Bacterial activity along a young barley root measured by the thymidine and leucine incorporation techniques

Söderberg, Katarina; Bååth, Erland

doi:10.1016/s0038-0717(98)00058-3

Cited by 72 publications

(48 citation statements)

References 31 publications

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“…The total amount of PLFA serves as an estimate for sediment microbial biomass [34]. Rhizosphere sediment contained higher microbial biomass compared to the control sediment, which was likely due to greater availability of substrates for microbial growth [35,36]. A variety of microbial PLFAs representative of total bacteria, gram-positive bacteria, gram-negative bacteria, fungi, and actinomycetes were identified from the sediment (Fig.…”

Section: Discussionmentioning

confidence: 99%

Root Radial Oxygen Loss and the Effects on Rhizosphere Microarea of Two Submerged Plants

Tian¹,

Wang²,

Tian³

et al. 2015

Pol. J. Environ. Stud.

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Radial oxygen loss (ROL) has been suggested to be a major process to protect plants exposed to the anaerobic by-products of soil anaerobiosis. The aim of the present study was to test the effects of root ROL from two submerged plants (Hydrilla verticillata and Vallisneria spiralis) on the rhizosphere oxygen profile and rhizosphere microarea. Phospholipid fatty acids (PLFAs) of sediment samples were used to characterize and quantify the microbial community. The results showed clearly that there were significant differences between the two plants in radial oxygen loss, which affected rhizosphere physicochemical parameters and the microbial community. Rhizosphere total biomass, bacteria, gram-positive bacteria, actinomycetes, and microbial diversity of V. spiralis were significantly higher than those of H. verticillata. The present study highlights root ROL as a key parameter affecting the microbial community of the rhizosphere microarea.

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Section: Discussionmentioning

confidence: 99%

Root Radial Oxygen Loss and the Effects on Rhizosphere Microarea of Two Submerged Plants

Tian¹,

Wang²,

Tian³

et al. 2015

Pol. J. Environ. Stud.

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“…It has been shown that there are positive correlations between activity and cell size (3), cell size and culturability (1,2), and activity and culturability (33). Thus, while they may carry a large proportion of the genetic material, the numerically dominant component of soil bacterial communities (consisting of very small cells [15]) does not contribute greatly to biomass or metabolic activity (1).…”

mentioning

confidence: 99%

Cultivation-Dependent and -Independent Approaches for Determining Bacterial Diversity in Heavy-Metal-Contaminated Soil

Ellis

Morgan²,

Weightman

et al. 2003

Appl Environ Microbiol

456

259

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In recent years, culture-independent methods have been used in preference to traditional isolation techniques for microbial community analysis. However, it is questionable whether uncultured organisms from a given sample are important for determining the impact of anthropogenic stress on indigenous communities. To investigate this, soil samples were taken from a site with patchy metal contamination, and the bacterial community structure was assessed with a variety of approaches. There were small differences in microscopic epifluorescence bacterial counts. Denaturing gradient gel electrophoresis (DGGE) profiles of 16S rRNA gene fragments (16S-DGGE) amplified directly from soil samples were highly similar. A clone library generated from the most contaminated sample revealed a diverse bacterial community, which showed similarities to pristine soil communities from other studies. However, the proportion of bacteria from the soil samples that were culturable on standard plate-counting media varied between 0.08 and 2.2%, and these values correlated negatively with metal concentrations. The culturable communities from each sample were compared by 16S-DGGE of plate washes and by fatty acid profiling of individual isolates. Each approach indicated that there were considerable differences between the compositions of the culturable communities from each sample. DGGE bands from both culture-based and culture-independent approaches were sequenced and compared. These data indicated that metal contamination did not have a significant effect on the total genetic diversity present but affected physiological status, so that the number of bacteria capable of responding to laboratory culture and their taxonomic distribution were altered. Thus, it appears that plate counts may be a more appropriate method for determining the effect of heavy metals on soil bacteria than culture-independent approaches.

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“…In fact, the rhizosphere has been recognized as an oligotrophic environment which contains minute cells whose growth is limited by a lack of substrates (22). On the other hand, probably due to variations in nutrient availability, as well as differences in the compositions of plant-derived compounds, spatial heterogeneity and temporal heterogeneity in microbial activity have been observed in the rhizosphere (8,17,27,35,45,51).…”

mentioning

confidence: 99%

“…The methods that have been used to assess the physiological state of cells in the rhizosphere include indirect estimation of growth rates based on differences in the number of CFU or the total bacterial counts measured at various times (47) and estimation of bacterial activity by determining the rate of respiration (56) and the rate of DNA and/or protein synthesis (35,51). To ascertain the in situ physiology of microbial cells in the rhizosphere, workers can use a number of methods based on cell extraction and subsequent microscopic observation; these methods include enumeration of cells having a measurable membrane potential by using redox dyes (27,46) and assessment of variations in cell length by using fluorescent dyes in combination with image analysis (5).…”

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confidence: 99%

Bacterial Activity in the Rhizosphere Analyzed at the Single-Cell Level by Monitoring Ribosome Contents and Synthesis Rates

Ramos

Mølbak

Molin

2000

Appl Environ Microbiol

165

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The growth activity of Pseudomonas putida cells colonizing the rhizosphere of barley seedlings was estimated at the single-cell level by monitoring ribosomal contents and synthesis rates. Ribosomal synthesis was monitored by using a system comprising a fusion of the ribosomal Escherichia coli rrnBP1 promoter to a gene encoding an unstable variant of the green fluorescent protein (Gfp). Gfp expression in a P. putida strain carrying this system inserted into the chromosome was strongly dependent on the growth phase and growth rate of the strain, and cells growing exponentially at rates of >0.17 h ؊1 emitted growth rate-dependent green fluorescence detectable at the single-cell level. The single-cell ribosomal contents were very heterogeneous, as determined by quantitative hybridization with fluorescently labeled rRNA probes in P. putida cells extracted from the rhizosphere of 1-day-old barley seedlings grown under sterile conditions. After this, cells extracted from the root system had ribosomal contents similar to those found in starved cells. There was a significant decrease in the ribosomal content of P. putida cells when bacteria were introduced into nonsterile bulk or rhizosphere soil, and the Gfp monitoring system was not induced in cells extracted from either of the two soil systems. The monitoring system used permitted nondestructive in situ detection of fast-growing bacterial microcolonies on the sloughing root sheath cells of 1-and 2-day-old barley seedlings grown under sterile conditions, which demonstrated that it may be possible to use the unstable Gfp marker for studies of transient gene expression in plant-microbe systems.

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Bacterial activity along a young barley root measured by the thymidine and leucine incorporation techniques

Cited by 72 publications

References 31 publications

Root Radial Oxygen Loss and the Effects on Rhizosphere Microarea of Two Submerged Plants

Root Radial Oxygen Loss and the Effects on Rhizosphere Microarea of Two Submerged Plants

Cultivation-Dependent and -Independent Approaches for Determining Bacterial Diversity in Heavy-Metal-Contaminated Soil

Bacterial Activity in the Rhizosphere Analyzed at the Single-Cell Level by Monitoring Ribosome Contents and Synthesis Rates

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