Fukuyoa paulensis gen. et sp. nov., a New Genus for the Globular Species of the Dinoflagellate Gambierdiscus (Dinophyceae)

The marine epiphytic dinoflagellate Gambierdiscus is a toxicologically important genus responsible for ciguatera fish poisoning, the principal cause of non-bacterial illness associated with fish consumption. The genus currently contains species exhibiting either globular or anterior-posteriorly compressed morphologies with marked differences in cell shape and plate arrangement. Here we report a third globular, epiphytic and tychoplanktonic species from the coasts of Ubatuba, Brazil. The new species can be distinguished from G. yasumotoi and G. ruetzleri by its broader first apical plate that occupies a larger portion of the epitheca. Accordingly, phylogenetic trees from small subunit (SSU) and large subunit (LSU) ribosomal DNA sequences also showed strongly supported separation of the new species from the G. yasumotoi / G. ruetzleri group albeit with short distance. The molecular phylogenies, which included new sequences of the planktonic species Goniodoma polyedricum, further indicated that the globular species of Gambierdiscus formed a tight clade, clearly separated (with strong bootstrap support) from the clade of lenticular species including the type for Gambierdiscus. The morphological and molecular data in concert support the split of Gambierdiscus sensu lato into two genera. Gambierdiscus sensu stricto should be reserved for the species with lenticular shapes, highly compressed anterioposteriorly, with short-shank fishhook apical pore plate, large 2'' plate, low and ascending cingular displacement, and pouch-like sulcal morphology. The new genus name Fukuyoa gen. nov. should be applied to the globular species, slightly laterally compressed, with long-shank fishhook apical pore plate, large 1'' plate, greater and descending cingular displacement, and not pouch-like vertically-oriented sulcal morphology. Fukuyoa contains the new species Fukuyoa paulensis gen. et sp. nov., and F. yasumotoi comb. nov. and F. ruetzleri comb. nov.     

Growth and epiphytic behavior of three Gambierdiscus species (Dinophyceae) associated with various macroalgal substrates

Species of the benthic dinoflagellate Gambierdiscus produce polyether neurotoxins that caused ciguatera fish/shellfish poisoning in human. The toxins enter marine food webs by foraging of herbivores on the biotic substrates like macroalgae that host the toxic dinoflagellates. Interaction of Gambierdiscus and their macroalgal substrate hosts is believed to shape the tendency of substrate preferences and habitat specialization. This was supported by studies that manifested epiphytic preferences and behaviors in Gambierdiscus species toward different macroalgal hosts. To further examine the supposition, a laboratory-based experimental study was conducted to examine the growth, epiphytic behaviors and host preferences of three Gambierdiscus species towards four macroalgal hosts over a culture period of 40 days. The dinoflagellates Gambierdiscus balechii, G. caribaeus, and a new ribotype, herein designated as Gambierdiscus type 7 were initially identified based on the thecal morphology and molecular characterization. Our results showed that Gambierdiscus species tested in this study exhibited higher growth rates in the presence of macroalgal hosts. Growth responses and attachment behaviors, however, differed among different species and strains of Gambierdiscus over different macroalgal substrate hosts. Cells of Gambierdiscus mostly attached to substrate hosts at the beginning of the experiments but detached at the later time. Localized Gambierdiscus-host interactions, as demonstrated in this study, could help to better inform efforts of sampling and monitoring of this benthic toxic dinoflagellate.     

Induction of host nuclear DNA synthesis in coccidia-infected chicken intestinal cells

When Eimeria maxima (gamonts) infects villus epithelial cells of the chicken duodenum there is extensive cellular enlargement with no alteration in nuclear size. Feulgen DNA microspectrophotometric measurements indicated that the infected host-cell nucleus contains the same amount of DNA as an uninfected cell nucleus. Evidence is presented to indicate that second generation schizonts of E. necatrix develop in crypt epithelial cells that are displaced/migrate into the lamina propria. The developing parasite causes cellular and nuclear hypertrophy in these cells as does E. tenella in cecal cells of the chicken. In these two cases nuclear enlargement is accompanied by induced rounds of DNA synthesis in the host-cell. Analyses indicated that the DNA content of enlarged nuclei does not fall into classes that correspond to a geometric series 2:4:6:8:16: etc. times the DNA content of a 2C equivalent, and that nuclear size and DNA content in infected cells are not significantly correlated. Autoradiographic studies on E. necatrix infected chicks administered ³H-thymidine show that DNA synthesis takes place in the nuclei of cells containing all developing stages but not mature schizonts, and that this synthesis is not a continuous process. The data suggest that intestinal cells that are capable of undergoing cell division and therefore additional rounds of DNA synthesis, can be induced by coccidial infection in the absence of concomitant cell division.     

Gambierdiscus balechii sp. nov (Dinophyceae), a new benthic toxic dinoflagellate from the Celebes Sea (SW Pacific Ocean)

A new benthic toxic dinoflagellate is described from the Celebes Sea. Gambierdiscus balechii sp. nov. was isolated from seaweeds growing in tidal ponds. Its morphology was studied by means of LM and SEM; G. balechii has a very ornamented theca, a hatchet shaped second apical plate, a narrow second antapical plate and an asymmetrical third precigular plate, a unique combination of characters among Gambierdiscus species. It has a very wide size range with widths from 36 to 88 μm. Phylogenetic analyses of two G. balechii strains, based on LSU rRNA (D8–D10) and partial SSUrRNA sequences confirmed that these clustererd in its’ own group, separated from the rest of Gambierdiscus species and with G. pacificus, G. belizeanus and G. scabrosus as its closest relatives. Thecate cysts are described from culture as non motile vegetative-like cells which germinated after being isolated and transferred to fresh medium. Mouse tests showed that this species is toxic and hence it is a potential cause of ciguatera in the Celebes Sea.     

THE FEMALE GAMETOPHYTE OF MACHAERANTHERA PATTERSONII (ASTER PATTERSONII) AND OF M. TANACETIFOLIA

The nucellus of Machaeranthera pattersonii (A. Gray) Greene (Aster pattersonii A. Gray) contains only one megaspore mother cell, and the female gametophyte develops from the chalazal megaspore of a row of four, thus conforming to the Polygonum type of development. These observations are contrary to the older work of Palm. Three nuclear divisions produce the typical eight nuclei with the egg apparatus, primary endosperm cell with two polar nuclei, and two antipodal cells, the micropylar one containing two nuclei. Usually no more antipodal cells are formed, although there is further nuclear division, apparently followed by nuclear fusion. The antipodal cells remain about the same size without forming an antipodal haustorium. Cell division accompanies the first division of the primary endosperm nucleus. The early stages of the embryo resemble those of other Compositae. Machaeranthera tanacetifolia (HBK) Nees also shows the Polygonum type of development of the female gametophyte. It is suggested that Palm may have been working on some species of Erigeron that had been wrongly identified, which would account for the difference in observations.     

Positional control of nuclear differentiation in paramecium

Nuclear reorganization, which results in the differentiation between macronuclear anlagen and micronuclei during autogamy or conjugation in Paramecium tetraurelia, was compared in wild-type cells and in two mutants, mic44 and kin241, which form abnormal numbers of macronuclear anlagen and micronuclei. Our observations show that all macronuclear anlagen derive from the nuclei positioned at the posterior pole of the cell at the second postzygotic division. This posterior localization is transient and correlated with a marked change in cell shape and decrease of cell length. These results suggest that cytoplasmic or cortical factors precisely located in the posterior pole are essential to trigger macronuclear differentiation and that the control of nuclear positioning is dependent upon precise modifications of cell shape.     

Comparative morphological analysis of compound eye miniaturization in minute hymenoptera

Due to their small size, diminutive parasitic wasps are outstanding subjects for investigating aspects of body miniaturization. Information on minute compound eyes is still scarce, and we therefore investigated eye morphology in one of the smallest known hymenopteran species Megaphragma mymaripenne (body size 0.2 mm) relative to Anaphes flavipes (body size 0.45 mm) and compared the data with available information for Trichogramma evanescens (body size 0.4 mm). The eyes of all three species are of the apposition kind, and each ommatidium possesses the typical cellular organization of ommatidia found in larger hymenopterans. Compound eye miniaturization does not therefore involve a reduction in cell numbers or elimination of cell types. Six size-related adaptations were detected in the smallest eyes investigated, namely a) a decrease in the radius of curvature of the cornea compared with larger hymenopterans; b) the lack of extensions to the basal matrix from secondary pigment cells; c) the interlocking arrangement of the retinula cell nuclei in neighboring ommatidia; d) the distal positions of retinula cell nuclei in M. mymaripenne; e) the elongated shape of retinula cell pigment granules of both studied species; and f) an increase in rhabdom diameter in M. mymaripenne compared with A. flavipes and T. evanescens. The adaptations are discussed with respect to compound eye miniaturizations as well as their functional consequences based on optical calculations.     

Nanoparticles from culture media are internalized by in vitro-produced bovine embryos and its depletion affect expression of pluripotency genes

Extracellular vesicles are nanoparticles secreted by cell and have been proposed as suitable markers to identify competent embryos produced in vitro. Characterizing EVs secreted by individual embryos is challenging because culture medium itself contributes to the pool of nanoparticles that are co-isolated. To avoid this, culture medium must be depleted of nanoparticles that are present in natural protein source. The aim of this study was to evaluate if the culture medium subjected to nanoparticle depletion can support the proper in vitro development of bovine embryos. Zygotes were cultured in groups on depleted or control medium for 8 days. Nanoparticles from the medium were characterized by their morphology, size and expression of EVs surface markers. Isolated nanoparticles were labelled and added to depleted medium containing embryos at different developmental stages and evaluated after 24 hours at 2, 8-16 cells, morula and blastocyst stages. There were no statistical differences on blastocyst rate at day 7 and 8, total cell count neither blastocyst diameter between groups. However, morphological quality was better in blastocysts cultured in non-depleted medium and the expression of SOX2 was significantly lower whereas NANOG expression was significantly higher. Few nanoparticles from medium had a typical morphology of EVs but were positive to specific surface markers. Punctuated green fluorescence near the nuclei of embryonic cells was observed in embryos from all developmental stages. In summary, nanoparticles from culture medium are internalized by in vitro cultured bovine embryos and their depletion affects the capacity of medium to support the proper embryo development.     

Toxicity of the dinoflagellate Gambierdiscus sp. toward the marine copepod Tigriopus japonicus

The toxic dinoflagellate Gambierdiscus sp. has recently been observed in temperate areas in the Southern Sea of the Republic of Korea. The purpose of this study was to examine the toxicity of Gambierdiscus sp. toward the marine copepod Tigriopus japonicus. T. japonicus adult females and nauplii were exposed to various concentrations of algae or culture medium to assess toxicity and analyze gene expression patterns in the copepod. Based on the toxicity tests, Gambierdiscus sp. increased the mortality of nauplii and the immobility of adult females. The survival and mobility of T. japonicus were not affected by culture medium lacking Gambierdiscus sp. cells in the toxicity test. However, based on the analysis of gene expression in the copepod, exposure of the copepod to culture medium affected the expression of stress or detoxification-related genes. Further studies to identify toxins in Gambierdiscus sp. are required to increase our understanding of dinoflagellate toxicity.     

A plaque assay for titration of alfalfa looper nuclear polyhedrosis virus in a cabbage looper (TN-368) cell line

This is the first report of plaque formation by a pathogenic insect virus. Trichoplusia ni (TN-368) cells overlaid with medium containing 0.6% methyl cellulose continued to multiply, developed into monolayers, and produced plaques after infection with alfalfa looper nuclear polyhedrosis virus. Viral polyhedral inclusion bodies were first observed 24 hr after exposure of cells to virus, and plaques continued to increase in size for 72 hr. Two different types of plaques were observed: one in which all cells had many polyhedra in their nuclei, and another in which few cells had inclusion bodies. When virus from either plaque was injected into T. ni larvae, they died of typical nuclear polyhedrosis virus disease. The assay was reproducible, and plaque numbers were related to virus concentration.     

Neuroglia in the corpus callosum of the primate, slow loris (Nycticebus coucang coucang)

The corpus callosum of adult slow loris consists of a mixed population of several cell types, i.e. free subependymal cells, oligodendrocytes, astrocytes and microglia. The free subependymal cell is rather small and slender with a somewhat patchy nucleus. It shows scanty cytoplasm with free ribosomes. Oligodendrocytes vary both in nuclear and cytoplasmic densities and can be divided into three classes: light, medium dense and dark types. Their cytoplasm contains microtubules, rough endoplasmic reticulum and Golgi saccules. Astrocytes are pale cells with large amount of filaments in their cytoplasm. Microglia are small cells with granulated nuclei. The cells often show large cytoplasmic protrusions containing the usual cell organelles and lipofuscin bodies in their cytoplasm. Lastly, cells with typical features of neurons are occasionally encountered among the white matter.     

Endopolyploidy Changes with Age-Related Polyethism in the Honey Bee,Apis mellifera

Honey bees (Apis mellifera) exhibit age polyethism, whereby female workers assume increasingly complex colony tasks as they age. While changes in DNA methylation accompany age polyethism, other DNA modifications accompanying age polyethism are less known. Changes in endopolyploidy (DNA amplification in the absence of cell division) with increased larval age are typical in many insect cells and are essential in adults for creating larger cells, more copies of essential loci, or greater storage capacity in secretory cells. However, changes in endopolyploidy with increased adult worker age and polyethism are unstudied. In this study, we examined endopolyploidy in honey bee workers ranging in age from newly emerged up to 55 days old. We found a nonsignificant increase in ploidy levels with age (P < 0.1) in the most highly endopolyploid secretory cells, the Malpighian tubules. All other cell types decreased ploidy levels with age. Endopolyploidy decreased the least amount (nonsignificant) in neural (brain) cells and the stinger (P < 0.1). There was a significant reduction of endopolyploidy with age in leg (P < 0.05) and thoracic (P < 0.001) muscles. Ploidy in thoracic muscle dropped from an average of 0.5 rounds of replication in newly emerged workers to essentially no rounds of replication (0.125) in the oldest workers. Ploidy reduction in flight muscle cells is likely due to the production of G1 (2C) nuclei by amitotic division in the multinucleate striated flight muscles that are essential to foragers, the oldest workers. We suggest that ploidy is constrained by the shape, size and makeup of the multinucleate striated muscle cells. Furthermore, the presence of multiple 2C nuclei might be optimal for cell function, while higher ploidy levels might be a dead-end strategy of some aging adult tissues, likely used to increase cell size and storage capacity in secretory cells.     

Suspension Culture of Endosperm Callus Cell and Amitosis In Vitro

The endosperm calli were induced on MS basic medium supplemented with lppm 2,4-D, 0.5ppm KT and 5% sucrose. The medium which contained lppm BAP, 0.1ppm NAA and 2% sucrose was used for cell suspension culture. In suspension cell culture, amitosis of cleavage division of nucleus have been observed after 5 days of culture. First the nuclear membrane and nucleolus disappeared. The crevice appeared in the center of the nucleus, and the nucleus divided into two daughter nuclei of similar size and each with a nucleolus. The daughter nucleus resembled an eye in shape. Following the emergence of cell wall, the two new unequal cells were produced. Such amitotic division proceeded repeatedly until the callus developed and eventually plantlet regenerated.     

Nuclear Envelope Composition Determines the Ability of Neutrophil-type Cells to Passage through Micron-scale Constrictions

Neutrophils are characterized by their distinct nuclear shape, which is thought to facilitate the transit of these cells through pore spaces less than one-fifth of their diameter. We used human promyelocytic leukemia (HL-60) cells as a model system to investigate the effect of nuclear shape in whole cell deformability. We probed neutrophil-differentiated HL-60 cells lacking expression of lamin B receptor, which fail to develop lobulated nuclei during granulopoiesis and present an in vitro model for Pelger-Huët anomaly; despite the circular morphology of their nuclei, the cells passed through micron-scale constrictions on similar timescales as scrambled controls. We then investigated the unique nuclear envelope composition of neutrophil-differentiated HL-60 cells, which may also impact their deformability; although lamin A is typically down-regulated during granulopoiesis, we genetically modified HL-60 cells to generate a subpopulation of cells with well defined levels of ectopic lamin A. The lamin A-overexpressing neutrophil-type cells showed similar functional characteristics as the mock controls, but they had an impaired ability to pass through micron-scale constrictions. Our results suggest that levels of lamin A have a marked effect on the ability of neutrophils to passage through micron-scale constrictions, whereas the unusual multilobed shape of the neutrophil nucleus is less essential.     

Fine structure of division in ciliate protozoa. I. Micronuclear mitosis in Blepharisma

The mitotic, micronuclear division of the heterotrichous genus Blepharisma has been studied by electron microscopy. Dividing ciliates were selected from clone-derived mass cultures and fixed for electron microscopy by exposure to the vapor of 2% osmium tetroxide; individual Blepharisma were encapsulated and sectioned. Distinctive features of the mitosis are the presence of an intact nuclear envelope during the entire process and the absence of centrioles at the polar ends of the micronuclear figures. Spindle microtubules (SMT) first appear in advance of chromosome alignment, become more numerous and precisely aligned by metaphase, lengthen greatly in anaphase, and persist through telophase. Distinct chromosomal and continuous SMT are present. At telophase, daughter nuclei are separated by a spindle elongation of more than 40 µ, and a new nuclear envelope is formed in close apposition to the chromatin mass of each daughter nucleus and excludes the great amount of spindle material formed during division. The original nuclear envelope which has remained structurally intact then becomes discontinuous and releases the newly formed nucleus into the cytoplasm. The micronuclear envelope seems to lack the conspicuous pores that are typical of nuclear envelopes. The morphology, size, formation, and function of SMT and the nature of micronuclear division are discussed.     

Ultrastructural Observations on Proliferating Storage Cells of Mature Cotyledons of Phaseolus vulgaris L. Cultured in vitro

Explants of mature cotyledons of Phaseolus vulgaris form callusrapidly when cultured in vitro with their adaxial surfaces embeddedin a solidified nutrient medium containing coconut milk, kinetinand 2,4-D. Proliferation is confined to the highly polyploidstorage cells and commences near the adaxial epidermis, whichis soon ruptured by the callus developing internally. Callusformation progresses to the abaxial tissue and within 3–4weeks sub-culturing is possible. The in vitro grown storage cells undergo thinning of their walls,loss of food reserves, hypertrophy, development of various new-wallsand nuclear activation leading to division. The induction ofnuclear and cell divisions within this mature storage tissuecontrasts with normal germination in which these cells undergorapid senescence after depletion of their food reserves. Nuclear division in early callus growth is apparently mainlyamitotic. It is preceded by the development of multiple nucleoli.The nuclear envelope also becomes more complex and deeply lobed;leading to formation of a nuclear isthmus and final separationinto two nuclei. No chromosomes are visible during nuclear fragmentation.Amitosis is accompanied by freely-forming walls, which may developadjacent to a nuclear isthmus and perhaps participate in nuclearfragmentation. Large labyrinthine wall bodies frequently occuron these walls. Mitoses are only observed in already dividedstorage cells. A cell plate forms between the two daughter nuclei,and microtubules are present at its margins in contrast to freely-formingwalls where none are evident. Phaseolus vulgaris L., bean, in-vitro culture, cotyledon, ultrastructure     

PARASITIC INTERACTIONS AND VEGETATIVE ULTRASTRUCTURE OF CHOREOAEMA THURETII (CORALLINALES,RHODOPHYTA)1

The monotypic coralline red alga, Choreonema thuretii (Bornet) Schmitz (Choreonematoideae), grows endophytically within three geniculate genera of the Corallinoideae. Although the thallus of Choreonema is reduced, lacks differentiated plastids, and is endophytic except for its conceptacles, its status as a parasite has been questioned because cellular connections to the host had not been ob served. Transmission electron microscopy, however, disclosed a previously undescribed type of parasitic interaction in which Choreonema interacts with its host through specialized cells known as lenticular cells. These small, lens-shaped cells are produced from the single file of host-penetrating vegetative cells. Pit plug morphology between vegetative and lenticular cells is polarized. Plug caps facing the vegetative cell have normal coralline morphology, while those facing the lenticular cell are composed of three layers. Regions of lenticular cells near host cells protrude toward the host cell; upon encountering the host cell wall, the prolrusion produces numerous finger-like fimbriate processes that make cellular connections with the host cell. Lenticular cells may extend several protrusions toward a host cell or penetrate more than one host cell; two or more lenticular cells may also penetrate the same host cell. The lack of secondary pit connections, cell fusions, and passage of parasitic nuclei suggest that this parasitic relationship may be evolutionarily older than previously reported cases of parasitism in red algae.     

A relationship between nuclear DNA and RNA synthetic activities and the changes produced by n-methyl-n-nitroso urethane: A study using Amoeba proteus as a single cell model

Changes caused by a carcinogen generally vary from one cell to another even among similar types of cells. The following work investigates the degree to which damage (inhibition of division, lethality, or inherited cellular changes) caused by N-methyl-N-nitroso urethane (MNU) alters at different times during the cell cycle, and relates fluctuations in the sensitivity of cells to changes in their DNA and RNA synthetic activities—possibly in the configuration of their DNA—at the time of treatment.Studies on amoebae exposed to MNU for short periods at 50 different times in their cell cycle led to the following conclusions: amoebae are sensitive to MNU at all ages, but the dose needed to produce lethal damage to young and old cells varies by a factor of 3. Cells are most sensitive at the time of division and during the peak of DNA synthesis. Smaller changes are found during the G₂ phase, some of which occur at times of intensive RNA synthesis. Transfer of nuclei between treated and control cells proved that the changing sensitivity of the cells, as shown by both inherited changes and lethal damage, was dependent on changes in their nuclei. Though the cytoplasm could be affected directly by MNU, i.e. in the absence of a nucleus, supralethal doses 2–6 times whole cell dose were required to either kill the cell or to cause a recognizable change in the offspring of viable cells. Experiments with cells having altered nuclear/cytoplasmic ratios showed that the relative insensitivity of older cells was not due to the increased volume of their cytoplasm. However, a possible involvement of cytoplasm in the repair of nuclear damage is suggested by the ability of control cytoplasm to alleviate some nuclear damage, particularly in S phase cells.     

Occurrence of amitotic division of trophoblast cell nuclei in blastocysts of the western spotted skunk (Spilogale putorius latifrons)

A cytogenetic examination of spreaded cells of diapausing and early activated blastocysts obtained from 7 female western spotted skunks was performed. Mitosis was not observed in 1626 cells obtained from 9 diapausing blastocysts; however, 12 (1.5%) figures of diploid mitosis were seen in 851 cells from 5 early activated embryos. Diameter of the cell nuclei varied from 4 to 29 microm during diapause, and from 5 to 40 microm in activated blastocyst, and the heterogeneity in nuclear size was significantly different between diapausing and activated embryos (P<0.01). About 80% of nuclei from diapausing blastocysts measured 9 to 16 microm, whereas a similar percentage of nuclei from activated blastocysts ranged from 15 to 27 microm. Many enlarged nuclei exhibited morphological features characteristic of mammalian polytene (i.e. endopolyploid with polytenic organization of chromosomes) trophoblast cells. The number of silver stained nucleoli in all the nuclei did not exceed 2, which corresponds to the number of nucleolus organizers in the diploid karyotype in this species of skunk and suggests the polytene organization of chromosomes in enlarged nuclei. About 10% of large interphase nuclei were observed to undergo amitosis, i.e. direct division by constriction. The resulting nuclear fragments in diapausing blastocysts usually had normal morphology and active nucleoli. In activated embryos, nearly 15% of amitotically divided nuclei appeared to be dividing into fragments of unequal size, one of which had normal cell nuclear morphology and extremely large silver positive nucleoli, and the other fragment exhibited signs of cell death. We interpret these data as indicating that 1) amitotic division of trophoblast endopolyploid cell nuclei in the skunk blastocysts may generate new trophoblast cells which contribute to increased cell number during both diapause and activation stages, and 2) activation of blastocysts after diapause is related to the production of trophoblast cells with enhanced synthetic capabilities.     

BamA is a pivotal protein in cell envelope synthesis and cell division in Deinococcus radiodurans

The beta-barrel assembly machinery (BAM) is an indispensable complex for protein transportation located at the outer membrane of bacteria. BAM is composed of five subunits (BamA-E) in the model bacterium Escherichia coli. DR_0379 is a BamA homolog in Deinococcus radiodurans, but the other subunits have not been detected in this species. In the present study, deletion of bamA resulted in decreased growth rate and altered morphology of D. radiodurans. ΔbamA cells underwent abnormal cell division, leading to aggregated bacteria of diverse size and shape, and the cell envelope was detached from the cell surface, resulting in reduced resistance to high ionic strength. Oxidative stress resistance was significantly enhanced in the mutant, which may be attributed to increased manganese ion concentration and Mn/Fe ratio. Numerous proteins were released into the medium from ΔbamA cells, including surface layer (S-layer) proteins and various transporters located in the periplasm and outer membrane. These results indicate that BamA affects the synthesis and assembly of the outer membrane and S-layer, and thereby influences material transport and cell division. The findings highlight the special functions of BamA in D. radiodurans, and promote our understanding of the multi-layer structure of the D. radiodurans cell envelope.