Gene transfer in the marine environment

Hermansson, Malte; Linberg, Christel

doi:10.1111/j.1574-6941.1994.tb00228.x

Cited by 27 publications

(13 citation statements)

References 38 publications

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“…Examples of such natural hot spots are the scum layers on standing bodies of water and the surface microlayers (SML) in lakes and oceans (17,28). Our postulate is corroborated by various studies that observed plasmid transfer or detected plasmids in such natural ecosystems (4,19,20,32,38,44). There are multiple possible explanations for the observed increased plasmid transfer at the air-liquid interface compared to that in submerged biofilms, and they likely involve a combination of the physical properties of the environment as well as the physiological state of the cells.…”

Section: Discussionsupporting

confidence: 73%

Increased Transfer of a Multidrug Resistance Plasmid in Escherichia coli Biofilms at the Air-Liquid Interface

Król

Nguyen

Rogers

et al. 2011

Appl Environ Microbiol

102

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Although biofilms represent a common bacterial lifestyle in clinically and environmentally important habitats, there is scant information on the extent of gene transfer in these spatially structured populations. The objective of this study was to gain insight into factors that affect transfer of the promiscuous multidrug resistance plasmid pB10 in Escherichia coli biofilms. Biofilms were grown in different experimental settings, and plasmid transfer was monitored using laser scanning confocal microscopy and plate counting. In closed flow cells, plasmid transfer in surface-attached submerged biofilms was negligible. In contrast, a high plasmid transfer efficiency was observed in a biofilm floating at the air-liquid interface in an open flow cell with low flow rates. A vertical flow cell and a batch culture biofilm reactor were then used to detect plasmid transfer at different depths away from the air-liquid interface. Extensive plasmid transfer occurred only in a narrow zone near that interface. The much lower transfer frequencies in the lower zones coincided with rapidly decreasing oxygen concentrations. However, when an E. coli csrA mutant was used as the recipient, a thick biofilm was obtained at all depths, and plasmid transfer occurred at similar frequencies throughout. These results and data from separate aerobic and anaerobic matings suggest that oxygen can affect IncP-1 plasmid transfer efficiency, not only directly but also indirectly, through influencing population densities and therefore colocalization of donors and recipients. In conclusion, the air-liquid interface can be a hot spot for plasmid-mediated gene transfer due to high densities of juxtaposed donor and recipient cells.

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Section: Discussionsupporting

confidence: 73%

Increased Transfer of a Multidrug Resistance Plasmid in Escherichia coli Biofilms at the Air-Liquid Interface

Król

Nguyen

Rogers

et al. 2011

Appl Environ Microbiol

102

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“…Similar results were reported by Ogram et al (25) for extracellular DNA extracted from freshwater sediments and by De Flaun and Jeffrey (4) for extracellular DNA in the dissolved fraction of seawater samples. Therefore, although the presence of intact 16S rRNA genes in extracellular DNA could not be confirmed for our sediment samples, we could not exclude the possibility that other intact gene sequences could be present and might participate in natural transformation processes (11).…”

Section: Resultsmentioning

confidence: 99%

Simultaneous Recovery of Extracellular and Intracellular DNA Suitable for Molecular Studies from Marine Sediments

Corinaldesi

Danovaro

Dell’Anno

2005

Appl Environ Microbiol

249

205

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The occurrence of high extracellular DNA concentrations in aquatic sediments (concentrations that are 3 to 4 orders of magnitude greater than those in the water column) might play an important role in biogeochemical cycling, as well as in horizontal gene transfer through natural transformation. Since isolation of extracellular DNA from sediments is a difficult and unsolved task, in this study we developed an efficient procedure to recover simultaneously DNA associated with microbial cells and extracellular DNA from the same sediment sample. This procedure is specifically suitable for studying extracellular DNA because it avoids any contamination with DNA released by cell lysis during handling and extraction. Applying this procedure to different sediment types, we obtained extracellular DNA concentrations that were about 10 to 70 times higher than the intracellular DNA concentrations. Using specific targeted prokaryotic primers, we obtained evidence that extracellular DNA recovered from different sediments did not contain amplifiable 16S rRNA genes. By contrast, using DNA extracted from microbial cells as the template, we always amplified 16S rRNA genes. Although 16S rRNA genes were not detected in extracellular DNA, analyses of the sizes of extracellular DNA indicated the presence of high-molecular-weight fragments that might have contained other gene sequences. This protocol allows investigation of extracellular DNA and its possible participation in natural transformation processes.All aquatic sediments are characterized by high DNA concentrations (concentrations that are 3 to 4 orders of magnitude greater than those found in the water column), mostly (up to 90%) due to extracellular DNA (3,5,7,8,23). Previous studies reported that complex refractory organic molecules and/or inorganic particles are able to bind, adsorb, and stabilize free DNA in sediments (17,21,28). Dell'Anno et al. (8) reported that the free extracellular DNA fraction represented less than 5% of the total extracellular DNA pool. The adsorption of extracellular DNA in the sediment might reduce its degradability, and indeed only about 50% of this DNA can be hydrolyzed by nucleases (8). Consequently, the residence time of extracellular DNA in sediments can be much longer than the residence time in the water column (17,22). The presence and persistence of large amounts of extracellular DNA in the deeper sediment layers (2, 5) might have important implications for bacterial metabolism, providing a source of nitrogen and phosphorous and/or exogenous nucleotides (3,7,14,27,32), and may also contribute to horizontal gene transfer through natural transformation (17,24).In the last few years, several protocols for extraction of DNA from soils and sediments have been developed and improved (13,15,29,31,35). In fact, application of culture-independent nucleic acid techniques involving DNA extraction and molecular analyses has allowed the detection and identification of microorganisms in natural environments (10). At the same time, much effort has also b...

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“…Heterogeneous and contradictory results have been reported on the influence of plasmids on bacterial survival. Some authors reported that in aquatic systems plasmid bearing strains can survive as well as their wild‐type counterparts, or even better [53–63]. In contrast, other authors have not observed effects of plasmids on the survival of their hosts [55].…”

Section: Environmental Factors Affecting Survivalmentioning

confidence: 99%

Survival of allochthonous bacteria in aquatic systems: a biological approach

Barcina¹,

Lebaron²,

Vives-Rego³

2006

FEMS Microbiology Ecology

151

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The survival of allochthonous bacteria in aquatic systems is affected by biotic and abiotic environmental factors. Grazing by protozoa is one of the main biological processes that control allochthonous bacterial density. Its extent depends on the concentration of bacteria and the digestion capacity of the grazer. The physiological state of bacteria is affected by multiple physicochemical stresses, to which they respond by entering a dormant, viable but non‐culturable state. Starved bacteria show a tendency to shrink, and a generally enhanced resistance to heat, oxidative and osmotic shock is observed. Nutrient scarcity, temperature, osmotic stress and visible light seem to be the abiotic factors that most negatively influence survival. The negative effect of light upon the culturability of enterobacteria in aquatic systems has long been recognized. In relation to the influence of plasmids on bacterial survival, heterogeneous and contradictory results have been reported. Some authors reported that plasmid‐bearing strains can survive as well as their wild‐type counterparts or even better, whereas in other reports the effects of various plasmids on the survival of their hosts were very variable. Plasmid transfer could be affected by the physiological status of donors and recipients during survival. Flow cytometry is a recent approach with great potential, especially for assessing the heterogeneity of cell size, metabolic state and molecular content in the population.

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Gene transfer in the marine environment

Cited by 27 publications

References 38 publications

Increased Transfer of a Multidrug Resistance Plasmid in Escherichia coli Biofilms at the Air-Liquid Interface

Increased Transfer of a Multidrug Resistance Plasmid in Escherichia coli Biofilms at the Air-Liquid Interface

Simultaneous Recovery of Extracellular and Intracellular DNA Suitable for Molecular Studies from Marine Sediments

Survival of allochthonous bacteria in aquatic systems: a biological approach

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