Oligotrophy

Poindexter, Jeanne S.

doi:10.1007/978-1-4615-8306-6_2

Cited by 283 publications

(62 citation statements)

References 51 publications

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“…The fact that there is no competitive difference between a mutant defective in its ability to utilize an exogenous source of histidine and the wild-type indicates that the ability to utilize histidine in the plant environment does not contribute significantly toward competitive fitness in this environment. This finding is not surprising, given both the oligotrophic nature of the rhizosphere (Poindexter, 1981) and the diverse nutritional capabilities of P. fluorescens (Stanier et al, 1966).…”

Section: Discussionmentioning

confidence: 82%

The histidine utilization (hut) genes of Pseudomonas fluorescens SBW25 are active on plant surfaces, but are not required for competitive colonization of sugar beet seedlings

et al. 2006

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The histidine utilization (hut) genes of Pseudomonas fluorescens SBW25 are active on plant surfaces, but are not required for competitive colonization of sugar beet seedlings The ability to monitor the spatial and temporal distribution of signals in complex environments is necessary for an understanding of the function of bacteria in the wild. To this end, an existing recombinase-based transcriptional reporter strategy (recombinase-based in vivo expression technology, RIVET) has been extended and applied to the plant-colonizing bacterium Pseudomonas fluorescens SBW25. Central to the project was a rhizosphere-inducible locus, rhi14, which functional analyses show is hutT, a histidine-inducible gene that is required for histidine utilization. A transcriptional fusion between hutT and a promoterless site-specific recombinase (tnpR mut168 ) results in excision of a chromosomally integrated tetracycline-resistance cassette in a histidine-dependent manner. The dose-and time-responsiveness of the promoterless recombinase to histidine closely mirrored the histidine responsiveness of an identical hutT fusion to promoterless lacZ. To demonstrate the effectiveness of the strategy, the activity of hutT was monitored on sugar beet seedlings. Low levels of transcriptional activity were detected in the phyllosphere, rhizosphere and in plant extract, but not in vermiculite devoid of seedlings. The histidine concentration in the rhizosphere was estimated to be 0?6 mg ml "1 . The ecological significance of the hut locus was examined by competing a hutT deletion mutant against the wild-type during colonization of sugar beet seedlings. No impact on competitive fitness was detected, suggesting that the ability to utilize plant-derived histidine is not essential for bacterial colonization.

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Section: Discussionmentioning

confidence: 82%

The histidine utilization (hut) genes of Pseudomonas fluorescens SBW25 are active on plant surfaces, but are not required for competitive colonization of sugar beet seedlings

et al. 2006

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“…Despite the fact that such environments are, by volume, by far the most important on earth (i.e. the ocean below the photic zone), very little is known about the way in which the organisms that inhabit such environments have adapted to life under conditions of permanent nutrient scarcity (96). The study of such organisms presents very much of a challenge ~tnd to us appears to be potentially very exciting and rewarding.…”

Section: Discussionmentioning

confidence: 99%

Physiological Responses to Nutrient Limitation

Harder¹,

Dijkhuizen²

1983

Annu. Rev. Microbiol.

342

166

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“…Viable counts of heterotrophic bacteria were observed to be three to five times higher on low-nutrient agar media than on conventional agar media in a previous work concerning the colony-forming, as well as the "non-colony-forming," bacterial cells in soil [18]. Considering soil as a low nutrient environment, in which the flux of nutrients through the ecosystem is small relative to the volume [12], the heterotrophic, autochtonous soil microflora is assumed to be dominated by oligotrophic bacteria [17,20,24]. Oligotrophic bacteria can generally be isolated using a low-nutrient medium [11,24] and can often be grown on agar plates without any added nutrients [5].…”

Section: Introductionmentioning

confidence: 99%

The use of various substrates and substrate concentrations by a Hyphomicrobium sp. isolated from soil: Effect on growth rate and growth yield

Aa¹,

Olsen²

1996

Microb Ecol

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The content of Hyphomicrobium sp. was estimated from a clay loam soil using the most probable number technique with methanol as the sole carbon source. The method enumerated Hyphomicrobia as 0.2% of the total bacteria determined by acridine orange direct counts. Hyphomicrobium sp. was not able to use C-C compounds such as glucose or acetate for growth. Maximal growth yield and growth rate were obtained when the concentration of methanol was in the range of 0.5-5 mg C/liter. Substrate affinity measurements revealed Ks values of 0.8 μM and 5.8 μM when the methanol concentration was 0.5-2.5 μM and 5-200 μM, respectively. Hyphomicrobium sp. had the ability to assimilate volatile organic compounds from air for growth. A growth yield of 0.7 mg/liter cell carbon was obtained in a mineral medium that contained no additions of organic compounds but had been stored for 4 weeks in flasks, allowing volatile compounds from the air to dissolve in the medium. When air was pumped into the culture during cultivating, the growth yield was proportional to the flow rate of air into the culture.

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Oligotrophy

Cited by 283 publications

References 51 publications

The histidine utilization (hut) genes of Pseudomonas fluorescens SBW25 are active on plant surfaces, but are not required for competitive colonization of sugar beet seedlings

The histidine utilization (hut) genes of Pseudomonas fluorescens SBW25 are active on plant surfaces, but are not required for competitive colonization of sugar beet seedlings

Physiological Responses to Nutrient Limitation

The use of various substrates and substrate concentrations by a Hyphomicrobium sp. isolated from soil: Effect on growth rate and growth yield

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