Bacterial communities in Fe/Mn films, sulphate crusts, and aluminium glazes from Swedish Lapland: implications for astrobiology on Mars

2013 ◽  
Vol 12 (4) ◽  
pp. 345-356 ◽  
Author(s):  
Cassandra L. Marnocha ◽  
John C. Dixon
Keyword(s):  
Bacterial Communities ◽  
Sem Analysis ◽  
Molecular Techniques ◽  
Surface Conditions ◽  
Rock Varnish ◽  
Coating Formation ◽  
Mars Pathfinder ◽  
Mineral Coatings ◽  
Rock Coatings ◽  
Mars Exploration Rovers

AbstractRock coatings have been observed on Mars by Mars Pathfinder, Viking and the Mars Exploration Rovers. Although rock varnish has been studied for its potential as a biosignature, other types of rock coating have been largely ignored. In Kärkevagge, Swedish Lapland, sulphate crusts, aluminium glazes and Fe/Mn films occur with mineralogies mimicking those observed on the surface of Mars. Molecular analysis and scanning electron microscopy (SEM) were used to investigate the bacterial communities associated with these rock coatings. Molecular techniques revealed differences in community structure and metabolisms associated with the production of secondary minerals between the three coating types. SEM analysis showed evidence of encrustation in mineral coatings in the Fe/Mn films and aluminium glazes, and evidence of abundant microbial communities in all three coating types. These observations provide evidence for bacterial participation in the genesis of rock coatings. For astrobiology on Mars, rock coatings are an attractive biosignature target scientifically and logistically: they are surface environments easily accessible by rovers, endoliths are afforded protection from surface conditions, and evidence of life could potentially be preserved through biomineralization and lithification. This study describes the bacterial communities from rock coatings compatible with martian mineralogy, explores the potential for biologically facilitated rock-coating formation, and supports rock coatings as targets of astrobiological interest on Mars.

The Use of Metallographic and SEM Analysis for Characterization of Sidewall Surfaces in MEMS Devices with DRIE Processing

2010 ◽  
Vol 2010 (1) ◽  
pp. 000703-000706
Author(s):  
Colin Stevens ◽  
Robert Dean ◽  
Samuel Lawrence ◽  
Lee Levine
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Measurement Techniques ◽  
Sem Analysis ◽  
Defect Structures ◽  
Mems Devices ◽  
Depth Of Focus ◽  
Surface Conditions ◽  
Side Walls

The Bosch Deep Reactive Ion Etch Process is commonly used for the manufacture of MEMS and MOEMS devices that require deep high aspect ratio trenches. In many cases fully released, high aspect ratio features can be generated in one pass. However the process must be understood to avoid generating some of the defect structures that are characteristic of the process. Defects such as scalloping, silicon grass, and undercutting at the interface of a nonconductive layer can be controlled by process parameters and optimization. Measurement and characterization of the defective structures is a key element of controlling them. The use of SEM measurement techniques for characterizing the small features associated with scalloping and silicon grass is essential. No other technique is capable of providing the large depth of focus required to visualize these features. The use of metallographic techniques furthers understanding of the surface conditions on the side walls of these deep trenches.

Analysis of nitrifying bacterial communities in aerobic biofilm reactors with different DO conditions using molecular techniques

2008 ◽  
Vol 57 (12) ◽  
pp. 1889-1899 ◽  
Author(s):  
J. J. Park ◽  
I. G. Byun ◽  
J. C. Yu ◽  
S. R. Park ◽  
D. J. Ju ◽  
...  
Keyword(s):  
Bacterial Communities ◽  
Denaturing Gradient Gel Electrophoresis ◽  
In Situ Hybridisation ◽  
Amoa Gene ◽  
Biofilm Reactor ◽  
Molecular Techniques ◽  
Fluorescence In Situ Hybridisation ◽  
Do Concentration ◽  
Pcr Targeting ◽  
The Relationship

In order to assess the relationship between the dissolved oxygen (DO) concentration and the characteristics of nitrifying bacterial communities in an aerobic biofilm reactor, molecular techniques including denaturing gradient gel electrophoresis (DGGE)/cloning based on PCR targeting 16S rRNA and the amoA gene and fluorescence in situ hybridisation (FISH) were conducted. The D-1, D-2, D-3 and D-4 reactors with different DO concentrations (1, 3, 5 and 7 mg/L, respectively) were set up in the thermostat and acclimated. The optimal DO concentration with stable nitrification efficiency was above 5.0 mg/L. As was shown by the results of DGGE and cloning, the community of ammonia-oxidising bacteria (AOB) and the ratio of Nitrosomonas sp. changed only slightly despite their differing nitrification efficiencies. The results of FISH indicated that higher DO concentrations resulted in an increase in AOB and nitrite-oxidising bacteria (NOB), and a reduction in heterotrophic microorganisms. The INT-dehydrogenase activity (DHA) test demonstrated that the activity of AOB decreased with reductions in the DO concentration. This means that the DO concentration does not influence the community of AOB, but rather the activity of AOB. In the relationship between the attached biomass and the nitrification efficiency, only the active biomass affected the nitrification efficiencies.

Diversity of rock varnish bacterial communities from Black Canyon, New Mexico

2010 ◽  
Vol 115 (G2) ◽  
pp. n/a-n/a ◽  
Author(s):  
Diana E. Northup ◽  
Jessica R. Snider ◽  
Michael N. Spilde ◽  
Megan L. Porter ◽  
Jodie L. van de Kamp ◽  
...  
Keyword(s):  
New Mexico ◽  
Bacterial Communities ◽  
Rock Varnish

scholarly journals Mars Pathfinder Spacecraft, Lander, and Rover Testing in Simulated Deep Space and Mars Surface Environments

1997 ◽  
Vol 40 (5) ◽  
pp. 17-26
Author(s):  
Kenneth Johnson
Keyword(s):  
Environmental Conditions ◽  
Thermal Characteristics ◽  
Thermal Response ◽  
Thermal Design ◽  
Deep Space ◽  
Test Program ◽  
Mars Rover ◽  
Surface Conditions ◽  
Wind Speeds ◽  
Mars Pathfinder

The Mars Pathfinder (MPF) spacecraft was built and tested at the Jet Propulsion Laboratory during 1995 and 1996. MPF was launched December 4, 1996, and successfully landed on Mars on July 4, 1997. The testing program required that the mission hardware be subjected to both deep space and Mars surface conditions. A series of tests were devised and conducted from January, 1995, to July, 1996, to study the thermal response of the MPF spacecraft to the environmental conditions to which it was to be exposed during the cruise phase (on the way to Mars) and the lander phase (landed on Mars). In addition, several tests were conducted to study the thermal characteristics of the Mars rover. Sojourner, under Mars surface environmental conditions. Several special test fixtures and methods were devised to simulate the required environmental conditions. Creating simulated Mars surface conditions was a challenging undertaking since the Mars surface is subjected to diurnal cycling between -20°C and -85°C, with wind speeds to 20 m/sec, occurring in an 8 torr CO2 atmosphere. This paper describes the MPF test program conducted at JPL to verify the MPF thermal design.

scholarly journals Coral-Associated Bacteria and Their Role in the Biogeochemical Cycling of Sulfur

2009 ◽  
Vol 75 (11) ◽  
pp. 3492-3501 ◽  
Author(s):  
Jean-Baptiste Raina ◽  
Dianne Tapiolas ◽  
Bette L. Willis ◽  
David G. Bourne
Keyword(s):  
16S Rrna ◽  
Acrylic Acid ◽  
16S Rrna Gene ◽  
Bacterial Communities ◽  
Sulfur Compounds ◽  
Molecular Techniques ◽  
Rrna Gene ◽  
Coral Mucus ◽  
Associated Bacteria ◽  
Cooling Effects

ABSTRACT Marine bacteria play a central role in the degradation of dimethylsulfoniopropionate (DMSP) to dimethyl sulfide (DMS) and acrylic acid, DMS being critical to cloud formation and thereby cooling effects on the climate. High concentrations of DMSP and DMS have been reported in scleractinian coral tissues although, to date, there have been no investigations into the influence of these organic sulfur compounds on coral-associated bacteria. Two coral species, Montipora aequituberculata and Acropora millepora, were sampled and their bacterial communities were characterized by both culture-dependent and molecular techniques. Four genera, Roseobacter, Spongiobacter, Vibrio, and Alteromonas, which were isolated on media with either DMSP or DMS as the sole carbon source, comprised the majority of clones retrieved from coral mucus and tissue 16S rRNA gene clone libraries. Clones affiliated with Roseobacter sp. constituted 28% of the M. aequituberculata tissue libraries, while 59% of the clones from the A. millepora libraries were affiliated with sequences related to the Spongiobacter genus. Vibrio spp. were commonly isolated from DMS and acrylic acid enrichments and were also present in 16S rRNA gene libraries from coral mucus, suggesting that under “normal” environmental conditions, they are a natural component of coral-associated communities. Genes homologous to dddD, and dddL, previously implicated in DMSP degradation, were also characterized from isolated strains, confirming that bacteria associated with corals have the potential to metabolize this sulfur compound when present in coral tissues. Our results demonstrate that DMSP, DMS, and acrylic acid potentially act as nutrient sources for coral-associated bacteria and that these sulfur compounds are likely to play a role in structuring bacterial communities in corals, with important consequences for the health of both corals and coral reef ecosystems.

Phylogenetic analysis of bacterial populations in waters of the former Texcoco Lake, Mexico

2004 ◽  
Vol 50 (12) ◽  
pp. 1049-1059 ◽  
Author(s):  
Janet Jan-Roblero ◽  
Xochitl Magos ◽  
Luis Fernández ◽  
César Hernández-Rodríguez ◽  
Sylvie Le Borgne
Keyword(s):  
16S Rdna ◽  
Bacterial Communities ◽  
Soda Lakes ◽  
Phylogenetic Analyses ◽  
Bacterial Species ◽  
Intergenic Spacer ◽  
Molecular Techniques ◽  
Preliminary Evaluation ◽  
Gram Positive ◽  
Gram Positive Bacteria

Molecular techniques were used to compare the compositions of the bacterial communities of the 2 following lagoons from the former soda Texcoco Lake, Mexico: the restored Facultativa lagoon and the Nabor Carrillo lagoon. Ribosomal intergenic spacer analysis (RISA) revealed that bacterial communities of the 2 lagoons were different and presented a relatively low diversity. Clone libraries of 16S rDNA genes were constructed, and significant phylotypes were distinguished by restriction fragment length polymorphism (RFLP). A representative clone from each phylotype was partially sequenced. Molecular identification and phylogenetic analyses based on ribosomal sequences revealed that the Facultativa lagoon harbored mainly γ- and β-Proteobacteria, low G+C Gram-positive bacteria, and several members of the Halobacteriaceae family of archaea. The Nabor Carrillo lagoon mainly included typical halophilic and alkaliphilic low G+C Gram-positive bacteria, γ-Proteobacteria, and β-Proteobacteria similar to those found in other soda lakes. Several probably noncultured new bacterial species were detected. Three strains were isolated from the Nabor Carrillo lagoon, their partial 16S rDNA sequences were obtained. On this basis, they were identified as Halomonas magadiensis (H1), Halomonas eurihalina (H2), and Staphylococcus sciuri (H3). This is the first study that uses molecular techniques to investigate potential genetic diversity in the Texcoco lakes. In this preliminary evaluation, we infer the presence of alkalophilic, halophilic, or haloalkaliphilic bacteria potentially useful for biotechnology.Key words: bacterial diversity, 16S rDNA gene, soda lakes, former soda Texcoco Lake, Mexico, alkaliphiles, halophiles, haloalkaliphiles.

scholarly journals Changes in Bacterial Communities of the Marine Sponge Mycale laxissima on Transfer into Aquaculture†

2007 ◽  
Vol 74 (4) ◽  
pp. 1209-1222 ◽  
Author(s):  
Naglaa M. Mohamed ◽  
Julie J. Enticknap ◽  
Jayme E. Lohr ◽  
Scott M. McIntosh ◽  
Russell T. Hill
Keyword(s):  
16S Rrna ◽  
Marine Sponge ◽  
Bacterial Communities ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Molecular Techniques ◽  
Rrna Gene ◽  
Surrounding Water ◽  
Clone Libraries ◽  
Recirculating Aquaculture Systems ◽  
Mycale Laxissima

ABSTRACT The changes in bacterial communities associated with the marine sponge Mycale laxissima on transfer to aquaculture were studied using culture-based and molecular techniques. M. laxissima was maintained alive in flowthrough and closed recirculating aquaculture systems for 2 years and 1 year, respectively. The bacterial communities associated with wild and aquacultured sponges, as well as the surrounding water, were assessed using 16S rRNA gene clone library analysis and denaturing gradient gel electrophoresis (DGGE). Bacterial richness and diversity were measured using DOTUR computer software, and clone libraries were compared using S-LIBSHUFF. DGGE analysis revealed that the diversity of the bacterial community of M. laxissima increased when sponges were maintained in aquaculture and that bacterial communities associated with wild and aquacultured M. laxissima were markedly different than those of the corresponding surrounding water. Clone libraries of bacterial 16S rRNA from sponges confirmed that the bacterial communities changed during aquaculture. These communities were significantly different than those of seawater and aquarium water. The diversity of bacterial communities associated with M. laxissima increased significantly in aquaculture. Our work shows that it is important to monitor changes in bacterial communities when examining the feasibility of growing sponges in aquaculture systems because these communities may change. This could have implications for the health of sponges or for the production of bioactive compounds by sponges in cases where these compounds are produced by symbiotic bacteria rather than by the sponges themselves.

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