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PubMed2005

Island size and bacterial diversity in an archipelago of engineering machines.

There is an increasing realization that progress in bacterial ecology can be further advanced by applying theories and models developed in ecology. Consequently, there is a significant need to assess the applicability of such tools, developed specifically for macroorganisms, for investigating the underlying issues that determine bacterial diversity and community assemblage. In this study, we employed the island biogeography species-area model, originally conceived to assess colonization of islands by macroorganisms, to assess bacterial communities colonizing metal-cutting fluids from machines of increasing sump tank size, taking these to be analogous to islands of variable size. This system was selected because it is well studied and compared with other natural bacterial communities has a relatively low (manageable) diversity. Our findings show that island biogeography theory holds for the bacterial communities studied, in that smaller sump tanks contained lower and putatively less stable diversity, and larger sumps had greater diversity and were temporally stable. It was found that the calculated power law indices (i.e. z-values) were similar for all sample sets, and strikingly, typical of those observed in classical ecology. This was not expected as bacteria have significant distinguishing features such as huge population sizes, rapid asexual reproduction and small body size that facilitate dispersal, and are particularly resistant to extinction.

Bacteria↗

PubMed1992

Biodegradation of phenoxyacetic acid in soil by Pseudomonas putida PP0301(pR0103), a constitutive degrader of 2,4-dichlorophenoxyacetate.

The efficacy of using genetically engineered microbes (GEMs) to degrade recalcitrant environmental toxicants was demonstrated by the application of Pseudomonas putida PP0301(pR0103) to an Oregon agricultural soil amended with 500 micrograms/g of a model xenobiotic, phenoxyacetic acid (PAA). P. putida PP0301(pR0103) is a constitutive degrader of 2,4-dichlorophenoxyacetate (2,4-D) and is also active on the non-inducing substrate, PAA. PAA is the parental compound of 2,4-dichlorophenoxyacetic acid (2,4-D) and whilst the indigenous soil microbiota degraded 500 micrograms/g 2,4-D to less than 10 micrograms/g, PAA degradation was insignificant during a 40-day period. No significant degradation of PAA occurred in soil inoculated with the parental strain P. putida PP0301 or the inducible 2,4-D degrader P. putida PP0301(pR0101). Moreover, co-amendment of soil with 2,4-D and PAA induced the microbiota to degrade 2,4-D; PAA was not degraded. P. putida PP0301-(pR0103) mineralized 500-micrograms/g PAA to trace levels within 13 days and relieved phytotoxicity of PAA to Raphanus sativus (radish) seeds with 100% germination in the presence of the GEM and 7% germination in its absence. In unamended soil, survival of the plasmid-free parental strain P. putida PP0301 was similar to the survival of the GEM strain P. putida PP0301(pR0103). However, in PAA amended soil, survival of the parent strain was over 10,000-fold lower (< 3 colony forming units per gram of soil) than survival of the GEM strain after 39 days.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2004

Survival and ecological fitness of Pseudomonas fluorescens genetically engineered with dual biocontrol mechanisms.

The antibiotic 2,4-diacetylphloroglucinol (Phl) is produced by a range of naturally occurring fluorescent pseudomonads. One isolate, Pseudomonas fluorescens F113, protects pea plants from the pathogenic fungus Pythium ultimum by reducing the number of pathogenic lesions on plant roots, but with a concurrent reduction in the emergence of plants such as pea. The genes responsible for Phl production have been shown to be functionally conserved between the wild-type (wt) P. fluorescens strains F113 and Q2-87. In this study the genes from F113 were isolated using an optimized long PCR method and a 6.7-kb gene cluster inserted into the chromosome of the non-Phl-producing P. fluorescens strain SBW25 EeZY6KX. This strain is a lacZY, km(R) marked derivative of the wt SBW25 which effects biological control against the plant pathogen Pythium ultimum by competitive exclusion as a result of its strong rhizosphere-colonizing ability. We describe here the integration of the Phl antifungal and competitive exclusion mechanisms into a single strain, and the impact this has on survival and plant emergence in microcosms. The insertion of the Phl biosynthetic genes from the F113 into the SBW25 chromosome gave a Phl-producing transformant (strain Pa21) able to suppress P. ultimum through antibiotic production. The growth of Pa21 was not reduced in flask culture at 20 degrees C compared with its parent strain. When inoculated on pea seedlings, the strain containing the Phl operon behaved similarly to the SBW25 EeZY6KX parent but did not show the tendency of the wt Phl producer F113 to cause lower pea seed emergence. Pea roots inoculated with SBW25 EeZY6KX have significantly lower indigenous populations than with F113 and the control. This is indicative of this strain's strong colonising presence. Pa21, the Phl-modified strain, is able to exclude the resident population from roots to the same degree as the SBW25 EeZY6KX from which it is derived. This suggests that it has maintained its competitiveness around the root systems of plants even with the introduction of the Phl locus. Thus, strain Pa21 possesses the qualities necessary to provide effective integrated biocontrol, through maintaining both its wt trait of competitive exclusion on the plant roots, while also expressing the genes from the F113 biocontrol strain for Phl production. Interestingly, however, an additional beneficial trait appears to emerge with the strain Pa21's lowered survival competence compared with SBW25 EeZY6KX in the rhizosphere soil. With fears of the spread of genetically modified organisms and persistence in the soil, this trait may be of some ecological and commercial benefit and becomes a candidate for further investigation and possible exploitation.

Biodiversity↗

PubMed2006

Contribution of the arbuscular mycorrhizal symbiosis to heavy metal phytoremediation.

High concentrations of heavy metals (HM) in the soil have detrimental effects on ecosystems and are a risk to human health as they can enter the food chain via agricultural products or contaminated drinking water. Phytoremediation, a sustainable and inexpensive technology based on the removal of pollutants from the environment by plants, is becoming an increasingly important objective in plant research. However, as phytoremediation is a slow process, improvement of efficiency and thus increased stabilization or removal of HMs from soils is an important goal. Arbuscular mycorrhizal (AM) fungi provide an attractive system to advance plant-based environmental clean-up. During symbiotic interaction the hyphal network functionally extends the root system of their hosts. Thus, plants in symbiosis with AM fungi have the potential to take up HM from an enlarged soil volume. In this review, we summarize current knowledge about the contribution of the AM symbiosis to phytoremediation of heavy metals.

Biodegradation, Environmental↗

PubMed2003

Screening and genetic manipulation of plants for decontamination of pollutants from the environments.

In this review, we will describe our study on "nitrogen-philic plants", which can grow with nitrogen dioxide (NO2) as the sole nitrogen source, by screening of naturally occurring plants for the assimilation of nitrogen dioxide and genetic manipulation of plants for those genes involved in the primary nitrate metabolism. Finally, we will briefly describe "Green walls with nitrogen-dioxide-philic plants" for decontamination of pollution in urban areas.

Air Pollutants↗

PubMed2005

Need for multidisciplinary research towards a second green revolution.

Despite recent achievements in conventional plant breeding and genomics, the rate of increase of crop yields is declining and thus there is a need for a second green revolution. Advances within single disciplines, alone, cannot solve the challenges of increasing yield. As scientific disciplines have become increasingly diversified, a more complete understanding of the mechanisms by which genetic and environmental variation modify grain yield and composition is needed, so that specific quantitative and quality targets can be identified. To achieve this aim, the expertise of plant genomics, physiology and agronomy, as well as recently developed plant modelling techniques, must be combined. There has been recent progress in these individual disciplines, but multidisciplinary approaches must be implemented to tackle drought stress and salinity as major constraints to achieving sufficient grain yield in the future.

Agriculture↗

PubMed2004

Abandoning 'responsive' GM risk assessment.

Concerns over the potential for GM crops to cause unwanted environmental change have spawned intense research activity. Studies have ranged in scope from small-scale laboratory experiments aiming to specify unwanted changes that could occur (hazard identification studies) through to large-scale initiatives designed to calculate the likelihood that a particular hazard will occur (exposure and risk assessment studies).

Crops, Agricultural↗

PubMed2001

The case for genetically modified crops with a poverty focus.

Recently seven National Academies of Science produced a report on transgenic plants and world agriculture. The report provides scientific perspectives to the ongoing public debate about the potential role for transgenic technology in world agriculture. In this article, we develop the themes of the report and emphasize the potential for future genetically modified (GM) crops with a poverty focus, emphasizing the potential of GM resistance to plant parasitic nematodes for subsistence potato farmers in Bolivia. We judge that a range of incremental gains to crop yields from many transgenes are valuable for future world security. We advocate the establishment of a standard that GM crops must achieve before they are both biosafe and appropriate for resource-poor farmers and we believe that the best interests of the poor require biotechnologists to work towards that objective.

Agriculture↗

PubMed2002

Biological substitutes for pesticides.

In the 20th century an increasing number of pesticides, based on biocidal molecules, were the means for a substantial increase in food and fibre production and quality. Because of health and environmental concerns continued extensive use of such molecules is intensively debated and substitutes are often urgently required. Beside crop plant resistance, various biological control methods based on natural pest suppressing organisms are regarded as main alternatives. Several approaches and concepts also have been tested and commercial organism-based preparations are steadily increasing. However, further biotechnological efforts are required to give them status of being practical substitutes to pesticides. At present they are not comparable to pesticides in meeting efficacy, market and other expectations, but they still have a promising future, especially where genetically modified organisms can be used.

Agriculture↗

PubMed1997

The ecology and biosafety of baculoviruses.

Advances in the use of molecular techniques-particularly for virus identification, the investigation of latency and the infection process, plus the development of a theoretical framework containing a higher degree of biological realism-have pushed baculovirus ecology forward in the past few years. This has created a scenario in which many hitherto intractable questions about the behaviour of natural and genetically modified baculoviruses can now be addressed.

Animals↗

PubMed1989