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Results for “environmental transmission electron microscopy”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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22 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Acronema sippewissettensis Gen. Nov. Sp. Nov., microbial mat bicosoecid (Bicosoecales = Bicosoecida)

A heterotrophic mastigote from the flat laminated Microcoleus-dominated intertidal microbial mat at the Sippewissett salt marsh, Cape Cod, Massachusetts, was isolated into monoprotist culture in the same anoxic medium that led to spirochete and other anaerobic bacterial enrichments. The protist grew vigorously and was transferred indefinitely in oxic marine medium. Videomicroscopy as well as scanning and transmission electron microscopy were used to document its features. The swimming and perching behavior, nutritional mode (bactivory) and morphology including ultra-structure identify it as an aloricate bicosoecid. The presence of heteromorphic acronematic undulipodia, bilateral bipartite tubular mastigonemes, absence of a cytostome, absence of extrusomes, and presence of "Dauerstadien" (duration stages) distinguish this from other Cafeteriaceae bicosoecids. Cell division involves a closed intranuclear spindle. The unspecialized bicosoecid morphology and behavior juxtaposed with oomycete-like vesicles and mastigonemes suggest that this protist may be an extant descendant of a common ancestor of bicosoecids and other stramenopiles (e.g. labyrinthulids, thraustochytrids and oomycetes). A new genus and species, Acronema sippewissettensis, are proposed.

Non-NASA Center↗
NASA NTRS1998

Bacterial mineralization patterns in basaltic aquifers: implications for possible life in martian meteorite ALH84001

To explore the formation and preservation of biogenic features in igneous rocks, we have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy. Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition. Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e.g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martian meteorite ALH84001.

NASA Discipline Exobiology↗
NASA NTRS1989

Ecology and life history of an amoebomastigote, Paratetramitus jugosus, from a microbial mat: new evidence for multiple fission

Five microbial habitats (gypsum crust, gypsum photosynthetic community, Microcoleus mat, Thiocapsa scum, and black mud) were sampled for the presence of the euryhaline, rapidly growing amoebomastigote, Paratetramitus jugosus. Field investigations of microbial mats from Baja California Norte, Mexico, and Salina Bido near Matanzas, Cuba, reveal that P. jugosus is most frequently found in the Thiocapsa layer of microbial mats. Various stages of the life history were studied using phase-contrast, differential-interference, and transmission electron microscopy. Mastigote stages were induced and studied by electron microscopy; mastigotes that actively feed on bacteria bear two or more undulipodia. A three-dimensional drawing of the kinetid ("basal apparatus") based on electron micrographs is presented. Although promitoses were occasionally observed, it is unlikely that they can account for the rapid growth of P. jugosus populations on culture media. Dense, refractile, spherical, and irregular-shaped bodies were seen at all times in all cultures along with small mononucleate (approximately 2-7 micrometers diameter) amoebae. Cytochemical studies employing two different fluorescent stains for DNA (DAPI, mithramycin) verified the presence of DNA in these small bodies. Chromatin-like material seen in electron micrographs within the cytoplasm and blebbing off nuclei were interpreted to the chromatin bodies. Our interpretation, consistent with the data but not proven, is that propagation by multiple fission of released chromatin bodies that become small amoebae may occur in Paratetramitus jugosus. These observations are consistent with descriptions of amoeba propagules in the early literature (Hogue, 1914).

Non-NASA Center↗
NASA NTRS2004

Brassica rapa plants adapted to microgravity with reduced photosystem I and its photochemical activity

The photosynthetic apparatus contains several protein complexes, many of which are regulated by environmental conditions. In this study, the influences of microgravity on PSI and PSII in Brassica rapa plants grown aboard the space shuttle were examined. We found that Brassica plants grown in space had a normal level of growth relative to controls under similar conditions on Earth. Upon return to Earth, cotyledons were harvested and thylakoid membranes were isolated. Analysis of chlorophyll contents showed that the Chl a/b ratio (3.5) in flight cotyledons was much higher than a ratio of 2.42 in the ground controls. The flight samples also had a reduction of PSI complexes and a corresponding 30% decrease of PSI photochemical activity. Immunoblotting showed that the reaction centre polypeptides of PSI were more apparently decreased (e.g. by 24-33% for PsaA and PsaB, and 57% for PsaC) than the light-harvesting complexes. In comparison, the accumulation of PSII complex was less affected in microgravity, thus only a slight reduction in D1, D2 and LHCII was observed in protein blots. However, there was a 32% decrease of OEC1 in the flight samples, indicating a defective OEC subcomplex. In addition, an average 54% increase of the 54 kDa CF1-beta isoform was found in the flight samples, suggesting that space-grown plants suffered from certain stresses, consistent with implications of the increased Chl a/b ratio. Taken together, the results demonstrated that Brassica plants can adapt to spaceflight microgravity, but with significant alterations in chloroplast structures and photosynthetic complexes, and especially reduction of PSI and its activity.

Non-NASA Center↗