Methanocorpusculaceae fam. nov., represented by Methanocorpusculum parvum,Methanocorpusculum sinense spec. nov. and Methanocorpusculum bavaricum spec. nov.

Two new methanogenic bacteria, Methanocorpusculum sinense spec. nov. strain DSM 4274 from a pilot plant for treatment of distillery wastewater in Chengdu (Province Sichuan, China), and Methanocorpusculum bavaricum spec. nov. strain DSM 4179, from a wastewater pond of the sugar factory in Regensburg (Bavaria, FRG) are described. Methanocorpusculum strains are weakly motile and form irregularly coccoid cells, about 1 μm in diameter. The cell envelope consists of a cytoplasmic membrane and a S-layer, composed of hexagonally arranged glycoprotein subunits with molecular weights of 90000 (Methanocorpusculum parvum), 92000 (M. sinense), and 94000 (M. bavaricum). The center-to-center spacings are 14.3 nm, 15.8 nm and 16.0 nm, respectively. Optimal growth of strains is obtained in the mesophilic temperature range and at a pH around 7. Methane is produced from H₂/CO₂, formate, 2-propanol/CO₂ and 2-butanol/CO₂ by M. parvum and M. bavaricum, whereas M. sinense can only utilize H₂/CO₂ and formate. Growth of M. sinense and M. bavaricum is dependent on the presence of clarified rumen fluid. The G+C content of the DNA of the three strains is ranging from 47.7–53.6 mol% as determined by different methods. A similar, but distinct polar lipid pattern indicates a close relationship between the three Methanocorpusculum species. The polyamine patterns of M. parvum, M. sinense and M. bavaricum are similar, but distinct from those of other methanogens and are characterized by a high concentration of the otherwise rare 1,3-diaminopropane. Quantitative comparison of the antigenic fingerprint of members of Methanocorpusculum revealed no antigenic relationship with any one of the reference methanogens tested. On the basis of the distant phylogenetic position of M. parvum and the data presented in this paper a new family, the Methanocorpusculaceae fam. nov., is defined.     

Role of cell division in branching morphogenesis and differentiation of the embryonic pancreas

A new culture system for the embryonic pancreas enables the formation of a branched organ in vitro. In such cultures, each terminal branch originates as a small bud and the number of buds and of terminal branches increases progressively with the expansion of the culture. However buds can also be resorbed during growth. The normal labelling index of cells in incipient buds ("tips") is greater than between buds ("dips") suggesting that budding may be driven by a local increase of cell division. Consistent with this, treatments that reduce cell division repress the formation of buds and branches. It is not possible to initiate budding in isolated endodermal epithelium by treatment with fibroblast growth factor, although this does increase the degree of differentiation of exocrine cells. Cultures in which cell division is completely inhibited by aphidicolin treatment will produce more endocrine cells than usual and inhibit the differentiation of exocrine cells. Consistent with this it is found that in untreated cultures the division of endocrine precursors cannot be detected by BrdU labelling whereas the division of exocrine precursors is frequent. It is concluded that cell division is necessary for bud formation in the embryonic pancreas and that the growth factors required for this normally come from the mesenchyme. Cell division is also necessary for exocrine differentiation. Endocrine cells, however, can arise from undifferentiated progenitors without cell division.     

Asymmetric cell division of a triangular halophilic archaebacterium

Abstract The cell division of the halophilic archaebacterium, Haloarcula japonicus , which has a characteristic triangular shape in high salt concentration media, was analysed by time lapse microscopic cinematography. Cell division on an agar medium occured on average every 3.7 h. Cell plates were laid down asymmetrically, generating triangular or rhomboid shape daughter cells which then separated. Cell plate formation was clearly observed because the cells are flat and thin enough to see through using a conventional light microscope.     

Cellular morphogenesis in a halophilic archaebacterium

Cultures of a red halophilic archaebacterium exhibiting a complex morphology and cellular morphogenesis were obtained on a medium containingHalobacterium cutirubrum cell lysate. On primary culture the organism grew as an amorphous cellular mass 20 or more micrometers in diameter and underwent multiple internal cellular subdivision to produce a multicellular structure consisting of cuboidal cells of submicron dimensions. These disaggregated, elongated, cells became motile and multiplied by budding, thereby resembling the eubacteriumGeodermatophilus. The new isolates are identified as archaebacteria on the basis of their response to antibiotics, probable absence of peptidoglycan, and the presence of ether-linked lipids.     

Asymmetric cell division in the morphogenesis of Drosophila melanogaster macrochaetae

Asymmetric cell division (ACD) is the basic process which creates diversity in the cells of multicellular organisms. As a result of asymmetric cell division, daughter cells acquire the ability to differentiate and specialize in a given direction, which is different from that of their parent cells and from each other. This type of division is observed in a wide range of living organisms from bacteria to vertebrates. It has been shown that the molecular-genetic control mechanism of ACD is evolutionally conservative. The proteins involved in the process of ACD in different kinds of animals have a high degree of homology. Sensory organs--setae (macrochaetae)--of Drosophila are widely used as a model system for studying the genetic control mechanisms of asymmetric division. Setae located in an orderly manner on the head and body of the fly play the role of mechanoreceptors. Each of them consists of four specialized cells--offspring of the only sensory organ precursor cell (SOPC), which differentiates from the imaginal wing disc at the larval stage of the late third age. The basic differentiation and further specialization of the daughter cells of SOPC is an asymmetric division process. In this summary, experimental data on genes and their products controlling asymmetric division of SOPC and daughter cells, and also the specialization of the latter, have been systemized. The basic mechanisms which determine the time cells enter into asymmetric mitosis and which provides the structural characteristics of the asymmetric division process--the polar distribution of protein determinants Numb and Neuralized--the orientation of the mitotic spindle in relation to these determinants, and the uneven segregation of the determinants into the daughter cells that determines the direction of their development have been discussed.     

The role of cortical pattern in timing of cell division and morphogenesis in Stentor.

This paper describes experiments involving reciprocal exchange of the oral apparatus between a large (L) and a small (S) strain of Stentor coeruleus. Mature L-strain stentors given and S-strain oral apparatus formed an oral primordium in response to the presence of abnormally small oral structures and mostly divided although a few reorganized instead. Conversely, when S-strain stentors in early division were given a large L-strain oral apparatus, they resorbed the developing primordium and returned to interphase. When combined with previous results, these findings provide evidence for the hypothesis that the time of cell division in Stentor is determined by a "critical" ratio between the size of the oral apparatus and the size of the cell body (somatic) cortex. This ratio develops because the somatic cortex grows during interphase and the oral apparatus does not. Cell division in Stentor therefore appears to be initiated by a cortical pattern change resulting from cell surface growth during interphase.     

Macromolecular synthesis and cell division during morphogenesis of Arthrobacter crystallopoietes

The sphere-rod-sphere morphology cycle of Arthrobacter crystallopoietes was accompanied by changes in the rate of growth and the rates of DNA, RNA and protein synthesis. The patterns of macromolecule synthesis resembled those found in other bacteria during a step-up followed by a step-down in growth rate. During the step-up in growth spherical cells grew into rods and macromolecules were synthesized in the absence of cell division. During stepdown, successive rounds of septation produced progressively smaller cells which did not separate and remained in chains. The morphology of the cells was dependent on the growth rate and could be altered by changing the dilution rate in a malate-limited chemostat. Gradual transitions in morphology and gradual increases in macromolecule content of the cells occurred as the growth rate was increased in the chemostat. Sphere to rod morphogenesis occurred when DNA synthesis was inhibited by treatment with mitomycin C or by thymine starvation. The DNA-deficient rods did not divide and eventually lysed. DNA, RNA and protein synthesis were continuously required for the reductive division of rods to spheres.Abbreviations MS mineral salts - GS mineral salts plus glucose - CA casamino acids - GSCA mineral salts plus glucose plus casamino acids - cAMP cyclic adenosine-3,5-monophosphate - RNA ribonucleic acid - DNA deoxyribonucleic acid     

Electron microscopic study of cell surface rings during cell division and morphogenesis of Arthrobacter crystallopoietes.

The whole cell ultrastructure during cell division and morphogenesis of Arthrobacter crystallopoietes was monitored using electron microscopic techniques. Glucose-grown spherical cells were inoculated into succinate-based medium. In this medium, the organism undergoes a morphogenetic cycle consisting of elongation of spheres to rods, exponential growth as rods, and fragmentation of rods to spherical cells. Raised bands or rings that encircled the cells were evident on the cell surface of both sphere- and rod-shaped cells. Many rod-shaped cells possessed two or more rings arranged adjacent to each other in a parallel orientation. At each cell division a new ring was formed on both siblings. However, as predicted by the proposed model of unidirectional cell growth and by maintaining a ring from the previous generation, unequal numbers of rings were observed on sibling cells. Only one ring was visible on most of the spherical inoculum cells, but in some cases a second ring perpendicular to the other ring was observed. Parallel rings were found on spherical cells resulting from fragmentation or reductive cell division of rods during the stationary growth phase. Thus, these spheres could be distinguished from inoculum spheres containing a single ring or perpendicular orientation of rings. The number of rings per cell and arrangement of rings on the cell surface of sibling cells after cell division, but before cell separation, are discussed with respect to cell age, cell division, and sphere-rod-sphere morphogenesis of A. crystallopoietes.     

RNA synthesis and control of cell division in the yeast S. cerevisiae.

Cells of the yeast Saccharomyces cerevisiae rapidly accumulated in the G1 phase of the cell cycle when exposed to the chelating agents o-phenanthroline (OP) or 8-hydroxyquinoline (HQ). Zinc salts fully reversed the growth-inhibitory effect of both OP and HQ. Cells treated with these chelating agents showed limited RNA accumulation and little RNA degradation. Rates of RNA synthesis were drastically reduced by low concentrations of these compounds. Whereas rates of protein synthesis were essentially unaffected. Rates of synthesis of mRNA and tRNA were less affected than were rates of synthesis of high molecular weight RNA. Processing of ribosomal precursor RNA was altered. these results suggest that the primary effect of OP and HQ is on rRNA synthesis. RNA metabolism must therefore have a key role in the regulation of the cell cycle.     

Role of the sfiA-dependent cell division regulation system in Escherichia coli.

Several authors have suggested that the SOS-associated (sfiA-dependent) system of division inhibition, normally induced by perturbations of DNA replication, also regulates steady-state (unperturbed) cell division. The present work shows that mean cell mass is identical in sfiA+ and sfiA mutant cultures during steady-state growth, that mass adjustment is identical after shift up, that sfiA expression is not induced by shift up, and that a sfiA mutation does not cause aberrant chromosome segregation.     

Role of penicillin-binding proteins in bacterial cell morphogenesis

The penicillin-binding proteins (PBPs) polymerize and modify peptidoglycan, the stress-bearing component of the bacterial cell wall. As part of this process, the PBPs help to create the morphology of the peptidoglycan exoskeleton together with cytoskeleton proteins that regulate septum formation and cell shape. Genetic and microscopic studies reveal clear morphological responsibilities for class A and class B PBPs and suggest that the mechanism of shape determination involves differential protein localization and interactions with specific cell components. In addition, the low molecular weight PBPs, by varying the substrates on which other PBPs act, alter peptidoglycan synthesis or turnover, with profound effects on morphology.     

Role of murein lipoprotein in morphogenesis of the bacterial division septum: phenotypic similarity of lkyD and lpo mutants.

Phenotypes were compared in two different classes of mutants with defects in murein-lipoprotein (lkyD mutants of Salmonella typhimurium and an lpo mutant of Escherichia coli). Both mutations are associated with the same triad of phenotypic abnormalities, consisting of defective formation of the division septum, leakage of periplasmic proteins during growth, and increased sensitivity to several unrelated external toxic agents. The abnormality in septum formation consists of a defect in invagination of the outer membrane during formation of the nascent septum. The results suggest that formation of the murein-lipoprotein link plays an important role in differentiation of the division septum and perhaps also in maintaining the normal barrier function of the outer membrane.     

RHO GTPase of plants regulates polarized cell growth and cell division orientation during morphogenesis

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Cell division and morphogenesis in angiosperm embryogenesis

Angiosperm embryogenesis generates the basic body organization of flowering plants. The underlying processes of pattern formation, which establishes the diversity of position-dependent cell fates, and morphogenesis, which brings about the shape of the embryo, may not only involve intercellular communication and controlled cell expansion but also non-random cell divisions. Genetic analysis ofArabidopsisembryogenesis which displays a large invariant pattern of cell divisions suggests that unequal cell divisions segregate cell fates and are thus involved in pattern formation whereas other oriented cell divisions and differential mitotic rates reflect patterning and rather play a role in morphogenesis.