Microorganisms as research tools 8

MICROORGANISMS AS RESEARCH TOOLSAbstractMicroorganisms have been used as a tool to explore fundamental life processes by researchers. Due to some advantages (e.g. rapid growth, growth manipulation, easy & quick culture) microbes frequently used as research tools in different fields. Microbes play an important role in the research of enzyme structure & mode of action, drug invention, cellular regulatory mechanism, energy metabolism, protein synthesis, structure of viruses. Bacteria infect host cells, often using toxins, and shield themselves with inbuilt protective mechanisms.The team looked at the common bacteria Streptococcus pyogenes to determine the structures of its toxin and antitoxin. The antitoxin deactivates the toxin by binding to it. When not bound, the antitoxin changes shape.British bacteriologist Frederick Griffith discovered that a harmless strain of Streptococcus pneumoniae could be made virulent after being exposed to heat-killed virulent strains. An efficient and convenient procedure for transforming bacteria and opened the way for molecular cloning in biotechnology and research. A biofilm is an aggregate of microorganisms in which cells adhere to each other and/or to a surface.The engineered bacteria-attacking virus, or phage, was built using a plug and play library of genes. The same approach could be used to build viruses custom tailored to target specific bacteria species, the researchers say.Keywords: advantages, result & rewards of using microorganism as research tools, Bacterias self defense mechanism, Transformation (genetics),Scientists engineer viruses to destroy bacteria,Use of bacteria as anticancer agent. Any noncellular or unicellular (including colonial) organism, most of which are too small to be seen with the unaided eye. Microorganisms comprise bacteria (including cyanobacteria), lichens, microfungi, protozoa, rickettsiae, virinos, viroids, and viruses, and also some algae; all prokaryotes are included.The study of microorganisms is called microbiology, a subject that began with Anton van Leeuwenhoek's discovery of microorganisms in 1675, using a microscope of his own design.( Pelczar,1990)Microorganisms have been used as a tool to explore fundamental life processes because of many advantages(Smith, 2000) :1. They grow (produce) very rapidly2. Growth can be manipulated easily by chemical or physical means3. Microorganisms can be cultured small or vast quantities conveniently and rapidly4. Their cells can be broken apart & the contents separated into fractions of various particle sizes5. Lysed cells can be studied in terms of specific chemical reactions, specific products and specific structures involved.Scientists from many disciplines recognized the usefulness of microorganisms experimental models. Then physicists, chemists and biologist joined with microbiologists in molecular biology. The result & rewards from the field of research is spectaculars.( Sharma, 2006) . The contribution includes :1.Elucidation of enzyme structure & mode of action.2.Celluler regulatory mechanism3.Energy metabolism4.Protein synthesis5.Structure of virusesHere we discussed about some microbes whcich were used as a resechal model or tool in experiments:Bacterias self defense mechanism might work against fighting infectionsBacteria infect host cells, often using toxins, and shield themselves with inbuilt protective mechanisms. These pathways could become their Achilles heel, according to researchers from Washington University in a study published on Feb. 9 in the journal Structure.The team looked at the common bacteria Streptococcus pyogenes to determine the structures of its toxin and antitoxin. The antitoxin deactivates the toxin by binding to it. When not bound, the antitoxin changes shape.Thats the Achilles heel that we would like to exploit, said Dr. Thomas Ellenberger, head of the universitys Department of Biochemistry and Molecular Biophysics, in a release. A drug that would stabilize the inactive form of the immunity factor would liberate the toxin in the bacteria.Experts say that the bacterium protects itself from the secreted toxic by keeping it in an inactive form, by counter producing its antidote. When toxin complexes with the antitoxin molecule (immunity factor), it remains inactive and is unable to cause any harm to the host or the bacterial cell itself.

Figure 1 :Microalgae under the electron microscope. The bacterias toxin is called Streptococcus pyogenes beta-NAD+ glycohydrolase, or SPN. Cells store the coenzyme NAD+ as part of their metabolism, and the toxin works by draining these stores. The bacterias energy supply is protected by the antitoxin, the immunity factor for SPN (IFS), which blocks the toxins access to NAD+.The most important aspect of the structure is that it tells us a lot about how the antitoxin blocks the toxin activity and spares the bacterium, said Ellenberger.Understanding how these bacteria cause disease in humans is important in drug design.There is a war going on between bacteria and their hosts, said coauthor Dr. Craig Smith, a postdoctoral researcher at the university, in the press release. Bacteria secrete toxins and we have ways to counterattack through our immune systems and with the help of antibiotics. But, as bacteria develop antibiotic resistance, we need to develop new generations of antibiotics.Antibiotics work in different ways; some block bacterial cell wall synthesis, while others interfere with DNA synthesis or even inhibit bacterial metabolism.As of yet, there are no classes of drugs that attack the protective antitoxin mechanisms of bacteria.Obviously they could evolve resistance once you target the antitoxin, Ellenberger said. But this would be a new target. Understanding structures is a keystone of drug design. ( Arshdeep 2011)Transformation (genetics)Transformation was first demonstrated in 1928 by British bacteriologist Frederick Griffith. Griffith discovered that a harmless strain of Streptococcus pneumoniae could be made virulent after being exposed to heat-killed virulent strains. Griffith hypothesized that some "transforming principle" from the heat-killed strain was responsible for making the harmless strain virulent. In 1944 this "transforming principle" was identified as being genetic by Oswald Avery, Colin MacLeod, and Maclyn McCarty. They isolated DNA from a virulent strain of S. pneumoniae and using just this DNA were able to make a harmless strain virulent. They called this uptake and incorporation of DNA by bacteria "transformation" See Avery-MacLeod-McCarty experiment.The results of Avery et al.'s experiments were at first sceptically received by the scientific community and it was not until the development of genetic markers and the discovery of other methods of genetic transfer (conjugation in 1947 and transduction in 1953) by Joshua Lederberg that Avery's experiments were accepted. Transformation did not become routine procedure in laboratories until 1972 when Stanley Cohen, Annie Chang and Leslie successfully transformed Escherichia coli by treating the bacteria with calcium chloride. This created an efficient and convenient procedure for transforming bacteria and opened the way for molecular cloning in biotechnology and research.Transformation using electroporation was developed in the late 1980s thus increasing the efficiency and number of bacterial strains that could be transformed. Transformation of animal and plant cells was also investigated with the first transgenic mouse being created by injecting a gene for a rat growth hormone into a mouse embryo in 1982. In 1907 a bacterium that caused plant tumors, Agrobacterium tumefaciens, was discovered and in the early 1970s the tumor inducing agent was found to be a DNA plasmid called the Ti plasmid. By removing the genes in the plasmid that caused the cancer and adding in novel genes researchers were able to infect plants with A. tumefaciens and let the bacteria insert their chosen DNA into the genomes of the plants. Not all plant cells are susceptible to infection by A. tumefaciens so other methods were developed including electroporation and micro-injection. Particle bombardment was made possible with the invention of the Biolistic Particle Delivery System (gene gun) by John Sanford in 1990. (wikipedia, 2011)Scientists engineer viruses to destroy bacteriaSynthetic creation attacked biofilms that can form on teeth, in crevices.A biofilm is an aggregate of microorganisms in which cells adhere to each other and/or to a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS). Biofilm EPS, which is also referred to as slime (although not everything described as slime is a biofilm), is a polymeric conglomeration generally composed of extracellular DNA, proteins, and polysaccharides. Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial and hospital settings.

Figure 2: Staphylococcus aureus biofilmThe engineered bacteria-attacking virus, or phage, was built using a plug and play library of genes. The same approach could be used to build viruses custom tailored to target specific bacteria species, the researchers say. The library could contain different phages that target different species or strains of bacteria, each constructed using related design principles to express different enzymes, said study leader James Collins, a biomedical engineer at Boston University. (Jain KK 2011) Use of bacteria as anticancer agent Historically, bacteria were used as oncolytic agents for malignant brain tumours. Advances in bacteriology and molecular biology have widened the scope of bacterial approaches to cancer therapy and various possibilities include the use of bacteria as sensitising agents for chemotherapy, as delivery agents for anticancer drugs, and as vectors for gene therapy. Bacterial toxins can be used for tumour destruction and cancer vaccines can be based immunotoxins of bacterial origin. The most promising approaches are the use of genetically modified bacteria for selective destruction of tumours, and bacterial gene-directed enzyme prodrug therapy.

Figure 3 : Salmonella Knowledge gained from study of bacterial genomes forms an important basis of use of bacteria as anticancer agents. TAPET (Tumour Amplified Protein Expression Therapy) uses a genetically altered strain of Salmonella as a bacterial vector, or vehicle, for preferentially delivering anticancer drugs to solid tumours. Verotoxin 1 (VT1) of Escherichia coli has been used for ex vivo purging of human bone marrow of cancer cells before autologous bone marrow transplant.E. coli genes and enzymes have become part of well-known prodrug approaches to cancer in which inert prodrugs can be converted in vivo to highly active species. IL-4 fused with Pseudomonas exotoxin has been administered directly into malignant brain tumours and binds with high affinity to IL-4 receptors, which do not exist on normal brain cells, thus destroying a major part of the tumour without harming the normal brain tissue. It is in Phase I/II clinical trials in patients with glioblastoma. No ideal anticancer agent of bacterial origin that is applicable to all types of cancers has been discovered yet. The most promising approach to malignant brain tumours appears to be the use of genetically engineered bacteria that destroy the tumour selectively while sparing the normal brain tissue. (Ker Than 2007)ReferencesArshdeep Sarao,Epoch Times 2011, Bacterias Self Defense Mechanism Might Work Against It.A.Smith (2000), Oxford Dictionary of Biochemistry and Molecular Biology,Revised edition (February 24, 2000) , Oxford University Press, USA Jain KK ,PharmaBiotech, Blsiring 7, CH-4057 Basel, Switzerland.Ker Than ,Live Science Magazine 2007Pelczar, M.J, Chan, E.C.S & N. R. Krieg. Microbiology- Concepts and Applications (International Edition), .McGraw- Hill Inc. New DelhiS. Sharma,,General microbiology,Microbial World, History and Development of Microbiology, Scope of Microbiology,(Revised 12-Dec-2006)Wikipedia , 23 February 2011From : http://en.wikipedia.org/wiki/Transformation_%28genetics%29