Symbiotic Between Plant and Bacteria

oleh: Evah Luviah (10604101)

Symbiotic Between Plant and Bacteria

Under natural environmental conditions, successful of plant development and crop depend on the internal factor and external factor. The internal factor includes genetic constitution. The external factor involves soil, water, and light. Soil provides nutrition like mineral salt and chemical inorganic compound, ground water, and beneficial microorganisms. Water is needed by plant for its survival and growth. Light is needed by plant for photosynthesis or obtaining nutrition and energy source.
The most important here is how plant get nutrition especially nitrogen from their habit. The plant doesn't have ability to fix nitrogen from atmosphere directly because of the triple bond of Nitrogen, (Pasternak, 1998). It must be converted first to be complex compound as nitrate. So, to obtain nitrate from soil, plant must be symbiotic with some beneficial soil bacteria or diazotrophic bacteria.
Diazotrophic bacteria live in soil and help plant directly or indirectly. Commonly, beneficial soil bacteria help plant directly by providing fixed nitrogen and supplying it to the plant.
Nowadays, almost all farmers in Indonesia use chemical fertilizer to help them for increasing crops yields. Using chemical fertilizer continuously has triggered pollution problems which results runoff and decreases nutrient availability of the soil, (Black, 2004) those factors has led to find an alternative to increase crops yields besides using chemical fertilizer. Scientist has developed some diazotrophic bacteria as "bacterial fertilizer". Some of techniques in genetic engineering have been going on in order to get new products by means transgenic bacterial soil.
Nitrogen fixation is a very complicated process. It is requiring the action of a large number of different proteins. Those proteins are encoded by multigenes called nif gene, (Pasternak, 1998). Some of techniques in genetic engineering try to isolate this gene and then try to insert this gene to the plant. But it is not possible. Glick and Pasternak (1998) noted that, those multigenes by means nif gene can not be inserted to plant because of two reasons. First, plant doesn't have a promoter for nif gene; second, plant is not a bacterium which able to transcript multigenes and results more than one protein in once transcription processes, this ability called as polycystronic, (Weaver, 2005). For plant, once transcription process is for one protein.
Other study has led to find a new way for better harvest. Scientists try to manipulate hydrogenase, to make a mutant of diazotrophic bacteria, to manipulate oxygen level in diazotrophic bacteria, or to manipulate regulator gene of nif gene. Those experiments have been success to increase crops yields and ever been applied in some developed countries.

References
Weaver, Robert F. 2002. Molecular Biology 3rd edition. New York: Mc.Graw Hill.

Glick, R., Bernard and Pasternak, J. Jack. 1998. Molecular Biotechnology 3rd edition:
Principles and Applications of Recombinant DNA. Washington: University of Waterloo.

Black, G. Jacquelyn. 1999. Microbiology 4th edition: Principles and Explorations. New Jersey:
Prentice Hall, Inc.

oleh : Evah Luviah (10604101)