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Биотехнологии Clearing of industrial sewage from arsenic with the help of Pseudomonas putida cells, immobilized on plastic or wood shavings
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Lectures 18-19

Pseudomonas putida is a gram-negative rod-shaped saprotrophic soil bacterium. Based on 16S rRNA analysis, P. putida has been placed in the P. putida group, to which it lends its name.

It is the first patented organism in the world. Because it is a living organism the patent was disputed and brought before the United States Supreme Court in the historic court case Diamond v. Chakrabarty which the inventor, Ananda Mohan Chakrabarty, won. It demonstrates a very diverse metabolism, including the ability to degrade organic solvents such as toluene. This ability has been put to use in bioremediation, or the use of microorganisms to biodegrade oil. Use of P. putida is preferable to some other Pseudomonas species capable of such degradation as it is a safe species of bacteria, unlike P. aeruginosa for example, which is an opportunistic human pathogen.

The diverse metabolism of P. putida may be exploited for bioremediation; for example, it is used as a soil inoculant to remedy naphthalene contaminated soils.

P. putida is capable of converting styrene oil into the biodegradable plastic PHA. This may be of use in the effective recycling of Polystyrene foam, otherwise thought to be non-biodegradable.

Di- to pentanucleotide usage and the list of the most abundant octa- to tetradecanucleotides are useful measures of the bacterial genomic signature. The Pseudomonas putida KT2440 chromosome is characterized by strand symmetry and intra-strand parity of complementary oligonucleotides. Each tetranucleotide occurs with similar frequency on the two strands. Tetranucleotide usage is biased by G+C content and physicochemical constraints such as base stacking energy, dinucleotide propeller twist angle or trinucleotide bendability. The 105 regions with atypical oligonucleotide composition can be differentiated by their patterns of oligonucleotide usage into categories of horizontally acquired gene islands, multidomain genes or ancient regions such as genes for ribosomal proteins and RNAs. A species-specific extragenic palindromic sequence is the most common repeat in the genome that can be exploited for the typing of P. putida strains. In the coding sequence of P. putida LLL is the most abundant tripeptide.

Bioremediation refers to the use of microorganisms to degrade contaminants that pose environmental and especially human risks. Due to its safety and convenience, it has become an accepted remedy for cleaning polluted soil and water. Bioremediation processes typically involve many different microbes acting in parallel or sequence to complete the degradation process. The ability of microbes to degrade a vast array of pollutants makes bioremediation a technology that can applied in different soil conditions.

A widely used approach to bioremediation involves stimulating a group of organisms in order to shift the microbial ecology toward the desired process. This is termed "Biostimulation." Biostimulation can be achieved through changes in pH, moisture, aeration, or nutrient additions. The other widely used approach is termed "Bioaugmentation" where organisms selected for high degradation abilities are used to inoculate the contaminated site. These two approaches are not mutually exclusive- they can be used simultaneously.

Bioremediation is accomplished either in situ or ex situ. In situ remediation efforts focus on treating the contaminant at the polluted site. Ex situ remediation refers to the treatment of contaminated water or soil at an off site location. In such cases, soil and groundwater from the contaminated site are transported to a place (like a bioreactor), where conditions favorable for biological degradation can be controlled and enhanced.

Recent awareness of the dangers of many chemicals has led to products that are more easily degraded in the environment. These products are usually made of materials, like starches, that can be naturally broken down by microbes.

Environmental biotechnology – serving the future

Like white biotechnology, environmental biotechnology, often referred to as “grey biotechnology”, also focuses on sustainability. For instance, environmental biotechnology deals with the treatment of sewage water, the purification of exhaust gas or the decontamination of soils or ground water using specific microorganisms.

The use of organisms for the removal of contamination or pollutants is generally referred to as bioremediation. Originally, bioremediation was mainly used in cleanup operations, including the decomposition of spilt oil or slagheaps containing radioactive waste. In addition, bioremediation is also the method of choice when solvents, plastics or heavy metals and toxic substances like DDT, dioxins or TNT need to be removed.

Bioadsorption processes using newly developed bioadsorbers made from renewable materials are currently being developed. These adsorbers function as ion exchangers and are used in the elimination and disposal of toxic heavy metals. The industrial use of mineral resources leads to the drastic accumulation of these pollutants in the biosphere. The new bioadsorbers are used for the elimination of heavy metals and radionuklids from industrial wastewater, ore mine wastewater, seepage water from dumpsites or wastewater from nuclear power stations.

Control questions:

  1. What is the importance of Pseudomonas putida?
  2. What test will differentiate between pseudomonas putida and pseudomonas aerugionsa?
  3. What are the characteristics of pseudomonas fluorescens?
  4. What are the morphological characteristics of pseudomonas aeruginosa?