiodiniaceae species were solely associated with apicomplexan taxa. A comparison of Breviolum minutum CDK and cyclin gene expression between free-living and symbiotic states showed that several alveolate-specific CDKs and two P/U-type cyclins exhibited altered expression in hospite, suggesting that symbiosis influences the cell cycle of symbionts on a molecular level. These results highlight the divergence of Symbiodiniaceae cell-cycle proteins across species. These results have important implications for host control of the symbiont cell cycle in novel cnidarian–dinoflagellate symbioses.

Nisin Induces Cell-Cycle Arrest in Free-Living Amoebae Acanthamoeba castellanii

2021 ◽  
Author(s):  
Marianna de Carvalho Clímaco ◽  
Yrna Lorena Matos de Oliveira ◽  
Anne Caroline Santos Ramos ◽  
Jucicleide Ramos-de-Souza ◽  
Audrey Rouse Soares Tavares Silva ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Acanthamoeba Castellanii ◽  
Free Living ◽  
Cycle Arrest

scholarly journals Sinorhizobium meliloti CtrA Stability Is Regulated in a CbrA-Dependent Manner That Is Influenced by CpdR1

2015 ◽  
Vol 197 (13) ◽  
pp. 2139-2149 ◽  
Author(s):  
Karla B. Schallies ◽  
Craig Sadowski ◽  
Julia Meng ◽  
Peter Chien ◽  
Katherine E. Gibson
Keyword(s):  
Cell Cycle ◽  
Living Cell ◽  
Sinorhizobium Meliloti ◽  
Cell Cycle Progression ◽  
Caulobacter Crescentus ◽  
Ectopic Expression ◽  
Dependent Manner ◽  
Free Living ◽  
Cycle Progression ◽  
Content Type

ABSTRACTCbrA is a DivJ/PleC-like histidine kinase of DivK that is required for cell cycle progression and symbiosis in the alphaproteobacteriumSinorhizobium meliloti. Loss ofcbrAresults in increased levels of CtrA as well as its phosphorylation. While many of the knownCaulobacter crescentusregulators of CtrA phosphorylation and proteolysis are phylogenetically conserved withinS. meliloti, the latter lacks the PopA regulator that is required for CtrA degradation inC. crescentus. In order to investigate whether CtrA proteolysis occurs inS. meliloti, CtrA stability was assessed. During exponential growth, CtrA is unstable and therefore likely to be degraded in a cell cycle-regulated manner. Loss ofcbrAsignificantly increases CtrA stability, but this phenotype is restored to that of the wild type by constitutive ectopic expression of a CpdR1 variant that cannot be phosphorylated (CpdR1D53A). Addition of CpdR1D53Afully suppressescbrAmutant cell cycle defects, consistent with regulation of CtrA stability playing a key role in mediating proper cell cycle progression inS. meliloti. Importantly, thecbrAmutant symbiosis defect is also suppressed in the presence of CpdR1D53A. Thus, regulation of CtrA stability by CbrA and CpdR1 is associated with free-living cell cycle outcomes and symbiosis.IMPORTANCEThe cell cycle is a fundamental process required for bacterial growth, reproduction, and developmental differentiation. Our objective is to understand how a two-component signal transduction network directs cell cycle events during free-living growth and host colonization. TheSinorhizobium melilotinitrogen-fixing symbiosis with plants is associated with novel cell cycle events. This study identifies a link between the regulated stability of an essential response regulator, free-living cell cycle progression, and symbiosis.

scholarly journals Cellular, Biochemical, and Molecular Changes during Encystment of Free-Living Amoebae

2012 ◽  
Vol 11 (4) ◽  
pp. 382-387 ◽  
Author(s):  
Emilie Fouque ◽  
Marie-Cécile Trouilhé ◽  
Vincent Thomas ◽  
Philippe Hartemann ◽  
Marie-Hélène Rodier ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Signaling Pathways ◽  
Pathogenic Bacteria ◽  
Molecular Level ◽  
Differentiation Process ◽  
Free Living ◽  
Molecular Changes ◽  
Cell Responses ◽  
New Findings ◽  
Soil And Water

ABSTRACTFree-living amoebae are protozoa found in soil and water. Among them, some are pathogenic and many have been described as potential reservoirs of pathogenic bacteria. Their cell cycle is divided into at least two forms, the trophozoite and the cyst, and the differentiation process is named encystment. As cysts are more resistant to disinfection treatments than trophozoites, many studies focused on encystment, but until recently, little was known about cellular, biochemical, and molecular modifications operating during this process. Important signals and signaling pathways at play during encystment, as well as cell responses at the molecular level, have been described. This review summarizes our knowledge and focuses on new findings.

scholarly journals A free-living protist that lacks canonical eukaryotic DNA replication and segregation systems

2021 ◽  
Author(s):  
Dayana Elizabeth E Salas-Leiva ◽  
Eelco C. Tromer ◽  
Bruce A. Curtis ◽  
Jon Jerlstrom-Hultqvist ◽  
Martin Kolisko ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Origin Recognition Complex ◽  
Draft Genome ◽  
Cell Cycle Checkpoint ◽  
Free Living ◽  
Molecular Systems ◽  
Draft Genome Assembly ◽  
Eukaryotic Diversity ◽  
M Phase ◽  
Cycle Checkpoint

Cells must replicate and segregate their DNA with precision. In eukaryotes, these processes are part of a regulated cell-cycle that begins at S-phase with the replication of DNA and ends after M-phase. Previous studies showed that these processes were present in the last eukaryotic common ancestor and the core parts of their molecular systems are conserved across eukaryotic diversity. However, some unicellular parasites, such as the metamonad Giardia intestinalis, have secondarily lost components of the DNA processing and segregation apparatuses. To clarify the evolutionary history of these systems in these unusual eukaryotes, we generated a high-quality draft genome assembly for the free-living metamonad Carpediemonas membranifera and carried out a comparative genomics analysis. We found that parasitic and free-living metamonads harbor a conspicuously incomplete set of canonical proteins for processing and segregating DNA. Unexpectedly, Carpediemonas species are further streamlined, completely lacking the origin recognition complex, Cdc6 and other replisome components, most structural kinetochore subunits including the Ndc80 complex, as well as several canonical cell-cycle checkpoint proteins. Carpediemonas is the first eukaryote known to have lost this large suite of conserved complexes, suggesting that it has a highly unusual cell cycle and that unlike any other known eukaryote, it must rely on a novel set of mechanisms to carry out these fundamental processes.

scholarly journals DNA Methylation in Ensifer Species during Free-Living Growth and during Nitrogen-Fixing Symbiosis with Medicago spp.

mSystems ◽  
2022 ◽  
Author(s):  
George C. diCenzo ◽  
Lisa Cangioli ◽  
Quentin Nicoud ◽  
Janis H. T. Cheng ◽  
Matthew J. Blow ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Methylation ◽  
Nitrogen Fixation ◽  
Terminal Differentiation ◽  
Nitrogen Fixing ◽  
Bacterial Transformation ◽  
Free Living

Nitrogen fixation by rhizobia in symbiosis with legumes is economically and ecologically important. The symbiosis can involve a complex bacterial transformation—terminal differentiation—that includes major shifts in the transcriptome and cell cycle.

scholarly journals The Sinorhizobium meliloti sensor histidine kinase CbrA contributes to free-living cell cycle regulation

Microbiology ◽  
2013 ◽  
Vol 159 (Pt_8) ◽  
pp. 1552-1563 ◽  
Author(s):  
Craig S. Sadowski ◽  
Daniel Wilson ◽  
Karla B. Schallies ◽  
Graham Walker ◽  
Katherine E. Gibson
Keyword(s):  
Cell Cycle ◽  
Histidine Kinase ◽  
Living Cell ◽  
Cell Cycle Regulation ◽  
Sinorhizobium Meliloti ◽  
Free Living ◽  
Sensor Histidine Kinase ◽  
Cycle Regulation

scholarly journals HdaB: a novel and conserved DnaA-related protein that targets the RIDA process to stimulate replication initiation

2019 ◽  
Author(s):  
Antonio Frandi ◽  
Justine Collier
Keyword(s):  
Cell Cycle ◽  
Stationary Phase ◽  
Replication Initiation ◽  
Lag Phase ◽  
Related Protein ◽  
Free Living ◽  
Changing Environments ◽  
A Cell ◽  
The Impact

ABSTRACTExquisite control of the DnaA initiator is critical to ensure that bacteria initiate chromosome replication in a cell cycle-coordinated manner. In many bacteria, the DnaA-related and replisome-associated Hda/HdaA protein interacts with DnaA to trigger the regulatory inactivation of DnaA (RIDA) and prevent over-initiation events. In the C. crescentus Alphaproteobacterium, the RIDA process also targets DnaA for its rapid proteolysis by Lon. The impact of the RIDA process on adaptation of bacteria to changing environments remains unexplored. Here, we identify a novel and conserved DnaA-related protein, named HdaB, and show that homologs from three different Alphaproteobacteria can inhibit the RIDA process, leading to over-initiation and cell death when expressed in actively growing C. crescentus cells. We further show that HdaB interacts with HdaA in vivo, most likely titrating HdaA away from DnaA. Strikingly, we find that HdaB accumulates mainly during stationary phase and that it shortens the lag phase upon exit from stationary phase. Altogether, these findings suggest that expression of hdaB during stationary phase prepares cells to restart the replication of their chromosome as soon as conditions improve, a situation often met by free-living or facultative intracellular Alphaproteobacteria.

Maytansine-Induced Mitotic Arrest in Human Lymphoblasts

1977 ◽  
Vol 35 ◽  
pp. 460-461
Author(s):  
Tai-Te Chao ◽  
John Sullivan ◽  
Awtar Krishan
Keyword(s):  
Electron Microscopy ◽  
Cell Cycle ◽  
Transmission Electron Microscopy ◽  
Tubulin Polymerization ◽  
Vinca Alkaloids ◽  
Antimitotic Activity ◽  
Transmission Electron ◽  
Flow Microfluorometry ◽  
Brain Tubulin

Maytansine, a novel ansa macrolide (1), has potent anti-tumor and antimitotic activity (2, 3). It blocks cell cycle traverse in mitosis with resultant accumulation of metaphase cells (4). Inhibition of brain tubulin polymerization in vitro by maytansine has also been reported (3). The C-mitotic effect of this drug is similar to that of the well known Vinca- alkaloids, vinblastine and vincristine. This study was carried out to examine the effects of maytansine on the cell cycle traverse and the fine struc- I ture of human lymphoblasts.Log-phase cultures of CCRF-CEM human lymphoblasts were exposed to maytansine concentrations from 10-6 M to 10-10 M for 18 hrs. Aliquots of cells were removed for cell cycle analysis by flow microfluorometry (FMF) (5) and also processed for transmission electron microscopy (TEM). FMF analysis of cells treated with 10-8 M maytansine showed a reduction in the number of G1 cells and a corresponding build-up of cells with G2/M DNA content.

Fibronexus-Like Adhesion Sites are Present at the Invasive Zones of Human Epidermoid Carcinomas

1982 ◽  
Vol 40 ◽  
pp. 106-109
Author(s):  
Irwin I. Singer
Keyword(s):  
Cell Cycle ◽  
Serum Concentration ◽  
Substrate Binding ◽  
High Serum ◽  
Adhesion Sites ◽  
Substrate Adhesion ◽  
Focal Contacts ◽  
Adhesion Complex ◽  
Low Serum

Our previous results indicate that two types of fibronectin-cytoskeletal associations may be formed at the fibroblast surface: dorsal matrixbinding fibronexuses generated in high serum (5% FBS) cultures, and ventral substrate-adhering units formed in low serum (0.3% FBS) cultures. The substrate-adhering fibronexus consists of at least vinculin (VN) and actin in its cytoplasmic leg, and fibronectin (FN) as one of its major extracellular components. This substrate-adhesion complex is localized in focal contacts, the sites of closest substratum approach visualized with interference reflection microscopy, which appear to be the major points of cell-tosubstrate adhesion. In fibroblasts, the latter substrate-binding complex is characteristic of cultures that are arrested at the G1 phase of the cell cycle due to the low serum concentration in their medium. These arrested fibroblasts are very well spread, flattened, and immobile.

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