scholarly journals Biomass, community structure and nutritional status attributes of the deep subsurface microbiota---at Idaho and Hanford sites

1991 ◽  
Author(s):  
D. White ◽  
D. Ringelberg
Keyword(s):  
Community Structure ◽  
Nutritional Status ◽  
Deep Subsurface

In situ measurement of microbial biomass, community structure and nutritional status

1993 ◽  
Vol 344 (1670) ◽  
pp. 59-67 ◽  
Keyword(s):  
Fatty Acids ◽  
Community Structure ◽  
Microbial Biomass ◽  
Nutritional Status ◽  
Metabolic Activity ◽  
Total Phospholipid ◽  
Quantitative Measure ◽  
Essential Component ◽  
Quantitative Definition

In sediments and soils the extant microbiota that can be counted by direct microscopy have proved exceedingly difficult to isolate and culture. Classical tests are time consuming and provide little indication of the interactions within the community, the community nutritional status or metabolic activity. The in situ method is based on the extraction of ‘signature’ lipid biomarkers (SLB) from the cell membranes and walls of microorganisms. Lipids are cellular components that are recoverable by extraction with organic solvents. Lipids are an essential component of the membrane of all cells and play a role as storage materials. Extraction of the lipid components of the microbiota from soils and sediments provides both purification and concentration together with an in situ quantitative analysis of the microbial biomass, community structure, and nutritional status. The determination of the total phospholipid ester-linked fatty acids (PLFA) provides a quantitative measure of the viable biomass. Viable microbes have an intact membrane which contains phospholipids (and PLFA). With cell death enzymes hydrolyze the phosphate group within minutes to hours. The lipid core remains as diglyceride (DG). The resulting DG has the same signature fatty acids as the phospholipids (until it degrades) so a comparison of the ratio of PLFA to DG provides an indication of the viable and nonviable microbes. Analysis by SLB technique provides a quantitative definition of the microbial community structure as specific groups of microbes contain characteristic PLFA patterns. The analysis of other lipids such as the sterols (for the microeukaryotes -nematodes, algae, protozoa), glycolipids (for the phototrophs, gram-positive bacteria), or the hydroxy fatty acids in the lipopolysaccharide of the lipid A (gramnegative bacteria) can provide more detailed community structure analysis. The formation of poly (3-hydroxyalkanoic acid (PHA) in bacteria or triglyceride (TG) in the microeukaryotes relative to the PLFA provides a measure of the nutritional status. Bacteria grown with adequate carbon and terminal electron acceptors form PHA when they cannot divide, because some essential component is missing. Rates of incorporation of 14 C-acetate into PHA relative to PLFA is a sensitive indicator of disturbance artifacts in estimates of metabolic activity in sediments with redox gradients. Exposure to toxic environments can lead to minicell formation and increases in specific PLFAS. Respiratory quinone structure indicates the proportions of aerobic/anaerobic activities in the community. The SLB technology provides quantitative in situ information that define the microbial ecology in sedimentary geochemical processes.

Diversity and Community Structure of Archaea in Deep Subsurface Sediments from the Tropical Western Pacific

2009 ◽  
Vol 60 (6) ◽  
pp. 439-445 ◽  
Author(s):  
Wei Zhang ◽  
Gaowa Saren ◽  
Tiegang Li ◽  
Xinke Yu ◽  
Linbao Zhang
Keyword(s):  
Community Structure ◽  
Western Pacific ◽  
Deep Subsurface ◽  
Tropical Western Pacific ◽  
Subsurface Sediments

scholarly journals Rhizosphere Microbial Community Structure in Relation to Root Location and Plant Iron Nutritional Status

2000 ◽  
Vol 66 (1) ◽  
pp. 345-351 ◽  
Author(s):  
Ching-Hong Yang ◽  
David E. Crowley
Keyword(s):  
Community Structure ◽  
Nutritional Status ◽  
Microbial Communities ◽  
16S Rdna ◽  
Bacterial Communities ◽  
Root Exudate ◽  
Primary Root ◽  
Root Tips ◽  
Root Zones ◽  
The Impact

ABSTRACT Root exudate composition and quantity vary in relation to plant nutritional status, but the impact of the differences on rhizosphere microbial communities is not known. To examine this question, we performed an experiment with barley (Hordeum vulgare) plants under iron-limiting and iron-sufficient growth conditions. Plants were grown in an iron-limiting soil in root box microcosms. One-half of the plants were treated with foliar iron every day to inhibit phytosiderophore production and to alter root exudate composition. After 30 days, the bacterial communities associated with different root zones, including the primary root tips, nonelongating secondary root tips, sites of lateral root emergence, and older roots distal from the tip, were characterized by using 16S ribosomal DNA (rDNA) fingerprints generated by PCR-denaturing gradient gel electrophoresis (DGGE). Our results showed that the microbial communities associated with the different root locations produced many common 16S rDNA bands but that the communities could be distinguished by using correspondence analysis. Approximately 40% of the variation between communities could be attributed to plant iron nutritional status. A sequence analysis of clones generated from a single 16S rDNA band obtained at all of the root locations revealed that there were taxonomically different species in the same band, suggesting that the resolving power of DGGE for characterization of community structure at the species level is limited. Our results suggest that the bacterial communities in the rhizosphere are substantially different in different root zones and that a rhizosphere community may be altered by changes in root exudate composition caused by changes in plant iron nutritional status.

scholarly journals Phytoplankton and Eutrophication Degree Assessment of Baiyangdian Lake Wetland, China

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Xing Wang ◽  
Yu Wang ◽  
Lusan Liu ◽  
Jianmin Shu ◽  
Yanzhong Zhu ◽  
...  
Keyword(s):  
Community Structure ◽  
Nutritional Status ◽  
Dominant Species ◽  
Phytoplankton Community ◽  
Phytoplankton Community Structure ◽  
Baiyangdian Lake

Eight typical sampling sites were chosen to investigate the phytoplankton community structure and to assess the eutrophication degree of Baiyangdian Lake in 2009. Our results showed that among the total 133 species identified, Cyanophyta, Chlorophyta, and Bacillariophyta dominated the phytoplankton community. In spring, Chlorophyta and Bacillariophyta were the dominant phyla, and the dominant species includedChlorellasp.,Chroomonas acutaUterm., andMicrocystis incertaLemm.; the density of the phytoplankton ranged from496×104to6256×104 cells/L with an average of2384×104 cells/L. However, Chlorophyta and Cyanophyta became the dominant phyla in summer, and the dominant species wereChlorellasp.,Leptolyngbya valderianaAnagn., andNephrocytium agardhianumNageli.; the density of the phytoplankton varied from318×104to4630×104 cells/L with an average of1785×104 cells/L. The density of the phytoplankton has increased significantly compared to the previous investigations in 2005. The index of Carlson nutritional status (TSIM) and the dominant genus assessment indicated that the majority of Baiyangdian Lake was in eutrophic state.

scholarly journals The nutritional status of zooplankton in a tropical reservoir: effects of food quality and community structure

2005 ◽  
Vol 65 (2) ◽  
pp. 313-324 ◽  
Author(s):  
R. M. Pinto-Coelho ◽  
A. Giani ◽  
C. A. Morais-Jr. ◽  
E. R. Carvalho-Jr. ◽  
J. F. Bezerra-Neto
Keyword(s):  
Community Structure ◽  
Nutritional Status ◽  
Temporal Variability ◽  
Lipid Levels ◽  
Phytoplankton Composition ◽  
Tropical Reservoir ◽  
Elementary Composition ◽  
Annual Cycles ◽  
Specific Composition ◽  
Energetic Reserves

The temporal variability of energetic reserves of zooplankton in the eutrophic Pampulha reservoir was investigated during two successive annual cycles. The effects of dominance of large filter-feeding cladocerans (Daphnia) and the occurrence of massive blooms of the cyanobacteria Microcystis on the energetic reserves of zooplankton were tested. This study showed that phytoplankton composition has a greater effect on energetic reserves of zooplankton. Some associations between lipid levels and the specific composition of zooplankton were also found. This study also demonstrated that the elementary composition of phosphorus in zooplankton can be used as an estimator of the nutritional status of zooplankton.

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