In situ survival of plasmid-bearing and plasmidless Pseudomonas aeruginosa in pristine tropical waters

Cruz-Cruz, Norma E.; Toranzos, Gary A.; Ahearn, Donald G.; Hazen, Terry C.

doi:10.1128/aem.54.10.2574-2577.1988

Cited by 27 publications

(7 citation statements)

References 20 publications

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“…The alternate hypothesis that the particular pBRC60bearing isolates characterized in this work maintained the plasmid but did not express the 3Cba genes in situ, and that our techniques failed to isolate those bacteria actually de-grading 3Cba, must also be acknowledged. Recent studies have reported the stability of plasmids after introduction to soil or aquatic systems (2,7,9) or in continuous cultures (4,30). Host bacteria experience long-term growth disadvantages only when plasmids carry constitutive genes or large pieces of heterologous DNA (28,30).…”

Section: Resultsmentioning

confidence: 99%

Transfer and Expression of the Catabolic Plasmid pBRC60 in Wild Bacterial Recipients in a Freshwater Ecosystem

Fulthorpe

Wyndham

1991

Appl Environ Microbiol

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Chlorobenzoate (3Cba)-degrading bacteria were isolated from the waters and sediments of flowthrough mesocosms dosed with various concentrations of 3Cba and inoculated with a 3Cba-degrading Alcaligenes sp., strain BR60. Bacteria capable of 3Cba degradation which were distinct from BR60 were isolated. They carried pBRC60, a plasmid introduced with Alcaligenes sp. strain BR60 that carries a transposable element (Tn5271) encoding 3Cba degradation. The isolates expressed these genes in different ways. The majority of pBRC60 recipients were motile, yellow-pigmented, gram-negative rods related to the group III pseudomonads and to BR60 by substrate utilization pattern. They were capable of complete 3Cba degradation at both millimolar and micromolar concentrations. Two isolates, Pseudomonas fluorescens PR24B(pBRC60) and Pseudomonas sp. strain PR120(pBRC60), are more distantly related to BR60 and both produced chlorocatechol when exposed to 3Cba at millimolar concentrations in the presence of yeast extract. These species showed poor growth in liquid 3Cba minimal medium but could degrade 3Cba in continuous cultures dosed with micromolar levels of the chemical. Laboratory matings confirm that pBRC60 can transfer from BR60 to species in both the beta and gamma subgroups of the proteobacteria and that 3Cba gene expression is variable between species. Selection pressures acting on pBRC60 recipients are discussed.

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Section: Resultsmentioning

confidence: 99%

Transfer and Expression of the Catabolic Plasmid pBRC60 in Wild Bacterial Recipients in a Freshwater Ecosystem

Fulthorpe

Wyndham

1991

Appl Environ Microbiol

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“…In more recent work, Morgan et al (26) found that the metabolic burden imposed by overexpression of a recombinant gene carried on a plasmid exerted a negative selection pressure on maintenance of the plasmid in a P. putida strain released into sterile lake water. In contrast, other studies show no plasmid loss when a number of Pseudomonas and E. coli strains were introduced into lake water, seawater, or sediments (5,8,10,15,30,32). Furthermore, selection pressure for retention of plasmid-encoded traits is not always necessary for plasmid maintenance by bacteria in natural waters, as revealed by studies involving plasmids carrying nonselected traits in P. putida strains (6,21).…”

Section: Discussionmentioning

confidence: 97%

Adaptation of model genetically engineered microorganisms to lake water: growth rate enhancements and plasmid loss

Sobecky

Schell

Moran

et al. 1992

Appl Environ Microbiol

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When a genetically engineered microorganism (GEM) is released into a natural ecosystem, its survival, and hence its potential environmental impact, depends on its genetic stability and potential for growth under highly oligotrophic conditions. In this study, we compared plasmid stability and potential for growth on low concentrations of organic nutrients of strains ofPseudomonas putida serving as model GEMs. Plasmid-free and plasmid-bearing (NAH7) prototrophic isogenic strains and two amino-acid auxotrophs, all containing antibiotic resistance markers, were held physically separate from but in chemical contact with lake water containing the natural bacterium-sized microbial populations. Cells were reisolated at intervals over a 2-month period to determine the percent retaining the plasmid and the specific growth rate on various media. Plasmid stability in lake water was strongly strain specific; the NAH7 plasmid was stably maintained by the prototrophic strain for the duration of the test but was lost within 24 h by both of the auxotrophs. Specific growth rates of reisolates, compared with those of the corresponding non-lake water-exposed strains (i.e., parental strains), were not different when measured in rich medium (Luria-Bertani broth). However, specific growth rates were 42, 55, and 63% higher in reisolates of auxotrophs and the plasmid-free prototroph, respectively, when measured in 10-fold-diluted medium after exposure of 15 days or longer to lake water. Moreover, lake water-exposed strains grew actively when reintroduced into sterile lake water (28to 33-fold increase in numbers over 7 days), while the corresponding unadapted parental strains exhibited no growth over the same period. Postrelease adaptations to oligotrophic environments tend to increase the fitness of GEMs for survival and establishment of populations in aquatic ecosystems. Such genetic changes might not be detectable by using standard laboratory characterizations of parental strains yet may be critical to assessments of a particular GEM's efficacy or the risks associated with its release into the environment.

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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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In situ survival of plasmid-bearing and plasmidless Pseudomonas aeruginosa in pristine tropical waters

Cited by 27 publications

References 20 publications

Transfer and Expression of the Catabolic Plasmid pBRC60 in Wild Bacterial Recipients in a Freshwater Ecosystem

Transfer and Expression of the Catabolic Plasmid pBRC60 in Wild Bacterial Recipients in a Freshwater Ecosystem

Adaptation of model genetically engineered microorganisms to lake water: growth rate enhancements and plasmid loss

Survival of allochthonous bacteria in aquatic systems: a biological approach

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